Mediation analysis of chronic kidney disease risk factors using kidney biomarkers in women living with HIV

OBJECTIVE

Novel urinary biomarkers reflecting kidney tubule health are associated with chronic kidney disease (CKD) risk in persons living with HIV. However, it is unknown whether these biomarkers provide mechanistic insight into the associations between clinical risk factors for CKD and subsequent CKD risk.

METHODS

Among 636 women living with HIV in the Women's Interagency HIV Study with estimated glomerular filtration rate (eGFR) >60 ml/min/1.73 m 2 , we used a counterfactual approach to causal mediation analysis to evaluate the extent to which systolic blood pressure (SBP), diastolic blood pressure (DBP), hemoglobin a1c (Hba1c) and serum albumin associations with incident CKD were mediated by eight urine proteins. These biomarkers reflect proximal tubular reabsorptive dysfunction (α1-microglobulin [a1m], β2-microglobulin, trefoil factor 3); tubular injury (interleukin 18 [IL-18], kidney injury molecule 1 [KIM-1]); kidney repair (epidermal growth factor); tubular reserve (uromodulin); and glomerular injury (urinary albumin). Incident CKD was defined as eGFR <60 ml/min/1.73 m 2 measured at two consecutive 6-month visits with an average annual eGFR decline ≥3% per year.

RESULTS

During a median follow-up of 7 years, 11% developed CKD. Urinary albumin and KIM-1 mediated 32% (95% CI: 13.4%, 76.6%) and 23% (6.9%, 60.7%) of the association between SBP and incident CKD, respectively; and 19% (5.1%, 42.3%) and 22% (8.1%, 45.7%) of the association between DBP and incident CKD, respectively. Urinary albumin, α1m, and IL-18 were significant mediators of the association between Hba1c and incident CKD. None of the eight biomarkers mediated the association between serum albumin and incident CKD.

CONCLUSIONS

Among women living with HIV, several urinary biomarkers reflecting distinct dimensions of kidney health may partially explain the associations between SBP, DBP, and Hba1c and subsequent CKD risk.

Modification of Association of Cystatin C With Kidney and Cardiovascular Outcomes by Obesity

RATIONALE & OBJECTIVE

Cystatin C-based estimated glomerular filtration rate (eGFRcys) has stronger associations with adverse clinical outcomes than creatinine-based eGFR (eGFRcr). Obesity may be associated with higher cystatin C levels, independent of kidney function, but it is unknown whether obesity modifies associations of eGFRcys with kidney and cardiovascular outcomes.

STUDY DESIGN

Cohort study.

SETTING & PARTICIPANTS

27,249 US adults in the Reasons for Geographic and Racial Differences in Stroke Study.

PREDICTORS

eGFRcys, eGFRcr, waist circumference, and body mass index (BMI).

OUTCOME

All-cause mortality, kidney failure, incident atherosclerotic cardiovascular disease (ASCVD), and incident heart failure (HF).

ANALYTICAL APPROACH

Multivariable Cox and Fine-Gray models with multiplicative interaction terms were constructed to investigate whether waist circumference quartiles or BMI categories modified associations of eGFRcys with risks of 4 clinical outcomes.

RESULTS

Participants had a mean age of 65 years; 54% were women, 41% were Black, and 21% had an eGFRcys<60mL/min/1.73m2. The baseline prevalence of abdominal obesity (waist circumference≥88cm for women or≥102cm for men) was 48% and obesity was 38%. In multivariable adjusted analyses, each 15mL/min/1.73m2 lower eGFRcys was associated with higher HR and 95% CI of mortality in each waist circumference quartile (first quartile, 1.19 [1.15-1.24]; second quartile, 1.22 [1.18-1.26]; third quartile, 1.20 [1.16-1.24]; fourth quartile, 1.19 [1.15-1.23]) as well as within each BMI category (BMI<24.9: 1.21 [1.17-1.25]; BMI 25.0-29.9: 1.21 [1.18-1.25]; BMI 30.0-34.9: 1.20 [1.16-1.25]; BMI≥35: 1.17, [1.12-1.22]). Neither waist circumference nor BMI modified the association of eGFRcys with mortality, kidney failure, incident ASCVD, or incident HF (all Pinteraction>0.05).

LIMITATIONS

Included only Black and White persons in the United States.

CONCLUSION

Obesity did not modify the association of eGFRcys with all-cause mortality, kidney failure, incident ASCVD, or incident HF. Among individuals with obesity, cystatin C may be used to provide eGFR-based risk prognostication for adverse outcomes.

PLAIN-LANGUAGE SUMMARY

Cystatin C is increasingly used in clinical practice to estimate kidney function, and cystatin C-based eGFR (eGFRcys) may be used to determine risk for adverse clinical outcomes. Adiposity may increase serum levels of cystatin C, independent of kidney function. This cohort study investigated whether associations of eGFRcys with adverse kidney and cardiovascular outcomes are modified by measures of obesity, waist circumference, and body mass index. We found that obesity does not modify associations of eGFRcys with 4 clinical outcomes and conclude that among individuals with obesity, cystatin C may be used to provide eGFR-based risk prognostication for adverse outcomes.

Cystatin C- and Creatinine-based Estimated GFR Differences: Prevalence and Predictors in the UK Biobank

Rationale & Objective

Large differences between estimated glomerular filtration rate (eGFR) based on cystatin C (eGFRcys) and creatinine (eGFRcr) occur commonly. A comprehensive evaluation of factors that contribute to these differences is needed to guide the interpretation of discrepant eGFR values.

Study Design

Cohort study.

Setting & Participants

468,969 participants in the UK Biobank.

Exposures

Candidate sociodemographic, lifestyle factors, comorbidities, medication usage, and physical and laboratory predictors.

Outcomes

eGFRdiff, defined as eGFRcys minus eGFRcr, categorized into 3 levels: lower eGFRcys (eGFRdiff, less than -15 mL/min/1.73 m2), concordant eGFRcys and eGFRcr (eGFRdiff, -15 to < 15 mL/min/1.73 m2), and lower eGFRcr (eGFRdiff, ≥15 mL/min/1.73 m2).

Analytical Approach

Multinomial logistic regression models were constructed to identify predictors of lower eGFRcys or lower eGFRcr. We developed 2 prediction models comprising 375,175 participants: (1) a clinical model using clinically available variables and (2) an enriched model additionally including lifestyle variables. The models were internally validated in an additional 93,794 participants.

Results

Mean ± standard deviation of eGFRcys was 88 ± 16 mL/min/1.73 m2, and eGFRcr was 95 ± 13 mL/min/1.73 m2; 25% and 5% of participants were in the lower eGFRcys and lower eGFRcr groups, respectively. In the multivariable enriched model, strong predictors of lower eGFRcys were older age, male sex, South Asian ethnicity, current smoker (vs never smoker), history of thyroid dysfunction, chronic inflammatory disease, steroid use, higher waist circumference and body fat, and urinary albumin-creatinine ratio >300 mg/g. Odds ratio estimates for these predictors were largely inverse of those in the lower eGFRcr group. The model's area under the curve was 0.75 in the validation set, with good calibration (1.00).

Limitations

Limited generalizability.

Conclusions

This study highlights the multitude of demographic, lifestyle, and health characteristics that are associated with large eGFRdiff. The clinical model may identify individuals who are likely to have discrepant eGFR values and thus should be prioritized for cystatin C testing.

Association of urine biomarkers of kidney health with subclinical cardiovascular disease among men with and without HIV

OBJECTIVE

The aim of this study was to determine whether urine biomarkers of kidney health are associated with subclinical cardiovascular disease among men with and without HIV.

DESIGN

A cross-sectional study within the Multicenter AIDS Cohort Study (MACS) among 504 men with and without HIV infection who underwent cardiac computed tomography scans and had urine biomarkers measured within the preceding 2 years.

METHODS

Our primary predictors were four urine biomarkers of endothelial (albuminuria), proximal tubule dysfunction (alpha-1-microglobulin [A1 M] and injury (kidney injury molecule-1 [KIM-1]) and tubulointerstitial fibrosis (pro-collagen-III N-terminal peptide [PIIINP]). These were evaluated for association with coronary artery calcium (CAC) prevalence, CAC extent, total plaque score, and total segment stenosis using multivariable regression.

RESULTS

Of the 504 participants, 384 were men with HIV (MWH) and 120 were men without HIV. In models adjusted for sociodemographic factors, cardiovascular disease risk factors, eGFR, and HIV-related factors, each two-fold higher concentration of albuminuria was associated with a greater extent of CAC (1.35-fold higher, 95% confidence interval 1.11-1.65), and segment stenosis (1.08-fold greater, 95% confidence interval 1.01-1.16). Associations were similar between MWH and men without HIV in stratified analyses. The third quartile of A1 M showed an association with greater CAC extent, total plaque score, and total segment stenosis, compared with the lowest quartile.

CONCLUSION

Worse endothelial and proximal tubule dysfunction, as reflected by higher urine albumin and A1 M, were associated with greater CAC extent and coronary artery stenosis.

Association of Urinary Dickkopf-3 Levels with Cardiovascular Events and Kidney Disease Progression in Systolic Blood Pressure Intervention Trial

BACKGROUND

Urinary Dickkopf-3 (uDKK3) is a tubular epithelial-derived profibrotic protein secreted into the urine under tubular stress. It is associated with kidney disease progression in persons with chronic kidney disease (CKD) and diabetes, and post-operative and contrast-associated acute kidney injury (AKI). We explored associations of uDKK3 with cardiovascular disease (CVD), kidney and mortality outcomes within the subset of Systolic Blood Pressure Intervention Trial (SPRINT) participants with non-diabetic CKD.

METHODS

We included 2,344 participants with estimated glomerular filtration rate (eGFR) <60 ml/min/1.73 m2 at baseline. We used Cox proportional hazards models to evaluate associations of uDKK3 with CVD (acute decompensated heart failure, myocardial infarction, acute coronary syndrome, stroke or CVD death), kidney outcomes (incident end stage kidney disease [ESKD], incident AKI, and eGFR decline ≥30%), and all-cause mortality. We used linear mixed models to examine the association of uDKK3 with annual percentage change in eGFR. Models were adjusted for demographic and clinical characteristics, eGFR and albuminuria.

RESULTS

Over a median follow up of 3.5 years, there were 292 CVD, 73 ESKD, 183 AKI, 471 eGFR decline, and 228 mortality events. In multivariable models without adjustment for eGFR and albuminuria, uDKK3 was strongly associated with CVD, ESKD, AKI, eGFR decline ≥30%, and mortality. However, after further adjustment for eGFR and albuminuria, uDKK3 was no longer associated with risks for composite CVD (hazard ratio [HR] 1.07, 95% confidence interval [CI] 0.92-1.23), ESKD (0.80; 0.62-1.02), AKI (1.01; 0.85-1.21), eGFR decline >30% (0.88; 0.79-0.99) or mortality (1.02; 0.87-1.20). For the linear eGFR change outcome, higher uDKK3 also had no association in the fully adjusted model (-0.03; -0.41-0.36).

CONCLUSIONS

Among individuals with hypertension and non-diabetic CKD, higher uDKK3 appeared to have associations with a greater risk of CVD events, incident ESKD, incident AKI, eGFR decline ≥30%, and mortality, but was not independent of eGFR and albuminuria.

Associations of Baseline and Longitudinal Serum Uromodulin With Kidney Failure and Mortality: Results From the African American Study of Kidney Disease and Hypertension (AASK) Trial

RATIONALE & OBJECTIVE

Uromodulin (UMOD) is the most abundant protein found in urine and has emerged as a promising biomarker of tubule health. Circulating UMOD is also detectable, but at lower levels. We evaluated whether serum UMOD levels were associated with the risks of incident kidney failure with replacement therapy (KFRT) and mortality.

STUDY DESIGN

Prospective cohort.

SETTING & PARTICIPANTS

Participants in AASK (the African American Study of Kidney Disease and Hypertension) with available stored serum samples from the 0-, 12-, and 24-month visits for biomarker measurement.

PREDICTORS

Baseline log-transformed UMOD and change in UMOD over 2 years.

OUTCOMES

KFRT and mortality.

ANALYTICAL APPROACH

Cox proportional hazards and mixed-effects models.

RESULTS

Among 500 participants with baseline serum UMOD levels (mean age, 54y; 37% female), 161 KFRT events occurred during a median of 8.5 years. After adjusting for baseline demographic factors, clinical factors, glomerular filtration rate, log-transformed urine protein-creatinine ratio, and randomized treatment groups, a 50% lower baseline UMOD level was independently associated with a 35% higher risk of KFRT (adjusted HR, 1.35; 95% CI, 1.07-1.70). For annual UMOD change, each 1-standard deviation lower change was associated with a 67% higher risk of KFRT (adjusted HR, 1.67; 95% CI, 1.41-1.99). Baseline UMOD and UMOD change were not associated with mortality. UMOD levels declined more steeply for metoprolol versus ramipril (P<0.001) as well as for intensive versus standard blood pressure goals (P = 0.002).

LIMITATIONS

Small sample size and limited generalizability.

CONCLUSIONS

Lower UMOD levels at baseline and steeper declines in UMOD over time were associated with a higher risk of subsequent KFRT in a cohort of African American adults with chronic kidney disease and hypertension.

PLAIN-LANGUAGE SUMMARY

Prior studies of uromodulin (UMOD), the most abundant protein in urine, and kidney disease have focused primarily on urinary UMOD levels. The present study evaluated associations of serum UMOD levels with the risks of kidney failure with replacement therapy (KFRT) and mortality in a cohort of African American adults with hypertension and chronic kidney disease. It found that participants with lower levels of UMOD at baseline were more likely to experience KFRT even after accounting for baseline kidney measures. Similarly, participants who experienced steeper annual declines in UMOD also had a heightened risk of kidney failure. Neither baseline nor annual change in UMOD was associated with mortality. Serum UMOD is a promising biomarker of kidney health.

Ambulatory urine biomarkers associations with acute kidney injury and hospitalization in people with HIV

BACKGROUND

People with HIV (PWH) generally have worse ambulatory levels of kidney injury biomarkers and excess risk of acute kidney injury (AKI) compared to persons without HIV. We evaluated whether ambulatory measures of subclinical kidney injury among PWH are associated with subsequent AKI.

METHODS

In the Predictors of Acute Renal Injury Study (PARIS), which enrolled 468 PWH from April 2016 to August 2019, we measured 10 urine biomarkers of kidney health (albumin, a1m, b2M, NGAL, IL18, KIM-1, EGF, UMOD, MCP-1, YKL40) at baseline and annually during follow-up. Using multivariable Cox regression models, we evaluated baseline and time-updated biomarker associations with the primary outcome of AKI (≥0.3 mg/dl or ≥1.5-times increase in serum creatinine from baseline) and secondary outcome of all-cause hospitalization.

RESULTS

At baseline, the mean age was 53 years old, and 45% self-identified as female. In time-updated models adjusting for sociodemographic factors, comorbidities, albuminuria, estimated glomerular filtration rate, and HIV-associated factors, higher KIM-1 [hazard ratio (HR) = 1.30 per twofold higher; 95% confidence interval (CI) 1.03-1.63] and NGAL concentrations (HR = 1.24, 95% CI 1.06-1.44) were associated with higher risk of hospitalized AKI. Additionally, in multivariable, time-updated models, higher levels of KIM-1 (HR = 1.19, 95% CI 1.00, 1.41), NGAL (HR = 1.13, 95% CI 1.01-1.26), and MCP-1 (HR = 1.20, 95% CI 1.00, 1.45) were associated with higher risk of hospitalization.

CONCLUSIONS

Urine biomarkers of kidney tubular injury, such as KIM-1 and NGAL, are strongly associated with AKI among PWH, and may hold potential for risk stratification of future AKI.

CKD-EPI and EKFC GFR Estimating Equations: Performance and Other Considerations for Selecting Equations for Implementation in Adults

SIGNIFICANCE STATEMENT

New eGFR equations from Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) and European Kidney Function Consortium (EKFC) using creatinine (eGFRcr), cystatin C (eGFRcys), and both (eGFRcr-cys) have sufficient accuracy for use in clinical practice, leading to uncertainty in selecting equations for implementation. The authors evaluated performance of equations in an independent population of 4050 adults and evaluated other considerations important for implementation. They found that CKD-EPI and EKFC equations are approaching convergence, with better performance of eGFRcr-cys equations in the overall group and fewer differences among race, sex, and age subgroups than eGFRcr equations. Larger differences among eGFRcr equations reflect regional population differences in creatinine, forcing a trade-off between accuracy and uniformity in global implementation of eGFRcr equations. More widespread use of cystatin C could avoid this trade-off.

BACKGROUND

New CKD-EPI and EKFC eGFR equations using eGFRcr, eGFRcys, and both (eGFRcr-cys) have sufficient accuracy for use in clinical practice. A better understanding of the equations, including their performance in race, sex and age subgroups, is important for selection of eGFR equations for global implementation.

METHODS

We evaluated performance (bias and P 30 ) of equations and methods used for equation development in an independent study population comprising 4050 adults pooled from 12 studies. The mean (SD) measured GFR was 76.4 (29.6) ml/min per 1.73 m 2 and age 57.0 (17.4) years, with 1557 (38%) women and 579 (14%) Black participants.

RESULTS

Coefficients for creatinine, cystatin C, age, and sex in the CKD-EPI and EKFC equations are similar. Performance of the eGFRcr-cys equations in the overall population (bias <±5 ml/min per 1.73 m 2 and P 30 >90%) was better than the eGFRcr or eGFRcys equations, with fewer differences among race, sex, and age subgroups. Differences in performance across subgroups reflected differences in diversity of source populations and use of variables for race and sex for equation development. Larger differences among eGFRcr equations reflected regional population differences in non-GFR determinants of creatinine.

CONCLUSION

CKD-EPI and EKFC equations are approaching convergence. It is not possible to maximize both accuracy and uniformity in selecting one of the currently available eGFRcr equations for implementation across regions. Decisions should consider methods for equation development in addition to performance. Wider use of cystatin C with creatinine could maximize both accuracy and uniformity of GFR estimation using currently available equations.

Associations between abrupt transition, dialysis-requiring AKI, and early mortality in ESKD among U.S. veterans

BACKGROUND

Mortality is high within the first few months of starting chronic dialysis. Pre-ESKD trajectory of kidney function has been shown to be predictive of early death after dialysis initiation. We aim to better understand how two key aspects of pre-dialysis kidney function-an abrupt transition pattern and an episode of dialysis-requiring AKI (AKI-D) leading directly to ESKD-are associated with early mortality after dialysis initiation.

METHODS

We extracted national data from U.S. Veterans Health Administration cross-linked with the United States Renal Data System (USRDS) to identify patients who initiated hemodialysis during 2009-2013. We defined abrupt transition as having a mean outpatient eGFR ≥ 30 ml/min/1.73m2 within 1 year prior to ESKD. AKI-D was identified using inpatient serum creatinine measurements (serum Cr increase by at least 50% from baseline) along with billing codes for inpatient receipt of dialysis for AKI within 30 days prior to the ESKD start date. We used multivariable proportional hazards models to examine the association between patterns of kidney function prior to ESKD and all-cause mortality within 90 days after ESKD.

RESULTS

Twenty-two thousand eight hundred fifteen patients were identified in the final analytic cohort of Veterans who initiated hemodialysis and entered the USRDS. We defined five patterns of kidney function decline. Most (68%) patients (N = 15,484) did not have abrupt transition and did not suffer an episode of AKI-D prior to ESKD (reference group). The remaining groups had abrupt transition, AKI-D, or both. Patients who had an abrupt transition with (N = 503) or without (N = 3611) AKI-D had the highest risk of early mortality after ESKD onset after adjustment for demographics and comorbidities (adjusted HR 2.10, 95% CI 1.66-2.65 for abrupt transition with AKI-D; adjusted HR 2.10, 95% CI 1.90-2.33 for abrupt transition without AKI-D). In contrast, patients who experienced AKI-D without an abrupt transition pattern (N =  2141 had only a modestly higher risk of early death (adjusted HR 1.19, 95% CI 1.01-1.40).

CONCLUSIONS

An abrupt decline in kidney function within 1 year prior to ESKD occurred in nearly 1 in 5 incident hemodialysis patients (18%) in this national cohort of Veterans and was strongly associated with higher early mortality after ESKD onset.

Discordance Between Creatinine-Based and Cystatin C-Based Estimated GFR: Interpretation According to Performance Compared to Measured GFR

Rationale & Objective

Use of cystatin C in addition to creatinine to estimate glomerular filtration rate (estimated glomerular filtration rate based on cystatin C [eGFRcys] and estimated glomerular filtration rate based on creatinine [eGFRcr], respectively) is increasing. When eGFRcr and eGFRcys are discordant, it is not known which is more accurate, leading to uncertainty in clinical decision making.

Study Design

Cross-sectional analysis.

Setting & Participants

Four thousand fifty participants with measured glomerular filtration rate (mGFR) from 12 studies in North America and Europe.

Exposures

Serum creatinine and serum cystatin C.

Outcomes

Performance of creatinine-based and cystatin C-based glomerular filtration rate estimating equations compared to mGFR.

Analytical Approach

We evaluated the accuracy of eGFRcr, eGFRcys, and the combination (eGFRcr-cys) compared to mGFR according to the magnitude of the difference between eGFRcr and eGFRcys (eGFRdiff). We used CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equations to estimate glomerular filtration rate. eGFRdiff was defined as eGFRcys minus eGFRcr and categorized as less than -15, -15 to <15, and ≥15 mL/min/1.73 m2 (negative, concordant, and positive groups, respectively). We compared bias (median of mGFR minus eGFR) and the percentage of eGFR within 30% of mGFR.

Results

Thirty percent of participants had discordant eGFRdiff (21.0% and 9.6% negative and positive eGFRdiffs, respectively). In the concordant eGFRdiff group, all equations displayed similar accuracy. In the negative eGFRdiff groups, eGFRcr had a large overestimation of mGFR (-13.4 [-14.5 to -12.2] mL/min/1.73 m2) and eGFRcys had a large underestimation (9.9 [9.1-11.2] mL/min/1.73m2), with opposite results in the positive eGFRdiff group. In both negative and positive eGFRdiff groups, eGFRcr-cys was more accurate than either eGFRcr or eGFRcys. These results were largely consistent across age, sex, race, and body mass index.

Limitations

Few participants with major comorbid conditions.

Conclusions

Discordant eGFRcr and eGFRcys are common. eGFR using the combination of creatinine and cystatin C provides the most accurate estimates among persons with discordant eGFRcr or eGFRcys.

Association of marijuana, tobacco and alcohol use with estimated glomerular filtration rate in women living with HIV and women without HIV

OBJECTIVE

Marijuana, tobacco and alcohol use are prevalent among people with HIV and may adversely affect kidney function in this population. We determined the association of use of these substances with estimated glomerular filtration rate (eGFR) among women with HIV (WWH) and women without HIV.

DESIGN

We undertook a repeated measures study of 1043 WWH and 469 women without HIV within the United States Women's Interagency HIV Study, a multicenter, prospective cohort of HIV-seropositive and HIV-seronegative women.

METHODS

We quantified substance exposures using semi-annual questionnaires. Using pooled eGFR data from 2009 to 2019, we used linear regression models with multivariable generalized estimating equations to ascertain associations between current and cumulative substance use exposures with eGFR, adjusting for sociodemographics, chronic kidney disease risk factors and HIV-related factors.

RESULTS

Marijuana use of 1-14 days/month versus 0 days/month was associated with 3.34 ml/min per 1.73 m 2 [95% confidence interval (CI) -6.63, -0.06] lower eGFR and marijuana use of >0.02-1.6 marijuana-years versus 0-0.2 marijuana-years was associated with 3.61 ml/min per 1.73 m 2 (95% CI -5.97, -1.24) lower eGFR. Tobacco use was not independently associated with eGFR. Alcohol use of seven or more drinks/week versus no drinks/week was associated with 5.41 ml/min per 1.73 m 2 (95% CI 2.34, 8.48) higher eGFR and alcohol use of >0.7-4.27 drink-years and >4.27 drink-years versus 0-0.7 drink-years were associated with 2.85 ml/min per 1.73 m 2 (95% CI 0.55, 5.15) and 2.26 ml/min per 1.73 m 2 (95% CI 0.33, 4.20) higher eGFR, respectively.

CONCLUSION

Among a large cohort of WWH and women without HIV, marijuana use was associated with a lower eGFR while alcohol use was associated with a higher eGFR.

Estimated Prevalence and Testing for Albuminuria in US Adults at Risk for Chronic Kidney Disease

Importance

Albuminuria testing is crucial for guiding evidence-based treatments to mitigate chronic kidney disease (CKD) progression and cardiovascular morbidity, but it is widely underutilized among persons with or at risk for CKD.

Objective

To estimate the extent of albuminuria underdetection from lack of testing and evaluate its association with CKD treatment in a large US cohort of patients with hypertension or diabetes.

Design, Setting, and Participants

This cohort study examined adults with hypertension or diabetes, using data from the 2007 to 2018 National Health and Nutrition Examination Surveys (NHANES) and the Optum deidentified electronic health record (EHR) data set of diverse US health care organizations. Analyses were conducted from October 31, 2022, to May 19, 2023.

Main Outcomes and Measures

Using NHANES as a nationally representative sample, a logistic regression model was developed to estimate albuminuria (urine albumin-creatinine ratio ≥30 mg/g). This model was then applied to active outpatients in the EHR from January 1, 2017, to December 31, 2018. The prevalence of albuminuria among those with and without albuminuria testing during this period was estimated. A multivariable logistic regression was used to examine associations between having albuminuria testing and CKD therapies within the subsequent year (prescription for angiotensin-converting enzyme inhibitor [ACEi] or angiotensin II receptor blocker [ARB], prescription for sodium-glucose cotransporter 2 inhibitor [SGLT2i], and blood pressure control to less than 130/80 mm Hg or less than 140/90 mm Hg on the latest outpatient measure).

Results

The total EHR study population included 192 108 patients (mean [SD] age, 60.3 [15.1] years; 185 589 [96.6%] with hypertension; 50 507 [26.2%] with diabetes; mean [SD] eGFR, 84 [21] mL/min/1.73 m2). There were 33 629 patients (17.5%) who had albuminuria testing; of whom 11 525 (34.3%) had albuminuria. Among 158 479 patients who were untested, the estimated albuminuria prevalence rate was 13.4% (n = 21 231). Thus, only 35.2% (11 525 of 32 756) of the projected population with albuminuria had been tested. Albuminuria testing was associated with higher adjusted odds of receiving ACEi or ARB treatment (OR, 2.39 [95% CI, 2.32-2.46]), SGLT2i treatment (OR, 8.22 [95% CI, 7.56-8.94]), and having blood pressure controlled to less than 140/90 mm Hg (OR, 1.20 [95% CI, 1.16-1.23]).

Conclusions and Relevance

In this cohort study of patients with hypertension or diabetes, it was estimated that approximately two-thirds of patients with albuminuria were undetected due to lack of testing. These results suggest that improving detection of CKD with albuminuria testing represents a substantial opportunity to optimize care delivery for reducing CKD progression and cardiovascular complications.

Dietary Patterns, Apolipoprotein L1 Risk Genotypes, and CKD Outcomes Among Black Adults in the Reasons for Geographic and Racial Differences in Stroke (REGARDS) Cohort Study

Rationale & Objective

Dietary factors may impact inflammation and interferon production, which could influence phenotypic expression of Apolipoprotein1 (APOL1) genotypes. We investigated whether associations of dietary patterns with kidney outcomes differed by APOL1 genotypes.

Study Design

Prospective cohort.

Settings & Participants

5,640 Black participants in the Reasons for Geographic and Racial Differences in Stroke (REGARDS).

Exposures

Five dietary patterns derived from food frequency questionnaires: Convenience foods, Southern, Sweets and Fats, Plant-based, and Alcohol/Salads.

Outcomes

Incident chronic kidney disease (CKD), CKD progression, and kidney failure. Incident CKD was defined as a change in estimated glomerular filtration rate (eGFR) to <60 mL/min/1.73 m2 accompanied by a ≥25% decline from baseline eGFR or development of kidney failure among those with baseline eGFR ≥60 mL/1.73 m2 body surface area. CKD progression was defined as a composite of 40% reduction in eGFR from baseline or development of kidney failure in the subset of participants who had serum creatinine levels at baseline and completed a second in-home visit/follow-up visit.

Analytical Approach

We examined associations of dietary pattern quartiles with incident CKD (n=4,188), CKD progression (n=5,640), and kidney failure (n=5,640). We tested for statistical interaction between dietary patterns and APOL1 genotypes for CKD outcomes and explored stratified analyses by APOL1 genotypes.

Results

Among 5,640 Black REGARDS participants, mean age was 64 years (standard deviation = 9), 35% were male, and 682 (12.1%) had high-risk APOL1 genotypes. Highest versus lowest quartiles (Q4 vs Q1) of Southern dietary pattern were associated with higher adjusted odds of CKD progression (OR, 1.28; 95% CI, 1.01-1.63) but not incident CKD (OR, 0.92; 95% CI, 0.74-1.14) or kidney failure (HR, 1.48; 95% CI, 0.90-2.44). No other dietary patterns showed significant associations with CKD. There were no statistically significant interactions between APOL1 genotypes and dietary patterns. Stratified analysis showed no consistent associations across genotypes, although Q3 and Q4 versus Q1 of Plant-based and Southern patterns were associated with lower odds of CKD progression among APOL1 high- but not low-risk genotypes.

Limitations

Included overlapping dietary patterns based on a single time point and multiple testing.

Conclusions

In Black REGARDS participants, Southern dietary pattern was associated with increased risk of CKD progression. Analyses stratified by APOL1 genotypes suggest associations may differ by genetic background, but these findings require confirmation in other cohorts.

Improvement in Renal Function During the Treatment of Acute Decompensated Heart Failure: Relationship With Markers of Renal Tubular Injury and Prognostic Importance

BACKGROUND

Improvement in renal function (IRF) in acute decompensated heart failure is associated with adverse outcomes. The mechanisms driving this paradox remain undefined.

METHODS

Using the ROSE-AHF study (Renal Optimization Strategies Evaluation-Acute Heart Failure), 277 patients were grouped according to renal function, with IRF defined by a ≥20% increase (N=75), worsening renal function by a ≥20% decline (N=53), and stable renal function (SRF) by a <20% change (N=149) in estimated glomerular filtration rate between baseline and 72 hours. Three well-validated renal tubular injury markers, NGAL (neutrophil gelatinase-associated lipocalin), NAG (N-acetyl-β-d-glucosaminidase), and KIM-1 (kidney injury molecule 1), were evaluated at baseline and 72 hours. Patients were also classified by the pattern of change in these markers.

RESULTS

Patients with IRF had the lowest admission estimated glomerular filtration rate (IRF, 37 [28 to 51] mL/min per 1.73 m2; worsening renal function, 43 [35 to 55] mL/min per 1.73 m2; and SRF, 43 [32 to 55] mL/min per 1.73 m2; Ptrend=0.032) but greater cumulative urine output (IRF, 8780 [7025 to 11 208] mL; worsening renal function, 7860 [5555 to 9765] mL; and SRF, 8150 [6325 to 10 456] mL; Ptrend=0.024) and weight loss (IRF, -9.0 [-12.4 to -5.3] lb; worsening renal function, -5.1 [-8.1 to -1.3] lb; and SRF, -7.1 [-11.9 to -3.2] lb; Ptrend<0.001) despite similar diuretic doses (Ptrend=0.16). There were no differences in the relative change in NGAL, NAG, or KIM-1 between renal function groups (Ptrend>0.19 for all). Patients with IRF had worse survival than patients with SRF (27% versus 54%; hazard ratio, 1.98 [1.10-3.58]; P=0.024).

CONCLUSIONS

IRF during decongestive therapy for acute decompensated heart failure was not associated with improved markers of renal tubular injury and was associated with worsened survival, likely driven by the presence of greater underlying cardiorenal dysfunction and more severe congestion.

Effect of Adopting the New Race-Free 2021 Chronic Kidney Disease Epidemiology Collaboration Estimated Glomerular Filtration Rate Creatinine Equation on Racial Differences in Kidney Disease Progression Among People With Human Immunodeficiency Virus: An Observational Study

BACKGROUND

The impact of adopting a race-free estimated glomerular filtration rate (eGFR) creatinine (eGFRcr) equation on racial differences in chronic kidney disease (CKD) progression among people with human immunodeficiency virus (PWH) is unknown.

METHODS

We defined eGFR stages using the original race-adjusted Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) eGFRcr equation and the new race-free CKD-EPI eGFRcr equation. We then estimated 5-year probabilities of transitioning from baseline kidney function to more advanced eGFR stages and examined the association of race (black vs white) with rates of CKD progression using Markov models.

RESULTS

With the race-adjusted eGFRcr equation, black participants (n = 31 298) had a lower risk of progressing from eGFR stage 1 to 2 (hazard ratio [HR], 0.77; 95% confidence interval [CI], .73-.82), an equal risk of progressing from stage 2 to 3 (1.00; .92-.07) and a 3-fold risk of progressing from stage 3 to 4 or 5 (3.06; 2.60-3.62), compared with white participants (n = 27 542). When we used the race-free eGFRcr equation, 16% of black participants were reclassified into a more severe eGFR stage at baseline. The reclassified black individuals had a higher prevalence of CKD risk factors than black PWH who were not reclassified. With the race-free eGFRcr equation, black participants had a higher risk of disease progression across all eGFR stages than white participants.

CONCLUSIONS

The original eGFRcr equation systematically masked a subgroup of black PWH who are at high-risk of CKD progression. The new race-free eGFRcr equation unmasks these individuals and may allow for earlier detection and management of CKD.

Differential Associations of Cystatin C Versus Creatinine-Based Kidney Function With Risks of Cardiovascular Event and Mortality Among South Asian Individuals in the UK Biobank

Background South Asian individuals have increased cardiovascular disease and mortality risks. Reliance on creatinine- rather than cystatin C-based estimated glomerular filtration rate (eGFRcys) may underestimate the cardiovascular disease risk associated with chronic kidney disease. Methods and Results Among 7738 South Asian UK BioBank participants without prevalent heart failure (HF) or atherosclerotic cardiovascular disease, we investigated associations of 4 eGFRcys and creatinine-based estimated glomerular filtration rate categories (<45, 45-59, 60-89, and ≥90 mL/min per 1.73 m2) with risks of all-cause mortality, incident HF, and incident atherosclerotic cardiovascular disease. The mean age was 53±8 years; 4085 (53%) were women. Compared with creatinine, cystatin C identified triple the number of participants with estimated glomerular filtration <45 (n=35 versus n=113) and 6 times the number with estimated glomerular filtration 45 to 59 (n=80 versus n=481). After multivariable adjustment, the eGFRcys 45 to 59 category was associated with higher risks of mortality (hazard ratio [HR], 2.38 [95% CI, 1.55-3.65]) and incident HF (sub-HR [sHR], 1.87 [95% CI, 1.09-3.22]) versus the eGFRcys ≥90 category; the creatinine-based estimated glomerular filtration rate 45 to 59 category had no significant associations with outcomes. Of the 7623 participants with creatinine-based estimated glomerular filtration rate ≥60, 498 (6.5%) were reclassified into eGFRcys <60 categories. Participants who were reclassified as having eGFRcys <45 had higher risks of mortality (HR, 4.88 [95% CI, 2.56-9.31]), incident HF (sHR, 4.96 [95% CI, 2.21-11.16]), and incident atherosclerotic cardiovascular disease (sHR, 2.29 [95% CI, 1.14-4.61]) versus those with eGFRcys ≥90; those reclassified as having eGFRcys 45 to 59 had double the mortality risk (HR, 2.25 [95% CI, 1.45-3.51]). Conclusions Among South Asian individuals, cystatin C identified a high-risk chronic kidney disease population that was not detected by creatinine and enhanced estimated glomerular filtration rate-based risk stratification for mortality, incident HF, and incident atherosclerotic cardiovascular disease.

Clinical Risk Factors For Kidney Tubule Biomarker Abnormalities Among Hypertensive Adults With Reduced eGFR in the SPRINT Trial

BACKGROUND

Urine biomarkers of kidney tubule health may distinguish aspects of kidney damage that cannot be captured by current glomerular measures. Associations of clinical risk factors with specific kidney tubule biomarkers have not been evaluated in detail.

METHODS

We performed a cross-sectional study in the Systolic Blood Pressure Intervention Trial among 2,436 participants with a baseline estimated glomerular filtration rate (eGFR) <60 ml/min/1.73 m2. Associations between demographic and clinical characteristics with urine biomarkers of kidney tubule health were evaluated using simultaneous multivariable linear regression of selected variables.

RESULTS

Each standard deviation higher age (9 years) was associated with 13% higher levels of chitinase-3-like protein-1 (YKL-40), indicating higher levels of tubulointerstitial inflammation and repair. Men had 31% higher levels of alpha-1 microglobulin and 16% higher levels of beta-2 microglobulin, reflecting worse tubule resorptive function. Black race was associated with significantly higher levels of neutrophil gelatinase-associated lipocalin (12%) and lower kidney injury molecule-1 (26%) and uromodulin (22%). Each standard deviation (SD) higher systolic blood pressure (SBP) (16 mmHg) was associated with 10% higher beta-2 microglobulin and 10% higher alpha-1 microglobulin, reflecting lower tubule resorptive function.

CONCLUSIONS

Clinical and demographic characteristics, such as race, sex, and elevated SBP, are associated with unique profiles of tubular damage, which could reflect under-recognized patterns of kidney tubule disease among persons with decreased eGFR.

Association of Intra-individual Differences in Estimated GFR by Creatinine Versus Cystatin C With Incident Heart Failure

RATIONALE & OBJECTIVE

Lower estimated glomerular filtration rate (eGFR) is associated with heart failure (HF) risk. However, eGFR based on cystatin C (eGFRcys) and creatinine (eGFRcr) may differ substantially within an individual. The clinical implications of these differences for risk of HF among persons with chronic kidney disease (CKD) are unknown.

STUDY DESIGN

Prospective cohort study.

SETTING & PARTICIPANTS

4,512 adults with CKD and without prevalent HF who enrolled in the Chronic Renal Insufficiency Cohort (CRIC) Study.

EXPOSURE

Difference in GFR estimates (eGFRdiff; ie, eGFRcys minus eGFRcr).

OUTCOME

Incident HF hospitalization.

ANALYTICAL APPROACH

Fine-Gray proportional subhazards regression was used to investigate the associations of baseline, time-updated, and slope of eGFRdiff with incident HF.

RESULTS

Of 4,512 participants, one-third had eGFRcys and eGFRcr values that differed by over 15 mL/min/1.73 m2. In multivariable-adjusted models, each 15 mL/min/1.73 m2 lower baseline eGFRdiff was associated with higher risk of incident HF hospitalization (hazard ratio [HR], 1.20 [95% CI, 1.07-1.34]). In time-updated analyses, those with eGFRdiff less than -15 mL/min/1.73 m2 had higher risk of incident HF hospitalization (HR, 1.99 [95% CI, 1.39-2.86]), and those with eGFRdiff ≥15 mL/min/1.73 m2 had lower risk of incident HF hospitalization (HR, 0.67 [95% CI, 0.49-0.91]) compared with participants with similar eGFRcys and eGFRcr. Participants with faster declines in eGFRcys relative to eGFRcr had higher risk of incident HF (HR, 1.49 [95% CI, 1.19-1.85]) compared with those in whom eGFRcys and eGFRcr declined in parallel.

LIMITATIONS

Entry into the CRIC Study was determined by eGFRcr, which constrained the range of baseline eGFRcr-but not eGFRcys-values.

CONCLUSIONS

Among persons with CKD who have large differences between eGFRcys and eGFRcr, risk for incident HF is more strongly associated with eGFRcys. Diverging slopes between eGFRcys and eGFRcr over time are also independently associated with risk of incident HF.

Prescription Patterns of Cardiovascular- and Kidney-Protective Therapies Among Patients With Type 2 Diabetes and Chronic Kidney Disease

OBJECTIVE

To assess the prevalence and correlates of prescription of sodium-glucose cotransporter 2 inhibitors (SGLT2i) and/or glucagon-like peptide 1 receptor agonists (GLP1-RA) in individuals with type 2 diabetes mellitus (T2DM) with and without chronic kidney disease (CKD).

RESEARCH DESIGN AND METHODS

This was a cross-sectional analyses of SGLT2i and GLP1-RA prescriptions from 1 January 2019 to 31 December 2020 in the Veterans Health Administration System. The likelihood of prescriptions was examined by the presence or absence of CKD and by predicted risks of atherosclerotic cardiovascular disease (ASCVD) and end-stage kidney disease (ESKD).

RESULTS

Of 1,197,880 adults with T2DM, SGLT2i and GLP1-RA were prescribed to 11% and 8% of patients overall, and to 12% and 10% of those with concomitant CKD, respectively. In adjusted models, patients with severe albuminuria were less likely to be prescribed SGLT2i or GLP1-RA versus nonalbuminuric patients with CKD, with odds ratios (ORs) of 0.91 (95% CI 0.89, 0.93) and 0.97 (0.94, 1.00), respectively. Patients with a 10-year ASCVD risk >20% (vs. <5%), had lower odds of SGLT2i use (OR 0.66 [0.61, 0.71]) and GLP1-RA prescription (OR 0.55 [0.52, 0.59]). A 5-year ESKD risk >5%, compared with <1%, was associated with lower likelihood of SGLT2i prescription (OR 0.63 [0.59, 0.67]) but higher likelihood of GLP1-RA prescription (OR 1.53 [1.46, 1.61]).

CONCLUSIONS

Among a large cohort of patients with T2DM, prescription of SGLT2i and GLP1-RA was low in those with CKD. We observed a "risk-treatment paradox," whereby patients with higher risk of adverse outcomes were less likely to receive these therapies.

Albuminuria testing and nephrology care among insured US adults with chronic kidney disease: a missed opportunity

BACKGROUND

In chronic kidney disease (CKD), assessment of both estimated glomerular filtration rate (eGFR) and albuminuria are necessary for stratifying risk and determining the need for nephrology referral. The Kidney Disease: Improving Global Outcomes clinical practice guidelines for CKD recommend nephrology referral for eGFR < 30 ml/min/1.73m² or for urinary albumin/creatinine ratio ≥ 300 mg/g.

METHODS

Using a national claims database of US patients covered by commercial insurance or Medicare Advantage, we identified patients with CKD who were actively followed in primary care. We examined receipt of nephrology care within 1 year among these patients according to their stage of CKD, classified using eGFR and albuminuria categories. Multivariable logistic regression was used to examine odds of receiving nephrology care by CKD category, adjusting for age, sex, race/ethnicity, diabetes, heart failure, and coronary artery disease.

RESULTS

Among 291,155 patients with CKD, 55% who met guideline-recommended referral criteria had seen a nephrologist. Receipt of guideline-recommended nephrology care was higher among those with eGFR < 30 (64%; 11,330/17738) compared with UACR ≥300 mg/g (51%; 8789/17290). 59% did not have albuminuria testing. Those patients without albuminuria testing had substantially lower adjusted odds of recommended nephrology care (aOR 0.47 [0.43, 0.52] for eGFR < 30 ml/min/1.73m²). Similar patterns were observed in analyses stratified by diabetes status.

CONCLUSIONS

Only half of patients meeting laboratory criteria for nephrology referral were seen by a nephrologist. Underutilization of albuminuria testing may be a barrier to identifying primary care patients at elevated kidney failure risk who may warrant nephrology referral.

Black and White Adults With CKD Hospitalized With Acute Kidney Injury: Findings From the Chronic Renal Insufficiency Cohort (CRIC) Study

RATIONALE & OBJECTIVE

Few studies have investigated racial disparities in acute kidney injury (AKI), in contrast to the extensive literature on racial differences in the risk of kidney failure. We sought to study potential differences in risk in the setting of chronic kidney disease (CKD).

STUDY DESIGN

Prospective cohort study.

SETTING & PARTICIPANTS

We studied 2,720 self-identified Black or White participants with CKD enrolled in the Chronic Renal Insufficiency Cohort (CRIC) Study from July 1, 2013, to December 31, 2017.

EXPOSURE

Self-reported race (Black vs White).

OUTCOME

Hospitalized AKI (≥50% increase from nadir to peak serum creatinine).

ANALYTICAL APPROACH

Cox regression models adjusting for demographics (age and sex), prehospitalization clinical risk factors (diabetes, blood pressure, cardiovascular disease, estimated glomerular filtration rate, proteinuria, receipt of angiotensin-converting enzyme inhibitors or angiotensin-receptor blockers), and socioeconomic status (insurance status and education level). In a subset of participants with genotype data, we adjusted for apolipoprotein L1 gene (APOL1) high-risk status and sickle cell trait.

RESULTS

Black participants (n = 1,266) were younger but had a higher burden of prehospitalization clinical risk factors. The incidence rate of first AKI hospitalization among Black participants was 6.3 (95% CI, 5.5-7.2) per 100 person-years versus 5.3 (95% CI, 4.6-6.1) per 100 person-years among White participants. In an unadjusted Cox regression model, Black participants were at a modestly increased risk of incident AKI (HR, 1.22 [95% CI, 1.01-1.48]) compared with White participants. However, this risk was attenuated and no longer significant after adjusting for prehospitalization clinical risk factors (adjusted HR, 1.02 [95% CI, 0.83-1.25]). There were only 11 AKI hospitalizations among individuals with high-risk APOL1 risk status and 14 AKI hospitalizations among individuals with sickle cell trait.

LIMITATIONS

Participants were limited to research volunteers and potentially not fully representative of all CKD patients.

CONCLUSIONS

In this multicenter prospective cohort of CKD patients, racial disparities in AKI incidence were modest and were explained by differences in prehospitalization clinical risk factors.

Submaximal Angiotensin-Converting Enzyme Inhibitor and Angiotensin Receptor Blocker Dosing Among Persons With Proteinuria

For persons with proteinuria, angiotensin-converting enzyme inhibitors (ACEis) and angiotensin II receptor blockers (ARBs) are treatment mainstays for reducing kidney disease progression. Guidelines for managing hypertension and chronic kidney disease recommend titrating to the maximum ACEi/ARB dose tolerated. Using deidentified national electronic health record data from the Optum Labs Data Warehouse, we examined ACEi/ARB dosing among adults with proteinuria-defined as either a urine albumin to creatinine ratio of 30 mg/g or greater or a protein to creatinine ratio of 150 mg/g or greater-who were prescribed an ACEi/ARB medication between January 1, 2017, and December 31, 2018. Among 100,238 included patients (mean age, 65.1 years; 49,523 [49.4%] female), 29,883 (29.8%) were taking maximal ACEi/ARB doses. Among 74,287 patients without potential contraindications to dose escalation (systolic blood pressure <120 mm Hg, estimated glomerular filtration rate <15 mL/min per 1.73 m2, serum potassium level greater than 5.0 mEq/L, or acute kidney injury within the prior year), the frequency of maximal ACEi/ARB dosing was 32.3% (24,025 patients). In adjusted analyses, age less than 40 years, female sex, Hispanic ethnicity, lower urine albumin to creatinine ratio, lack of diabetes, heart failure, lower blood pressure, higher serum potassium level, and prior acute kidney injury were associated with lower odds of maximal ACEi/ARB dosing. Having a prior nephrologist visit was not associated with maximal dosing. Our results suggest that greater attention toward optimizing the dose of ACEi/ARB therapy may represent an opportunity to improve chronic kidney disease care and reduce excess morbidity and mortality associated with disease progression.

Improving chronic kidney disease detection and treatment in the United States: the chronic kidney disease cascade of care (C3) study protocol

BACKGROUND

There are major gaps in the implementation of guideline-concordant care for persons with chronic kidney disease (CKD). The CKD Cascade of Care (C³) initiative seeks to improve CKD care by improving detection and treatment of CKD in primary care.

METHODS

C³ is a multi-modal initiative deployed in three major academic medical centers within the Department of Veterans Affairs (VA) Health Care System: San Francisco VA, San Diego VA, and Houston VA. The main objective of the first phase of C³ described in this protocol is to establish the infrastructure for universal CKD detection among primary care patients at high-risk for CKD with a triple-marker screen comprising cystatin C, creatinine, and albuminuria. Across the three sites, a comprehensive educational intervention and the integration of primary care-based clinical champions will be employed with the goal of improving CKD detection and treatment. The San Francisco VA will also implement a practice-facilitation intervention leveraging telehealth and health informatics tools and capabilities for enhanced CKD detection. Parallel formative evaluation across the three sites will assess the feasibility and acceptability of integrating cystatin C as part of routine CKD detection in primary care practice. The effectiveness of the interventions will be assessed using a pre-post observational design for change in the proportion of patients tested annually for CKD. Secondary outcomes will assess change in the initiation of cardio-kidney protective therapies and in nephrology referrals of high-risk patients.

DISCUSSION

The first phase of C³ is a multi-facility multi-modal initiative that aims to improve CKD care by implementing a triple-marker screen for enhanced CKD detection in primary care.

Assessment of Cystatin C Level for Risk Stratification in Adults With Chronic Kidney Disease

Importance

Kidney function is usually estimated from serum creatinine level, whereas an alternative glomerular filtration marker (cystatin C level) associates more closely with future risk of cardiovascular disease (CVD) and mortality.

Objectives

To evaluate whether testing concordance between estimated glomerular filtration rates based on cystatin C (eGFRcys) and creatinine (eGFRcr) levels would improve risk stratification for future outcomes and whether estimations differ by age.

Design, Setting, and Participants

A prospective population-based cohort study (UK Biobank), with participants recruited between 2006-2010 with median follow-up of 11.5 (IQR, 10.8-12.2) years; data were collected until August 31, 2020. Participants had eGFRcr greater than or equal to 45 mL/min/1.73 m2, albuminuria (albumin <30 mg/g), and no preexisting CVD or kidney failure.

Exposures

Chronic kidney disease status was categorized by concordance between eGFRcr and eGFRcys across the threshold for hronic kidney disease (CKD) diagnosis (60 mL/min/1.73 m2).

Main Outcomes and Measures

Ten-year probabilities of CVD, mortality, and kidney failure were assessed according to CKD status. Multivariable-adjusted Cox proportional hazards models tested associations between CVD and mortality. Area under the receiving operating curve tested discrimination of eGFRcr and eGFRcys for CVD and mortality. The Net Reclassification Index assessed the usefulness of eGFRcr and eGFRcys for CVD risk stratification. Analyses were stratified by older (age 65-73 years) and younger (age <65 years) age.

Results

There were 428 402 participants: median age was 57 (IQR, 50-63) years and 237 173 (55.4%) were women. Among 76 629 older participants, there were 9335 deaths and 5205 CVD events. Among 351 773 younger participants, there were 14 776 deaths and 9328 CVD events. The 10-year probability of kidney failure was less than 0.1%. Regardless of the eGFRcr, the 10-year probabilities of CVD and mortality were low when eGFRcys was greater than or equal to 60 mL/min/1.73 m2; conversely, with eGFRcys less than 60 mL/min/1.73 m2, 10-year risks were nearly doubled in older adults and more than doubled in younger adults. Use of eGFRcys better discriminated CVD and mortality risk than eGFRcr. Across a 7.5% 10-year risk threshold for CVD, eGFRcys improved case Net Reclassification Index by 0.7% (95% CI, 0.6%-0.8%) in older people and 0.7% (95% CI, 0.7%-0.8%) in younger people; eGFRcr did not add to CVD risk estimation.

Conclusions and Relevance

The findings of this study suggest that eGFRcr 45 to 59 mL/min/1.73 m2 includes a proportion of individuals at low risk and fails to capture a substantial proportion of individuals at high-risk for CVD and mortality. The eGFRcys appears to be more sensitive and specific for CVD and mortality risks in mild CKD.

Markers of Kidney Tubular Secretion and Risk of Adverse Events in SPRINT Participants with CKD

BACKGROUND

Kidney tubular secretion is an essential mechanism for clearing many common antihypertensive drugs and other metabolites and toxins. It is unknown whether novel measures of tubular secretion are associated with adverse events (AEs) during hypertension treatment.

METHODS

Among 2089 SPRINT (Systolic Blood Pressure Intervention Trial) participants with baseline eGFR <60 ml/min per 1.73 m2, we created a summary secretion score by averaging across the standardized spot urine-to-plasma ratios of ten novel endogenous tubular secretion measures, with lower urine-to-plasma ratios reflecting worse tubular secretion. Multivariable Cox proportional hazards models were used to evaluate associations between the secretion score and risk of a composite of prespecified serious AEs (hypotension, syncope, bradycardia, AKI, electrolyte abnormalities, and injurious falls). The follow-up protocol for SPRINT routinely assessed two laboratory monitoring AEs (hyperkalemia and hypokalemia).

RESULTS

Overall, 30% of participants experienced at least one AE during a median follow-up of 3.0 years. In multivariable models adjusted for eGFR and albuminuria, lower (worse) secretion scores at baseline were associated with greater risk of the composite AE outcome (hazard ratio per 1-SD lower secretion score, 1.16; 95% confidence interval, 1.04 to 1.27). In analyses of the individual AEs, lower secretion score was associated with significantly greater risk of AKI, serious electrolyte abnormalities, and ambulatory hyperkalemia. Associations were similar across randomized treatment assignment groups.

CONCLUSION

Among SPRINT participants with CKD, worse tubular secretion was associated with greater risk of AEs, independent of eGFR and albuminuria.

Association of Race and Ethnicity With Prescription of SGLT2 Inhibitors and GLP1 Receptor Agonists Among Patients With Type 2 Diabetes in the Veterans Health Administration System

IMPORTANCE

Novel therapies for type 2 diabetes can reduce the risk of cardiovascular disease and chronic kidney disease progression. The equitability of these agents' prescription across racial and ethnic groups has not been well-evaluated.

OBJECTIVE

To investigate differences in the prescription of sodium-glucose cotransporter-2 inhibitors (SGLT2i) and glucagon-like peptide-1 receptor agonists (GLP-1 RA) among adult patients with type 2 diabetes by racial and ethnic groups.

DESIGN, SETTING, AND PARTICIPANTS

Cross-sectional analysis of data from the US Veterans Health Administration's Corporate Data Warehouse. The sample included adult patients with type 2 diabetes and at least 2 primary care clinic visits from January 1, 2019, to December 31, 2020.

EXPOSURES

Self-identified race and self-identified ethnicity.

MAIN OUTCOMES AND MEASURES

The primary outcomes were prevalent SGLT2i or GLP-1 RA prescription, defined as any active prescription during the study period.

RESULTS

Among 1 197 914 patients (mean age, 68 years; 96% men; 1% American Indian or Alaska Native, 2% Asian, Native Hawaiian, or Other Pacific Islander, 20% Black or African American, 71% White, and 7% of Hispanic or Latino ethnicity), 10.7% and 7.7% were prescribed an SGLT2i or a GLP-1 RA, respectively. Prescription rates for SGLT2i and GLP-1 RA, respectively, were 11% and 8.4% among American Indian or Alaska Native patients; 11.8% and 8% among Asian, Native Hawaiian, or Other Pacific Islander patients; 8.8% and 6.1% among Black or African American patients; and 11.3% and 8.2% among White patients, respectively. Prescription rates for SGLT2i and GLP-1 RA, respectively, were 11% and 7.1% among Hispanic or Latino patients and 10.7% and 7.8% among non-Hispanic or Latino patients. After accounting for patient- and system-level factors, all racial groups had significantly lower odds of SGLT2i and GLP-1 RA prescription compared with White patients. Black patients had the lowest odds of prescription compared with White patients (adjusted odds ratio, 0.72 [95% CI, 0.71-0.74] for SGLT2i and 0.64 [95% CI, 0.63-0.66] for GLP-1 RA). Patients of Hispanic or Latino ethnicity had significantly lower odds of prescription (0.90 [95% CI, 0.88-0.93] for SGLT2i and 0.88 [95% CI, 0.85-0.91] for GLP-1 RA) compared with non-Hispanic or Latino patients.

CONCLUSIONS AND RELEVANCE

Among patients with type 2 diabetes in the Veterans Health Administration system during 2019 and 2020, prescription rates of SGLT2i and GLP-1 RA medications were low, and individuals of several different racial groups and those of Hispanic ethnicity had statistically significantly lower odds of receiving prescriptions for these medications compared with individuals of White race and non-Hispanic ethnicity. Further research is needed to understand the mechanisms underlying these differences in rates of prescribing and the potential relationship with differences in clinical outcomes.

Advantages, Limitations, and Clinical Considerations in Using Cystatin C to Estimate GFR

Cystatin C has been shown to be a reliable and accurate marker of kidney function across diverse populations. The 2012 Kidney Disease Improving Global Outcomes (KDIGO) guidelines recommended using cystatin C to confirm the diagnosis of chronic kidney disease (CKD) determined by creatinine-based estimated glomerular filtration rate (eGFR) and to estimate kidney function when accurate eGFR estimates are needed for clinical decision-making. In the efforts to remove race from eGFR calculations in the United States, the National Kidney Foundation (NKF) and American Society of Nephrology (ASN) Joint Task Force recommended increasing availability and clinical adoption of cystatin C to assess kidney function. This review summarizes the key advantages and limitations of cystatin C use in clinical practice. Our goals were to review and discuss the literature on cystatin C; understand the evidence behind the recommendations for its use as a marker of kidney function to diagnose CKD and risk stratify patients for adverse outcomes; discuss the challenges of its use in clinical practice; and guide clinicians on its interpretation.

Kidney tubule health, mineral metabolism and adverse events in persons with CKD in SPRINT

BACKGROUND

Measures of kidney tubule health are risk markers for acute kidney injury (AKI) in persons with chronic kidney disease (CKD) during hypertension treatment, but their associations with other adverse events (AEs) are unknown.

METHODS

Among 2377 Systolic Blood Pressure Intervention Trial (SPRINT) participants with CKD, we measured at baseline eight urine biomarkers of kidney tubule health and two serum biomarkers of mineral metabolism pathways that act on the kidney tubules. Cox proportional hazards models were used to evaluate biomarker associations with risk of a composite of pre-specified serious AEs (hypotension, syncope, electrolyte abnormalities, AKI, bradycardia and injurious falls) and outpatient AEs (hyperkalemia and hypokalemia).

RESULTS

At baseline, the mean age was 73 ± 9 years and mean estimated glomerular filtration rate (eGFR) was 46 ± 11 mL/min/1.73 m2. During a median follow-up of 3.8 years, 716 (30%) participants experienced the composite AE. Higher urine interleukin-18, kidney injury molecule-1, neutrophil gelatinase-associated lipocalin (NGAL) and monocyte chemoattractant protein-1 (MCP-1), lower urine uromodulin (UMOD) and higher serum fibroblast growth factor-23 were individually associated with higher risk of the composite AE outcome in multivariable-adjusted models including eGFR and albuminuria. When modeling biomarkers in combination, higher NGAL [hazard ratio (HR) = 1.08 per 2-fold higher biomarker level, 95% confidence interval (CI) 1.03-1.13], higher MCP-1 (HR = 1.11, 95% CI 1.03-1.19) and lower UMOD (HR = 0.91, 95% CI 0.85-0.97) were each associated with higher composite AE risk. Biomarker associations did not vary by intervention arm (P > 0.10 for all interactions).

CONCLUSIONS

Among persons with CKD, several kidney tubule biomarkers are associated with higher risk of AEs during hypertension treatment, independent of eGFR and albuminuria.

Renin-Angiotensin-Aldosterone System Activation and Diuretic Response in Ambulatory Patients With Heart Failure

Rationale & Objective

Heart failure treatment relies on loop diuretics to induce natriuresis and decongestion, but the therapy is often limited by diuretic resistance. We explored the association of renin-angiotensin-aldosterone system (RAAS) activation with diuretic response.

Study Design

Observational cohort.

Setting & Population

Euvolemic ambulatory adults with chronic heart failure were administered torsemide in a monitored environment.

Predictors

Plasma total renin, active renin, angiotensinogen, and aldosterone levels. Urine total renin and angiotensinogen levels.

Outcomes

Sodium output per doubling of diuretic dose and fractional excretion of sodium per doubling of diuretic dose.

Analytical Approach

Robust linear regression models estimated the associations of each RAAS intermediate with outcomes.

Results

The analysis included 56 participants, and the median age was 65 years; 50% were women, and 41% were Black. The median home diuretic dose was 80-mg furosemide equivalents. In unadjusted and multivariable-adjusted models, higher levels of RAAS measures were generally associated with lower diuretic efficiency. Higher plasma total renin remained significantly associated with lower sodium output per doubling of diuretic dose (β = -0.41 [-0.76, -0.059] per SD change) with adjustment; higher plasma total and active renin were significantly associated with lower fractional excretion of sodium per doubling of diuretic dose (β = -0.48 [-0.83, -0.14] and β = -0.51 [-0.95, -0.08], respectively) in adjusted models. Stratification by RAAS inhibitor use did not substantially alter these associations.

Limitations

Small sample size; highly selected participants; associations may not be causal.

Conclusions

Among multiple measures of RAAS activation, higher plasma total and active renin levels were consistently associated with lower diuretic response. These findings highlight the potential drivers of diuretic resistance and underscore the need for high-quality trials of decongestive therapy enhanced by RAAS blockade.

Longitudinal TNFR1 and TNFR2 and Kidney Outcomes: Results from AASK and VA NEPHRON-D

BACKGROUND

Higher baseline levels of soluble TNF receptors (TNFR1 and TNFR2) have been associated with progressive CKD. Whether longitudinal changes in these biomarkers of inflammation are also associated with worse kidney outcomes has been less studied.

METHODS

We evaluated associations of longitudinal changes in TNFR1 and TNFR2 with ESKD in the African American Study of Kidney Disease and Hypertension (AASK; 38% female; 0% diabetes) and kidney function decline (first occurrence of ≥30 ml/min per 1.73 m2 or ≥50% eGFR decline if randomization eGFR ≥60 or <60 ml/min per 1.73 m2, respectively; ESKD) in the Veterans Affairs Nephropathy in Diabetes trial (VA NEPHRON-D; 99% male; 100% diabetes) using Cox models. Biomarkers were measured from samples collected at 0-, 12-, and 24-month visits for AASK (serum) and 0- and 12-month visits for VA NEPHRON-D (plasma). Biomarker slopes (AASK) were estimated using linear mixed-effects models. Covariates included sociodemographic/clinical factors, baseline biomarker level, and kidney function.

RESULTS

There were 129 ESKD events over a median of 7.0 years in AASK (n=418) and 118 kidney function decline events over a median of 1.5 years in VA NEPHRON-D (n=754). In AASK, each 1 SD increase in TNFR1 and TNFR2 slope was associated with 2.98- and 1.87-fold higher risks of ESKD, respectively. In VA NEPHRON-D, each 1 SD increase in TNFR1 and TNFR2 was associated with 3.20- and 1.43-fold higher risks of kidney function decline, respectively.

CONCLUSIONS

Among individuals with and without diabetes, longitudinal increases in TNFR1 and TNFR2 were each associated with progressive CKD, independent of initial biomarker level and kidney function.

Associations of High-Sensitivity Troponin and Natriuretic Peptide Levels With Serious Adverse Events in SPRINT

Background

Assessing the risk of serious adverse events (SAEs) during hypertension treatment is important for understanding the benefit‐harm trade‐offs of lower blood pressure goals. It is unknown whether high‐sensitivity cardiac troponin T (hs‐cTnT) and N‐terminal pro‐B‐type natriuretic peptide (NT‐proBNP) provide information about SAEs.

Methods and Results

In SPRINT (Systolic Blood Pressure Intervention Trial), hs‐cTnT and NT‐proBNP were measured at baseline in 8828 (94.3%) and 8836 (94.4%) participants, respectively. Multivariable Cox proportional hazards models were used to evaluate hs‐cTnT and NT‐proBNP associations with a composite of SPRINT’s SAEs of interest: hypotension, syncope, bradycardia, acute kidney injury, electrolyte abnormalities, and injurious falls. Elevations in hs‐cTnT and NT‐proBNP were associated with increased composite SAE risk (hazard ratio [HR] per 2‐fold higher hs‐cTnT: 1.15; 95% CI, 1.06‒1.25; HR per 2‐fold higher NT‐proBNP: 1.09; 95% CI, 1.05‒1.14). Compared with both hs‐cTnT and NT‐proBNP in the lower tertiles, both biomarkers in the highest tertile was associated with increased composite SAE risk (HR, 1.56; 95% CI, 1.32‒1.84). Composite SAE risk was higher in the intensive‐treatment group than in the standard‐treatment group for participants with both biomarkers in the lower tertiles, but similar between treatment groups for participants with both biomarkers in the highest tertile (P for interaction=0.008).

Conclusions

Elevations in hs‐cTnT and NT‐proBNP individually and in combination are associated with higher composite SAE risk in SPRINT. The differential impact of blood pressure treatment on SAE risk across combined biomarker categories may have implications for identifying individuals with more favorable benefit‐harm profiles for intensive blood pressure lowering.

Interdisciplinary Care and Preparedness for Kidney Failure Management in a High-Risk Population

Rationale & Objective

Interdisciplinary care may improve health outcomes in patients with chronic kidney disease (CKD). Few studies have evaluated this model of health care delivery in racial and ethnic minorities.

Study Design

Retrospective cohort study.

Setting & Participants

Incident end-stage kidney disease (ESKD) patients at Montefiore Medical Center from October 1, 2013, to October 31, 2019.

Exposure

Pre-ESKD interdisciplinary care.

Outcomes

Pre-ESKD transplant listing and optimal kidney replacement therapy (KRT) start (use of arteriovenous access at hemodialysis initiation, outpatient hemodialysis start, preemptive transplant, or peritoneal dialysis as the first modality).

Analytical Approach

We constructed multivariable logistic regression models adjusted for sociodemographic and clinical factors to determine the odds of transplant listing and optimal KRT start between interdisciplinary versus the usual care group.

Results

Of the 295 incident ESKD patients included in our study, 84 received interdisciplinary care and 211 received usual nephrology care. The mean age was 59.9 years (standard deviation, 13.9 years), 47% were women, and 87% were African American or Hispanic. Baseline characteristics were similar between the groups, except that the interdisciplinary care group had a lower prevalence of hypertension (60% vs 75%). Compared with usual care, a higher proportion of patients in the interdisciplinary care group were listed for kidney transplant (44% vs 16%) and had an optimal KRT start (53% vs 44%). Receipt of interdisciplinary care was associated with a higher odds (OR, 5.73; 95% CI, 2.78-11.80; P < 0.001) of transplant listing compared with usual care after adjusting for important sociodemographic and clinical factors. The odds of an optimal KRT start also favored interdisciplinary care (OR, 1.60; 95% CI, 0.88-2.89; P = 0.12) but did not achieve statistical significance.

Limitations

The study was non-randomized and had a small sample size.

Conclusions

Interdisciplinary care is associated with better ESKD preparedness compared with usual nephrology care alone in racial and ethnic minorities. Larger studies are needed to determine the effectiveness of interdisciplinary care in patients with advanced CKD.

Association of Intraindividual Difference in Estimated Glomerular Filtration Rate by Creatinine vs Cystatin C and End-stage Kidney Disease and Mortality

Importance

As cystatin C is increasingly adopted to estimate glomerular filtration rate (eGFR), clinicians will encounter patients in whom cystatin C-based eGFR (eGFRcys) and creatinine-based eGFR (eGFRcr) differ widely. The clinical implications of these differences, eGFRdiffcys-cr, are unknown.

Objective

To evaluate the associations of eGFRdiffcys-cr with end-stage kidney disease (ESKD) and mortality among individuals with chronic kidney disease (CKD).

Design, Setting, and Participants

This is a prospective cohort study of 4956 individuals with mild to moderate CKD from 7 clinical centers in the United States who enrolled in the Chronic Renal Insufficiency Cohort (CRIC) Study between 2003 to 2018. Statistical analyses were completed in December 2021.

Exposures

eGFRdiffcys-cr (eGFRcys - eGFRcr) was calculated at baseline and annually thereafter for 3 years. Because 15 mL/min/1.73 m2 represents a clinically meaningful difference in eGFR that also distinguishes CKD stages, eGFRdiffcys-cr was categorized as: less than -15 mL/min/1.73 m2, -15 to 15 mL/min/1.73 m2, and 15 mL/min/1.73 m2 or greater.

Main Outcomes and Measures

The outcomes of ESKD, defined as initiation of maintenance dialysis or receipt of a kidney transplant, and all-cause mortality were adjudicated from study entry until administrative censoring in 2018.

Results

Among 4956 participants with mean (SD) age of 59.5 (10.5) years, 2152 (43.4%) were Black, 515 (10.4%) were Hispanic, and 2113 (42.6%) were White. There were 2156 (43.5%) women and 2800 (56.5%) men. At baseline, eGFRcys and eGFRcr values differed by more than 15 mL/min/1.73 m2 in one-third of participants (1638 participants [33.1%]). Compared with participants with similar baseline eGFRcys and eGFRcr (eGFRdiffcys-cr -15 to 15 mL/min/1.73 m2), those in whom eGFRcys was substantially lower than eGFRcr (eGFRdiffcys-cr < -15 mL/min/1.73 m2) had a higher risk of mortality (hazard ratio [HR], 1.86; 95% CI, 1.40-2.48) while those with eGFRdiffcys-cr of 15 mL/min/1.73 m2 or greater had lower risks of ESKD (subHR [SHR], 0.73; 95% CI, 0.59-0.89) and mortality (HR, 0.68; 95% CI, CI 0.58-0.81). In time-updated analyses, participants with eGFRdiffcys-cr less than -15 mL/min/1.73 m2 had higher risks of ESKD (SHR, 1.83; 95% CI, 1.10-3.04) and mortality (HR, 3.03; 95% CI, 2.19-4.19) compared with participants with similar eGFRcys and eGFRcr. Conversely, participants with eGFRdiffcys-cr of 15 mL/min/1.73 m2 or greater had lower risks of ESKD (SHR, 0.50; 95% CI, 0.35-0.71) and mortality (HR, 0.58; 95% CI, 0.45-0.75). Longitudinal changes in eGFRdiffcys-cr were associated with mortality risk. Compared with participants who had similar slopes by eGFRcys and eGFRcr, those with smaller eGFRcr declines had an 8-fold increased mortality risk (HR, 8.20; 95% CI, 6.37-10.56), and those with larger apparent declines by eGFRcr had a lower mortality risk (HR, 0.14; 95% CI, 0.08-0.24).

Conclusions and Relevance

These findings suggest that large differences between eGFRcys and eGFRcr were common in persons with CKD. These differences and their changes over time may be informative of ESKD and mortality risks, warranting monitoring of both eGFRcys and eGFRcr in this high-risk population.

Association of abnormal electrocardiograph metrics with prolonged recovery time in incident hemodialysis patients

BACKGROUND

Patients receiving intermittent hemodialysis have variable times of recovery to feeling better after dialysis. QT prolongation, a precursor to clinical and subclinical cardiovascular events, may contribute to delayed recovery time. We hypothesized that abnormal electrocardiographic parameters indicating perturbations in ventricular action are associated with longer recovery times thus impacting a patient-centered quality of life.

METHODS

Among 242 incident in-center hemodialysis participants from the Predictors of Arrhythmic and Cardiovascular Risk in End Stage Renal Disease (PACE) study, corrected QT interval (QTc), QRST angle and heart rate variance were measured on non-dialysis days using a standard 5-min electrocardiograph recording. Left ventricular hypertrophy (LVH) was defined using the Cornell voltage product. Recovery time was ascertained during a phone interview with a standardized validated questionnaire. Associations between QTc, QRST angle, heart rate variance, and LVH and natural log-transformed recovery time were examined using linear regression adjusted for participant characteristics and electrolytes.

RESULTS

Mean age was 55 (standard deviation 13) years, 55% were male, 72% were African American. Longer QTc interval was associated with increased recovery time (per 10 ms increase in QTc, recovery time increased by 6.2%; 95% confidence interval: 0.0-10.5). QRST angle, heart rate, heart rate variability and LVH were not significantly associated with recovery time.

CONCLUSION

Longer QTc intervals are associated with longer recovery time independent of serum electrolytes. This supports a relationship between a patient's underlying arrhythmic status and time to recovery after hemodialysis. Future studies will determine if maneuvers to reduce QTc improves recovery time and quality of life of patients on hemodialysis.

Capitated versus fee-for-service reimbursement and quality of care for chronic disease: a US cross-sectional analysis

BACKGROUND

Upcoming alternative payment models Primary Care First (PCF) and Kidney Care Choices (KCC) incorporate capitated payments for chronic disease management. Prior research on the effect of capitated payments on chronic disease management has shown mixed results. We assessed the patient, physician, and practice characteristics of practices with capitation as the majority of revenue, and evaluated the association of capitated reimbursement with quality of chronic disease care.

METHODS

We performed a cross-sectional analysis of visits in the United States' National Ambulatory Medical Care Survey (NAMCS) for patients with hypertension, diabetes, or chronic kidney disease (CKD). Our predictor was practice reimbursement type, classified as 1) majority capitation, 2) majority FFS, or 3) other reimbursement mix. Outcomes were quality indicators of hypertension control, diabetes control, angiotensin-converting enzyme inhibitor or angiotensin receptor blocker (ACEi/ARB) use, and statin use.

RESULTS

About 9% of visits were to practices with majority capitation revenue. Capitated practices, compared with FFS and other practices, had lower visit frequency (3.7 vs. 5.2 vs. 5.2, p = 0.006), were more likely to be located in the West Census Region (55% vs. 18% vs. 17%, p < 0.001), less likely to be solo practice (21% vs. 37% vs. 35%, p = 0.005), more likely to be owned by an insurance company, health plan or HMO (24% vs. 13% vs. 13%, p = 0.033), and more likely to have private insurance (43% vs. 25% vs. 19%, p = 0.004) and managed care payments (69% vs. 23% vs. 26%, p < 0.001) as the majority of revenue. The prevalence of controlled hypertension, controlled diabetes, ACEi/ARB use, and statin use was suboptimal across practice reimbursement types. Capitated reimbursement was not associated with differences in hypertension, diabetes, or CKD quality indicators, in multivariable models adjusting for patient, physician, and practice characteristics.

CONCLUSIONS

Practices with majority capitation revenue differed substantially from FFS and other practices in patient, physician, and practice characteristics, but were not associated with consistent quality differences. Our findings establish baseline estimates of chronic disease quality of care performance by practice reimbursement composition, informing chronic disease care delivery within upcoming payment models.

The incidence of and risk factors for hospitalized acute kidney injury among people living with HIV on antiretroviral treatment

OBJECTIVES

The epidemiology of hospitalized acute kidney injury (AKI) among people living with HIV (PLWH) in the era of modern antiretroviral therapy (ART) for all PLWH is not well characterized. We evaluated the incidence of and risk factors for hospitalized AKI from 2005 to 2015 among PLWH on ART.

METHODS

We conducted a retrospective analysis of PLWH from the Johns Hopkins HIV Clinical Cohort. We defined hospitalized AKI as a rise of ≥ 0.3 mg/dL in serum creatinine (SCr) within any 48-h period or a 50% increase in SCr from baseline and assessed associations of risk factors with incident AKI using multivariate Cox regression models.

RESULTS

Most participants (75%) were black, 34% were female, and the mean age was 43 years. The incidence of AKI fluctuated annually, peaking at 40 per 1000 person-years (PY) [95% confidence interval (CI) 22-69 per 1000 PY] in 2007, and reached a nadir of 20 per 1000 PY (95% CI 11-34 per 1000 PY) in 2010. There was no significant temporal trend (-3.3% change per year; 95% CI -8.6 to 2.3%; P = 0.24). After multivariable adjustment, characteristics independently associated with AKI included black race [hazard ratio (HR) 2.44; 95% CI 1.42-4.20], hypertension (HR 1.62; 95% CI 1.09-2.38), dipstick proteinuria > 1 (HR 1.86; 95% CI 1.07-3.23), a history of AIDS (HR 1.82; 95% CI 1.29-2.56), CD4 count < 200 cells/µL (HR 1.46; 95% CI 1.02-2.07), and lower serum albumin (HR 1.73 per 1 g/dL decrease; 95% CI 1.02-2.07).

CONCLUSIONS

In this contemporary cohort of PLWH, the annual incidence of first AKI fluctuated during the study period. Attention to modifiable AKI risk factors and social determinants of health may further reduce AKI incidence among PLWH.

Coverage, Formulary Restrictions, and Affordability of Sodium-Glucose Cotransporter 2 Inhibitors by US Insurance Plan Types

This cross-sectional study evaluates the stipulations of coverage under commercial, health insurance exchange, Veterans Affairs, Medicare, Medicaid, or other insurance for canagliflozin, dapagliflozin, empagliflozin, and ertugliflozin.

New Creatinine- and Cystatin C-Based Equations to Estimate GFR without Race

BACKGROUND

Current equations for estimated glomerular filtration rate (eGFR) that use serum creatinine or cystatin C incorporate age, sex, and race to estimate measured GFR. However, race in eGFR equations is a social and not a biologic construct.

METHODS

We developed new eGFR equations without race using data from two development data sets: 10 studies (8254 participants, 31.5% Black) for serum creatinine and 13 studies (5352 participants, 39.7% Black) for both serum creatinine and cystatin C. In a validation data set of 12 studies (4050 participants, 14.3% Black), we compared the accuracy of new eGFR equations to measured GFR. We projected the prevalence of chronic kidney disease (CKD) and GFR stages in a sample of U.S. adults, using current and new equations.

RESULTS

In the validation data set, the current creatinine equation that uses age, sex, and race overestimated measured GFR in Blacks (median, 3.7 ml per minute per 1.73 m² of body-surface area; 95% confidence interval [CI], 1.8 to 5.4) and to a lesser degree in non-Blacks (median, 0.5 ml per minute per 1.73 m²; 95% CI, 0.0 to 0.9). When the adjustment for Black race was omitted from the current eGFR equation, measured GFR in Blacks was underestimated (median, 7.1 ml per minute per 1.73 m²; 95% CI, 5.9 to 8.8). A new equation using age and sex and omitting race underestimated measured GFR in Blacks (median, 3.6 ml per minute per 1.73 m²; 95% CI, 1.8 to 5.5) and overestimated measured GFR in non-Blacks (median, 3.9 ml per minute per 1.73 m²; 95% CI, 3.4 to 4.4). For all equations, 85% or more of the eGFRs for Blacks and non-Blacks were within 30% of measured GFR. New creatinine-cystatin C equations without race were more accurate than new creatinine equations, with smaller differences between race groups. As compared with the current creatinine equation, the new creatinine equations, but not the new creatinine-cystatin C equations, increased population estimates of CKD prevalence among Blacks and yielded similar or lower prevalence among non-Blacks.

CONCLUSIONS

New eGFR equations that incorporate creatinine and cystatin C but omit race are more accurate and led to smaller differences between Black participants and non-Black participants than new equations without race with either creatinine or cystatin C alone. (Funded by the National Institute of Diabetes and Digestive and Kidney Diseases.).

FGF-23 (Fibroblast Growth Factor-23) and Cardiorenal Interactions

BACKGROUND

Animal models implicate FGF-23 (fibroblast growth factor-23) as a direct contributor to adverse cardiorenal interactions such as sodium avidity, diuretic resistance, and neurohormonal activation, but this has not been conclusively demonstrated in humans. Therefore, we aimed to evaluate whether FGF-23 is associated with parameters of cardiorenal dysfunction in humans with heart failure, independent of confounding factors.

METHODS

One hundred ninety-nine outpatients with heart failure undergoing diuretic treatment at the Yale Transitional Care Center were enrolled and underwent blood collection, and urine sampling before and after diuretics.

RESULTS

FGF-23 was associated with several metrics of disease severity such as higher home loop diuretic dose and NT-proBNP (N-terminal pro-B-type natriuretic peptide), and lower estimated glomerular filtration rate, serum chloride, and serum albumin. Multivariable analysis demonstrated no statistically significant association between FGF-23 and sodium avidity measured by fractional excretion of sodium, or proximal or distal tubular sodium reabsorption, either before diuretic administration or at peak diuresis (P≥0.11 for all). Likewise, FGF-23 was not independently associated with parameters of diuretic resistance (diuretic excretion, cumulative urine and sodium output, and loop diuretic efficiency [P≥0.33 for all]) or neurohormonal activation (plasma or urine renin [P≥0.36 for all]). Moreover, the upper boundary of the 95% CI of all the partial correlations were ≤0.30, supporting the lack of meaningful correlations. FGF-23 was not associated with mortality in multivariable analysis (P=0.44).

CONCLUSIONS

FGF-23 was not meaningfully associated with any cardiorenal parameter in patients with heart failure. While our methods cannot rule out a small effect, FGF-23 is unlikely to be a primary driver of cardiorenal interactions.

Urine Alpha-1-Microglobulin Levels and Acute Kidney Injury, Mortality, and Cardiovascular Events following Cardiac Surgery

INTRODUCTION

Urine alpha-1-microglobulin (Uα1m) elevations signal proximal tubule dysfunction. In ambulatory settings, higher Uα1m is associated with acute kidney injury (AKI), progressive chronic kidney disease (CKD), cardiovascular (CV) events, and mortality. We investigated the associations of pre- and postoperative Uα1m concentrations with adverse outcomes after cardiac surgery.

METHODS

In 1,464 adults undergoing cardiac surgery in the prospective multicenter Translational Research Investigating Biomarker Endpoints for Acute Kidney Injury (TRIBE-AKI) cohort, we measured the pre-and postoperative Uα1m concentrations and calculated the changes from pre- to postoperative concentrations. Outcomes were postoperative AKI during index hospitalization and longitudinal risks for CKD incidence and progression, CV events, and all-cause mortality after discharge. We analyzed Uα1m continuously and categorically by tertiles using multivariable logistic regression and Cox proportional hazards regression adjusted for demographics, surgery characteristics, comorbidities, baseline estimated glomerular filtration rate, urine albumin, and urine creatinine.

RESULTS

There were 230 AKI events during cardiac surgery hospitalization; during median 6.7 years of follow-up, there were 212 cases of incident CKD, 54 cases of CKD progression, 269 CV events, and 459 deaths. Each 2-fold higher concentration of preoperative Uα1m was independently associated with AKI (adjusted odds ratio [aOR] = 1.36, 95% confidence interval 1.14-1.62), CKD progression (adjusted hazard ratio [aHR] = 1.46, 1.04-2.05), and all-cause mortality (aHR = 1.19, 1.06-1.33) but not with incident CKD (aHR = 1.21, 0.96-1.51) or CV events (aHR = 1.01, 0.86-1.19). Postoperative Uα1m was not associated with AKI (aOR per 2-fold higher = 1.07, 0.93-1.22), CKD incidence (aHR = 0.90, 0.79-1.03) or progression (aHR = 0.79, 0.56-1.11), CV events (aHR = 1.06, 0.94-1.19), and mortality (aHR = 1.01, 0.92-1.11).

CONCLUSION

Preoperative Uα1m concentrations may identify patients at high risk of AKI and other adverse events after cardiac surgery, but postoperative Uα1m concentrations do not appear to be informative.

Associations of CKD risk factors and longitudinal changes in urine biomarkers of kidney tubules among women living with HIV

BACKGROUND

Novel urine biomarkers have enabled the characterization of kidney tubular dysfunction and injury among persons living with HIV, a population at an increased risk of kidney disease. Even though several urine biomarkers predict progressive kidney function decline, antiretroviral toxicity, and mortality in the setting of HIV infection, the relationships among the risk factors for chronic kidney disease (CKD) and urine biomarkers are unclear.

METHODS

We assessed traditional and infection-related CKD risk factors and measured 14 urine biomarkers at baseline and at follow-up among women living with HIV in the Women's Interagency Health Study (WIHS). We then used simultaneously adjusted multivariable linear regression models to evaluate the associations of CKD risk factors with longitudinal changes in biomarker levels.

RESULTS

Of the 647 women living with HIV in this analysis, the majority (67%) were Black, the median age was 45 years and median follow-up time was 2.5 years. Each traditional and infection-related CKD risk factor was associated with a unique set of changes in urine biomarkers. For example, baseline hemoglobin a1c was associated with worse tubular injury (higher interleukin [IL]-18), proximal tubular reabsorptive dysfunction (higher α1-microglobulin), tubular reserve (lower uromodulin) and immune response to injury (higher chitinase-3-like protein-1 [YKL-40]). Furthermore, increasing hemoglobin a1c at follow-up was associated with further worsening of tubular injury (higher kidney injury molecule-1 [KIM-1] and IL-18), as well as higher YKL-40. HCV co-infection was associated with worsening proximal tubular reabsorptive dysfunction (higher β2-microglobulin [β2m]), and higher YKL-40, whereas HIV viremia was associated with worsening markers of tubular and glomerular injury (higher KIM-1 and albuminuria, respectively).

CONCLUSIONS

CKD risk factors are associated with unique patterns of biomarker changes among women living with HIV, suggesting that serial measurements of multiple biomarkers may help in detecting and monitoring kidney disease in this setting.

Kidney tubule health scores and their associations with incident CKD in women living with HIV

OBJECTIVES

Individual kidney tubule biomarkers are associated with chronic kidney disease (CKD) risk in people living with HIV (PLWH). Whether a combination of kidney biomarkers can be integrated into informative summary scores for PLWH is unknown.

METHODS

We measured eight urine biomarkers of kidney tubule health at two visits over a 3-year period in 647 women living with HIV in the Women's Interagency Health Study. We integrated biomarkers into factor scores using exploratory factor analysis. We evaluated associations between CKD risk factors and factor scores, and used generalized estimating equations to determine associations between factor scores and risk of incident CKD.

RESULTS

Factor analysis identified two unique factor scores: a tubule reabsorption score comprising alpha-1-microglobulin, beta-2-microglobulin and trefoil factor-3; and a tubule injury score comprising interleukin-18 and kidney injury molecule-1. We modelled the two factor scores in combination with urine epidermal growth factor (EGF) and urine albumin. Predominantly HIV-related CKD risk factors were independently associated with worsening tubule reabsorption scores and tubule injury scores. During a median follow-up of 7 years, 9.7% (63/647) developed CKD. In multivariable time-updated models that adjusted for other factor scores and biomarkers simultaneously, higher tubule reabsorption scores [risk ratio (RR) = 1.27, 95% confidence interval (CI): 1.01-1.59 per 1 SD higher time-updated score], higher tubule injury scores (RR = 1.36, 95% CI: 1.05-1.76), lower urine EGF (RR = 0.75, 95% CI: 0.64-0.87), and higher urine albumin (RR = 1.20, 95% CI: 1.02-1.40) were jointly associated with risk of incident CKD.

CONCLUSIONS

We identified two novel and distinct dimensions of kidney tubule health that appear to quantify informative metrics of CKD risk in PLWH.

Frailty, Age, and Postdialysis Recovery Time in a Population New to Hemodialysis

Background

Frailty, a phenotype characterized by decreased physiologic reserve and the inability to recover following confrontation with a stressor like hemodialysis, may help identify which patients on incident hemodialysis will experience longer postdialysis recovery times. Recovery time is associated with downstream outcomes, including quality of life and mortality. We characterized postdialysis recovery times among patients new to hemodialysis and quantified the association between frailty and hemodialysis recovery time.

Methods

Among 285 patients on hemodialysis enrolled in the Predictors of Arrhythmic and Cardiovascular Risk in End Stage Renal Disease (PACE) study, frailty was measured using the Fried phenotype. Self-reported recovery time was obtained by telephone interview. We estimated the association of frailty (intermediately frail and frail versus nonfrail) and postdialysis recovery time using adjusted negative binomial regression.

Results

Median time between dialysis initiation and study enrollment was 3.4 months (IQR, 2.7-4.9), and that between initiation and recovery time assessment was 11 months (IQR, 9.3-15). Mean age was 55 years, 24% were >65 years, and 73% were Black; 72% of individuals recovered in ≤1 hour, 20% recovered in 1-6 hours, 5% required 6-12 hours to recover, and <5% required >12 hours to recover. Those with intermediate frailty, frailty, and age ≤65 years had 2.56-fold (95% CI, 1.45 to 4.52), 1.72-fold (95% CI, 1.03 to 2.89), and 2.35-fold (95% CI, 1.44 to 3.85) risks, respectively, of longer recovery time independent of demographic characteristics, comorbidity, and dialysis-related factors.

Conclusions

In adults new to hemodialysis, frailty was independently associated with prolonged postdialysis recovery. Future studies should assess the effect of frailty-targeted interventions on recovery time to improve clinical outcomes.

Patient Awareness of CKD: A Systematic Review and Meta-analysis of Patient-Oriented Questions and Study Setting

RATIONALE & OBJECTIVE

Patient awareness of disease is the first step toward effective management and disease control. Awareness of chronic kidney disease (CKD) has consistently been shown to be low, but studies estimating patient awareness of CKD have used different methods. We sought to determine whether the estimated prevalence of CKD awareness differed by the wording used to ascertain awareness or by setting characteristics.

STUDY DESIGN

Systematic review and meta-analysis.

SETTING & STUDY POPULATIONS

Adults with CKD not receiving dialysis.

SELECTION CRITERIA FOR STUDIES

We included studies that estimated CKD awareness, determined CKD status by laboratory criteria, and provided the exact question wording used to ascertain awareness.

DATA EXTRACTION

2 reviewers independently extracted data for each study; discordance was resolved by a third independent reviewer.

ANALYTICAL APPROACH

Mixed-effects models were used to calculate pooled CKD awareness estimates and 95% CIs.

RESULTS

32 studies were included. Publication year ranged from 2004 to 2017, with study populations ranging from 107 to 28,923 individuals. CKD awareness in individual studies ranged from 0.9% to 94.0%. Pooled CKD awareness was 19.2% (95% CI, 10.0%-33.6%) overall and was 26.5% (95% CI, 11.9%-48.9%) among individuals with an estimated glomerular filtration rate < 60 mL/min/1.73 m2. "Kidney problem" was the most sensitive question for CKD awareness (58.7%; 95% CI, 32.4%-80.8%); "weak or failing kidneys" was the least sensitive (12.3%; 95% CI, 4.5%-29.4%). CKD awareness was highest among patients from nephrology practices (86.2%; 95% CI, 74.9%-93.0%) and lowest in the general population (7.3%; 95% CI, 5.0%-10.5%).

LIMITATIONS

Significant heterogeneity across studies overall and among examined subgroups of wording and study setting.

CONCLUSIONS

Differently worded questions may lead to widely different estimates of CKD awareness. Consistent terminology is likely needed to most effectively surveil and leverage CKD awareness to improve management and disease control.

Biomarkers of Kidney Tubule Health, CKD Progression, and Acute Kidney Injury in SPRINT (Systolic Blood Pressure Intervention Trial) Participants

RATIONALE & OBJECTIVE

The Systolic Blood Pressure Intervention Trial (SPRINT) compared the effect of intensive versus standard systolic blood pressure targets on cardiovascular morbidity and mortality. In this ancillary study, we evaluated the use of exploratory factor analysis (EFA) to combine biomarkers of kidney tubule health in urine and plasma and then study their role in longitudinal estimated glomerular filtration rate (eGFR) change and risk of acute kidney injury (AKI).

STUDY DESIGN

Observational cohort nested in a clinical trial.

SETTING & PARTICIPANTS

2,351 SPRINT participants with eGFR < 60 mL/min/1.73 m² at baseline.

EXPOSURE

Levels of neutrophil gelatinase-associated lipocalin (NGAL), interleukin 18 (IL-18), chitinase-3-like protein (YKL-40), kidney injury molecule 1 (KIM-1), monocyte chemoattractant protein 1 (MCP-1), α₁-microglobulin (A1M) and β₂-microglobulin (B2M), uromodulin (UMOD), fibroblast growth factor 23 (FGF-23), and intact parathyroid hormone (PTH).

OUTCOME

Longitudinal changes in eGFR and risk of AKI.

ANALYTICAL APPROACH

We performed EFA to capture different tubule pathophysiologic processes. We used linear mixed effects models to evaluate the association of each factor with longitudinal changes in eGFR. We evaluated the association of the tubular factors scores with AKI using Cox proportional hazards regression.

RESULTS

From 10 biomarkers, EFA generated 4 factors reflecting tubule injury/repair (NGAL, IL-18, and YKL-40), tubule injury/fibrosis (KIM-1 and MCP-1), tubule reabsorption (A1M and B2M), and tubule reserve/mineral metabolism (UMOD, FGF-23, and PTH). Each 1-SD higher tubule reserve/mineral metabolism factor score was associated with a 0.58% (95% CI, 0.39%-0.67%) faster eGFR decline independent of baseline eGFR and albuminuria. Both the tubule injury/repair and tubule injury/fibrosis factors were independently associated with future risk of AKI (per 1 SD higher, HRs of 1.18 [95% CI, 1.10-1.37] and 1.23 [95% CI, 1.02-1.48], respectively).

LIMITATIONS

The factors require validation in other settings.

CONCLUSIONS

EFA allows parsimonious subgrouping of biomarkers into factors that are differentially associated with progressive eGFR decline and AKI. These subgroups may provide insights into the pathological processes driving adverse kidney outcomes.