How should proteinuria be detected and measured?

Brief Report: Subclinical Kidney Dysfunction in HIV-Infected Children: A Cross-Sectional Study

OBJECTIVE

Most of the kidney dysfunction in HIV-positive children receiving antiretroviral therapy (ART) is attributed to tenofovir. There is a paucity of data on kidney dysfunction in tenofovir-naive children. The primary objective was to know the point prevalence of albuminuria and β2-microglobulinuria in HIV-infected children aged 3-18 years receiving ART. Albuminuria and β2-microglobulinuria were used as surrogates for glomerular and tubular dysfunction, respectively. The secondary objective was to determine their predictors.

DESIGN

Cross-sectional study-design.

METHODS

One hundred consecutive HIV-positive children (3-18 years) on ART were included. Spot urine sample was analyzed for urinary creatinine, total protein, microalbumin, and β2-microglobulin. Albuminuria was defined as albumin to creatinine ratio of >30 mg/g; proteinuria as urine dipstick ≥trace or spot urine protein to creatinine ratio (uPCR) of ≥0.2. β2-microglobulinuria was defined as β2-microglobulin levels of >350 µg/L.

RESULTS

There were 71 boys and 29 girls. Most of the children had WHO clinical stage I and were getting zidovudine-based regimen. Only 7 children were getting tenofovir. estimated Glomerular Filtration Rate and serum creatinine were normal in all children. Approximately half (48%) had renal dysfunction in the form of glomerular dysfunction (26%), tubular dysfunction (27%), or both (5%). Age at diagnosis was significantly associated with β2-microglobulinuria (P = 0.044). None of the selected variables were associated with albuminuria.

CONCLUSIONS

HIV-associated glomerular and tubular dysfunction is common in children receiving ART other than tenofovir. The standard guidelines should consider including routine urinary biomarker monitoring in children on ART.

Prediction of microalbuminuria from proteinuria in chronic kidney disease due to non-diabetic lifestyle-related diseases: comparison with diabetes

BACKGROUND

To suppress increases in kidney failure and cardiovascular disease due to lifestyle-related diseases other than diabetes, early intervention is desirable. We examined whether microalbuminuria could be predicted from proteinuria.

METHODS

The participants consisted of adults who exhibited a urinary protein-to-creatinine ratio (uPCR) of < 0.5 g/gCr and an eGFR of ≥ 15 ml/min/1.73 m² in their spot urine at their first examination for lifestyle-related disease. Urine was tested three times for each case, with microalbuminuria defined as a urinary albumin-to-creatinine ratio (uACR) of 30-299 mg/gCr, at least twice on three measurements. Youden's Index was used as an index of the cut-off value (CO) according to the ROC curve.

RESULTS

A single uPCR was useful for differentiating normoalbuminuria and micro- and macroalbuminuria in patients with non-diabetic lifestyle-related diseases. Regarding the GFR categories, the CO of the second uPCR was 0.09 g/gCr (AUC 0.89, sensitivity 0.76, specificity 0.89) in G1-4 (n = 197) and 0.07 g/gCr (AUC 0.92, sensitivity 0.85, specificity 0.88) in G1-3a (n = 125). Using the sum of two or three uPCR measurements was more useful than a single uPCR for differentiating microalbuminuria in non-diabetic lifestyle disease [CO, 0.16 g/gCr (AUC 0.91, sensitivity 0.85, specificity 0.87) and 0.23 g/gCr (AUC 0.92, sensitivity 0.88, specificity 0.84), respectively].

CONCLUSION

Microalbuminuria in Japanese individuals with non-diabetic lifestyle-related diseases can be predicted from the uPCR, wherein the CO of the uPCR that differentiates normoalbuminuria and micro- and macroalbuminuria was 0.07 g/gCr for G1-3a, while that in G3b-4 was 0.09 g/gCr.

The relationship between proteinuria and allograft survival in patients with transplant glomerulopathy: a retrospective single-center cohort study

Proteinuria and transplant glomerulopathy (TG) are common in kidney transplantation. To date, there is limited knowledge regarding proteinuria in different types of TG and its relationship to allograft survival. A retrospective cohort analysis of TG patients from indication biopsies was performed to investigate the relationship of proteinuria, histology, and graft survival. One hundred and seven (57.5%) out of 186 TG patients lost their grafts with a median survival of 14 [95% confidence interval (CI) 10-22] months after diagnosis. Proteinuria ≥1 g/24 h at the time of biopsy was detected in 87 patients (46.8%) and the median of proteinuria was 0.89 (range 0.05-6.90) g/24 h. TG patients with proteinuria ≥1 g/24 h had worse 5-year graft survival (29.9% vs. 53.5%, P = 0.001) compared with proteinuria <1 g/24 h. Proteinuria was associated with graft loss in univariable Cox regression [hazard ratio (HR) 1.25, 95% CI, 1.11-1.41, P < 0.001], and in multivariable analysis (adjusted HR 1.26, 95% CI 1.11-1.42, P < 0.001) independent of other risk factors including creatinine at biopsy, positive C4d, history of rejection, and Banff lesion score mesangial matrix expansion. In this cohort of TG patients, proteinuria at indication biopsy is common and associated with a higher proportion of graft loss.

Graft Function, Albuminuria, and the Risk of Hemorrhage and Thrombosis After Kidney Transplantation

Background:

Compared to the general population, kidney transplant recipients are at increased risk of hemorrhage and thrombosis. Whether this risk is affected by graft function and albuminuria is unknown.

Objective:

To determine the association between graft function and albuminuria and the risk of post-transplant hemorrhage and thrombosis.

Design:

Retrospective cohort study.

Setting:

We used linked health care databases in Alberta, Canada.

Patients/sample/participants:

We included adult kidney transplant recipients from 2002 to 2015 with a functioning graft at 1 year.

Measurements:

Estimated glomerular filtration rate (eGFR) and albuminuria measurements at 1 year post-transplant were used to categorize recipients (eGFR: ≥45 vs. <45 mL/min/1.73 m²; albuminuria: absence vs. presence). We determined the rates of post-transplant hemorrhage and venous thrombosis based on validated diagnostic and procedural codes.

Methods:

We determined the association between categories of eGFR and albuminuria and post-transplant hemorrhage and venous thrombosis using Poisson regression with log link.

Results:

Of 1284 kidney transplant recipients, 21% had an eGFR <45 mL/min/1.73 m² and 40% had presence of albuminuria at 1 year post-transplant. Over a median follow-up of 6 years, there were 100 hemorrhages (12.6 events per 1000 person-years) and 57 venous thrombosis events (7.1 events per 1000 person-years). The age- and sex-adjusted rate of hemorrhage and thrombosis was over 2-fold higher in recipients with lower eGFR and presence of albuminuria compared to higher eGFR and no albuminuria (hemorrhage: incidence rate ratio, IRR, 2.6, 95% confidence interval [CI]: 1.5-4.4, P = .001; thrombosis: IRR, 2.3, 95% CI: 1.1-5.0, P = .046).

Limitations:

Complete relevant medication information, such as anticoagulants, were not available in our datasets. Due to sample size, this study was underpowered to conduct a fully adjusted analysis.

Conclusion:

Among kidney transplant recipients, lower eGFR and presence of albuminuria at 1 year post-transplant were associated with an over 2-fold higher risk of hemorrhage and venous thrombosis. Graft function and albuminuria at 1 year post-transplant are important prognostic factors in determining risk of post-transplant hemorrhage and venous thrombosis. Further research, including medication data, are needed to further delineate outcomes and safety.

Trial registration:

Not applicable (cohort study).

Conversion of Urine Protein-Creatinine Ratio or Urine Dipstick Protein to Urine Albumin-Creatinine Ratio for Use in Chronic Kidney Disease Screening and Prognosis : An Individual Participant-Based Meta-analysis

BACKGROUND

Although measuring albuminuria is the preferred method for defining and staging chronic kidney disease (CKD), total urine protein or dipstick protein is often measured instead.

OBJECTIVE

To develop equations for converting urine protein-creatinine ratio (PCR) and dipstick protein to urine albumin-creatinine ratio (ACR) and to test their diagnostic accuracy in CKD screening and staging.

DESIGN

Individual participant-based meta-analysis.

SETTING

12 research and 21 clinical cohorts.

PARTICIPANTS

919 383 adults with same-day measures of ACR and PCR or dipstick protein.

MEASUREMENTS

Equations to convert urine PCR and dipstick protein to ACR were developed and tested for purposes of CKD screening (ACR ≥30 mg/g) and staging (stage A2: ACR of 30 to 299 mg/g; stage A3: ACR ≥300 mg/g).

RESULTS

Median ACR was 14 mg/g (25th to 75th percentile of cohorts, 5 to 25 mg/g). The association between PCR and ACR was inconsistent for PCR values less than 50 mg/g. For higher PCR values, the PCR conversion equations demonstrated moderate sensitivity (91%, 75%, and 87%) and specificity (87%, 89%, and 98%) for screening (ACR >30 mg/g) and classification into stages A2 and A3, respectively. Urine dipstick categories of trace or greater, trace to +, and ++ for screening for ACR values greater than 30 mg/g and classification into stages A2 and A3, respectively, had moderate sensitivity (62%, 36%, and 78%) and high specificity (88%, 88%, and 98%). For individual risk prediction, the estimated 2-year 4-variable kidney failure risk equation using predicted ACR from PCR had discrimination similar to that of using observed ACR.

LIMITATION

Diverse methods of ACR and PCR quantification were used; measurements were not always performed in the same urine sample.

CONCLUSION

Urine ACR is the preferred measure of albuminuria; however, if ACR is not available, predicted ACR from PCR or urine dipstick protein may help in CKD screening, staging, and prognosis.

PRIMARY FUNDING SOURCE

National Institute of Diabetes and Digestive and Kidney Diseases and National Kidney Foundation.

Clinical significance of single and persistent elevation of serum high-sensitivity C-reactive protein levels for prediction of kidney outcomes in patients with impaired fasting glucose or diabetes mellitus

BACKGROUND

The association between high-sensitivity C-reactive protein (hs-CRP) and chronic kidney disease remains controversial and long-term longitudinal studies are limited. We aim to investigate the impact of single and persistent elevation of hs-CRP on kidney outcomes.

METHODS

Our study was based on a subgroup of patients with hyperglycemia from the Kailuan cohort. Patients were divided into three groups according to two consecutive hs-CRP levels: (1) no elevation (twice hs-CRP < 3 mg/L); (2) single elevation (once hs-CRP ≥ 3 mg/L); (3) persistent elevation (twice hs-CRP ≥ 3 mg/L). Kidney outcomes include kidney function decline (glomerular filtration rate [GFR] decline ≥ 30% within two years or doubling of serum c reatinine or development of end stage kidney disease [ESKD]), development and progression of proteinuria.

RESULTS

Regarding the outcomes of kidney function decline, development and progression of proteinuria, we included 18,665, 11,754 and 1710 patients into analyses, respectively. After 5 years of follow-up, the number of incident cases of kidney function decline, development and progression of proteinuria were 1891, 1337 and 171, respectively. Compared to patients with no elevation of hs-CRP levels, those with persistent but not single elevation of hs-CRP were at higher risk of kidney function decline (hazard ratio [HR] 1.42, 95% confidence interval [CI] 1.23-1.64) and development of proteinuria (1.49, 1.26-1.76), but not progression of proteinuria. The results were consistent with propensity score analysis.

CONCLUSION

Persistent but not single elevation of hs-CRP was independently associated with increased risk of kidney function decline, and development of proteinuria but not progression in patients with impaired fasting glucose or diabetes.

Early Detection of CKD: Implications for Low-Income, Middle-Income, and High-Income Countries

CKD is common, costly, and associated with adverse health outcomes. Because inexpensive treatments can slow the rate of kidney function loss, and because CKD is asymptomatic until its later stages, the idea of early detection of CKD to improve outcomes ignites enthusiasm, especially in low- and middle-income countries where renal replacement is often unavailable or unaffordable. Available data and prior experience suggest that the benefits of population-based screening for CKD are uncertain; that there is potential for harms; that screening is not a wise use of resources, even in high-income countries; and that screening has substantial opportunity costs in low- and middle-income countries that offset its hypothesized benefits. In contrast, some of the factors that diminish the value of population-based screening (such as markedly higher prevalence of CKD in people with diabetes, hypertension, and cardiovascular disease, as well as high preexisting use of kidney testing in such patients) substantially increase the appeal of searching for CKD in people with known kidney risk factors (case finding) in high-income countries as well as in low- and middle-income countries. For both screening and case finding, detection of new cases is the easiest component; the real challenge is ensuring appropriate management for a chronic disease, usually for years or even decades. This review compares and contrasts the benefits, harms, and opportunity costs associated with these two approaches to early detection of CKD. We also suggest criteria (discussed separately for high-income countries and for low- and middle-income countries) to use in assessing when countries should consider case finding versus when they should consider foregoing systematic attempts at early detection and focus on management of known cases.

Trace Proteinuria and the Incidence of Overt Proteinuria After Five Years: Results of the Kanagawa Investigation of the Total Checkup Data From the National Database-5 (KITCHEN-5)

Background

Trace proteinuria (TrP), which is usually defined as ± by dipstick urinalysis, is considered as normal and of limited clinical significance. However, the relationship between TrP and overt proteinuria (OP) (≥ +1) in the future is unknown. Therefore, we investigated the association between TrP and future incidence of OP in a community-based cohort study.

Methods

TrP detected during the initial 2 years, which was classified into transient TrP (once/2 years) (T-TrP) and recurrent TrP (twice/2 years) (R-TrP); and the incidence of OP after 5 years were investigated in 292,257 general Japanese people aged 40 - 68 years who attended checkups. To determine TrP and OP, dipstick urinalysis was conducted with visual reading (VR) by medical staff or automated reading (AR) using a machine reader.

Results

Overall, T-TrP and R-TrP were observed in 24,782 (8.5%) and 3,767 (1.3%) subjects, respectively. Both types of TrP were prevalent in the detection with AR than VR. The prevalences of T-TrP and R-TrP showed J-shaped relationships against baseline body mass index (BMI), regardless of sex and BMI categories. The incident of OP after 5 years was larger (around 10%) in R-TrP than T-TrP (around 5%): approximately two times. Logistic regression analysis showed that T-TrP and R-TrP were significantly associated with OP, even after adjustment for relevant confounding factors including age, sex, and BMI (odds ratios (95% confidence intervals (CIs)): 2.77 (2.60 - 2.95) and 4.85 (4.34 - 5.43)), which were not largely altered when sub-analysis was conducted according to men and women, non-obesity and obesity, or AR and VR. In all analysis above, the odds ratios (95% CIs) of R-TrP for OP were higher than T-TrP.

Conclusions

Our findings suggest that TrP, particularly R-TrP, is substantially associated with the future incidence of OP, which may be independent of confounding factors and the methods detecting TrP.

Clinical update: The important role of dual kidney function testing (ACR and eGFR) in primary care: Identification of risk and management in type 2 diabetes

Diabetic kidney disease (DKD) is common complication of type 1 and type 2 diabetes and may lead to progressive kidney dysfunction culminating in end-stage kidney disease. Kidney function is evaluated less frequently than other care procedures in patients with diabetes, even though the opportunity to identify DKD early and slow or even halt renal damage early in the disease progression represents a potentially important clinical opportunity for early intervention. The following review provides an overview of the under-recognised importance of kidney function in T2D and current best-practice to support the identification of DKD as part of primary care T2D management.

An independent validation of the kidney failure risk equation in an Asian population

Predicting the risk of end-stage renal disease (ESRD) progression facilitates appropriate nephrology care of patients with chronic kidney disease (CKD). Previously, the kidney failure risk equations (KFREs) were developed and validated in several cohorts. The purpose of this study is to validate the KFREs in a Korean population and to recalibrate the equations. A total of 38,905 adult patients, including 13,244 patients with CKD stages G3–G5, who were referred to nephrology were recruited. Using the original KFREs (4-, 6- and 8-variable equations) and recalibration equations, we predicted the risk of 2- and 5-year ESRD progression. All analyses were conducted in CKD stages G3-G5 patients as well as the total population. In CKD stages G3–G5 patients, All the original 4-, 6- and 8-variable equations showed excellent areas under the receiver operating characteristic curve of 0.87 and 0.83 for the 2- and 5-year risk of ESRD, respectively. The results of net reclassification improvement, integrated discrimination index and Brier score showed that recalibration improved the prediction models in some cases. The original KFREs showed high discrimination in both CKD stages G3–G5 patients and the total population referred to nephrology in this large Korean cohort. KFREs can be implemented in Korean health systems and can guide nephrology referrals and other CKD-related treatment decisions.

Proteomics-Based Machine Learning Approach as an Alternative to Conventional Biomarkers for Differential Diagnosis of Chronic Kidney Diseases

Diabetic nephropathy, hypertension, and glomerulonephritis are the most common causes of chronic kidney diseases (CKD). Since CKD of various origins may not become apparent until kidney function is significantly impaired, a differential diagnosis and an appropriate treatment are needed at the very early stages. Conventional biomarkers may not have sufficient separation capabilities, while a full-proteomic approach may be used for these purposes. In the current study, several machine learning algorithms were examined for the differential diagnosis of CKD of three origins. The tested dataset was based on whole proteomic data obtained after the mass spectrometric analysis of plasma and urine samples of 34 CKD patients and the use of label-free quantification approach. The k-nearest-neighbors algorithm showed the possibility of separation of a healthy group from renal patients in general by proteomics data of plasma with high confidence (97.8%). This algorithm has also be proven to be the best of the three tested for distinguishing the groups of patients with diabetic nephropathy and glomerulonephritis according to proteomics data of plasma (96.3% of correct decisions). The group of hypertensive nephropathy could not be reliably separated according to plasma data, whereas analysis of entire proteomics data of urine did not allow differentiating the three diseases. Nevertheless, the group of hypertensive nephropathy was reliably separated from all other renal patients using the k-nearest-neighbors classifier “one against all” with 100% of accuracy by urine proteome data. The tested algorithms show good abilities to differentiate the various groups across proteomic data sets, which may help to avoid invasive intervention for the verification of the glomerulonephritis subtypes, as well as to differentiate hypertensive and diabetic nephropathy in the early stages based not on individual biomarkers, but on the whole proteomic composition of urine and blood.

Chronic Kidney Disease Increases the Risk of Hip Fracture: A Prospective Cohort Study in Korean Adults

This study was conducted to examine the association between renal function and hip fracture. We followed up 352,624 Korean adults, who participated in health examinations during 2009-2010 until 2013. Kidney function was assessed by creatinine-based estimated glomerular filtration rate (eGFR) and albuminuria using urine reagent strip results. The incidence of hip fracture was examined by hospital discharge records. Hazard ratios (HRs) for hip fracture were calculated using Cox proportional hazard models after adjusting for multiple confounders. During a mean follow-up of 4.0 years, 1177 participants suffered a hip fracture. Lower eGFR and more severe albuminuria were associated with a higher risk of hip fracture. The HRs for hip fracture were 1.89 (95% confidence interval [CI] 1.47-2.43) and 3.75 (95% CI 2.30-6.11) among participants with eGFRs of 30 to 44 and 15 to 29 mL/min/1.73m² relative to those with an eGFR ≥60 mL/min/1.73m² , respectively. The HRs were 1.30 (95% CI 1.02-1.65) for moderate albuminuria and 1.58 (95% CI 1.07-2.35) for severe albuminuria (p for trend = 0.002). Participants with albuminuria had a higher risk of hip fracture than those without albuminuria, even when they belonged to the same eGFR category (HR = 1.75 versus 3.30 for an eGFR of 30 to 44 mL/min/1.73m² ; HR = 2.72 versus 7.84 for an eGFR of 15 to 29 mL/min/1.73m² ). The effects of each 10 mL/min/1.73m² decrease in eGFR were stronger with advancing albuminuria severity (p_interaction = 0.016). In conclusion, both low eGFR and albuminuria were risk factors for incident hip fracture in Korean adults. Moreover, these factors exerted a synergistic effect on the risk of hip fracture. © 2020 American Society for Bone and Mineral Research.

Changes in kidney function follow living donor nephrectomy

Better understanding of kidney function after living donor nephrectomy and how it differs by donor characteristics can inform patient selection, counselling, and follow-up care. To evaluate this, we conducted a retrospective matched cohort study of living kidney donors in Alberta, Canada between 2002-2016, using linked healthcare administrative databases. We matched 604 donors to 2,414 healthy non-donors from the general population based on age, sex, year of cohort entry, urban residence and the estimated glomerular filtration rate (eGFR) before cohort entry (nephrectomy date for donors and randomly assigned date for non-donors). The primary outcome was the rate of eGFR change over time (median follow-up seven years; maximum 15 years). The median age of the cohort was 43 years, 64% women, and the baseline (pre-donation) eGFR was 100 mL/min/1.73 m². Overall, from six weeks onwards, the eGFR increased by +0.35 mL/min/1.73 m² per year (95% confidence interval +0.21 to +0.48) in donors and significantly decreased by -0.85 mL/min/1.73 m² per year (-0.94 to -0.75) in the matched healthy non-donors. The change in eGFR between six weeks to two years, two to five years, and over five years among donors was +1.06, +0.64, and -0.06 mL/min/1.73 m² per year, respectively. In contrast to the steady age-related decline in kidney function in non-donors, post-donation kidney function on average initially increased by 1 mL/min/1.73 m² per year attributable to glomerular hyperfiltration, which began to plateau by five years post-donation. Thus, the average change in eGFR over time is significantly different between donors and non-donors.

Estimating Urine Albumin-to-Creatinine Ratio from Protein-to-Creatinine Ratio: Development of Equations using Same-Day Measurements

BACKGROUND

Urine albumin-to-creatinine ratio (ACR) and protein-to-creatinine ratio (PCR) are used to measure urine protein. Recent guidelines endorse ACR use, and equations have been developed incorporating ACR to predict risk of kidney failure. For situations in which PCR only is available, having a method to estimate ACR from PCR as accurately as possible would be useful.

METHODS

We used data from a population-based cohort of 47,714 adults in Alberta, Canada, who had simultaneous assessments of urine ACR and PCR. After log-transforming ACR and PCR, we used cubic splines and quantile regression to estimate the median ACR from a PCR, allowing for modification by specified covariates. On the basis of the cubic splines, we created models using linear splines to develop equations to estimate ACR from PCR. In a subcohort with eGFR<60 ml/min per 1.73 m2, we then used the kidney failure risk equation to compare kidney failure risk using measured ACR as well as estimated ACR that had been derived from PCR.

RESULTS

We found a nonlinear association between log(ACR) and log(PCR), with the implied albumin-to-protein ratio increasing from <30% in normal to mild proteinuria to about 70% in severe proteinuria, and with wider prediction intervals at lower levels. Sex was the most important modifier of the relationship between ACR and PCR, with men generally having a higher albumin-to-protein ratio. Estimates of kidney failure risk were similar using measured ACR and ACR estimated from PCR.

CONCLUSIONS

We developed equations to estimate the median ACR from a PCR, optionally including specified covariates. These equations may prove useful in certain retrospective clinical or research applications where only PCR is available.

Diagnostic utility of protein to creatinine ratio (P/C ratio) in spot urine sample within routine clinical practice

The spot (random) urine protein to creatinine ratio (P/C ratio) is an alternative, fast and simple method of detecting and estimating the quantitative assessment of proteinuria. The aim of the work was to review the literature concerning the usefulness of spot urine P/C ratio evaluation in the diagnosis of proteinuria in the course of kidney disease, hypertension, gestational hypertension, preeclampsia, immunological diseases, diabetes mellitus, and multiple myeloma, and in the diagnosis of proteinuria in children. We searched the PubMed and Google Scholar databases using the following keywords: proteinuria, spot urine protein to creatinine ratio, spot urine P/C ratio, protein creatinine index, PCR (protein to creatinine ratio), P/C ratio and methods, Jaffe versus enzymatic creatinine methods, urine protein methods, spot urine protein to creatinine ratio versus ACR (albumin to creatinine ratio), proteinuria versus albuminuria, limitations of the P/C ratio. More weight was given to the articles published in the last 10-20 years. A spot urine P/C ratio >20 mg/mmol (0.2 mg/mg) is the most commonly reported cutoff value for detecting proteinuria, while a P/C ratio value >350 mg/mmol (3.5 mg/mg) confirms nephrotic proteinuria. The International Society for the Study of Hypertension in Pregnancy recommends a P/C ratio of 30 mg/mmol (0.3 mg/mg) for the classification of proteinuria in pregnant women at risk of preeclampsia. A high degree of correlation was observed between P/C ratio values and the protein concentration in 24-h urine collections. The spot urine P/C ratio is a quick and reliable test that can eliminate the need for a daily 24-h urine collection. However, in doubtful situations, it is still recommended to assess proteinuria in a 24-h urine collection. The literature review indicates the usefulness of the spot P/C ratio in various disease states; therefore, this test should be available in every laboratory. However, the challenge for the primary care physician is to know the limitations of the methods used to determine the protein and creatinine concentrations that are used to calculate the P/C ratio. Moreover, the P/C ratio cutoff used should be determined in individual laboratories because it depends on the patient population and the laboratory methodologies.

Influence of low free thyroxine on progression of chronic kidney disease

BACKGROUND

Hypothyroidism is highly prevalent in patients with chronic kidney disease (CKD) and has been associated with poorer clinical outcomes, including faster decline of kidney function. However, there is no consensus whether low free thyroxin (LFT) affects the rate of estimated glomerular filtration rate (eGFR) decline and how the presence of proteinuria influences the progression of renal dysfunction in hypothyroidism.

METHODS

We assessed thyroid status, proteinuria, and progression of eGFR by Modification of Diet in Renal Disease equation and CKD-EPI equation in a cohort of CKD patients followed in general nephrology clinics. We estimated the association of LFT levels, and the degree of proteinuria on progression of eGFR. We adjusted for other covariables: age, gender, body mass index, diabetes, hypertension, HbA1c, uric acid, cholesterol, and triglycerides levels..

RESULTS

One thousand six hundred ten patients (64 ± 15 years, 46.8% men, 25.3% diabetic) were included. At beggnining of follow up eGFR was between 45 and 60, 30-45 and 15-30 ml/min/1.73m2 in 479 (29.8%), 551(34.2%), and 580(36.0%) patients, respectively. LFT levels were available at initial evaluation in 288(17.9%) patients and 735(48.5%) had assessment of proteinuria (19.6% with LFT vs. 15.4% without LFT, p = 0.032). Median follow-up time was of 21 months, and 1223(76%) had at least 1 year of follow up. Overall, eGFR decline per month was - 0.05(- 0.26, 0.23) ml/min/1.73m2, reaching 1.7(1.3, 2.4) ml/min/1.73m2 by the end of study period. Similar results were obtained using CKD-EPI. Multivariable mixed linear analysis showed that proteinuria and age were independently associated with eGFR decline, with no effect of LFT, and no interaction between proteinuria and LFT. In patients without proteinuria, there was an improvement of eGFR despite the presence of LFT.

CONCLUSIONS

We confirmed a faster rate of eGFR declined in patients with proteinuria. However, despite the pathophysiological rational that hypothyroidism can lead to increased rate of CKD progression, we failed to demonstrate an association between LFT and rate of CKD progression. We conclude that the benefit of hypothyroidism treatment in CKD patients needs to be evaluate in prospective studies.

Effect of Renin-Angiotensin System Blockade on Mortality in Korean Hypertensive Patients with Proteinuria

Background

Although renin-angiotensin system (RAS) blockade is recommended for hypertensive patients with proteinuria, the effect of RAS blockade on Korean hypertensive patients has not been investigated.

Methods

Among individuals who underwent a National Health Examination between 2002 and 2003 in Korea, hypertensive patients with proteinuria (defined as a dipstick test result ≥2+) were enrolled in this study. We investigated the outcomes of two groups stratified by RAS blockade prescription (with RAS blockade vs. without RAS blockade). Moreover, Cox proportional hazard regression and Kaplan-Meier analyses were performed to examine the effects of RAS blockade on mortality and end-stage renal disease (ESRD).

Results

A total of 8,460 patients were enrolled in this study, of whom 6,236 (73.7%) were prescribed with RAS blockade. The mean follow-up period was 129 months. A total of 1,003 (11.9%) patients died, of whom 273 (3.2%) died of cardiovascular (CV) events. The Kaplan-Meier curves for all-cause or CV mortality showed that the survival probability was significantly higher in the RAS blockade group than in the non-RAS blockade group. Multivariate Cox analysis also revealed RAS blockade significantly reduced the all-cause and CV mortality rates by 39.1% and 33.7%, respectively, compared with non-RAS blockade, even after adjusting for age, sex, and comorbid diseases; however, ESRD was not affected.

Conclusion

In this study, we found that RAS blockade was significantly associated with a reduction in mortality but not in the incidence of ESRD. However, 26.3% of the enrolled patients did not use RAS blockade. Physicians need to consider the usefulness of RAS blockade in hypertensive patients with proteinuria.

Reduction in Serum High-Sensitivity C-Reactive Protein Favors Kidney Outcomes in Patients with Impaired Fasting Glucose or Diabetes

OBJECTIVE

We aimed to evaluate whether the reduction in serum high-sensitivity C-reactive protein (hs-CRP) favors kidney outcomes.

METHODS

This study was a subanalysis including patients with impaired fasting glucose or diabetes of the Kailuan cohort study. The predictor was based on two consecutive visits of hs-CRP levels in 2006 and 2008. A total of 3924 patients with hs-CRP ≥ 3 mg/L in 2006 were divided into two groups according to whether the levels of hs-CRP were reduced in 2008: Group 1: no reduction: hs-CRP ≥ 3 mg/L in 2008; Group 2: reduction: hs-CRP < 3 mg/L in 2008. Kidney outcomes include kidney function decline and development and progression of proteinuria and were followed up until the end of 2015.

RESULTS

There were 3905, 2049, and 493 patients included into our analysis for the outcomes of kidney function decline and the development and progression of proteinuria, respectively. A total of 398, 297, and 47 events occurred after 5 years of follow-up, respectively. Cox regression revealed that patients with reduction in hs-CRP have lower risk of kidney function decline (HR 0.71, 95% CI 0.57-0.89, and P = 0.002) and development of proteinuria (0.77, 0.61-0.99, and P = 0.038) after controlling for potential confounders as compared to those with no reduction in hs-CRP levels.

CONCLUSIONS

Reduction in serum hs-CRP levels favors kidney outcomes in patients with impaired fasting glucose or diabetes.

Validation of the kidney failure risk equation for end-stage kidney disease in Southeast Asia

BACKGROUND

Patients with chronic kidney disease (CKD) are at high risk of end-stage kidney disease (ESKD). The Kidney Failure Risk Equation (KFRE), which predicts ESKD risk among patients with CKD, has not been validated in primary care clinics in Southeast Asia (SEA). Therefore, we aimed to (1) evaluate the performance of existing KFRE equations, (2) recalibrate KFRE for better predictive precision, and (3) identify optimally feasible KFRE thresholds for nephrologist referral and dialysis planning in SEA.

METHODS

All patients with CKD visiting nine primary care clinics from 2010 to 2013 in Singapore were included and applied 4-variable KFRE equations incorporating age, sex, estimated glomerular filtration rate (eGFR), and albumin-to-creatinine ratio (ACR). ESKD onset within two and five years were acquired via linkage to the Singapore Renal Registry. A weighted Brier score (the squared difference between observed vs predicted ESKD risks), bias (the median difference between observed vs predicted ESKD risks) and precision (the interquartile range of the bias) were used to select the best-calibrated KFRE equation.

RESULTS

The recalibrated KFRE (named Recalibrated Pooled KFRE SEA) performed better than existing and other recalibrated KFRE equations in terms of having a smaller Brier score (square root: 2.8% vs. 4.0-9.3% at 5 years; 2.0% vs. 6.1-9.1% at 2 years), less bias (2.5% vs. 3.3-5.2% at 5 years; 1.8% vs. 3.2-3.6% at 2 years), and improved precision (0.5% vs. 1.7-5.2% at 5 years; 0.5% vs. 3.8-4.2% at 2 years). Area under ROC curve for the Recalibrated Pooled KFRE SEA equations were 0.94 (95% confidence interval [CI]: 0.93 to 0.95) at 5 years and 0.96 (95% CI: 0.95 to 0.97) at 2 years. The optimally feasible KFRE thresholds were > 10-16% for 5-year nephrologist referral and > 45% for 2-year dialysis planning. Using the Recalibrated Pooled KFRE SEA, an estimated 82 and 89% ESKD events were included among 10% of subjects at highest estimated risk of ESKD at 5-year and 2-year, respectively.

CONCLUSIONS

The Recalibrated Pooled KFRE SEA performs better than existing KFREs and warrants implementation in primary care settings in SEA.

A Portable System to Monitor Saliva Conductivity for Dehydration Diagnosis and Kidney Healthcare

Chronic kidney disease (CKD) has become a major issue in long-term healthcare. It is caused by recurrent kidney injury, which is possible induced by dehydration and heat stress. Therefore, it is important to access the dehydration diagnosis on fields. Conventional instruments for assessing dehydration from blood and urine samples are expensive and time-consuming. These disadvantages limit their applications in high-risk groups susceptible to kidney disease. To address this unmet need, this study presents a portable miniaturized device for dehydration diagnosis with clinical saliva samples. With co-plane coating-free gold electrodes, the dehydration diagnosis was achieved with a saliva specimen at low volumes (50–500 μL). To examine the characteristics, the developed device was assessed by using standard conductivity solutions and the examined variation was <5%. To validate the use for field applications, saliva samples were measured by the developed device and the measured results were compared with standard markers of serum osmolality (N = 30). These data indicate that the measured saliva conductivity is consistent with serum osmolality. And it shows significant difference between healthy adults and healthy farmers (p < 0.05), who typically suffer high risks of CKD. Based on this work, the proposed device and measurement offer a useful method to diagnosis dehydrations and indicate possible potential for CKD.

Impact of AKI on Urinary Protein Excretion: Analysis of Two Prospective Cohorts

BACKGROUND

Prior studies of adverse renal consequences of AKI have almost exclusively focused on eGFR changes. Less is known about potential effects of AKI on proteinuria, although proteinuria is perhaps the strongest risk factor for future loss of renal function.

METHODS

We studied enrollees from the Assessment, Serial Evaluation, and Subsequent Sequelae of AKI (ASSESS-AKI) study and the subset of the Chronic Renal Insufficiency Cohort (CRIC) study enrollees recruited from Kaiser Permanente Northern California. Both prospective cohort studies included annual ascertainment of urine protein-to-creatinine ratio, eGFR, BP, and medication use. For hospitalized participants, we used inpatient serum creatinine measurements obtained as part of clinical care to define an episode of AKI (i.e., peak/nadir inpatient serum creatinine ≥1.5). We performed mixed effects regression to examine change in log-transformed urine protein-to-creatinine ratio after AKI, controlling for time-updated covariates.

RESULTS

At cohort entry, median eGFR was 62.9 ml/min per 1.73 m² (interquartile range [IQR], 46.9-84.6) among 2048 eligible participants, and median urine protein-to-creatinine ratio was 0.12 g/g (IQR, 0.07-0.25). After enrollment, 324 participants experienced at least one episode of hospitalized AKI during 9271 person-years of follow-up; 50.3% of first AKI episodes were Kidney Disease Improving Global Outcomes stage 1 in severity, 23.8% were stage 2, and 25.9% were stage 3. In multivariable analysis, an episode of hospitalized AKI was independently associated with a 9% increase in the urine protein-to-creatinine ratio.

CONCLUSIONS

Our analysis of data from two prospective cohort studies found that hospitalization for an AKI episode was independently associated with subsequent worsening of proteinuria.

Peritoneal Protein Loss, Leakage or Clearance in Peritoneal Dialysis, Where do we Stand?

Peritoneal protein loss (PPL) through peritoneal effluent has been a well-recognized detrimental result of peritoneal dialysis (PD) treatment since its inception. Investigation has focused mainly on PPL quantitative and qualitative determinations and evaluation of its prognostic value.

A comprehensive review of the pathophysiology of PPL (3-pore model revisited), methods of quantification, dialysate protein composition, and impact on clinical outcomes is presented herein. The author summarizes a brief analysis of associated cardiovascular disease and nutritional consequences, exploring the controversial cause-effect on mortality and technique failure.

Therapeutic modalities aiming to reduce PPL (angiotensin-converting enzyme inhibitors [ACEI]s and vitamin D therapies) were explored, although it is unclear whether PPL represents a valid therapeutic target or, on the other hand, is solely a manifestation of endothelial dysfunction.

Low-normal hemoglobin levels and anemia are associated with increased risk of end-stage renal disease in general populations: A prospective cohort study

Background

The impact of low-normal hemoglobin (Hb) levels and anemia on the risk of end-stage renal disease (ESRD) in general populations has rarely been examined.

Methods

510,620 Korean adults aged 40–80 years without known chronic kidney disease (CKD) underwent health examinations during 2002–2003 and were followed-up until 2013. Incidence of ESRD was identified by hospital discharge and clinical visit records.

Results

During a mean follow-up of 10.5, 575 women and 1047 men were diagnosed with ESRD. Lower Hb levels were associated with an increased risk of ESRD at given severity of albuminuria and at given estimated glomerular filtration rate (eGFR). Hb 13–13.9 g/dL in men, Hb 11–11.9 g/dL in women, and trace albuminuria assessed by dipstick urinalysis were associated with more than doubled risk. The risk associated with lower Hb was stronger in older (≥60 years) than younger women. Among 349,993 participants with information on eGFR, the multivariable-adjusted HRs associated with 1 g/dL lower Hb in participants with eGFR values ≥60, 30–59, and <30 mL/min/1.73 m² were 1.34 (95% CI, 1.17–1.54), 1.55 (1.38–1.74), and 1.75 (1.47–2.09), respectively (Pinteraction between eGFR groups = .06).

Conclusions

Low-normal Hb levels and anemia are risk factors for ESRD incidence in person without CKD and for CKD progression to ESRD. Lower Hb increases the risk of ESRD through synergistic biological interactions with lower eGFR and albuminuria. The impacts of lower Hb may be stronger in older than younger women. Proper management and screening at earlier stage of Hb decline and anemia might reduce the burden of CKD.

Maximizing the Accuracy of Continuous Quantification Measures Using Discrete PackTest Products with Deep Learning and Pseudocolor Imaging

Using the standard colors provided in the instructions, PackTest products can approximate and quickly estimate the chemical characteristics of liquid samples. The combination of PackTest products and deep learning was examined for its accuracy and precision in quantifying chemical oxygen demand, ammonium ion, and phosphate ion using a pseudocolor imaging method. Each PackTest product underwent reactions with standard solutions. The generated color was scanner-read. From the color image, ten grayscale images representing the intensity values of red, green, blue, cyan, magenta, yellow, key black, and L ^∗ , and the values of a ^∗ and b ^∗ were generated. Using the grayscale images representing the red, green, and blue intensity values, 73 other grayscale images were generated. The grayscale intensity values were used to prepare datasets for the ten and 83 (=10 + 73) images. For both datasets, chemical oxygen demand quantification was successful, resulting in values of normalized mean absolute error of less than 0.4% and coefficients of determination that were greater than 0.9996. However, the quantification of ammonium and phosphate ions commonly provided false positive results for the standard solution that contained no ammonium ion/phosphate ion. For ammonium ion, multiple regression markedly improved the accuracy using the pseudocolor method. Phosphate ion quantification was also improved by avoiding the use of an estimated value for the reference solution that contained no phosphate ion. Real details of the measurements and the perspectives were discussed.

Incidence and Prognosis of Acute Kidney Diseases and Disorders Using an Integrated Approach to Laboratory Measurements in a Universal Health Care System

Importance

Abnormal measurements of kidney function or structure may be identified that do not meet criteria for acute kidney injury (AKI) or chronic kidney disease (CKD) but nonetheless may require medical attention. The Kidney Disease: Improving Global Outcomes Clinical Practice Guideline for AKI proposed criteria for the definition of acute kidney diseases and disorders (AKD), which include AKI; however, the incidence and prognosis of AKD without AKI remain unknown.

Objective

To characterize the incidence and outcomes of AKD without AKI, with or without CKD.

Design, Setting, and Participants

Retrospective cohort study including all adult residents in a universal health care system in Alberta, Canada, without end-stage kidney disease (ESKD) and with at least 1 serum creatinine measurement between January 1 and December 31, 2008, in a community or hospital setting. Data analysis took place in 2018.

Main Outcomes and Measures

The Kidney Disease: Improving Global Outcomes guideline definitions for CKD, AKI, and AKD based on serum creatinine, estimated glomerular filtration rate, and albuminuria criteria were applied to estimate the proportion of patients with CKD, AKI, and AKD without AKI, and combinations of the conditions. Patients were followed up for up to 8 years (study end date, June 31, 2016) to characterize their risks of mortality, development of new CKD, progression of preexisting CKD, and ESKD.

Results

Among 1 109 099 Alberta residents included in the cohort, the mean (SD) age was 52.3 (17.6) years, and 43.0% were male. Findings showed that AKD without AKI was common (3.8 individuals without preexisting CKD and 0.6 with preexisting CKD per 100 population tested). In Cox proportional hazards and competing risks models over a median (interquartile range) of 6.0 (5.7-6.3) years of follow-up, AKD without AKI (compared with no kidney disease) was associated with higher risks of developing new CKD (37.4% vs 7.4%%; adjusted sub-hazard ratio [sHR], 3.17; 95% CI, 3.10-3.23), progression of preexisting CKD (49.5% vs 34.6%; adjusted sHR, 1.38; 95% CI, 1.33-1.44), ESKD (0.6% vs 0.1%; adjusted sHR, 8.56; 95% CI, 7.32-10.01), and death (25.8% vs 7.3%; adjusted hazard ratio, 1.42; 95% CI, 1.39-1.45).

Conclusions and Relevance

Criteria for AKD identified many patients who did not meet the criteria for CKD or AKI but had overall modestly increased risks of incident and progressive CKD, ESKD, and death. The clinical importance of AKD remains to be determined.

Sequence variants associating with urinary biomarkers

Urine dipstick tests are widely used in routine medical care to diagnose kidney and urinary tract and metabolic diseases. Several environmental factors are known to affect the test results, whereas the effects of genetic diversity are largely unknown. We tested 32.5 million sequence variants for association with urinary biomarkers in a set of 150 274 Icelanders with urine dipstick measurements. We detected 20 association signals, of which 14 are novel, associating with at least one of five clinical entities defined by the urine dipstick: glucosuria, ketonuria, proteinuria, hematuria and urine pH. These include three independent glucosuria variants at SLC5A2, the gene encoding the sodium-dependent glucose transporter (SGLT2), a protein targeted pharmacologically to increase urinary glucose excretion in the treatment of diabetes. Two variants associating with proteinuria are in LRP2 and CUBN, encoding the co-transporters megalin and cubilin, respectively, that mediate proximal tubule protein uptake. One of the hematuria-associated variants is a rare, previously unreported 2.5 kb exonic deletion in COL4A3. Of the four signals associated with urine pH, we note that the pH-increasing alleles of two variants (POU2AF1, WDR72) associate significantly with increased risk of kidney stones. Our results reveal that genetic factors affect variability in urinary biomarkers, in both a disease dependent and independent context.

Clinical features and long-term outcomes of diabetic kidney disease - A prospective cohort study from China

BACKGROUND

Information regarding the clinical phenotypes of diabetic kidney disease (DKD) might guide better practice for clinicians. We aim to compare the clinical features and long-term outcomes of proteinuric and non-proteinuric phenotypes of DKD, based on a prospective cohort of Chinese population.

METHODS

Altogether 8811 Chinese participants with diabetes were included. Kidney function decline was defined as estimated glomerular filtration rate <60 mL/min·1.73 m^-2. The presence of proteinuria by urine dipstick test was further divided into micro-proteinuria (trace or 1+) and overt-proteinuria (≥2+). Participants were then stratified into 5 groups: no DKD, isolated kidney function decline, isolated micro-proteinuria, isolated overt-proteinuria, and proteinuria combined with kidney function decline. Outcomes include the first occurrence of composite cardiovascular events, end-stage renal disease (ESRD), and all-cause mortality.

MAIN FINDINGS

After a median follow-up of 6.9 years, there were 646 composite cardiovascular events, 31 ESRD events, and 718 deaths. Isolated kidney function decline was only associated with the higher risk of ESRD (HRs 31.33 (95% CI 3.65-269.27)). Participants of overt-proteinuria and proteinuria combined with kidney function decline phenotypes were associated with increased risk of all predefined adverse outcomes.

CONCLUSIONS

Proteinuric and non-proteinuric DKD phenotypes might follow different pathophysiological pathways, and result in heterogeneous clinical features and prognosis.

Glomerular isolated microscopic hematuria: urinary features and long term follow-up of a selected cohort of patients

BACKGROUND

Isolated microscopic hematuria is a condition characterized by the presence in the urine of an "abnormal" number of erythrocytes in the absence of proteinuria. Several studies have been published on this condition, but with heterogeneous inclusion criteria and variable outcomes at follow-up. In this retrospective study, we describe a selected and homogenous cohort of patients who presented with isolated microscopic hematuria of glomerular origin.

METHODS

We included in the study patients with isolated microscopic hematuria of glomerular origin (> 1 erythrocyte/high power field at 400× and ≥ 40% dysmorphic erythrocytes and/or ≥ 5% acanthocytes and proteinuria ≤ 150 mg/24 h) with a follow-up of > 60 months from the first documentation of microscopic hematuria.

RESULTS

Forty-two patients (M 12, F 30, age at presentation 14-68 years, eGFR < 60 ml/min/1.73 m²: 1 patient) were included. During a medium term follow-up, microscopic hematuria was persistent in 25 patients (59.5%), transiently absent in 17 (40.5%), always glomerular in 16 patients (38.1%), and occasionally non-glomerular in 26 (61.9%); proteinuria, observed in 16 patients (38.1%), was always transient and < 500 mg/24 h. At the end of a follow-up of 181.8 ± 97.9 (median 168) months, only 2 patients (4.8%) had eGFR < 60 ml/min/1.73 m², one of whom had reduced eGFR already at presentation.

CONCLUSIONS

This study on a small but selected and homogeneous cohort of patients with isolated microscopic hematuria of glomerular origin demonstrates that urinary features can transiently change over time and that the renal outcome is good.

Renal Function, Albuminuria, and the Risk of Cardiovascular Events After Kidney Transplantation

BACKGROUND

The risk of mortality and graft loss is higher in kidney transplant recipients with reduced estimated glomerular filtration rate (eGFR) and albuminuria. It is unclear whether these markers are also associated with cardiovascular events.

METHODS

We examined linked healthcare databases in Alberta, Canada to identify kidney transplant recipients between 2002 and 2013 who had at least 1 outpatient serum creatinine and albuminuria measurement at 1-year posttransplant. We determined the relationship between categories of eGFR and albuminuria and the risk of subsequent cardiovascular events.

RESULTS

Among 1069 eligible kidney transplant recipients, the median age was 52 years, 37% were female, and 52% had eGFR ≥60 mL/min per 1.73 m2. Over a median follow-up of 6 years, the adjusted rate of all-cause mortality and cardiovascular events was 2.7-fold higher for recipients with eGFR 15-29 mL/min per 1.73 m2 and heavy albuminuria compared to recipients with eGFR ≥60 mL/min per 1.73 m2 and normal albuminuria (rate ratio, 2.7; 95% confidence interval, 1.3-5.7). Similarly, recipients with heavy albuminuria had a threefold increased risk of all-cause mortality and heart failure compared with recipients with eGFR ≥60 mL/min per 1.73 m2 and normal albuminuria.

CONCLUSIONS

These findings suggest that eGFR and albuminuria should be used together to determine the risk of cardiovascular outcomes in transplant recipients.

Bethony J. Diagnostic performance of urinary IgG antibody detection: A novel approach for population screening of strongyloidiasis

The diagnosis of strongyloidiasis by coprological methods has a low sensitivity, underestimating the prevalence of Strongyloides stercoralis in endemic areas. Serodiagnostic tests for strongyloidiasis have shown robust diagnostic properties. However, these methods require a blood draw, an invasive and labor-intensive sample collection method, especially in the resource-limited settings where S. stercoralis is endemic. Our study examines a urine-based assay for strongyloidiasis and compares its diagnostic accuracy with coprological and serological methods. Receiver operating characteristic (ROC) curve analyses determined the diagnostic sensitivity (D-Sn) and specificity (D-Sp) of the urine ELISA, as well as estimates its positive predictive value and diagnostic risk. The likelihood ratios of obtaining a positive test result (LR+) or a negative test result (LR-) were calculated for each diagnostic positivity threshold. The urine ELISA assay correlated significantly with the serological ELISA assay for strongyloidiasis, with a D-Sn of 92.7% and a D-Sp of 40.7%, when compared to coprological methods. Moreover, the urine ELISA IgG test had a detection rate of 69%, which far exceeds the coprological method (28%). The likelihood of a positive diagnosis of strongyloidiasis by the urine ELISA IgG test increased significantly with increasing units of IgG detected in urine. The urine ELISA IgG assay for strongyloidiasis assay has a diagnostic accuracy comparable to serological assay, both of which are more sensitive than coprological methods. Since the collection of urine is easy and non-invasive, the urine ELISA IgG assay for strongyloidiasis could be used to screen populations at risk for strongyloidiasis in S. stercoralis endemic areas.

Derivation and External Validation of Prediction Models for Advanced Chronic Kidney Disease Following Acute Kidney Injury

IMPORTANCE

Some patients will develop chronic kidney disease after a hospitalization with acute kidney injury; however, no risk-prediction tools have been developed to identify high-risk patients requiring follow-up.

OBJECTIVE

To derive and validate predictive models for progression of acute kidney injury to advanced chronic kidney disease.

DESIGN, SETTING, AND PARTICIPANTS

Data from 2 population-based cohorts of patients with a prehospitalization estimated glomerular filtration rate (eGFR) of more than 45 mL/min/1.73 m2 and who had survived hospitalization with acute kidney injury (defined by a serum creatinine increase during hospitalization > 0.3 mg/dL or > 50% of their prehospitalization baseline), were used to derive and validate multivariable prediction models. The risk models were derived from 9973 patients hospitalized in Alberta, Canada (April 2004-March 2014, with follow-up to March 2015). The risk models were externally validated with data from a cohort of 2761 patients hospitalized in Ontario, Canada (June 2004-March 2012, with follow-up to March 2013).

EXPOSURES

Demographic, laboratory, and comorbidity variables measured prior to discharge.

MAIN OUTCOMES AND MEASURES

Advanced chronic kidney disease was defined by a sustained reduction in eGFR less than 30 mL/min/1.73 m2 for at least 3 months during the year after discharge. All participants were followed up for up to 1 year.

RESULTS

The participants (mean [SD] age, 66 [15] years in the derivation and internal validation cohorts and 69 [11] years in the external validation cohort; 40%-43% women per cohort) had a mean (SD) baseline serum creatinine level of 1.0 (0.2) mg/dL and more than 20% had stage 2 or 3 acute kidney injury. Advanced chronic kidney disease developed in 408 (2.7%) of 9973 patients in the derivation cohort and 62 (2.2%) of 2761 patients in the external validation cohort. In the derivation cohort, 6 variables were independently associated with the outcome: older age, female sex, higher baseline serum creatinine value, albuminuria, greater severity of acute kidney injury, and higher serum creatinine value at discharge. In the external validation cohort, a multivariable model including these 6 variables had a C statistic of 0.81 (95% CI, 0.75-0.86) and improved discrimination and reclassification compared with reduced models that included age, sex, and discharge serum creatinine value alone (integrated discrimination improvement, 2.6%; 95% CI, 1.1%-4.0%; categorical net reclassification index, 13.5%; 95% CI, 1.9%-25.1%) or included age, sex, and acute kidney injury stage alone (integrated discrimination improvement, 8.0%; 95% CI, 5.1%-11.0%; categorical net reclassification index, 79.9%; 95% CI, 60.9%-98.9%).

CONCLUSIONS AND RELEVANCE

A multivariable model using routine laboratory data was able to predict advanced chronic kidney disease following hospitalization with acute kidney injury. The utility of this model in clinical care requires further research.

NLRP3 expression and urinary HSP72 in relation to biomarkers of inflammation and oxidative stress in diabetic nephropathy patients

Diabetic nephropathy (DN) is one of the major causes of end-stage renal disease. Nod-like receptors nucleotide-binding domain and leucine-rich repeat pyrin-3 domain (NLRP3) inflammasome displays a considerable role in the chronic inflammatory state observed in diabetic patients. Urinary heat shock protein 72 (uHSP72) is a sensitive and specific biomarker for the early detection of acute kidney injury. The aim of this study was to evaluate NLRP3 relative gene expression, its correlation with inflammatory and oxidative stress markers, and to assess the value of uHSP72 in the early detection of DN in type 2 diabetic patients with different degrees of DN. Forty-five type 2 diabetic patients: 15 normoalbuminuric, 15 microalbuminuric, 15 macroalbuminuric, in addition to 15 healthy controls were enrolled in this study. Clinical examination and routine laboratory investigations were performed. NLRP3 mRNA expression was assessed by real time polymerase chain reaction. Serum 8-hydroxy-2'-deoxyguanosine (8-OHdG), interleukin 1β (IL-1β), and uHSP72 levels were estimated by enzyme-linked immunosorbent assay. Serum chitotriosidase (CHIT1) activity was examined. NLRP3 mRNA relative expression, serum levels of 8-OHdG, IL-1β, and uHSP72, in addition to CHIT 1 activity were significantly increased in the macroalbuminuric patient group as compared to control and the other two diabetic groups. Also, a significant positive correlation was documented between the previously mentioned parameters and urinary albumin/creatinine ratio, serum creatinine, and HbA1c. Multiple linear regression analysis using urinary albumin/creatinine ratio as dependent variable confirmed that uHSP72 and NLRP3 mRNA relative expression were the independent predictors of DN (β were 0.432 and 0.448 respectively, P < 0.001). Receiver operating characteristic analyses revealed that both NLRP3 mRNA relative expression and uHSP72 levels were useful biomarkers discriminating DN patients from patients with type 2 diabetes mellitus (AUC were 0.957 and 0.983, respectively). uHSP72 may be considered as a novel potential diagnostic biomarker for the early detection of DN. Moreover, these data support the pivotal role of NLRP3 in the development and progression of DN. © 2017 IUBMB Life, 69(8):623-630, 2017.

Growth arrest-specific protein 6 (Gas6) as a noninvasive biomarker for early detection of diabetic nephropathy

BACKGROUND

To investigate the diagnostic level of cystatin C and growth arrest-specific gene 6 (Gas6) levels in elderly type 2 diabetic patients with different degrees of diabetic nephropathy (DN).

METHODS

Four hundred and eighty-two old people, including 130 healthy controls, 130 normoalbuminuric diabetic patients, 122 with microalbuminuria, and 100 with macroalbuminuria, were recruited. Plasma Gas6 and serum cystatin C levels were measured.

RESULTS

Plasma Gas6 concentration was significantly lower in diabetic patients with microalbuminuria or macroalbuminuria, as compared with diabetic subjects with normoalbuminuria; while cystatin C was significantly higher. Gas6 was inversely correlated with BMI, WHR, and HbA1c, while cystatin C was inversely correlated with urea nitrogen and creatinine. Multivariate logistic regression analysis showed that, after adjusted for established diabetes risk factors, higher plasma Gas6 was significantly associated with a decreased risk of DN, while higher serum cystatin C was significantly associated with an increased risk. Receiver operating characteristic curve analysis showed that Gas6 was better than cystatin C as a biomarker for early diagnosis and detection of DN, with a cutoff value of 9.435 ng/mL (86.1% sensitivity and 84.6% specificity).

CONCLUSION

Compared to cystatin C, Gas6 may be potentially a better noninvasive diagnostic biomarker for early detection of DN.

Albuminuria and posttransplant chronic kidney disease stage predict transplant outcomes

In 2012, the KDIGO guidelines updated the classification system for chronic kidney disease to include albuminuria. Whether this classification system predicts adverse clinical outcomes among kidney transplant recipients is unclear. To evaluate this, we conducted a retrospective study using linked databases in Alberta, Canada to follow kidney transplant recipients from 2002-2011. We examined the association between an estimated glomerular filtration rate (eGFR of 60 or more, 45-59, 30-44, 15-29 mL/min/1.73 m²) and albuminuria (normal, mild, heavy) at one year post-transplant and subsequent mortality and graft loss. There were 900 recipients with a functioning graft and at least one outpatient serum creatinine and urine protein measurement at one year post-transplant. The median age was 51.2 years, 38.7% were female, and 52% had an eGFR of 60 mL/min/1.73 m² or more. The risk of all-cause mortality and death-censored graft loss was increased in recipients with reduced eGFR or heavier albuminuria. The adjusted incidence rate per 1000 person-years of all-cause mortality for recipients with an eGFR of 15-29 mL/min/1.73 m² and heavy albuminuria vs. an eGFR 60 mL/min/1.73 m² or more and normal protein excretion was 117 (95% confidence interval 38-371) vs. 15 (9-23) (rate ratio 8). Corresponding rates for death-censored graft loss were 273 (88-1203) vs. 6 (3-9) (rate ratio 49). Reduced eGFR and heavier albuminuria in kidney transplant recipients are associated with an increased risk of mortality and graft loss. Thus, eGFR and albuminuria may be used together to identify, evaluate, and manage transplant recipients who are at higher risk of adverse clinical outcomes.

Urinary heme oxygenase-1 as a potential biomarker for early diabetic nephropathy

BACKGROUND

Our previous study showed that increases of urinary heme oxygenase-1 (uHO-1) could be a potential biomarker indicating evaluating intrarenal oxidative damage in obstructive nephropathy. Activation of oxidative stress is an important mediator of diabetic nephropathy (DN). The aim of this study was to investigate the clinical implications of uHO-1 levels in patients with type 2 diabetes.

METHODS

Eighty-four type 2 diabetic patients with normoalbuminuria (n=28), microalbuminuria (n=28), and macroalbuminuria (n=28) were included in this study. Control samples were collected from healthy volunteers (n=28) who had normal albuminuria and renal function. Urine HO-1 levels were evaluated by enzyme-linked immunosorbent assay.

RESULTS

Urinary HO-1/creatinine (cr.) levels were significantly elevated in diabetic patients with microalbuminuria and macroalbuminuria compared to those in diabetic patients with normoalbuminuria (P<0.001) and control subjects (all P<0.001). In diabetic patients with normoalbuminuria, uHO-1/cr. levels were also higher than those in controls (P<0.001). Multivariate regression analyses revealed that uHO-1/cr. levels were positively correlated to urinary albumin/creatinine ratio and inversely correlated to glomerular filtration rate. Receiver operating characteristic (ROC) curve analysis of uHO-1/cr. levels for early diagnosis and detection of DN revealed that the cut-off value of uHO-1/cr. was 4.59 ng/mg (sensitivity 75%, specificity 78.6%).

CONCLUSIONS

The findings of this study indicate that increases of urine HO-1 levels can be detected in patients with type 2 diabetes before the onset of significant albuminuria, and associated with renal derangement in patients with established diabetic nephropathy. Urinary HO-1 may be used as an early biomarker for diabetic renal injury.

The role of laboratory testing in detection and classification of chronic kidney disease: national recommendations

Chronic kidney disease (CKD) is a common clinical condition with significant adverse consequences for the patient and it is recognized as a significant public health problem. The role of laboratory medicine in diagnosis and management of CKD is of great importance: the diagnosis and staging are based on estimation of glomerular filtration rate (eGFR) and assessment of albuminuria (or proteinuria). Therefore, the joint working group of the Croatian society of medical biochemistry and laboratory medicine and Croatian chamber of medical biochemists for laboratory diagnostics in CKD issued this national recommendation regarding laboratory diagnostics of CKD.
Key factors for laboratories implementing the national guidelines for the diagnosis and management of CKD are:
1. Ensure good communication between laboratory professionals and clinicians, such as nephrologists or specialists in general/family medicine,
2. Ensure all patients are provided with the same availability of laboratory diagnostics,
3. Ensure creatinine assays are traceable to isotope dilution mass spectrometry (IDMS) method and have minimal bias and acceptable imprecision,
4. Select the appropriate GFR estimating formula. Recommended equation is the 2009 Chronic Kidney Disease Epidemiology Collaboration (CKD - EPI) equation,
5. In reporting the key laboratory tests (creatinine, eGFR, urine albumin-to-creatinine ratio, urine protein-to-creatinine ratio) use the appropriate reporting units,
6. Provide adequate information on limitations of creatinine measurement.
The manuscript has been organized to identify critical points in laboratory tests used in basic laboratory diagnostics of CKD and is based on the Kidney Disease: Improving Global Outcomes (KDIGO) 2012 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease.

Low Rice Intake Is Associated with Proteinuria in Participants of Korea National Health and Nutrition Examination Survey

Little is known about the risk factors of proteinuria in the Asian population. On the basis of the association between rice intake patterns and chronic diseases, we hypothesized that rice intake patterns are associated with proteinuria in the Asian population. Data, including data regarding rice intake frequency and dipstick urinalysis results, from the Korea National Health and Nutrition Examination Survey in 1998, 2001, 2005, and 2007 were analyzed. The study involved 19,824 participants who were older than 20 years of age. Low rice intake was defined as consumption of rice ≤ 1 time/day. Proteinuria was defined as dipstick urinalysis protein ≥ 1 positive. Among the 19,824 participants, the prevalence of low rice intake and proteinuria were 17.3% and 2.9%, respectively. The low rice intake group showed a higher rate of proteinuria than the non-low rice intake group did (3.8% vs. 2.7%, P < 0.001). In multivariate logistic regression analysis, the odds ratio (OR) of low rice intake for proteinuria was 1.54 (95% confidence interval (CI): 1.25-1.89; P < 0.001). Low rice intake was also independently associated with high blood pressure (OR: 1.43, 95% CI: 1.31-1.56; P < 0.001) and diabetes (OR: 1.43, 95% CI: 1.27-1.62; P < 0.001). In conclusion, low rice intake was found to be independently associated with proteinuria in the Asian population, which might have been affected by the associations of low rice intake with high blood pressure and diabetes. Future prospective studies are needed to confirm the results of this study.

Addition of nonalbumin proteinuria to albuminuria improves prediction of type 2 diabetic nephropathy progression

BACKGROUND

Albuminuria is generally accepted as a sensitive marker of diabetic nephropathy but has limitations in predicting its progression. The aim of this study was to evaluate the use of nonalbumin proteinuria in addition to albuminuria for predicting the progression of type 2 diabetic nephropathy.

METHODS

In this retrospective observational study, the urine albumin-to-creatinine ratio (ACR) and the nonalbumin protein-to-creatinine ratio (NAPCR) were measured in 325 patients with type 2 diabetes and estimated glomerular filtration rates (eGFR) ≥30 mL/min/1.73 m². The patients were divided into four groups based on the cutoff points for the urinary ACR (30 mg/g) and NAPCR (120 mg/g). The renal outcomes were chronic kidney disease (CKD) progression and accelerated eGFR decline.

RESULTS

During the 4.3-year follow-up period, 25 (7.7%) patients showed CKD progression and 69 (21.2%) patients showed accelerated eGFR decline. After adjusting for nine clinical parameters, the group with a NAPCR greater than 120 mg/g exhibited higher cumulative incidences of CKD progression (hazard ratio 6.84; P = 0.001) and accelerated eGFR decline (hazard ratio 1.95; P = 0.011) than the group with a NAPCR < 120 mg/g. In patients with normoalbuminuria, the group with NAPCR levels greater than 120 mg/g also exhibited a higher cumulative incidence than that with NAPCR levels <120 mg/g of CKD progression (hazard ratio 21.82; P = 0.005). The addition of NAPCR to ACR improved the model fit for CKD progression and accelerated eGFR decline.

CONCLUSION

Nonalbumin proteinuria showed additional value over and above that of albuminuria for predicting the progression of CKD in patients with type 2 diabetes.

Integrated sensor-augmented pump therapy systems [the MiniMed® Paradigm™ Veo system and the Vibe™ and G4® PLATINUM CGM (continuous glucose monitoring) system] for managing blood glucose levels in type 1 diabetes: a systematic review and economic evaluation

BACKGROUND

In recent years, meters for continuous monitoring of interstitial fluid glucose have been introduced to help people with type 1 diabetes mellitus (T1DM) to achieve better control of their disease.

OBJECTIVE

The objective of this project was to summarise the evidence on the clinical effectiveness and cost-effectiveness of the MiniMed(®) Paradigm™ Veo system (Medtronic Inc., Northridge, CA, USA) and the Vibe™ (Animas(®) Corporation, West Chester, PA, USA) and G4(®) PLATINUM CGM (continuous glucose monitoring) system (Dexcom Inc., San Diego, CA, USA) in comparison with multiple daily insulin injections (MDIs) or continuous subcutaneous insulin infusion (CSII), both with either self-monitoring of blood glucose (SMBG) or CGM, for the management of T1DM in adults and children.

DATA SOURCES

A systematic review was conducted in accordance with the principles of the Centre for Reviews and Dissemination guidance and the National Institute for Health and Care Excellence Diagnostic Assessment Programme manual. We searched 14 databases, three trial registries and two conference proceedings from study inception up to September 2014. In addition, reference lists of relevant systematic reviews were checked. In the absence of randomised controlled trials directly comparing Veo or an integrated CSII + CGM system, such as Vibe, with comparator interventions, indirect treatment comparisons were performed if possible.

METHODS

A commercially available cost-effectiveness model, the IMS Centre for Outcomes Research and Effectiveness diabetes model version 8.5 (IMS Health, Danbury, CT, USA), was used for this assessment. This model is an internet-based, interactive simulation model that predicts the long-term health outcomes and costs associated with the management of T1DM and type 2 diabetes. The model consists of 15 submodels designed to simulate diabetes-related complications, non-specific mortality and costs over time. As the model simulates individual patients over time, it updates risk factors and complications to account for disease progression.

RESULTS

Fifty-four publications resulting from 19 studies were included in the review. Overall, the evidence suggests that the Veo system reduces hypoglycaemic events more than other treatments, without any differences in other outcomes, including glycated haemoglobin (HbA1c) levels. We also found significant results in favour of the integrated CSII + CGM system over MDIs with SMBG with regard to HbA1c levels and quality of life. However, the evidence base was poor. The quality of the included studies was generally low, often with only one study comparing treatments in a specific population at a specific follow-up time. In particular, there was only one study comparing Veo with an integrated CSII + CGM system and only one study comparing Veo with a CSII + SMBG system in a mixed population. Cost-effectiveness analyses indicated that MDI + SMBG is the option most likely to be cost-effective, given the current threshold of £30,000 per quality-adjusted life-year gained, whereas integrated CSII + CGM systems and Veo are dominated and extendedly dominated, respectively, by stand-alone, non-integrated CSII with CGM. Scenario analyses did not alter these conclusions. No cost-effectiveness modelling was conducted for children or pregnant women.

CONCLUSIONS

The Veo system does appear to be better than the other systems considered at reducing hypoglycaemic events. However, in adults, it is unlikely to be cost-effective. Integrated systems are also generally unlikely to be cost-effective given that stand-alone systems are cheaper and, possibly, no less effective. However, evidence in this regard is generally lacking, in particular for children. Future trials in specific child, adolescent and adult populations should include longer term follow-up and ratings on the European Quality of Life-5 Dimensions scale at various time points with a view to informing improved cost-effectiveness modelling.

STUDY REGISTRATION

PROSPERO Registration Number CRD42014013764.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Chronic kidney disease: identification and management in primary care

Chronic kidney disease (CKD) is an important and common noncommunicable condition globally. In national and international guidelines, CKD is defined and staged according to measures of kidney function that allow for a degree of risk stratification using commonly available markers. It is often asymptomatic in its early stages, and early detection is important to reduce future risk. The risk of cardiovascular outcomes is greater than the risk of progression to end-stage kidney disease for most people with CKD. CKD also predisposes to acute kidney injury - a major cause of morbidity and mortality worldwide. Although only a small proportion of people with CKD progress to end-stage kidney disease, renal replacement therapy (dialysis or transplantation) represents major costs for health care systems and burden for patients. Efforts in primary care to reduce the risks of cardiovascular disease, acute kidney injury, and progression are therefore required. Monitoring renal function is an important task, and primary care clinicians are well placed to oversee this aspect of care along with the management of modifiable risk factors, particularly blood pressure and proteinuria. Good primary care judgment is also essential in making decisions about referral for specialist nephrology opinion. As CKD commonly occurs alongside other conditions, consideration of comorbidities and patient wishes is important, and primary care clinicians have a key role in coordinating care while adopting a holistic, patient-centered approach and providing continuity. This review aims to summarize the vital role that primary care plays in predialysis CKD care and to outline the main considerations in its identification, monitoring, and clinical management in this context.

Measures of Urinary Protein and Albumin in the Prediction of Progression of IgA Nephropathy

BACKGROUND AND OBJECTIVES

Proteinuria is an independent predictor for IgA nephropathy (IgAN) progression. Urine albumin-to-creatinine ratio (ACR), protein-to-creatinine ratio, and 24-hour urine protein excretion (UPE) are widely used for proteinuria evaluation in clinical practice. Here, we evaluated the association of these measurements with clinical and histologic findings of IgAN and explored which was the best predictor of IgAN prognosis.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Patients with IgAN were followed up for ≥12 months, were diagnosed between 2003 and 2012, and had urine samples available (438 patients). Spot urine ACR, protein-to-creatinine ratio, and 24-hour UPE at the time of renal biopsy were measured on a Hitachi Automatic Biochemical Analyzer 7180 (Hitachi, Yokohama, Japan).

RESULTS

In our patients, ACR, protein-to-creatinine ratio, and 24-hour UPE were highly correlated (correlation coefficients: 0.71-0.87). They showed good relationships with acknowledged markers reflecting IgAN severity, including eGFR, hypertension, and the biopsy parameter (Oxford severity of tubular atrophy/interstitial fibrosis parameter). However, only ACR presented with positive association with the Oxford segmental glomerulosclerosis/adhesion parameter and extracapillary proliferation lesions. The follow-up time was 37.0 (22.0-58.0) months, with the last follow-up on April 18, 2014. In total, 124 patients reached the composite end point (30% eGFR decline, ESRD, or death). In univariate survival analysis, ACR consistently had better performance than protein-to-creatinine ratio and 24-hour UPE as represented by higher area under the curve using time-dependent survival analysis. When adjusted for well known risk factors for IgAN progression, ACR was most significantly associated with the composite end point (hazard ratio, 1.56 per 1-SD change of standard normalized square root-transformed ACR; 95% confidence interval, 1.29 to 1.89; P<0.001). Compared with protein-to-creatinine ratio and 24-hour UPE, addition of ACR to traditional risk factors resulted in more improvement in the predictive ability of IgAN progression (c statistic: ACR=0.70; protein-to-creatinine ratio =0.68; 24-hour UPE =0.69; Akaike information criterion: ACR=1217.85; protein-to-creatinine ratio =1229.28; 24-hour UPE =1234.96; P<0.001).

CONCLUSIONS

In IgAN, ACR, protein-to-creatinine ratio, and 24-hour UPE had comparable association with severe clinical and histologic findings. Compared with protein-to-creatinine ratio and 24-hour UPE, ACR showed slightly better performance in predicting IgAN progression.

The risk of death associated with proteinuria in heart failure is restricted to patients with an elevated blood urea nitrogen to creatinine ratio

BACKGROUND

Renal dysfunction (RD) is associated with reduced survival in HF; however, not all RD is mechanistically or prognostically equivalent. Notably, RD associated with "pre-renal" physiology, as identified by an elevated blood urea nitrogen to creatinine ratio (BUN/Cr), identifies a particularly high risk RD phenotype. Proteinuria, another domain of renal dysfunction, has also been associated with adverse events. Given that several different mechanisms can cause proteinuria, we sought to investigate whether the mechanism underlying proteinuria also affects survival in HF.

METHODS AND RESULTS

Subjects in the Studies of Left Ventricular Dysfunction (SOLVD) trial with proteinuria assessed at baseline were studied (n=6439). All survival models were adjusted for baseline characteristics and estimated glomerular filtration rate (eGFR). Proteinuria (trace or 1+) was present in 26% and associated with increased mortality (HR=1.2; 95% CI, 1.1-1.3, p=0.006). Proteinuria >1+ was less common (2.5%) but demonstrated a stronger relationship with mortality (HR=1.9; 95% CI, 1.5-2.5, p<0.001). In patients with BUN/Cr in the top tertile (≥17.3), any proteinuria (HR=1.3; 95% CI, 1.1-1.5, p=0.008) and >1+ proteinuria (HR=2.3; 95% CI, 1.7-3.3, p<0.001) both remained associated with mortality. However, in patients with BUN/Cr in the bottom tertile (≤13.3), any proteinuria (HR=0.95; 95% CI, 0.77-1.2, p=0.63, p interaction=0.015) and >1+ proteinuria (HR=1.3; 95% CI, 0.79-2.2, p=0.29, p interaction=0.036) were not associated with worsened survival.

CONCLUSION

Analogous to a reduced eGFR, the mechanism underlying proteinuria in HF may be important in determining the associated survival disadvantage.

Estimated glomerular filtration rate and albuminuria in Korean population evaluated for cardiovascular risk

PURPOSE

This study's purpose was to examine established cardiovascular risk prediction model scores for their associations with albuminuria and estimated glomerular filtration rate (eGFR) in Korean population.

METHODS

We calculated the 10-year atherosclerotic cardiovascular disease (ASCVD) risk estimated score, Korean coronary heart disease risk prediction score (KRS), and the Adult Treatment Panel (ATP) III risk score for 9733 South Koreans, aged 40-79 years, who were not diagnosed with stroke, angina pectoris, or myocardial ischemia using data from the 2011-2013 Korea National Health and Nutrition Examination Survey.

RESULTS

The associations between cardiovascular risk model scores and the urine albumin-to-creatinine ratio (UACR) and eGFR tended to be stronger for the ASCVD risk score than for the other risk scores. The area under the receiver operating characteristic curve for increased albuminuria (UACR ≥ 30 mg/g) and decreased eGFR (<60 mL/min/1.73 m(2)) was significantly higher for the ASCVD risk score than for the ATP III risk score and the KRS (except for increased albuminuria in women).

CONCLUSIONS

The ASCVD risk score had a stronger relationship with and better predicted albuminuria and eGFR than did the KRS and ATP III risk score.

A Meta-analysis of the Association of Estimated GFR, Albuminuria, Age, Race, and Sex With Acute Kidney Injury

BACKGROUND

Acute kidney injury (AKI) is a serious global public health problem. We aimed to quantify the risk of AKI associated with estimated glomerular filtration rate (eGFR), albuminuria (albumin-creatinine ratio [ACR]), age, sex, and race (African American and white).

STUDY DESIGN

Collaborative meta-analysis.

SETTING & POPULATION

8 general-population cohorts (1,285,049 participants) and 5 chronic kidney disease (CKD) cohorts (79,519 participants).

SELECTION CRITERIA FOR STUDIES

Available eGFR, ACR, and 50 or more AKI events.

PREDICTORS

Age, sex, race, eGFR, urine ACR, and interactions.

OUTCOME

Hospitalized with or for AKI, using Cox proportional hazards models to estimate HRs of AKI and random-effects meta-analysis to pool results.

RESULTS

16,480 (1.3%) general-population cohort participants had AKI over a mean follow-up of 4 years; 2,087 (2.6%) CKD participants had AKI over a mean follow-up of 1 year. Lower eGFR and higher ACR were strongly associated with AKI. Compared with eGFR of 80mL/min/1.73m(2), the adjusted HR of AKI at eGFR of 45mL/min/1.73m(2) was 3.35 (95% CI, 2.75-4.07). Compared with ACR of 5mg/g, the risk of AKI at ACR of 300mg/g was 2.73 (95% CI, 2.18-3.43). Older age was associated with higher risk of AKI, but this effect was attenuated with lower eGFR or higher ACR. Male sex was associated with higher risk of AKI, with a slight attenuation in lower eGFR but not in higher ACR. African Americans had higher AKI risk at higher levels of eGFR and most levels of ACR.

LIMITATIONS

Only 2 general-population cohorts could contribute to analyses by race; AKI identified by diagnostic code.

CONCLUSIONS

Reduced eGFR and increased ACR are consistent strong risk factors for AKI, whereas associations of AKI with age, sex, and race may be weaker in more advanced stages of CKD.