Proton Pump Inhibitors and Kidney Disease - GI Upset for the Nephrologist?

Widely regarded as safe and effective, proton pump inhibitors (PPIs) are among the most commonly used medications in the world today. However, a spate of observational studies suggest an association between PPI use and adverse events, including infection, bone fracture, and dementia. This review details evidence linking the use of PPI therapy to the development of kidney disease, including early case reports of acute interstitial nephritis and subsequent large observational studies of acute kidney injury (AKI), chronic kidney disease (CKD), and end-stage renal disease (ESRD). The majority of studies showed higher risk of kidney outcomes among persons prescribed PPI medications, with effect sizes that were slightly higher for AKI (∼2-3-fold) compared to CKD and ESRD (1.2-1.8-fold). Although observational pharmaco-epidemiology studies are limited by the possibility of residual confounding and confounding by indication, many of the described studies conducted rigorous sensitivity analyses aimed at minimizing these biases, including new-user design, comparison to similar agents (e.g., histamine₂ receptor antagonists), and evaluation for a dose-response, with robust results. Given the widespread use of PPIs, even a small effect on kidney outcomes could result in large public health burden. Timely cessation of PPI therapy when there is no clear indication for use might reduce the population burden of kidney disease.

Diet Soda Consumption and Risk of Incident End Stage Renal Disease

BACKGROUND AND OBJECTIVES

Diet soda consumption is common in the United States and is associated with impaired glucose metabolism, diabetes, and metabolic syndrome.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We prospectively analyzed diet soda consumption, assessed by food frequency questionnaire at baseline (1987-1989) and a follow-up examination (1993-1995), and incident ESRD through December 31, 2012 in the Atherosclerosis Risk in Communities study (n=15,368).

RESULTS

Baseline mean age of participants was 54 years, 55% were female, and 27% were black. The majority of participants (43.5%) consumed <1 glass/wk of diet soda; 17.8% consumed 1-4 glasses/wk; 25.3% consumed 5-7 glasses/wk; and 13.5% consumed >7 glasses/wk. Over a median follow-up of 23 years, 357 incident ESRD cases were observed. Relative to <1 glass/wk of diet soda, consuming 1-4 glasses/wk, 5-7 glasses/wk, and >7 glasses/wk, respectively, was associated with 1.08-times (95% confidence interval [95% CI], 0.75 to 1.55), 1.33-times (95% CI, 1.01 to 1.75), and 1.83-times (95% CI, 1.01 to 2.52) higher risk of ESRD after adjusting for age, sex, race-center, education level, smoking status, physical activity, total caloric intake, eGFR, body mass index category, diabetes, systolic BP, and serum uric acid (P value for trend <0.001). Results were similar after additional adjustment for dietary acid load, diet quality, dietary sodium, dietary fructose, sugar-sweetened beverages, and dietary phosphorus. Risk estimates were similar by body mass index category (P value for interaction = 0.82), but the association between diet soda and ESRD was only significant for those who were overweight or obese at baseline. Sugar-sweetened beverage consumption was not significantly associated with ESRD in the fully adjusted model.

CONCLUSIONS

Diet soda consumption was associated with higher ESRD risk in this general population sample. Further research is necessary to validate these findings in other study populations and to examine potential mechanisms through which diet soda could impact kidney disease.

Albuminuria changes are associated with subsequent risk of end-stage renal disease and mortality

Current guidelines for chronic kidney disease (CKD) recommend using albuminuria as well as estimated glomerular filtration rate (eGFR) to stage CKD. However, CKD progression is solely defined by change in eGFR with little regard to the risk implications of change in albuminuria. This is an observational study from the Stockholm CREAtinine Measurements (SCREAM) project, a health care utilization cohort from Stockholm, Sweden, with laboratory measures from 2006-2011 and follow-up through December 2012. Included were 31,732 individuals with two or more ambulatory urine albumin to creatinine ratio (ACR) tests. We assessed the association between change in ACR during a baseline period of 1, 2, or 3 years and end-stage renal disease (ESRD) or death. Using a 2-year baseline period, there were 378 ESRD events and 1712 deaths during a median of 3 years of follow-up. Compared to stable ACR, a 4-fold increase in ACR was associated with a 3.08-times (95% confidence interval 2.59 to 3.67) higher risk of ESRD while a 4-fold decrease in ACR was associated with a 0.34-times (0.26 to 0.45) lower risk of ESRD. Similar associations were found in people with and without diabetes mellitus, with and without hypertension, and also when adjusted for the change in eGFR during the same period. The association between change in ACR and mortality was weaker: ACR increase was associated with mortality, but the relationship was largely flat for ACR decline. Results were consistent for 1-, 2-, and 3-year ACR changes. Thus, changes in albuminuria are strongly and consistently associated with the risk of ESRD and death.

DASH (Dietary Approaches to Stop Hypertension) Diet and Risk of Subsequent Kidney Disease

BACKGROUND

There are established guidelines for recommended dietary intake for hypertension treatment and cardiovascular disease prevention. Evidence is lacking for effective dietary patterns for kidney disease prevention.

STUDY DESIGN

Prospective cohort study.

SETTING & PARTICIPANTS

Atherosclerosis Risk in Communities (ARIC) Study participants with baseline estimated glomerular filtration rate (eGFR) ≥ 60mL/min/1.73m2 (N=14,882).

PREDICTOR

The Dietary Approaches to Stop Hypertension (DASH) diet score was calculated based on self-reported dietary intake of red and processed meat, sweetened beverages, sodium, fruits, vegetables, whole grains, nuts and legumes, and low-fat dairy products, averaged over 2 visits.

OUTCOMES

Cases were ascertained based on the development of eGFRs<60mL/min/1.73m2 accompanied by ≥25% eGFR decline from baseline, an International Classification of Diseases, Ninth/Tenth Revision code for a kidney disease-related hospitalization or death, or end-stage renal disease from baseline through 2012.

RESULTS

3,720 participants developed kidney disease during a median follow-up of 23 years. Participants with a DASH diet score in the lowest tertile were 16% more likely to develop kidney disease than those with the highest score tertile (HR, 1.16; 95% CI, 1.07-1.26; P for trend < 0.001), after adjusting for sociodemographics, smoking status, physical activity, total caloric intake, baseline eGFR, overweight/obese status, diabetes status, hypertension status, systolic blood pressure, and antihypertensive medication use. Of the individual components of the DASH diet score, high red and processed meat intake was adversely associated with kidney disease and high nuts, legumes, and low-fat dairy products intake was associated with reduced risk for kidney disease.

LIMITATIONS

Potential measurement error due to self-reported dietary intake and lack of data for albuminuria.

CONCLUSIONS

Consuming a DASH-style diet was associated with lower risk for kidney disease independent of demographic characteristics, established kidney risk factors, and baseline kidney function. Healthful dietary patterns such as the DASH diet may be beneficial for kidney disease prevention.

Patterns of End-Stage Renal Disease Caused by Diabetes, Hypertension, and Glomerulonephritis in Live Kidney Donors

Inferences about late risk of end-stage renal disease (ESRD) in live kidney donors have been extrapolated from studies averaging <10 years of follow-up. Because early (<10 years) and late (≥10 years) postdonation ESRD may differ by causal mechanism, it is possible that extrapolations are misleading. To better understand postdonation ESRD, we studied patterns of common etiologies including diabetes, hypertension and glomerulonephritis (GN; as reported by providers) using donor registry data linked to ESRD registry data. Overall, 125 427 donors were observed for a median of 11.0 years (interquartile range 5.3-15.7 years; maximum 25 years). The cumulative incidence of ESRD increased from 10 events per 10 000 at 10 years after donation to 85 events per 10 000 at 25 years after donation (late vs. early ESRD, adjusted for age, race and sex: incidence rate ratio [IRR] _1.3 1.7_2.3 [subscripts are 95% confidence intervals]). Early postdonation ESRD was predominantly reported as GN-ESRD; however, late postdonation ESRD was more frequently reported as diabetic ESRD and hypertensive ESRD (IRR _2.3 7.7_25.2 and _1.4 2.6_4.6 , respectively). These time-dependent patterns were not seen with GN-ESRD (IRR _0.4 0.7_1.2 ). Because ESRD in live kidney donors has traditionally been reported in studies averaging <10 years of follow-up, our findings suggest caution in extrapolating such results over much longer intervals.

CKD and Risk for Hospitalization With Infection: The Atherosclerosis Risk in Communities (ARIC) Study

BACKGROUND

Individuals on dialysis therapy have a high risk for infection, but risk for infection in earlier stages of chronic kidney disease has not been comprehensively described.

STUDY DESIGN

Observational cohort study.

SETTING & PARTICIPANTS

9,697 participants (aged 53-75 years) in the Atherosclerosis Risk in Communities (ARIC) Study. Participants were followed up from 1996 to 1998 through 2011.

PREDICTORS

Estimated glomerular filtration rate (eGFR) and urinary albumin-creatinine ratio (ACR).

OUTCOMES

Risk for hospitalization with infection and death during or within 30 days of hospitalization with infection.

RESULTS

During follow-up (median, 13.6 years), there were 2,701 incident hospitalizations with infection (incidence rate, 23.6/1,000 person-years) and 523 infection-related deaths. In multivariable analysis, HRs of incident hospitalization with infection as compared to eGFRs≥90mL/min/1.73m² were 2.55 (95% CI, 1.43-4.55), 1.48 (95% CI, 1.28-1.71), and 1.07 (95% CI, 0.98-1.16) for eGFRs of 15 to 29, 30 to 59, and 60 to 89mL/min/1.73m², respectively. Corresponding HRs were 3.76 (95% CI, 1.48-9.58), 1.62 (95% CI, 1.20-2.19), and 0.99 (95% CI, 0.80-1.21) for infection-related death. Compared to ACRs<10mg/g, HRs of incident hospitalization with infection were 2.30 (95% CI, 1.81-2.91), 1.56 (95% CI, 1.36-1.78), and 1.34 (95% CI, 1.20-1.50) for ACRs≥300, 30 to 299, and 10 to 29mg/g, respectively. Corresponding HRs were 3.44 (95% CI, 2.28-5.19), 1.57 (95% CI, 1.18-2.09), and 1.39 (95% CI, 1.09-1.78) for infection-related death. Results were consistent when separately assessing risk for pneumonia, kidney and urinary tract infections, bloodstream infections, and cellulitis and when taking into account recurrent episodes of infection.

LIMITATIONS

Outcome ascertainment relied on diagnostic codes at time of discharge.

CONCLUSIONS

Increasing provider awareness of chronic kidney disease as a risk factor for infection is needed to reduce infection-related morbidity and mortality.

Prevalence and recognition of chronic kidney disease in Stockholm healthcare

BACKGROUND

Chronic kidney disease (CKD) is common, but the frequency of albuminuria testing and referral to nephrology care has been difficult to measure. We here characterize CKD prevalence and recognition in a complete healthcare utilization cohort of the Stockholm region, in Sweden.

METHODS

We included all adult individuals (n = 1 128 058) with at least one outpatient measurement of IDMS-calibrated serum creatinine during 2006-11. Estimated glomerular filtration rate (eGFR) was calculated via the CKD-EPI equation and CKD was solely defined as eGFR <60 mL/min/1.73 m². We also assessed the performance of diagnostic testing (albuminuria), nephrology consultations, and utilization of ICD-10 diagnoses.

RESULTS

A total of 68 894 individuals had CKD, with a crude CKD prevalence of 6.11% [95% confidence interval (CI): 6.07-6.16%] and a prevalence standardized to the European population of 5.38% (5.33-5.42%). CKD was more prevalent among the elderly (28% prevalence >75 years old), women (6.85 versus 5.24% in men), and individuals with diabetes (17%), hypertension (17%) or cardiovascular disease (31%). The frequency of albuminuria monitoring was low, with 38% of diabetics and 27% of CKD individuals undergoing albuminuria testing over 2 years. Twenty-three per cent of the 16 383 individuals satisfying selected KDIGO criteria for nephrology referral visited a nephrologist. Twelve per cent of CKD patients carried an ICD-10 diagnostic code of CKD.

CONCLUSIONS

An estimated 6% of the adult Stockholm population accessing healthcare has CKD, but the frequency of albuminuria testing, nephrology consultations and registration of CKD diagnoses was suboptimal despite universal care. Improving provider awareness and treatment of CKD could have a significant public health impact.

Chronic Kidney Disease and Risk for Gastrointestinal Bleeding in the Community: The Atherosclerosis Risk in Communities (ARIC) Study

BACKGROUND AND OBJECTIVES

Patients on dialysis are known to have higher risk for gastrointestinal (GI) bleeding. However, data on mild to moderate CKD, particularly elevated albuminuria, are limited.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Among 11,088 participants in the Atherosclerosis Risk in Communities (ARIC) Study, we investigated the association of eGFR and urinary albumin-to-creatinine ratio (ACR) with risk for hospitalization with GI bleeding. Kidney measures were assessed at visit four (1996-1998), and follow-up was continued through 2011.

RESULTS

During a median follow-up of 13.9 years, 686 first incident hospitalizations with GI bleeding were observed (incidence rate, 4.9 per 1000 person-years [95% confidence interval (95% CI), 4.5 to 5.3]). Multivariable Cox proportional hazards models revealed that both lower eGFR and higher ACR were associated with higher risk for GI bleeding. With eGFR≥90 ml/min per 1.73 m2 as a reference, risk for GI bleeding was significant in moderately decreased eGFR of 30-59 ml/min per 1.73 m2 (hazard ratio [HR], 1.51; 95% CI, 1.13 to 2.02), and was highest in severely decreased eGFR<30 ml/min per 1.73 m2 (HR, 7.06; 95% CI, 3.91 to 12.76). Compared with ACR<10 mg/g, risk for GI bleeding became significantly higher in mild albuminuria with ACR 10-29 mg/g (HR, 1.36; 95% CI, 1.08 to 1.69), and was nearly double in moderate and severe albuminuria (HR, 2.13; 95% CI, 1.66 to 2.71 for ACR 30-299 mg/g, and HR, 2.07; 95% CI, 1.33 to 3.22 for ACR≥300 mg/g). These results were largely consistent in demographic and clinical subgroups and independent of incident cardiovascular events or dialysis during follow-up.

CONCLUSIONS

Individuals with even mild to moderate CKD warrant clinical attention regarding the risk of hospitalization with GI bleeding.

Serum Potassium, Mortality, and Kidney Outcomes in the Atherosclerosis Risk in Communities Study

OBJECTIVES

To investigate the association between serum potassium, mortality, and kidney outcomes in the general population and whether potassium-altering medications modify these associations.

PATIENTS AND METHODS

We studied 15,539 adults in the Atherosclerosis Risk in Communities Study. Cox proportional hazard regression was used to investigate the association of serum potassium at baseline (1987-1989), evaluated categorically (hypokalemia, <3.5 mmol/L; normokalemia, ≥3.5 and <5.5 mmol/L; hyperkalemia, ≥5.5 mmol/L) and continuously using linear spline terms (knots at 3.5 and 5.5 mmol/L), with mortality, sudden cardiac death, incident chronic kidney disease, and end-stage renal disease. The end date of follow-up for all outcomes was December 31, 2012. We also evaluated whether classes of potassium-altering medications modified the association between serum potassium and adverse outcomes.

RESULTS

Overall, 413 (2.7%) of the participants had hypokalemia and 321 (2.1%) had hyperkalemia. In a fully adjusted model, hyperkalemia was significantly associated with mortality (hazard ratio, 1.24; 95% CI, 1.04-1.49) but not sudden cardiac death, chronic kidney disease, or end-stage renal disease. Hypokalemia as a categorical variable was not associated with any outcome; however, associations of hypokalemia with all-cause mortality and kidney outcomes were observed among those who were not taking potassium-wasting diuretics (all P for interaction, <.001).

CONCLUSIONS

Higher values of serum potassium were associated with a higher risk of mortality in the general population. Lower levels of potassium were associated with adverse kidney outcomes and mortality among participants not taking potassium-wasting diuretics.

Patterns of Kidney Function Decline Associated with APOL1 Genotypes: Results from AASK

BACKGROUND AND OBJECTIVES

Trajectories of eGFR in patients with CKD are highly variable. Only a subset of patients with CKD experiences a steady decline in eGFR. The objective of our study was to investigate whether eGFR trajectory patterns differ by APOL1 risk status.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Our study was a longitudinal observational study of 622 participants in the African American Study of Kidney Disease and Hypertension with APOL1 genotyping and sufficient follow-up for estimating GFR trajectories. The predictor was APOL1 high-risk status (having two copies of the G1 or G2 risk alleles) versus low-risk status (zero or one copy of the risk alleles), and the outcome was four eGFR trajectory patterns on the basis of the joint probabilities of linearity and progression: steady decline, unsteady decline, steady stable, and unsteady stable.

RESULTS

Over a median follow-up of 9 years, 24.0% of participants experienced steady eGFR decline, 25.9% had an unsteady decline, 25.6% were steady and stable, and 24.6% were unsteady but stable. Those experiencing steady decline had lower eGFR and higher urine protein-to-creatinine ratio at baseline than participants with the other eGFR trajectory patterns. The APOL1 high-risk group was associated with a greater odds for the steady decline pattern than the APOL1 low-risk group (unadjusted odds ratio, 2.45; 95% confidence interval, 1.62 to 3.69). This association remained significant after adjusting for demographic factors, baseline eGFR, urine protein-to-creatinine ratio, treatment assignment, and follow-up time (adjusted odds ratio, 1.59; 95% confidence interval, 1.00 to 2.52).

CONCLUSIONS

Among patients with CKD attributed to hypertension, those with the APOL1 high-risk genotype were more likely to experience a steady decline trajectory in eGFR than those without the APOL1 high-risk genotype. These findings suggest a persistent underlying pathophysiologic process in those patients with the APOL1 high-risk genotype.

Induction Immunosuppression and Clinical Outcomes in Kidney Transplant Recipients Infected With Human Immunodeficiency Virus

There is an increased risk of acute rejection (AR) in human immunodeficiency virus-positive (HIV+) kidney transplant (KT) recipients. Induction immunosuppression is standard of care for those at high risk of AR; however, use in HIV+ patients is controversial, given fears of increased infection rates. We sought to compare clinical outcomes between HIV+ KT recipients who were treated with (i) anti-thymocyte globulin (ATG), (ii) IL-2 receptor blocker, and (iii) no induction. We studied 830 HIV+ KT recipients between 2000 and 2014, as captured in the Scientific Registry of Transplant Recipients, and compared rates of delayed graft function (DGF), AR, graft loss and death. Infections and hospitalizations were ascertained by International Classification of Diseases, Ninth Revision codes in a subset of 308 patients with Medicare. Compared with no induction, neither induction agent was associated with an increased risk of infection (weighted hazard ratio [wHR] 0.80, 95% confidence interval [CI] 0.55-1.18). HIV+ recipients who received induction spent fewer days in the hospital (weighted relative risk [wRR] 0.70, 95% CI 0.52-0.95), had lower rates of DGF (wRR 0.66, 95% CI 0.51-0.84), less graft loss (wHR 0.47, 95% CI 0.24-0.89) and a trend toward lower mortality (wHR 0.60, 95% CI 0.24-1.28). Those who received induction with ATG had lower rates of AR (wRR 0.59, 95% CI 0.35-0.99). Induction in HIV+ KT recipients was not associated with increased infections; in fact, those receiving ATG, the most potent agent, had the lowest rates. In light of the high risk of AR in this population, induction therapy should be strongly considered.

Past Decline Versus Current eGFR and Subsequent Mortality Risk

A single determination of eGFR associates with subsequent mortality risk. Prior decline in eGFR indicates loss of kidney function, but the relationship to mortality risk is uncertain. We conducted an individual-level meta-analysis of the risk of mortality associated with antecedent eGFR slope, adjusting for established risk factors, including last eGFR, among 1.2 million subjects from 12 CKD and 22 other cohorts within the CKD Prognosis Consortium. Over a 3-year antecedent period, 12% of participants in the CKD cohorts and 11% in the other cohorts had an eGFR slope <-5 ml/min per 1.73 m(2) per year, whereas 7% and 4% had a slope >5 ml/min per 1.73 m(2) per year, respectively. Compared with a slope of 0 ml/min per 1.73 m(2) per year, a slope of -6 ml/min per 1.73 m(2) per year associated with adjusted hazard ratios for all-cause mortality of 1.25 (95% confidence interval [95% CI], 1.09 to 1.44) among CKD cohorts and 1.15 (95% CI, 1.01 to 1.31) among other cohorts during a follow-up of 3.2 years. A slope of +6 ml/min per 1.73 m(2) per year also associated with higher all-cause mortality risk, with adjusted hazard ratios of 1.58 (95% CI, 1.29 to 1.95) among CKD cohorts and 1.43 (95% CI, 1.11 to 1.84) among other cohorts. Results were similar for cardiovascular and noncardiovascular causes of death and stronger for longer antecedent periods (3 versus <3 years). We conclude that prior decline or rise in eGFR associates with an increased risk of mortality, independent of current eGFR.

Carotid Intima-Media Thickness and Incident ESRD: The Atherosclerosis Risk in Communities (ARIC) Study

BACKGROUND AND OBJECTIVES

Carotid intima-media thickness has been reported to predict kidney function decline. However, whether carotid intima-media thickness is associated with a hard kidney end point, ESRD, has not been investigated.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We studied 13,197 Atherosclerosis Risk in Communities participants at visit 1 (1987-1989) without history of cardiovascular disease, including coronary heart disease, stroke, and heart failure, at baseline and assessed whether carotid intima-media thickness measured by B-mode ultrasound is associated with ESRD risk using Cox proportional hazards models. Regarding carotid intima-media thickness parameters, we investigated the mean and maximum values of overall and segment-specific (common, bifurcation, and internal carotid arteries) measurements.

RESULTS

Mean age was 54.0 (SD=5.7) years old, and there were 3373 (25.6%) blacks and 7370 (55.8%) women. During a median follow-up of 22.7 years, 433 participants developed ESRD (1.4/1000 person-years). After adjusting for shared risk factors for atherosclerosis and kidney disease, including baseline kidney function, carotid intima-media thickness was significantly associated with ESRD risk (hazard ratio [HR] between quartiles 4 and 1, 1.46; 95% confidence interval [95% CI], 1.02 to 2.08 for overall mean intima-media thickness and HR between quartiles 4 and 1, 1.75; 95% CI, 1.24 to 2.48 for overall maximum intima-media thickness). The associations were largely consistent in demographic and clinical subgroups. When we explored segment-specific intima-media thicknesses, the associations with ESRD were most robust for bifurcation carotid (e.g., adjusted HR between quartiles 4 and 1 of mean intima-media thickness, 1.49; 95% CI, 1.04 to 2.13 for bifurcation; adjusted HR between quartiles 4 and 1 of mean intima-media thickness, 1.36; 95% CI, 0.94 to 1.97 for common; and adjusted HR between quartiles 4 and 1 of mean intima-media thickness, 0.93; 95% CI, 0.67 to 1.29 for internal).

CONCLUSIONS

Carotid intima-media thickness was independently associated with incident ESRD in the general population, suggesting the shared etiology of atherosclerosis and ESRD.

Acute Kidney Injury After Major Surgery: A Retrospective Analysis of Veterans Health Administration Data

BACKGROUND

Few trials of acute kidney injury (AKI) prevention after surgery have been conducted, and most observational studies focus on AKI following cardiac surgery. The frequency of, risk factors for, and outcomes after AKI following other types of major surgery have not been well characterized and may present additional opportunities for trials in AKI.

STUDY DESIGN

Observational cohort study.

SETTING & PARTICIPANTS

3.6 million US veterans followed up from 2004 to 2011 for the receipt of major surgery (cardiac; general; ear, nose, and throat; thoracic; vascular; urologic; and orthopedic) and postoperative outcomes.

FACTORS

Demographics, health characteristics, and type of surgery.

OUTCOMES

Postoperative AKI defined by the KDIGO creatinine criteria, postoperative length of stay, end-stage renal disease, and mortality.

RESULTS

Postoperative AKI occurred in 11.8% of the 161,185 major surgery hospitalizations (stage 1, 76%; stage 2, 15%, stage 3 [without dialysis], 7%; and AKI requiring dialysis, 2%). Cardiac surgery had the highest postoperative AKI risk (relative risk [RR], 1.22; 95% CI, 1.17-1.27), followed by general (reference), thoracic (RR, 0.92; 95% CI, 0.87-0.98), orthopedic (RR, 0.70; 95% CI, 0.67-0.73), vascular (RR, 0.68; 95% CI, 0.64-0.71), urologic (RR, 0.65; 95% CI, 0.61-0.69), and ear, nose, and throat (RR, 0.32; 95% CI, 0.28-0.37) surgery. Risk factors for postoperative AKI included older age, African American race, hypertension, diabetes mellitus, and, for estimated glomerular filtration rate < 90mL/min/1.73m(2), lower estimated glomerular filtration rate. Participants with postoperative AKI had longer lengths of stay (15.8 vs 8.6 days) and higher rates of 30-day hospital readmission (21% vs 13%), 1-year end-stage renal disease (0.94% vs 0.05%), and mortality (19% vs 8%), with similar associations by type of surgery and more severe stage of AKI relating to poorer outcomes.

LIMITATIONS

Urine output was not available to classify AKI; cohort included mostly men.

CONCLUSIONS

AKI was common after major surgery, with similar risk factor and outcome associations across surgery type. These results can inform the design of clinical trials in postoperative AKI to the noncardiac surgery setting.

Iterative Outlier Removal: A Method for Identifying Outliers in Laboratory Recalibration Studies

BACKGROUND

Extreme values that arise for any reason, including those through nonlaboratory measurement procedure-related processes (inadequate mixing, evaporation, mislabeling), lead to outliers and inflate errors in recalibration studies. We present an approach termed iterative outlier removal (IOR) for identifying such outliers.

METHODS

We previously identified substantial laboratory drift in uric acid measurements in the Atherosclerosis Risk in Communities (ARIC) Study over time. Serum uric acid was originally measured in 1990-1992 on a Coulter DACOS instrument using an uricase-based measurement procedure. To recalibrate previous measured concentrations to a newer enzymatic colorimetric measurement procedure, uric acid was remeasured in 200 participants from stored plasma in 2011-2013 on a Beckman Olympus 480 autoanalyzer. To conduct IOR, we excluded data points >3 SDs from the mean difference. We continued this process using the resulting data until no outliers remained.

RESULTS

IOR detected more outliers and yielded greater precision in simulation. The original mean difference (SD) in uric acid was 1.25 (0.62) mg/dL. After 4 iterations, 9 outliers were excluded, and the mean difference (SD) was 1.23 (0.45) mg/dL. Conducting only one round of outlier removal (standard approach) would have excluded 4 outliers [mean difference (SD) = 1.22 (0.51) mg/dL]. Applying the recalibration (derived from Deming regression) from each approach to the original measurements, the prevalence of hyperuricemia (>7 mg/dL) was 28.5% before IOR and 8.5% after IOR.

CONCLUSIONS

IOR is a useful method for removal of extreme outliers irrelevant to recalibrating laboratory measurements, and identifies more extraneous outliers than the standard approach.

Bariatric surgery is associated with improvement in kidney outcomes

Severe obesity is associated with increased risk of kidney disease. Whether bariatric surgery reduces the risk of adverse kidney outcomes is uncertain. To resolve this we compared the risk of estimated glomerular filtration rate (eGFR) decline of ≥30% and doubling of serum creatinine or end-stage renal disease (ESRD) in 985 patients who underwent bariatric surgery with 985 patients who did not undergo such surgery. Patients were matched on demographics, baseline body mass index, eGFR, comorbidities, and previous nutrition clinic use. Mean age was 45 years, 97% were white, 80% were female, and 33% had baseline eGFR <90 ml/min per 1.73 m(2). Mean 1-year weight loss was 40.4 kg in the surgery group compared with 1.4 kg in the matched cohort. Over a median follow-up of 4.4 years, 85 surgery patients had an eGFR decline of ≥30% (22 had doubling of serum creatinine/ESRD). Over a median follow-up of 3.8 years, 177 patients in the matched cohort had an eGFR decline of ≥30% (50 had doubling of serum creatinine/ESRD). In adjusted analysis, bariatric surgery patients had a significant 58% lower risk for an eGFR decline of ≥30% (hazard ratio 0.42, 95% confidence interval 0.32-0.55) and 57% lower risk of doubling of serum creatinine or ESRD (hazard ratio 0.43, 95% confidence interval: 0.26-0.71) compared with the matched cohort. Results were generally consistent among subgroups of patients with and without eGFR <90 ml/min per 1.73 m(2), hypertension, and diabetes. Thus, bariatric surgery may be an option to prevent kidney function decline in severely obese individuals.

Antihypertensive Medications and the Prevalence of Hyperkalemia in a Large Health System

Little is known about the frequency and patterns of hyperkalemia in clinical settings. We evaluated the association between baseline antihypertensive medications that may affect potassium levels (angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, β-blockers, loop/thiazide diuretics, and potassium-sparing diuretics) and hyperkalemia, defined by potassium >5 mEq/L and >5.5 mEq/L, over a 3-year time period in 194 456 outpatients in the Geisinger Health System, as well as actions taken after an episode of hyperkalemia. The proportions of patients with 0, <2, 2 to 4, and ≥4 potassium measurements per year were 20%, 58%, 16%, and 6%. Potassium levels >5 mEq/L and >5.5 mEq/L occurred in 10.8% and 2.3% of all patients over the 3-year period; among patients with ≥4 measurements per year, corresponding values were 39.4% and 14.6%. Most cases of hyperkalemia occurred only once during follow-up. The antihypertensive medication class most strongly associated with hyperkalemia was angiotensin-converting enzyme inhibitors. Among patients with a measurement of potassium >5.5 mEq/L, only 24% were seen by a nephrologist and 5.2% were seen by a dietician during the 3-year period. Short-term actions after a potassium measurement >5.5 mEq/L included emergency room visit (3.1% within 7 days), remeasurement of potassium (44.3% with 14 days), and change in a potassium-altering medication (26.4% within 60 days). The most common medication changes were discontinuation/dose reduction of an angiotensin-converting enzyme inhibitor/angiotensin receptor blocker or potassium-sparing diuretic, which occurred in 29.1% and 49.6% of people taking these medications, respectively. In conclusion, hyperkalemia is common. Future research may enable optimal renin-angiotensin-aldosterone system inhibitor use with improved management of hyperkalemia.

Relationship of the American Heart Association's Impact Goals (Life's Simple 7) With Risk of Chronic Kidney Disease: Results From the Atherosclerosis Risk in Communities (ARIC) Cohort Study

BACKGROUND

As part of its 2020 Impact Goals, the American Heart Association developed the Life's Simple 7 metric for cardiovascular health promotion. The relationship between the Life's Simple 7 metric and incident chronic kidney disease (CKD) is unknown.

METHODS AND RESULTS

We estimated the association between Life's Simple 7 and incident CKD in 14 832 Atherosclerosis Risk in Communities study participants. Ideal levels of Life's Simple 7 health factors were the following: nonsmoker or quit >1 year ago; body mass index <25 kg/m(2); ≥150 minutes/week of physical activity; healthy dietary pattern (high in fruits and vegetables, fish, and fiber-rich whole grains; low in sodium and sugar-sweetened beverages); total cholesterol <200 mg/dL; blood pressure <120/80 mm Hg; and fasting blood glucose <100 mg/dL. At baseline, mean age was 54 years, 55% were women, and 26% were African American. There were 2743 incident CKD cases over a median follow-up of 22 years. Smoking, body mass index, physical activity, blood pressure, and blood glucose were associated with CKD risk (all P<0.01), but diet and blood cholesterol were not. CKD risk was inversely related to the number of ideal health factors (P-trend<0.001). A model containing the Life's Simple 7 health factors was more predictive of CKD risk than the base model including only age, sex, race, and estimated glomerular filtration rate (Life's Simple 7 health factors area under the ROC curve: 0.73, 95% CI: 0.72, 0.74 versus base model area under the ROC curve: 0.68, 95% CI: 0.67, 0.69; P<0.001).

CONCLUSIONS

The AHA's Life's Simple 7 metric, developed to measure and promote cardiovascular health, predicts a lower risk of CKD.

Racial Differences in and Prognostic Value of Biomarkers of Hyperglycemia

OBJECTIVE

We compared levels and associations of traditional (fasting glucose, HbA1c) and nontraditional (fructosamine, glycated albumin, and 1,5-anhydroglucitol [1,5-AG]) biomarkers of hyperglycemia with incident cardiovascular disease (CVD), incident end-stage renal disease (ESRD), and prevalent retinopathy in black and white adults.

RESEARCH DESIGN AND METHODS

We included 10,373 participants without (8,096 white, 2,277 black) and 727 with diagnosed diabetes (425 white, 302 black) from the Atherosclerosis Risk in Communities (ARIC) Study. We used Cox proportional hazards models to compare hazards ratios of CVD and ESRD among blacks and whites from baseline (1990-1992) through 2012. We compared the odds ratios (from logistic regression) of retinopathy among blacks and whites. We tested for the interaction of each biomarker with race.

RESULTS

Median values of biomarkers were higher among blacks versus whites (all P < 0.001). Relative risks for each biomarker with incident CVD and ESRD, and odds ratios for each biomarker with prevalent retinopathy, were similar by race (all P values for interaction by race >0.10).

CONCLUSIONS

The prognostic value of HbA1c, fructosamine, glycated albumin, and 1,5-AG with incident CVD, incident ESRD, and prevalent retinopathy were similar by race. Our results support similar interpretation of HbA1c and nontraditional biomarkers of hyperglycemia among black and whites with respect to long-term complications.

Associations Between the Serum Metabolome and All-Cause Mortality Among African Americans in the Atherosclerosis Risk in Communities (ARIC) Study

Early and accurate identification of people at high risk of premature death may assist in the targeting of preventive therapies in order to improve overall health. To identify novel biomarkers for all-cause mortality, we performed untargeted metabolomics in the Atherosclerosis Risk in Communities (ARIC) Study. We included 1,887 eligible ARIC African Americans, and 671 deaths occurred during a median follow-up period of 22.5 years (1987-2011). Chromatography and mass spectroscopy identified and quantitated 204 serum metabolites, and Cox proportional hazards models were used to analyze the longitudinal associations with all-cause and cardiovascular mortality. Nine metabolites, including cotinine, mannose, glycocholate, pregnendiol disulfate, α-hydroxyisovalerate, N-acetylalanine, andro-steroid monosulfate 2, uridine, and γ-glutamyl-leucine, showed independent associations with all-cause mortality, with an average risk change of 18% per standard-deviation increase in metabolite level (P < 1.23 × 10(-4)). A metabolite risk score, created on the basis of the weighted levels of the identified metabolites, improved the predictive ability of all-cause mortality over traditional risk factors (bias-corrected Harrell's C statistic 0.752 vs. 0.730). Mannose and glycocholate were associated with cardiovascular mortality (P < 1.23 × 10(-4)), but predictive ability was not improved beyond the traditional risk factors. This metabolomic analysis revealed potential novel biomarkers for all-cause mortality beyond the traditional risk factors.