Diversity of plant DNA in stool is linked to dietary quality, age, and household income.

Eating a varied diet is a central tenet of good nutrition. Here, we develop a molecular tool to quantify human dietary plant diversity by applying DNA metabarcoding with the chloroplast trnL-P6 marker to 1,029 fecal samples from 324 participants across two interventional feeding studies and three observational cohorts. The number of plant taxa per sample (plant metabarcoding richness or pMR) correlated with recorded intakes in interventional diets and with indices calculated from a food frequency questionnaire in typical diets (ρ = 0.40 to 0.63). In adolescents unable to collect validated dietary survey data, trnL metabarcoding detected 111 plant taxa, with 86 consumed by more than one individual and four (wheat, chocolate, corn, and potato family) consumed by >70% of individuals. Adolescent pMR was associated with age and household income, replicating prior epidemiologic findings. Overall, trnL metabarcoding promises an objective and accurate measure of the number and types of plants consumed that is applicable to diverse human populations.

Role of Age and Competing Risk of Death in the Racial Disparity of Kidney Failure Incidence after Onset of CKD.

SIGNIFICANCE STATEMENT: Black adults in the United States have 2-4 times higher incidence of kidney failure than White adults. Yet, the reasons underlying this disparity remain poorly understood. Among 547,188 US veterans with new-onset CKD, according to a new race-free GFR equation, Black veterans had a 2.5-fold higher cumulative incidence of kidney failure, compared with White veterans, in any follow-up period from CKD onset. This disparity resulted from a combination of higher hazards of progression to kidney failure and lower hazards of competing-risk death in Black veterans. Both, in turn, were largely explained by the younger age at CKD onset in Black veterans, underscoring an urgent need to prevent early onset and slow progression of CKD in younger Black adults. BACKGROUND: The Black adult population is well known to have higher incidence of kidney failure than their White counterpart in the United States, but the reasons underlying this disparity are unclear. We assessed the racial differences in kidney failure and death from onset of CKD on the basis of the race-free 2021 CKD Epidemiology Collaboration equation and examined the extent to which these differences could be explained by factors at the time of CKD onset. METHODS: We analyzed a national cohort consisting of 547,188 US veterans (103,821 non-Hispanic Black and 443,367 non-Hispanic White), aged 18-85 years, with new-onset CKD between 2005 and 2016 who were followed through 10 years or May 2018 for incident kidney failure with replacement therapy (KFRT) and pre-KFRT death. RESULTS: At CKD onset, Black veterans were, on average, 7.8 years younger than White veterans. In any time period from CKD onset, the cumulative incidence of KFRT was 2.5-fold higher for Black versus White veterans. Meanwhile, Black veterans had persistently >2-fold higher hazards of KFRT throughout follow-up (overall hazard ratio [95% confidence interval], 2.38 [2.31 to 2.45]) and conversely had 17%-48% decreased hazards of pre-KFRT death. These differences were reduced after accounting for the racial difference in age at CKD onset. CONCLUSIONS: The 2.5-fold higher cumulative incidence of kidney failure in Black adults resulted from a combination of higher hazards of progression to kidney failure and lower hazards of the competing risk of death, both of which can be largely explained by the younger age at CKD onset in Black compared with White adults.

Generalized Propensity Score Methods to Assess CKD-Associated Physiologic Factors and Risk of Kidney Failure in the Chronic Renal Insufficiency Cohort (CRIC) Study.

Epidemiologic studies have identified many biochemical risk factors for chronic kidney disease (CKD) progression that are correlates of kidney function, termed here 'CKD-associated physiologic factors'. Uncertainty remains if these factors are risk factors or risk markers accounting for aspects of kidney function not otherwise captured. We aimed to use flexible machine learning, a dynamic covariate history including kidney function informative markers, and generalized propensity score (GPS) weighting, to better control confounding for such exposures. We studied 3,052 adults with CKD in the Chronic Renal Insufficiency Cohort Study. We established a 2-year run-in period and assembled 90 variables that characterize variability and trends of selected CKD-associated physiologic factors and confounders. Using SuperLearner, we created a GPS for each CKD-associated physiologic factor and performed GPS-weighted Cox regressions. For context, we also evaluated results from traditional multivariable Cox proportional hazards models as in prior studies. Similar to traditional approaches, bicarbonate, calcium, potassium, hemoglobin, and PTH were each associated with risk of kidney failure using GPS weighting. The GPS approach detected non-linear associations in many factors, some of which were not detected with traditional models. We conclude that many associations between CKD-associated physiologic factors and kidney outcomes remain strong after GPS weighting.

Comparative Effectiveness of Alternative Treatment Approaches to Secondary Hyperparathyroidism in Patients Receiving Maintenance Hemodialysis: An Observational Trial Emulation.

RATIONALE & OBJECTIVE: Optimal approaches to treat secondary hyperparathyroidism (SHPT) in patients on maintenance hemodialysis (HD) have yet to be established in randomized controlled trials (RCTs). STUDY DESIGN: Two observational clinical trial emulations. SETTING & PARTICIPANTS: Both emulations included adults receiving in-center HD from a national dialysis organization. The patients who had SHPT in the period between 2009 and 2014, were insured for≥180 days by Medicare as primary payer, and did not have contraindications or poor health status limiting theoretical trial participation. EXPOSURE: The parathyroid hormone (PTH) Target Trial emulation included patients with new-onset SHPT (first PTH 300-600pg/mL), with 2 arms defined as up-titration of either vitamin D sterols or cinacalcet within 30 days (lower target) or no up-titration (higher target). The Agent Trial emulation included patients with a PTH≥300 pg/mL while on≥6µg weekly of vitamin D sterol (paricalcitol equivalent dose) and no prior history of cinacalcet. The 2 arms were defined by the first dose or agent change within 30 days (vitamin D-favoring [vitamin-D was up-titrated] vs cinacalcet-favoring [cinacalcet was added] vs nondefined [neither applies]). Multiple trials per patient were allowed in trial 2. OUTCOME: The primary outcome was all-cause death over 24 months; secondary outcomes included cardiovascular (CV) hospitalization or the composite of CV hospitalization or death. ANALYTICAL APPROACH: Pooled logistic regression. RESULTS: There were 1,152 patients in the PTH Target Trial (635 lower target and 517 higher target). There were 2,726 unique patients with 6,727 patient trials in the Agent Trial (6,268 vitamin D-favoring trials and 459 cinacalcet-favoring trials). The lower PTH target approach was associated with reduced adjusted hazard of death (HR, 0.71 [95% CI, 0.52-0.93]), CV hospitalization (HR, 0.78 [95% CI, 0.63-0.98]), and their composite (HR, 0.74 [95% CI, 0.61-0.89]). The cinacalcet-favoring approach demonstrated lower adjusted hazard of death compared to the vitamin D-favoring approach (HR, 0.79 [95% CI, 0.62-0.99]), but not of CV hospitalization or the composite outcome. LIMITATIONS: Potential for residual confounding; low use of cinacalcet with low power. CONCLUSIONS: SHPT management that is focused on lower PTH targets may lower mortality and CV disease in patients receiving HD. These findings should be confirmed in a pragmatic randomized trial. PLAIN-LANGUAGE SUMMARY: Optimal approaches to treat secondary hyperparathyroidism (SHPT) have not been established in randomized controlled trials. Data from a national dialysis organization was used to identify patients with SHPT in whom escalated treatment may be indicated. The approach to treatment was defined based on observed upward titration of SHPT-controlling medications: earlier titration (lower target) versus delayed titration (higher target); and the choice of medication (cinacalcet vs vitamin D sterols). In the first trial emulation, we estimated a 29% lower rate of death and 26% lower rate of cardiovascular disease or death for patients managed with a lower versus higher target approach. Cinacalcet versus vitamin D-favoring approaches were not consistently associated with outcomes in the second trial emulation. This observational study suggests the need for additional clinical trials of SHPT treatment intensity.

Designing an Implementable Clinical Prediction Model for Near-Term Mortality and Long-Term Survival in Patients on Maintenance Hemodialysis.

RATIONALE & OBJECTIVE: The life expectancy of patients treated with maintenance hemodialysis (MHD) is heterogeneous. Knowledge of life-expectancy may focus care decisions on near-term versus long-term goals. The current tools are limited and focus on near-term mortality. Here, we develop and assess potential utility for predicting near-term mortality and long-term survival on MHD. STUDY DESIGN: Predictive modeling study. SETTING & PARTICIPANTS: 42,351 patients contributing 997,381 patient months over 11 years, abstracted from the electronic health record (EHR) system of midsize, nonprofit dialysis providers. NEW PREDICTORS & ESTABLISHED PREDICTORS: Demographics, laboratory results, vital signs, and service utilization data available within dialysis EHR. OUTCOME: For each patient month, we ascertained death within the next 6 months (ie, near-term mortality) and survival over more than 5 years during receipt of MHD or after kidney transplantation (ie, long-term survival). ANALYTICAL APPROACH: We used least absolute shrinkage and selection operator logistic regression and gradient-boosting machines to predict each outcome. We compared these to time-to-event models spanning both time horizons. We explored the performance of decision rules at different cut points. RESULTS: All models achieved an area under the receiver operator characteristic curve of≥0.80 and optimal calibration metrics in the test set. The long-term survival models had significantly better performance than the near-term mortality models. The time-to-event models performed similarly to binary models. Applying different cut points spanning from the 1st to 90th percentile of the predictions, a positive predictive value (PPV) of 54% could be achieved for near-term mortality, but with poor sensitivity of 6%. A PPV of 71% could be achieved for long-term survival with a sensitivity of 67%. LIMITATIONS: The retrospective models would need to be prospectively validated before they could be appropriately used as clinical decision aids. CONCLUSIONS: A model built with readily available clinical variables to support easy implementation can predict clinically important life expectancy thresholds and shows promise as a clinical decision support tool for patients on MHD. Predicting long-term survival has better decision rule performance than predicting near-term mortality. PLAIN-LANGUAGE SUMMARY: Clinical prediction models (CPMs) are not widely used for patients undergoing maintenance hemodialysis (MHD). Although a variety of CPMs have been reported in the literature, many of these were not well-designed to be easily implementable. We consider the performance of an implementable CPM for both near-term mortality and long-term survival for patients undergoing MHD. Both near-term and long-term models have similar predictive performance, but the long-term models have greater clinical utility. We further consider how the differential performance of predicting over different time horizons may be used to impact clinical decision making. Although predictive modeling is not regularly used for MHD patients, such tools may help promote individualized care planning and foster shared decision making.

Association of Coprescribing of Gabapentinoid and Other Psychoactive Medications With Altered Mental Status and Falls in Adults Receiving Dialysis.

RATIONALE & OBJECTIVE: Prescribing psychoactive medications for patients with kidney disease is common, but for patients receiving dialysis, some medications may be inappropriate. We evaluated the association of coprescribing gabapentinoids and other psychoactive potentially inappropriate medications (PPIMs) (e.g., sedatives, opioids) with altered mental status (AMS) and falls, and whether the associations are modified by frailty. STUDY DESIGN: Observational cohort study. SETTING: & Participants: Adults receiving dialysis represented in the United States Renal Data System who had an active gabapentinoid prescription and no other PPIM prescriptions in the prior 6 months. EXPOSURE: PPIM coprescribing, or the presence of overlapping prescriptions of a gabapentinoid and ≥1 additional PPIM. OUTCOMES: Acute care visits for AMS and injurious falls. ANALYTICAL APPROACH: Prentice-Williams-Petersen Gap Time models estimated the association between PPIM coprescribing and each outcome, adjusting for demographics, comorbidities, and frailty (assessed by a validated frailty index (FI)). Each model tested for interaction between PPIM coprescribing and frailty. RESULTS: Overall, PPIM coprescribing was associated with increased hazard of AMS (HR: 1.66 [95% CI 1.44, 1.92]) and falls (HR: 1.55 [95% CI 1.36, 1.77]). Frailty significantly modified the effect of PPIM coprescribing on the hazard of AMS (interaction p=0.01), but not falls. Among individuals with low frailty (FI=0.15), the hazard ratio for AMS with PPIM co-prescribing was 2.14 (95% CI: 1.69, 2.71); while for individuals with severe frailty (FI=0.34), the hazard ratio for AMS with PPIM coprescribing was 1.64 (95% CI: 1.42, 1.89). Individuals with PPIM coprescribing and severe frailty (FI =0.34) had the highest hazard of AMS [HR 4.04 (95% CI: 3.20, 5.10)] and falls [HR 2.77 (95% CI: 2.27, 3.38)] compared to non-frail individuals without PPIM coprescribing. LIMITATIONS: Outcome ascertainment bias; residual confounding. CONCLUSIONS: Compared to gabapentinoid prescriptions alone, PPIM coprescribing was associated with an increased risk of AMS and falls. Clinicians should consider these risks when coprescribing PPIMs to patients receiving dialysis.

Progression of Coronary Artery Calcification and Risk of Clinical Events in CKD: The Chronic Renal Insufficiency Cohort Study.

RATIONALE & OBJECTIVE: Coronary artery calcification (CAC) progresses rapidly in people with chronic kidney disease (CKD) compared with the general population. We studied the association between CAC progression and higher risks of atherosclerotic cardiovascular disease (CVD), congestive heart failure, and all-cause mortality among adults with CKD. STUDY DESIGN: Prospective cohort study. SETTING: & Participants: 1,310 participants in the Chronic Renal Insufficiency Cohort (CRIC) Study who had at least one CAC scan with no prior history of CVD and with observed or imputed data on changes in CAC over time. EXPOSURE: Observed or imputed CAC progression, categorized as incident CAC among participants with zero CAC on the baseline scan, or progressive CAC when the baseline scan demonstrated CAC and there was an increase in CAC ≥50 Agatston units per year. OUTCOMES: Atherosclerotic CVD (myocardial infarction or stroke), congestive heart failure, and all-cause mortality. ANALYTICAL APPROACH: Cause-specific Cox proportional hazards regression, stratified by presence of CAC at baseline. RESULTS: A total of 545 participants without and 765 with prevalent CAC at baseline were included. During a mean 3.3 years between CAC assessments, 177 (32.5%) participants without baseline CAC developed incident CAC while 270 participants (35.3%) with baseline CAC developed a ≥50 Agatston units per year increase in CAC. After multivariable adjustment, incident CAC was associated with 2.42-fold higher rate of atherosclerotic CVD (95% confidence interval [CI]: 1.23-4.79) and 1.82-fold higher rate of all-cause mortality (95% CI: 1.03-3.22). Progressive CAC (≥50 units per year) was not associated with atherosclerotic CVD (hazard ratio [HR]: 1.42; 95% CI: 0.85-2.35) but was associated with a 1.73-fold higher rate of all-cause mortality (95% CI: 1.31-2.28). Progressive CAC was not associated with incident heart failure. LIMITATIONS: Residual confounding and limited statistical power for some outcomes. CONCLUSIONS: Among adults with CKD stages 2-4, CAC progression over a mean 3.3 years was associated with higher risk of atherosclerotic CVD and all-cause mortality. The associations were strongest among participants without CAC at baseline.

Fruit and Vegetable Intake Patterns, Kidney Failure, and Mortality in Adults with and without Chronic Kidney Disease in the United States.

BACKGROUND: Fruits and vegetables (F&Vs) are vital components of healthy diets but may be restricted in chronic kidney disease (CKD) to avoid high-potassium intake. We previously generated F&V patterns for patients in the National Health and Nutrition Examination Survey (NHANES) and demonstrated an increased prevalence of the overall low-intake pattern in patients with CKD. OBJECTIVE: To evaluate the association of F&V patterns (overall low intake, high unprocessed, moderate processed, and high ultraprocessed) with the risk of kidney failure and its composite with death. METHODS: Adults in NHANES III with valid dietary data and longitudinal follow-up for kidney failure and death were included. F&V patterns were identified using 24-h dietary recalls and latent class analysis, yielding 4 patterns. Cox models were used to evaluate the prospective association between each pattern and hazard of kidney failure or a composite of kidney failure or death over ≤20 y. Models were adjusted for demographics and select comorbidities and weighted for the complex survey design. Secondary analyses evaluated serum carotenoids as objective biomarkers of F&V intake. RESULTS: Among 16,726 eligible participants in NHANES III, F&V consumption consistent with the high-ultraprocessed pattern associated with the highest risk of kidney failure after demographic and comorbidity adjustment, but attenuated with adjustment for kidney function. The high unprocessed pattern associated with the lowest adjusted risk of death or kidney failure combined [hazard ratio (HR): 0.73; 95% confidence interval (CI): 0.65, 0.81 relative to overall low intake]. Higher-serum carotenoids were associated with a lower adjusted risk of death or kidney failure combined (HR: 0.57; 95% CI: 0.49, 0.65 for quartile 4 compared with quartile 1). Results were similar in patients with CKD at baseline. CONCLUSIONS: Higher intake of unprocessed F&Vs was associated with better outcomes in the general population and patients with CKD. Results emphasize the need to safely improve F&V intake in CKD.

Longitudinal Pilot Evaluation of the Gut Microbiota Comparing Patients With and Without Chronic Kidney Disease.

OBJECTIVE: The gut microbiota contributes to metabolic diseases, such as diabetes and hypertension, but is poorly characterized in chronic kidney disease (CKD). DESIGN AND METHODS: We enrolled 24 adults within household pairs, in which at least one member had self-reported kidney disease, diabetes, or hypertension. CKD was classified based on estimated glomerular filtration rate < 60 mL/min/1.73 m2 or urine-albumin-to-creatinine ratio of ≥ 30 mg/g. Participants collected stool and dietary recalls seasonally over a year. Gut microbiota was characterized using 16s rRNA and metagenomic sequencing. RESULTS: Ten participants had CKD (42%) with a median (interquartile range) estimated glomerular filtration rate of 49 (44, 54) mL/min/1.73 m2. By 16s rRNA sequencing, there was moderate to high intraclass correlation (ICC = 0.63) for seasonal alpha diversity (Shannon index) within individuals and modest differences by season (P < .01). ICC was lower with metagenomics, which has resolution at the species level (ICC = 0.26). There were no differences in alpha or beta diversity by CKD with either method. Among 79 genera, Frisingicoccus, Tuzzerella, Faecalitalea, and Lachnoclostridium had lower abundance in CKD, while Collinsella, Lachnospiraceae_ND3007, Veillonella, and Erysipelotrichaceae_UCG_003 were more abundant in CKD (each nominal P < .05) using 16s rRNA sequencing. Higher Collinsella and Veillonella and lower Lachnoclostridium in CKD were also identified by metagenomics. By metagenomics, Coprococcus catus and Bacteroides stercoris were more and less abundant in CKD, respectively, at false discovery rate corrected P = .02. CONCLUSIONS: We identified candidate taxa in the gut microbiota associated with CKD. High ICC in individuals with modest seasonal impacts implies that follow-up studies may use less frequent sampling.

Association of Acute Kidney Injury and Cardiovascular Disease Following Percutaneous Coronary Intervention: Assessment of Interactions by Race, Diabetes, and Kidney Function.

RATIONALE & OBJECTIVE: Black patients and those with diabetes or reduced kidney function experience a disproportionate burden of acute kidney injury (AKI) and cardiovascular events. However, whether these factors modify the association between AKI and cardiovascular events after percutaneous coronary intervention (PCI) is unknown and was the focus of this study. STUDY DESIGN: Observational cohort. SETTING & PARTICIPANTS: Patients who underwent PCI at Duke between January 1, 2003, and December 31, 2013, with data available in the Duke Databank for Cardiovascular Disease. EXPOSURE: AKI, defined as ≥1.5-fold relative elevation in serum creatinine within 7 days from a reference value ascertained 30 days before PCI, or a 0.3 mg/dL increase from the reference value within 48 hours. OUTCOME: A composite of all-cause death, myocardial infarction, stroke, or revascularization during the first year after PCI. ANALYTICAL APPROACH: Cox regression models adjusted for potential confounders and with interaction terms between AKI and race, diabetes, or baseline estimated glomerular filtration rate (eGFR). RESULTS: Among 9,422 patients, 9% (n = 865) developed AKI, and the primary composite outcome occurred in 21% (n = 2,017). AKI was associated with a nearly 2-fold higher risk of the primary outcome (adjusted HR, 1.94 [95% CI, 1.71-2.20]). The association between AKI and cardiovascular risk did not significantly differ by race (P interaction, 0.4), diabetes, (P interaction, 0.06), or eGFR (P interaction, 0.2). However, Black race and severely reduced eGFR, but not diabetes, each had a cumulative impact with AKI on risk for the primary outcome. Compared with White patients with no AKI as the reference, the risk for the outcome was highest in Black patients with AKI (HR, 2.27 [95% CI, 1.83-2.82]), followed by White patients with AKI (HR, 1.87 [95% CI, 1.58-2.21]), and was least in patients of other races with AKI (HR, 1.48 [95% CI, 0.88-2.48]). LIMITATIONS: Residual confounding, including the impact of clinical care following PCI on cardiovascular outcomes of AKI. CONCLUSIONS: Neither race, diabetes, nor reduced eGFR potentiated the association of AKI with cardiovascular risk, but Black patients with AKI had a qualitatively greater risk than White patients with AKI or patients of other races with AKI. PLAIN-LANGUAGE SUMMARY: This study examined differences by race, diabetes, or kidney function in the well-known association of AKI with increased risk for cardiovascular outcomes among patients undergoing percutaneous coronary intervention. The authors found that AKI was associated with a greater risk for cardiovascular outcomes, but this risk did not differ by patients' race, diabetes status, or level of kidney function before the procedure. That said, the risk for cardiovascular outcomes was numerically highest among Black patients compared with White patients or those of other races. These study findings suggest that future efforts to prevent AKI among patients undergoing the procedure could reduce racial disparities in risk for unfavorable cardiovascular outcomes afterward.

Patterns of Fruit and Vegetable Intake in Adults With and Without Chronic Kidney Disease in the United States.

OBJECTIVE: To characterize patterns of fruit and vegetable (F&V) intake in US adults with and without chronic kidney disease (CKD). METHODS: We used 24-hour dietary recall data from multiple cycles of the National Health and Nutrition Examination Survey spanning 3 groups from 1988 to 2018 (1988-1994; 2003-2010; 2011-2018). We categorized F&Vs based on food processing and phytochemical content. We assessed patterns of F&Vs using latent class analysis and compared intake patterns across the 3 temporal cohorts and CKD status using weighted multinomial logistic regression. RESULTS: Four similar patterns of F&Vs emerged in each cycle: Overall Low Intake, High Unprocessed, High Ultra-Processed, and Moderate Processed F&Vs. The Overall Low Intake pattern was most prevalent in all cohorts and CKD groups. After adjustment for demographic variables and selected health conditions, participants with compared to without CKD were more likely to be classified as Overall Low Intake in each cohort, although this was not significant in the National Health and Nutrition Examination Survey 2011-2018. CONCLUSIONS: Low consumption of F&Vs was more common in patients with CKD. Longitudinal studies are needed to determine if low intake is a risk factor for, or response to, CKD.

High-Throughput Metabolomics and Diabetic Kidney Disease Progression: Evidence from the Chronic Renal Insufficiency (CRIC) Study.

INTRODUCTION: Metabolomics could offer novel prognostic biomarkers and elucidate mechanisms of diabetic kidney disease (DKD) progression. Via metabolomic analysis of urine samples from 995 CRIC participants with diabetes and state-of-the-art statistical modeling, we aimed to identify metabolites prognostic to DKD progression. METHODS: Urine samples (N = 995) were assayed for relative metabolite abundance by untargeted flow-injection mass spectrometry, and stringent statistical criteria were used to eliminate noisy compounds, resulting in 698 annotated metabolite ions. Utilizing the 698 metabolites' ion abundance along with clinical data (demographics, blood pressure, HbA1c, eGFR, and albuminuria), we developed univariate and multivariate models for the eGFR slope using penalized (lasso) and random forest models. Final models were tested on time-to-ESKD (end-stage kidney disease) via cross-validated C-statistics. We also conducted pathway enrichment analysis and a targeted analysis of a subset of metabolites. RESULTS: Six eGFR slope models selected 9-30 variables. In the adjusted ESKD model with highest C-statistic, valine (or betaine) and 3-(4-methyl-3-pentenyl)thiophene were associated (p < 0.05) with 44% and 65% higher hazard of ESKD per doubling of metabolite abundance, respectively. Also, 13 (of 15) prognostic amino acids, including valine and betaine, were confirmed in the targeted analysis. Enrichment analysis revealed pathways implicated in kidney and cardiometabolic disease. CONCLUSIONS: Using the diverse CRIC sample, a high-throughput untargeted assay, followed by targeted analysis, and rigorous statistical analysis to reduce false discovery, we identified several novel metabolites implicated in DKD progression. If replicated in independent cohorts, our findings could inform risk stratification and treatment strategies for patients with DKD.

Racial Differences in AKI Incidence Following Percutaneous Coronary Intervention.

BACKGROUND: Undergoing percutaneous coronary intervention (PCI) is a risk factor for AKI development, but few studies have quantified racial differences in AKI incidence after this procedure. METHODS: We examined the association of self-reported race (Black, White, or other) and baseline eGFR with AKI incidence among patients who underwent PCI at Duke University Medical Center between January 1, 2003, and December 31, 2013. We defined AKI as a 0.3 mg/dl absolute increase in serum creatinine within 48 hours, or ≥1.5-fold relative elevation within 7 days post-PCI from the reference value ascertained within 30 days before PCI. RESULTS: Of 9422 patients in the analytic cohort (median age 63 years; 33% female; 75% White, 20% Black, 5% other race), 9% developed AKI overall (14% of Black, 8% of White, 10% of others). After adjustment for demographics, socioeconomic status, comorbidities, predisposing medications, PCI indication, periprocedural AKI prophylaxis, and PCI procedural characteristics, Black race was associated with increased odds for incident AKI compared with White race (odds ratio [OR], 1.79; 95% confidence interval [95% CI], 1.48 to 2.15). Compared with Whites, odds for incident AKI were not significantly higher in other patients (OR, 1.30; 95% CI, 0.93 to 1.83). Low baseline eGFR was associated with graded, higher odds of AKI incidence (P value for trend <0.001); however, there was no interaction between race and baseline eGFR on odds for incident AKI (P value for interaction = 0.75). CONCLUSIONS: Black patients had greater odds of developing AKI after PCI compared with White patients. Future investigations should identify factors, including multiple domains of social determinants, that predispose Black individuals to disparate AKI risk after PCI.

Statins and atherosclerotic cardiovascular outcomes in patients on incident dialysis and with atherosclerotic heart disease.

Statins failed to reduce cardiovascular (CV) events in trials of patients on dialysis. However, trial populations used criteria that often excluded those with atherosclerotic heart disease (ASHD), in whom statins have the greatest benefit, and included outcome composites with high rates of nonatherosclerotic CV events that may not be modified by statins. Here, we study whether statin use associates with lower atherosclerotic CV risk among patients with known ASHD on dialysis, including in those likely to receive a kidney transplant, a group excluded within trials but with lower competing mortality risks. METHODS: Using data from the United States Renal Data System including Medicare claims, we identified adults initiating dialysis with ASHD. We matched statin users 1:1 to statin nonusers with propensity scores incorporating hard matches for age and kidney transplant listing status. Using Cox models, we evaluated associations of statin use with the primary composite of fatal/nonfatal myocardial infarction and stroke (including within prespecified subgroups of younger age [<50 years] and waitlisting status); secondary outcomes included all-cause mortality and the composite of all-cause mortality, nonfatal myocardial infarction, or stroke. RESULTS: Of 197,716 patients with ASHD, 47,562 (24%) were consistent statin users from which we created 46,186 matched pairs. Over a median 662 days, statin users had similar risk of fatal/nonfatal myocardial infarction or stroke overall (hazard ratio [HR] 1.00, 95% CI 0.97-1.02), or in subgroups (age< 50 years [HR = 1.05, 95% CI 0.95-1.17]; waitlisted for kidney transplant [HR 0.99, 95% CI 0.97-1.02]). Statin use was modestly associated with lower all-cause mortality (HR 0.96, 95% CI 0.94-0.98; E value = 1.21) and, similarly, a modest lower composite risk of all-cause mortality, nonfatal myocardial infarction, or stroke over the first 2 years (HR 0.90, 95% CI 0.88-0.91) but attenuated thereafter (HR 0.98, 95% CI 0.96-1.01). CONCLUSIONS: Our large observational analyses are consistent with trials in more selected populations and suggest that statins may not meaningfully reduce atherosclerotic CV events even among incident dialysis patients with established ASHD and those likely to receive kidney transplants.

State-of-the-Art Management of Hyperphosphatemia in Patients With CKD: An NKF-KDOQI Controversies Perspective.

Phosphate binders are among the most common medications prescribed to patients with kidney failure receiving dialysis and are often used in advanced chronic kidney disease (CKD). In patients with CKD glomerular filtration rate category 3a (G3a) or worse, including those with kidney failure who are receiving dialysis, clinical practice guidelines suggest "lowering elevated phosphate levels towards the normal range" with possible strategies including dietary phosphate restriction or use of binders. Additionally, guidelines suggest restricting the use of oral elemental calcium often contained in phosphate binders. Nutrition guidelines in CKD suggest<800-1,000mg of calcium daily, whereas CKD bone and mineral disorder guidelines do not provide clear targets, but<1,500mg in maintenance dialysis patients has been previously recommended. Many different classes of phosphate binders are now available and clinical trials have not definitively demonstrated the superiority of any class of phosphate binders over another with regard to clinical outcomes. Use of phosphate binders contributes substantially to patients' pill burden and out-of-pocket costs, and many have side effects. This has led to uncertainty regarding the use and best choice of phosphate binders for patients with CKD or kidney failure. In this controversies perspective, we discuss the evidence base around binder use in CKD and kidney failure with a focus on comparisons of available binders.

Effect of Bicarbonate on Net Acid Excretion, Blood Pressure, and Metabolism in Patients With and Without CKD: The Acid Base Compensation in CKD Study.

RATIONALE & OBJECTIVE: Patients with CKD are at elevated risk of metabolic acidosis due to impaired net acid excretion (NAE). Identifying early markers of acidosis may guide prevention in chronic kidney disease (CKD). This study compared NAE in participants with and without CKD, as well as the NAE, blood pressure (BP), and metabolomic response to bicarbonate supplementation. STUDY DESIGN: Randomized order, cross-over study with controlled feeding. SETTING & PARTICIPANTS: Participants consisted of 8 patients with CKD (estimated glomerular filtration rate 30-59mL/min/1.73m2 or 60-70mL/min/1.73m2 with albuminuria) and 6 patients without CKD. All participants had baseline serum bicarbonate concentrations between 20 and 28 mEq/L; they did not have diabetes mellitus and did not use alkali supplements at baseline. INTERVENTION: Participants were fed a fixed-acid-load diet with bicarbonate supplementation (7 days) and with sodium chloride control (7 days) in a randomized order, cross-over fashion. OUTCOMES: Urine NAE, 24-hour ambulatory BP, and 24-hour urine and plasma metabolomic profiles were measured after each period. RESULTS: During the control period, mean NAE was 28.3±10.2 mEq/d overall without differences across groups (P=0.5). Urine pH, ammonium, and citrate were significantly lower in CKD than in non-CKD (P<0.05 for each). Bicarbonate supplementation reduced NAE and urine ammonium in the CKD group, increased urine pH in both groups (but more in patients with CKD than in those without), and increased; urine citrate in the CKD group (P< 0.2 for interaction for each). Metabolomic analysis revealed several urine organic anions were increased with bicarbonate in CKD, including 3-indoleacetate, citrate/isocitrate, and glutarate. BP was not significantly changed. LIMITATIONS: Small sample size and short feeding duration. CONCLUSIONS: Compared to patients without CKD, those with CKD had lower acid excretion in the form of ammonium but also lower base excretion such as citrate and other organic anions, a potential compensation to preserve acid-base homeostasis. In CKD, acid excretion decreased further, but base excretion (eg, citrate) increased in response to alkali. Urine citrate should be evaluated as an early and responsive marker of impaired acid-base homeostasis. FUNDING: National Institute of Diabetes and Digestive and Kidney Diseases and the Duke O'Brien Center for Kidney Research. TRIAL REGISTRATION: Registered at ClinicalTrials.gov with study number NCT02427594.

Novel Risk Factors for Progression of Diabetic and Nondiabetic CKD: Findings From the Chronic Renal Insufficiency Cohort (CRIC) Study.

RATIONALE & OBJECTIVE: Identification of novel risk factors for chronic kidney disease (CKD) progression may inform mechanistic investigations and improve identification of high-risk subgroups. The current study aimed to characterize CKD progression across levels of numerous risk factors and identify independent risk factors for CKD progression among those with and without diabetes. STUDY DESIGN: The Chronic Renal Insufficiency Cohort (CRIC) Study is a prospective cohort study of adults with CKD conducted at 7 US clinical centers. SETTING & PARTICIPANTS: Participants (N=3,379) had up to 12.3 years of follow-up; 47% had diabetes. PREDICTORS: 30 risk factors for CKD progression across sociodemographic, behavioral, clinical, and biochemical domains at baseline. OUTCOMES: Study outcomes were estimated glomerular filtration rate (eGFR) slope and the composite of halving of eGFR or initiation of kidney replacement therapy. ANALYTICAL APPROACH: Stepwise selection of independent risk factors was performed stratified by diabetes status using linear mixed-effects and Cox proportional hazards models. RESULTS: Among those without and with diabetes, respectively, mean eGFR slope was-1.4±3.3 and-2.7±4.7mL/min/1.73m2 per year. Among participants with diabetes, multivariable-adjusted hazard of the composite outcome was approximately 2-fold or greater with higher levels of the inflammatory chemokine CXCL12, the cardiac marker N-terminal pro-B-type natriuretic peptide (NT-proBNP), and the kidney injury marker urinary neutrophil gelatinase-associated lipocalin (NGAL). Among those without diabetes, low serum bicarbonate and higher high-sensitivity troponin T, NT-proBNP, and urinary NGAL levels were all significantly associated with a 1.5-fold or greater rate of the composite outcome. LIMITATIONS: The observational study design precludes causal inference. CONCLUSIONS: Strong associations for cardiac markers, plasma CXCL12, and urinary NGAL are comparable to that of systolic blood pressure≥140mm Hg, a well-established risk factor for CKD progression. This warrants further investigation into the potential mechanisms that these markers indicate and opportunities to use them to improve risk stratification.

Estimated Glomerular Filtration Rate Variability in Patients With Heart Failure and Chronic Kidney Disease.

BACKGROUND: Greater variability in the estimated glomerular filtration rate (eGFR) is associated with higher mortality in patients with chronic kidney disease (CKD). Heart failure (HF) is common in CKD and may increase variability through changes in hemodynamic and volume regulation. We sought to determine if patients with vs without HF have higher kidney function variability in CKD, and to define the association with mortality. METHODS AND RESULTS: Patients undergoing coronary angiography from 2003 to 2013 with an eGFR of less than 60 mL/min/1.73 m2 were evaluated from the Duke Databank for Cardiovascular Disease. Variability in the eGFR, measured as the coefficient of variation (CV) of residuals from the regression of eGFR vs time, was calculated spanning 3 months to 2 years after catheterization. Mortality was assessed 2 to 7 years after catheterization. Patients were grouped into 3 HF phenotypes: HF with reduced ejection fraction, HF with preserved ejection, and no HF. Regression was used to evaluate associations between HF phenotypes and variability in the eGFR and between variability in the eGFR and mortality rate with stratification by HF phenotype. Among 3767 participants, the median eGFR at baseline was 45 mL/min/1.73 m2 (interquartile range 33-53 mL/min/1.73 m2), and longitudinal measures of eGFR over 21 months had within-patient residual variability (CV) of 14% (9%-20%). In adjusted analyses, variability in the eGFR was greater in those with HF with preserved ejection (n = 695, CV difference 0.98%, 95% confidence interval 0.14%-1.81%) or HF with reduced ejection fraction (n = 800, CV difference 2.51%, 95% confidence interval 1.66%-3.37%) relative to no HF (n = 2272). In 3068 participants eligible for mortality analysis, the presence of HF and greater variability in the eGFR were each associated independently with higher mortality, but there was no evidence of interaction between variability in the eGFR and any HF phenotype (all P for interaction ≥.49). CONCLUSIONS: Variability in the eGFR is greater in patients with HF and associated with mortality. Prediction algorithms and classification schemes should consider not only static, but also dynamic eGFR variability in HF and CKD prognostication.

Urine tricarboxylic acid cycle signatures of early-stage diabetic kidney disease.

INTRODUCTION: Urine tricarboxylic acid (TCA) cycle organic anions (OAs) are elevated in diabetes and may be biomarkers for diabetic kidney disease (DKD) progression. OBJECTIVES: We assessed associations of 10 urine TCA cycle OAs with estimated glomerular filtration rate (eGFR) and eGFR slope. METHODS: This study is ancillary to the Simultaneous Risk Factor Control Using Telehealth to SlOw Progression of Diabetic Kidney Disease (STOP-DKD) Trial-a randomized trial of pharmacist-led medication and behavior management in 281 patients with early to moderate DKD at Duke from 2014 to 2015. We used linear mixed models to assess associations of urine TCA cycle OAs with outcomes and modelled TCA cycle OAs as: (1) the average of z-scores for each OA; and (2) principal component (PC) scores derived by principal component analysis (PCA). Untargeted urine metabolomics were added for additional discovery. RESULTS: Among 132 participants with 24 h urine samples (50% men; 58% Black; mean age 64 years [SD 9]; mean eGFR 74 ml/min/1.73m2 [SD 21] and median urine albumin-to-creatinine [UACR] 20 mg/g [IQR 8-95]), PCA identified 3 OA metabolite PCs. Malate, fumarate, pyruvate, α-ketoglutarate, lactate, succinate and citrate/isocitrate loaded positively on PC1; methylsuccinate, ethylmalonate and succinate loaded positively on PC2; and methylmalonate, ethylmalonate and citrate/isocitrate loaded negatively on PC3. Over a median follow-up of 1.8 years (IQR, 1.2 to 2.2), higher average OA z-score was strongly associated with higher eGFR after covariate adjustment (p = 0.01), but not with eGFR slope (p = 0.9). Higher PC3, but not other PCs, was associated with lower eGFR (p < 0.001). Conditional random forests and smooth clipped absolute deviation models confirmed methylmalonate, citrate/isocitrate, and ethylmalonate, and added lactate as top ranked metabolites in models of baseline eGFR (R-squared 0.32 and 0.33, respectively). Untargeted urine metabolites confirmed association of urine TCA cycle OAs with kidney function. CONCLUSION: Thus, lower urine TCA cycle OAs, most notably lower methylmalonate, ethylmalonate and citrate/isocitrate, are potential indicators of kidney impairment in early stage DKD.

Clinical events and patient-reported outcome measures during CKD progression: findings from the Chronic Renal Insufficiency Cohort Study.

BACKGROUND: Patients with chronic kidney disease (CKD) face risks of not only end-stage kidney disease (ESKD), cardiovascular disease (CVD) and death, but also decline in kidney function, quality of life (QOL) and mental and physical well-being. This study describes the multidimensional trajectories of CKD using clinical events, kidney function and patient-reported outcome measures (PROMs). We hypothesized that more advanced CKD stages would associate with more rapid decline in each outcome. METHODS: Among 3939 participants enrolled in the Chronic Renal Insufficiency Cohort (CRIC) Study, we evaluated multidimensional disease trajectories by G- and A-stages of enrollment estimated glomerular filtration rate (eGFR) and albuminuria, respectively. These trajectories included clinical events (ESKD, CVD, heart failure and death), eGFR decline and PROMs [kidney disease QOL (KDQOL) burden, effects and symptoms questionnaires, as well as the 12-item short form mental and physical component summaries]. We also evaluated a group-based multitrajectory model to group participants on the basis of longitudinal PROMs and compared group assignments by enrollment G- and A-stage. RESULTS: The mean participant age was 58 years, 45% were women, mean baseline eGFR was 44 mL/min/1.73 m2 and median urine albumin:creatinine ratio was 52 mg/g. The incidence of all clinical events was greater and eGFR decline was faster with more advanced G- and A-stages. While baseline KDQOL and physical component measures were lower with more advanced G- and A-stage of CKD, changes in PROMs were inconsistently related to the baseline CKD stage. Groups formed on PROM trajectories were fairly distinct from existing CKD staging (observed agreement 60.6%) and were associated with the risk of ESKD, CVD, heart failure and death. CONCLUSIONS: More advanced baseline CKD stage was associated with a higher risk of clinical events and faster eGFR decline, and was only weakly related to changes in patient-reported metrics over time.