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BackgroundThe growing amount of high dimensional biomolecular data has spawned new statistical and computational models for risk prediction and disease classification. Yet, many of these methods do not yield biologically interpretable models, despite offering high classification accuracy. An exception, the top-scoring pair (TSP) algorithm derives parameter-free, biologically interpretable single pair decision rules that are accurate and robust in disease classification. However, standard TSP methods do not accommodate covariates that could heavily influence feature selection for the top-scoring pair. Herein, we propose a covariate-adjusted TSP method, which uses residuals from a regression of features on the covariates for identifying top scoring pairs. We conduct simulations and a data application to investigate our method, and compare it to existing classifiers, LASSO and random forests.ResultsOur simulations found that features that were highly correlated with clinical variables had high likelihood of being selected as top scoring pairs in the standard TSP setting. However, through residualization, our covariate-adjusted TSP was able to identify new top scoring pairs, that were largely uncorrelated with clinical variables. In the data application, using patients with diabetes (n = 977) selected for metabolomic profiling in the Chronic Renal Insufficiency Cohort (CRIC) study, the standard TSP algorithm identified (valine-betaine, dimethyl-arg) as the top-scoring metabolite pair for classifying diabetic kidney disease (DKD) severity, whereas the covariate-adjusted TSP method identified the pair (pipazethate, octaethylene glycol) as top-scoring. Valine-betaine and dimethyl-arg had, respectively, ≥ 0.4 absolute correlation with urine albumin and serum creatinine, known prognosticators of DKD. Thus without covariate-adjustment the top-scoring pair largely reflected known markers of disease severity, whereas covariate-adjusted TSP uncovered features liberated from confounding, and identified independent prognostic markers of DKD severity. Furthermore, TSP-based methods achieved competitive classification accuracy in DKD to LASSO and random forests, while providing more parsimonious models.ConclusionsWe extended TSP-based methods to account for covariates, via a simple, easy to implement residualizing process. Our covariate-adjusted TSP method identified metabolite features, uncorrelated from clinical covariates, that discriminate DKD severity stage based on the relative ordering between two features, and thus provide insights into future studies on the order reversals in early vs advanced disease states.

Rationale & objectivePlasma kidney injury molecule 1 (KIM-1) is a sensitive marker of proximal tubule injury, but its association with risks of adverse clinical outcomes across a spectrum of kidney diseases is unknown.Study designProspective, observational cohort study.Setting & participants524 individuals enrolled into the Boston Kidney Biopsy Cohort (BKBC) Study undergoing clinically indicated native kidney biopsy with biopsy specimens adjudicated for semiquantitative scores of histopathology by 2 kidney pathologists and 3,800 individuals with common forms of chronic kidney disease (CKD) enrolled into the Chronic Renal Insufficiency Cohort (CRIC) Study.ExposureHistopathologic lesions and clinicopathologic diagnosis in cross-sectional analyses, baseline plasma KIM-1 levels in prospective analyses.OutcomesBaseline plasma KIM-1 levels in cross-sectional analyses, kidney failure (defined as initiation of kidney replacement therapy) and death in prospective analyses.Analytical approachMultivariable-adjusted linear regression models tested associations of plasma KIM-1 levels with histopathologic lesions and clinicopathologic diagnoses. Cox proportional hazards models tested associations of plasma KIM-1 levels with future kidney failure and death.ResultsIn the BKBC Study, higher plasma KIM-1 levels were associated with more severe acute tubular injury, tubulointerstitial inflammation, and more severe mesangial expansion after multivariable adjustment. Participants with diabetic nephropathy, glomerulopathies, and tubulointerstitial disease had significantly higher plasma KIM-1 levels after multivariable adjustment. In the BKBC Study, CKD in 124 participants progressed to kidney failure and 85 participants died during a median follow-up time of 5 years. In the CRIC Study, CKD in 1,153 participants progressed to kidney failure and 1,356 participants died during a median follow-up time of 11.5 years. In both cohorts, each doubling of plasma KIM-1 level was associated with an increased risk of kidney failure after multivariable adjustment (hazard ratios of 1.19 [95% CI, 1.03-1.38] and 1.10 [95% CI, 1.06-1.15] for BKBC and CRIC, respectively). There was no statistically significant association of plasma KIM-1 levels with death in either cohort.LimitationsGeneralizability and unmeasured confounding.ConclusionsPlasma KIM-1 is associated with underlying tubulointerstitial and mesangial lesions and progression to kidney failure in 2 cohort studies of individuals with kidney diseases.

BackgroundMechanisms by which AKI leads to CKD progression remain unclear. Several urine biomarkers have been identified as independent predictors of progressive CKD. It is unknown whether AKI may result in long-term changes in these urine biomarkers, which may mediate the effect of AKI on CKD progression.MethodsWe selected 198 episodes of hospitalized AKI (defined as peak/nadir inpatient serum creatinine values ≥ 1.5) among adult participants in the Chronic Renal Insufficiency Cohort (CRIC) Study. We matched the best non-AKI hospitalization (unique patients) for each AKI hospitalization using pre-hospitalization characteristics including eGFR and urine protein/creatinine ratio. Biomarkers were measured in banked urine samples collected at annual CRIC study visits.ResultsUrine biomarker measurements occurred a median of 7 months before and 5 months after hospitalization. There were no significant differences in the change in urine biomarker-to-creatinine ratio between the AKI and non-AKI groups: KIM-1/Cr + 9% vs + 7%, MCP-1/Cr + 4% vs + 1%, YKL-40/Cr + 7% vs -20%, EGF/Cr -11% vs -8%, UMOD/Cr -2% vs -7% and albumin/Cr + 17% vs + 13% (all p > 0.05).ConclusionIn this cohort of adults with CKD, AKI did not associate with long-term changes in urine biomarkers.

Rationale & objectiveRecent studies suggest that periodontal disease may be associated with incident chronic kidney disease (CKD). However, studies have focused on older populations, and US Hispanics/Latinos were not well represented.Study designObservational cohort.Setting & participantsWe analyzed data from the Hispanic Community Health Study/Study of Latinos who completed a baseline visit with a periodontal examination and a follow-up visit, and did not have CKD at baseline.PredictorsPredictors included ≥30% of sites with clinical attachment loss ≥3 mm, ≥30% of sites with probing depth ≥4 mm, percentage of sites with bleeding on probing, and absence of functional dentition (

BackgroundStudies in the general population suggest that atrial fibrillation (AF) is an independent risk factor for decline in cognitive function, but this relationship has not been examined in adults with chronic kidney disease (CKD). We investigated the association between incident AF and changes in cognitive function over time in this population.Methods and resultsWe studied a subgroup of 3254 adults participating in the Chronic Renal Insufficiency Cohort Study. Incident AF was ascertained by 12-lead electrocardiogram (ECG) obtained at a study visit and/or identification of a hospitalization with AF during follow-up. Cognitive function was assessed biennially using the Modified Mini-Mental State Exam. Linear mixed effects regression was used to evaluate the association between incident AF and longitudinal change in cognitive function. Compared with individuals without incident AF (n = 3158), those with incident AF (n = 96) were older, had a higher prevalence of cardiovascular disease and hypertension, and lower estimated glomerular filtration rate. After median follow-up of 6.8 years, we observed no significant multivariable association between incident AF and change in cognitive function test score.ConclusionIn this cohort of adults with CKD, incident AF was not associated with a decline in cognitive function.

Rationale & objectiveAmong individuals with chronic kidney disease (CKD), poor self-reported health is associated with adverse outcomes including hospitalization and death. We sought to examine the association between health-related quality-of-life (HRQoL) and depressive symptoms in advanced CKD and subsequent access to the kidney transplant waiting list.Study designProspective cohort study.Setting & population1,676 Chronic Renal Insufficiency Cohort (CRIC) study participants with estimated glomerular filtration rates ≤ 30 mL/min/1.73 m2 at study entry or during follow-up.ExposuresHRQoL ascertained by 5 scales of the Kidney Disease Quality of Life-36 Survey (Physical Component Summary [PCS], Mental Component Summary, Symptoms, Burdens, and Effects), with higher scores indicating better HRQoL, and depressive symptoms ascertained using the Beck Depression Inventory.OutcomesTime to kidney transplant wait-listing and time to pre-emptive wait-listing.Analytic approachTime-to-event analysis using Cox proportional hazards regression.ResultsDuring a median follow-up of 5.1 years, 652 (39%) participants were wait-listed, of whom 304 were preemptively wait-listed. Adjusted for demographics, comorbid conditions, estimated glomerular filtration rate slope, and cognitive function, participants with the highest scores on the Burden and Effects scales, respectively, had lower rates of wait-listing than those with the lowest scores on the Burden (wait-listing adjusted hazard ratio [aHR], 0.70; 95% CI, 0.57-0.85; P

Rationale & objectivesFew studies have investigated racial disparities in survival among dialysis patients in a manner that considers risk factors and mortality during the phase of kidney disease before maintenance dialysis. Our objective was to explore racial variations in survival among dialysis patients and relate them to racial differences in comorbid conditions and rates of death in the setting of kidney disease not yet requiring dialysis therapy.Study designRetrospective cohort study.Settings & participants3,288 black and white participants in the Chronic Renal Insufficiency Cohort (CRIC), none of whom were receiving dialysis at enrollment.ExposureRace.OutcomeMortality.Analytic approachCox proportional hazards regression was used to examine the association between race and mortality starting at: (1) time of dialysis initiation and (2) entry into the CRIC.ResultsDuring 7.1 years of median follow-up, 678 CRIC participants started dialysis. Starting from the time of dialysis initiation, blacks had lower risk for death (unadjusted HR, 0.67; 95% CI, 0.51-0.87) compared with whites. Starting from baseline CRIC enrollment, the strength of the association between some risk factors and dialysis was notably stronger for whites than blacks. For example, the HR for dialysis onset in the presence (vs absence) of heart failure at CRIC enrollment was 1.30 (95% CI, 1.01-1.68) for blacks versus 2.78 (95% CI, 1.90-4.50) for whites, suggesting differential severity of these risk factors by race. When we included deaths occurring both before and after dialysis, risk for death was higher among blacks (vs whites) starting from CRIC enrollment (HR, 1.41; 95% CI, 1.22-1.64), but this finding was attenuated in adjusted models (HR, 1.08; 95% CI, 0.91-1.28).LimitationsResidual confounding.ConclusionsThe apparent survival advantage among blacks over whites treated with dialysis may be attributed to selected transition of a subset of whites with more severe comorbid conditions onto dialysis.

BackgroundFew studies have investigated the changes in weight that may occur over time among adults with the progression of chronic kidney disease (CKD). Whether such weight changes are independently associated with death after the onset of end-stage renal disease has also not been rigorously examined.Study designProspective cohort study.Setting & participantsWe studied 3,933 participants of the Chronic Renal Insufficiency Cohort (CRIC) Study, a longitudinal cohort of patients with CKD. We also performed similar analyses among 1,067 participants of the African American Study of Kidney Disease and Hypertension (AASK).PredictorsEstimated glomerular filtration rate (eGFR) and weight change during CKD.OutcomeWeight and all-cause mortality after dialysis therapy initiation.ResultsDuring a median follow-up of 5.7 years in CRIC, weight change was not linear. Weight was stable until cystatin C-based eGFR (eGFRcys) decreased to 5% annualized weight loss after eGFR decreased to

BACKGROUND AND AIMS:Coronary artery calcification (CAC) is common among patients with chronic kidney disease (CKD) and predicts the risk for cardiovascular disease (CVD). We examined the associations of novel risk factors with CAC progression among patients with CKD. METHODS:Among 1123 CKD patients in the Chronic Renal Insufficiency Cohort (CRIC) Study, CAC was measured in Agatston units at baseline and a follow-up visit using electron beam computed tomography or multidetector computed tomography. RESULTS:Over an average 3.3-year follow-up, 109 (25.1%) participants without CAC at baseline had incident CAC and 124 (18.0%) participants with CAC at baseline had CAC progression, defined as an annual increase of ≥100 Agatston units. After adjustment for established atherosclerotic risk factors, several novel risk factors were associated with changes in CAC over follow-up. Changes in square root transformed CAC score associated with 1 SD greater level of risk factors were -0.20 (95% confidence interval, -0.31 to -0.10; p < 0.001) for estimated glomerular filtration rate, 0.14 (0.02-0.25; p = 0.02) for 24-h urine albumin, 0.25 (0.15-0.34; p < 0.001) for cystatin C, -0.17 (-0.27 to -0.07; p < 0.001) for serum calcium, 0.14 (0.03-0.24; p = 0.009) for serum phosphate, 0.24 (0.14-0.33; p < 0.001) for fibroblast growth factor-23, 0.13 (0.04-0.23; p = 0.007) for total parathyroid hormone, 0.17 (0.07-0.27; p < 0.001) for interleukin-6, and 0.12 (0.02-0.22; p = 0.02) for tumor necrosis factor-α. CONCLUSIONS:Reduced kidney function, calcium and phosphate metabolism disorders, and inflammation, independent of established CVD risk factors, may progress CAC among CKD patients.

BackgroundChronic kidney disease (CKD) is associated with increased risk of cardiovascular disease (CVD) and it is especially common among Blacks. Left ventricular hypertrophy (LVH) is an important subclinical marker of CVD, but there are limited data on racial variation in left ventricular structure and function among persons with CKD.MethodsIn a cross-sectional analysis of the Chronic Renal Insufficiency Cohort Study, we compared the prevalence of different types of left ventricular remodeling (concentric hypertrophy, eccentric hypertrophy, and concentric remodeling) by race/ethnicity. We used multinomial logistic regression to test whether race/ethnicity associated with different types of left ventricular remodeling independently of potential confounding factors.ResultsWe identified 1,164 non-Hispanic Black and 1,155 non-Hispanic White participants who completed Year 1 visits with echocardiograms that had sufficient data to categorize left ventricular geometry type. Compared to non-Hispanic Whites, non-Hispanic Blacks had higher mean left ventricular mass index (54.7 ± 14.6 vs. 47.4 ± 12.2 g/m2.7; P < 0.0001) and prevalence of concentric LVH (45.8% vs. 24.9%). In addition to higher systolic blood pressure and treatment with >3 antihypertensive medications, Black race/ethnicity was independently associated with higher odds of concentric LVH compared to White race/ethnicity (odds ratio: 2.73; 95% confidence interval: 2.02, 3.69).ConclusionIn a large, diverse cohort with CKD, we found significant differences in left ventricular mass and hypertrophic morphology between non-Hispanic Blacks and Whites. Future studies will evaluate whether higher prevalence of LVH contribute to racial/ethnic disparities in cardiovascular outcomes among CKD patients.

BackgroundPredialysis nephrology care for adults with late stage chronic kidney disease (CKD) is associated with improved outcomes. Less is known about the effects of nephrology care in earlier stages of CKD.ObjectiveWe aimed to evaluate the effect of nephrology care on management of CKD risk factors and complications, CKD progression, incident cardiovascular disease (CVD), and death.DesignThis was a prospective cohort study.ParticipantsParticipants included 3855 men and women aged 21 to 74 years enrolled in the Chronic Renal Insufficiency Cohort (CRIC) Study with a mean (SD) estimated glomerular filtration rate (eGFR) at entry of 45 (17) ml/min/1.73 m(2), followed for a median of 6.6 years.Main measuresThe main predictor was self-reported prior contact with a nephrologist at study enrollment. Outcomes evaluated included CKD progression (≥ 50 % eGFR loss or end-stage renal disease), incident CVD, and death.ResultsTwo-thirds (67 %) of the participants reported prior contact with a nephrologist at study enrollment. They were younger, more likely to be male, non-Hispanic white, and had lower eGFR and higher urine protein (p < 0.05). A subgroup with eGFR 30- < 60 ml/min/1.73 m(2) and prior contact with a nephrologist were more likely to receive pharmacologic treatment for CKD-related complications and to report angiotensin-converting enzyme inhibitor or angiotensin receptor blocker (ACEi/ARB) use. After propensity score matching (for reporting prior contact with a nephrologist vs. not) and adjusting for demographic and clinical variables, prior contact with a nephrologist was not significantly associated with CKD progression, incident CVD or death (p > 0.05).ConclusionsOne-third of CRIC participants had not seen a nephrologist before enrollment, and this prior contact was subject to age, sex, and ethnic-related disparities. While prior nephrology care was associated with more frequent treatment of CKD complications and use of ACEi/ARB medications, there was neither an association between this care and achievement of guideline-recommended intermediate measures, nor long-term adverse outcomes.

BackgroundPrevious studies have not shown a consistent link between body mass index (BMI) and outcomes such as mortality and kidney disease progression in non-dialysis-dependent chronic kidney disease (CKD) patients. Therefore, we aimed to complete a systematic review and meta-analysis study on this subject.MethodsWe searched MEDLINE, EMBASE, Web of Science, Cumulative Index to Nursing and Allied Health Literature (CINAHL), and Cochrane Central Register of Controlled Trials (CENTRAL), and screened 7,123 retrieved studies for inclusion. Two investigators independently selected the studies using predefined criteria and assessed each study's quality using the Newcastle-Ottawa quality assessment scale. We meta-analyzed the results based on the BMI classification system by the WHO.ResultsWe included 10 studies (with a total sample size of 484,906) in the systematic review and 4 studies in the meta-analyses. The study results were generally heterogeneous. However, following reanalysis of the largest reported study and our meta-analyses, we observed that in stage 3-5 CKD, being underweight was associated with a higher risk of death while being overweight or obese class I was associated with a lower risk of death; however, obesity classes II and III were not associated with risk of death. In addition, reanalysis of the largest available study showed that a higher BMI was associated with an incrementally higher risk of kidney disease progression; however, this association was attenuated in our pooled results. For earlier stages of CKD, we could not complete meta-analyses as the studies were sparse and had heterogeneous BMI classifications and/or referent BMI groups.ConclusionAmong the group of patients with stage 3-5 CKD, we found a differential association between obesity classes I-III and mortality compared to the general population, indicating an obesity paradox in the CKD population.

Apolipoprotein L1 gene (APOL1) G1 and G2 coding variants are strongly associated with chronic kidney disease (CKD) in African Americans (AAs). Here APOL1 association was tested with baseline estimated glomerular filtration rate (eGFR), urine albumin:creatinine ratio (UACR), and prevalent cardiovascular disease (CVD) in 2571 AAs from the Systolic Blood Pressure Intervention Trial (SPRINT), a trial assessing effects of systolic blood pressure reduction on renal and CVD outcomes. Logistic regression models that adjusted for potentially important confounders tested for association between APOL1 risk variants and baseline clinical CVD (myocardial infarction, coronary, or carotid artery revascularization) and CKD (eGFR under 60 ml/min per 1.73 m(2) and/or UACR over 30 mg/g). AA SPRINT participants were 45.3% female with a mean (median) age of 64.3 (63) years, mean arterial pressure 100.7 (100) mm Hg, eGFR 76.3 (77.1) ml/min per 1.73 m(2), and UACR 49.9 (9.2) mg/g, and 8.2% had clinical CVD. APOL1 (recessive inheritance) was positively associated with CKD (odds ratio 1.37, 95% confidence interval 1.08-1.73) and log UACR estimated slope (β) 0.33) and negatively associated with eGFR (β -3.58), all significant. APOL1 risk variants were not significantly associated with prevalent CVD (1.02, 0.82-1.27). Thus, SPRINT data show that APOL1 risk variants are associated with mild CKD but not with prevalent CVD in AAs with a UACR under 1000 mg/g.

We evaluated the cross-sectional associations of N-terminal pro-B-type natriuretic peptide (NT-proBNP) with cardiac structural and functional abnormalities in a cohort of patients with chronic kidney disease without clinical heart failure, the Chronic Renal Insufficiency Cohort (n = 3,232). The associations of NT-proBNP with echocardiographically determined left ventricular (LV) mass and LV systolic and diastolic function were evaluated using multivariate logistic and linear regression models. Reclassification of participants' predicted risk of LV hypertrophy (LVH), systolic and diastolic dysfunction was performed using a category-free net reclassification improvement index that compared a clinical model with and without NT-proBNP. The median NT-proBNP was 126.6 pg/ml (interquartile range 55.5 to 303.7). The greatest quartile of NT-proBNP was associated with a nearly threefold odds of LVH (odds ratio 2.7, 95% confidence interval [CI] 1.8 to 4.0) and LV systolic dysfunction (odds ratio 2.7, 95% CI 1.7 to 4.5) and a twofold odds of diastolic dysfunction (odds ratio 2.0, 95% CI 1.3 to 2.9) in the fully adjusted models. When evaluated alone as a screening test, NT-proBNP functioned modestly for the detection of LVH (area under the curve 0.66) and LV systolic dysfunction (area under the curve 0.62) and poorly for the detection of diastolic dysfunction (area under the curve 0.51). However, when added to the clinical model, NT-proBNP significantly reclassified participants' likelihood of having LVH (net reclassification improvement 0.14, 95% CI 0.13-0.15; p

Background: Hispanic/Latino individuals are less likely to receive optimal treatment for chronic kidney disease than non-Hispanic whites. This may be particularly detrimental for women of reproductive age as chronic kidney disease increases risk for infertility, menstrual irregularities, and pregnancy loss. While these maternal outcomes have been associated with advanced chronic kidney disease, their occurrence in early chronic kidney disease is unclear. Objectives/Design: Using baseline (2008–2011) and second study visit (2014–2017) data from the Hispanic Community Health Study/Study of Latinos, we retrospectively assessed the prevalence of chronic kidney disease as well as the association between chronic kidney disease and self-reported infertility, cessation of menses, hysterectomy, and nonviable pregnancy loss (experienced at less than 24 weeks gestation) in women of reproductive age (18–45 years). Methods: Multivariable survey logistic regression analyses determined the unadjusted and multivariable-adjusted prevalence odds ratios with 95% confidence intervals between chronic kidney disease and the separate outcomes. Results: Among 2589 Hispanic/Latino women included (mean age = 31.4 years), 4.6% were considered to have chronic kidney disease. In adjusted analyses, women with chronic kidney disease did not have a significantly increased odds of infertility (odds ratio = 1.02, 95% confidence interval = 0.42–2.49), cessation of menses (odds ratio = 1.25, 95% confidence interval = 0.52–3.04), or hysterectomy (odds ratio = 1.17, 95% confidence interval = 0.61–2.25) compared to those without chronic kidney disease. In those with chronic kidney disease, the adjusted odds of a nonviable pregnancy loss occurring after baseline visit were increased (odds ratio = 2.11, 95% confidence interval = 0.63–7.02) but not statistically significance. Conclusion: The presence of early stage chronic kidney disease did not confer a significant risk of infertility, cessation of menses, or nonviable pregnancy loss. Plain language summary: The Hispanic Community Health Study/Study of Latinos is a population-based study of over 16,000 Hispanic/Latino individuals throughout the United States. Within this cohort, we assessed the prevalence of chronic kidney disease in women of reproductive age (18–45 years old) and the associations between kidney disease and infertility, cessation of menses, and nonviable pregnancy loss (loss occurring before the 24th week of pregnancy). We found that kidney disease affected 1 in 20 women of reproductive age and those with kidney disease were more likely to have obesity, diabetes, and hypertension. Compared to those without kidney disease, the presence of kidney disease did not increase risk of infertility, cessation of menses, or nonviable pregnancy loss. [ABSTRACT FROM AUTHOR]

Background Limited health literacy has been associated with adverse outcomes in children. We evaluated this association in the setting of chronic kidney disease (CKD). Methods We assessed the parental health literacy of 367 children enrolled in the Chronic Kidney Disease in Children (CKiD) Study, using the Short Test of Functional Health Literacy (STOFHLA). We evaluated the association between parental health literacy and CKD progression, defined as time to the composite event of renal replacement therapy (RRT, dialysis, or kidney transplant) or 50% decline in estimated glomerular filtration rate (eGFR). Results Median CKiD participant age was 9.5 years, 63% were male, and 59% non-Hispanic white. Median eGFR at baseline was 63 ml/min/1.73 m.sup.2, and median urine protein-to-creatinine ratio was 0.22. The median STOFHLA score was 98. Over a median follow-up of 3.7 years, the overall CKD progression rate was 2.8 per 100 person-years. After adjustment for demographic and clinical factors, the relative time to CKD progression was 28% longer per 1 SD increase in STOFHLA score (relative time, 95% CI, 1.28, 1.06-1.53). Conclusions In this cohort of children with CKD, higher parental health literacy was associated with a nearly 30% longer time to the composite CKD progression outcome., Author(s): Ana C. Ricardo [sup.1] , Lynn N. Pereira [sup.2] , Aisha Betoko [sup.2] , Vivien Goh [sup.1] , Amatur Amarah [sup.1] , Bradley A. Warady [sup.3] , Marva Moxey-Mims [...]