Association between Acute Declines in Estimated Glomerular Filtration Rate during Renin-Angiotensin System Inhibition and Risk of Adverse Outcomes.

BACKGROUND: Declines in glomerular filtration rate (GFR) occur commonly when renin-angiotensin system (RAS) inhibitors are started. Our objective was to determine the relation between declines in estimated GFR during trials of RAS inhibition and kidney outcomes. METHODS: We included participants with CKD (estimated GFR<60 mL/min/1.73m2) from 16 trials of RAS inhibition. The exposure was subacute declines in estimated GFR expressed as % change between randomization and month 3, and in the subset of trials with data available, we also examined % change in eGFR between randomization and month 1. The primary outcome was kidney failure with replacement therapy. Cox proportional hazards models were used to examine the association between subacute declines in eGFR and risk of kidney failure. We used spline models to identify the threshold of change in eGFR below which RAS inhibition was favorable (conservatively comparing a given decline in eGFR with RAS inhibition to no decline in the comparator). RESULTS: 11,800 individuals with mean eGFR 43 (SD 11) mL/min/1.73m2 and median urine albumin/creatinine ratio of 362 mg/g (IQR 50, 1367) were included, and 1,162 (10%) developed kidney failure. The threshold of decline in eGFR that favored use of RAS inhibitors for kidney failure was estimated to be up to 13% (95%CI 8%, 17%) over a 3-month interval and up to 21% (95%CI 15%, 27%) over a 1-month interval after starting RAS inhibitors. CONCLUSIONS: In people treated with RAS inhibitors, ≤ 13% decline in eGFR over a 3-month period or ≤21% decline over a 1-month period was associated with lower risk of kidney failure compared with no decline with the use of placebo or other agents.

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

BACKGROUND: Current equations for estimated glomerular filtration rate (eGFR) that use serum creatinine or cystatin C incorporate age, sex, and race to estimate measured GFR. However, race in eGFR equations is a social and not a biologic construct. METHODS: We developed new eGFR equations without race using data from two development data sets: 10 studies (8254 participants, 31.5% Black) for serum creatinine and 13 studies (5352 participants, 39.7% Black) for both serum creatinine and cystatin C. In a validation data set of 12 studies (4050 participants, 14.3% Black), we compared the accuracy of new eGFR equations to measured GFR. We projected the prevalence of chronic kidney disease (CKD) and GFR stages in a sample of U.S. adults, using current and new equations. RESULTS: In the validation data set, the current creatinine equation that uses age, sex, and race overestimated measured GFR in Blacks (median, 3.7 ml per minute per 1.73 m2 of body-surface area; 95% confidence interval [CI], 1.8 to 5.4) and to a lesser degree in non-Blacks (median, 0.5 ml per minute per 1.73 m2; 95% CI, 0.0 to 0.9). When the adjustment for Black race was omitted from the current eGFR equation, measured GFR in Blacks was underestimated (median, 7.1 ml per minute per 1.73 m2; 95% CI, 5.9 to 8.8). A new equation using age and sex and omitting race underestimated measured GFR in Blacks (median, 3.6 ml per minute per 1.73 m2; 95% CI, 1.8 to 5.5) and overestimated measured GFR in non-Blacks (median, 3.9 ml per minute per 1.73 m2; 95% CI, 3.4 to 4.4). For all equations, 85% or more of the eGFRs for Blacks and non-Blacks were within 30% of measured GFR. New creatinine-cystatin C equations without race were more accurate than new creatinine equations, with smaller differences between race groups. As compared with the current creatinine equation, the new creatinine equations, but not the new creatinine-cystatin C equations, increased population estimates of CKD prevalence among Blacks and yielded similar or lower prevalence among non-Blacks. CONCLUSIONS: New eGFR equations that incorporate creatinine and cystatin C but omit race are more accurate and led to smaller differences between Black participants and non-Black participants than new equations without race with either creatinine or cystatin C alone. (Funded by the National Institute of Diabetes and Digestive and Kidney Diseases.).

Glomerular Filtration Rate Estimation Using ß2-Microglobulin and ß-Trace Protein in Adults With Solid Tumors: A Prospective Cross-Sectional Study.

RATIONALE & OBJECTIVE: ß2-Microglobulin (B2M) and ß-trace protein (BTP) are novel endogenous filtration markers that may improve the accuracy of estimated glomerular filtration rate (eGFR) beyond creatinine and cystatin C (eGFRcr-cys), but they have not been assessed in patients with cancer. STUDY DESIGN: Cross-sectional analysis. SETTING & PARTICIPANTS: Prospective cohort of 1,200 patients with active solid tumors recruited between April 2015 and September 2017. EXPOSURE: CKD-EPI equations without race combining B2M and/or BTP with creatinine with or without cystatin C (2-, 3-, or 4-marker panel eGFR). OUTCOME: Performance of equations compared with eGFRcr-cys and non-GFR determinants of serum B2M and BTP (SB2M, and SBTP, respectively). Measured GFR (mGFR) was determined using the plasma clearance of chromium-51 labeled ethylenediamine tetraacetic acid (51Cr-EDTA). ANALYTICAL APPROACH: Bias was defined as the median of the differences between mGFR and eGFR, and 1-P30 was defined as the percentage of estimates that differed by more than 30% from the mGFR (1-P30). Linear regression was used to assess association of clinical and laboratory variables with SB2M, and SBTP after adjustment for mGFR. RESULTS: Mean age and mGFR were 58.8±13.2 SD years and 78.4±21.7 SD mL/min/1.73m2, respectively. Performance of the 3-marker and 4-marker panel equations was better than eGFRcr-cys (lesser bias and 1-P30). Performance of 2-marker panel equations was as good as eGFRcr-cys (lesser bias and similar 1-P30). SB2M and SBTP were not strongly influenced by cancer site. LIMITATIONS: Participants may have had better clinical performance status than the general population of patients with solid tumors. CONCLUSIONS: B2M and BTP can improve the accuracy of eGFR and may be useful as confirmatory tests in patients with solid tumors, either by inclusion in a multimarker panel equation with creatinine and cystatin C, or by substituting for cystatin C in combination with creatinine. PLAIN-LANGUAGE SUMMARY: The most accurate method to assess estimate kidney function is estimated glomerular filtration rate (eGFR) using creatinine and cystatin C (eGFRcr-cys). We studied whether using ß2-microglobulin (B2M) and/or ß-trace protein (BTP) with creatinine with or without cystatin C (2-, 3-, or 4-marker panel eGFR) might be useful in patients with active solid tumors. The performance of the 3-marker and 4-marker panel equations was better than eGFRcr-cys. Performance of 2-marker panel equations was as good as eGFRcr-cys. We conclude that B2M and BTP can improve the accuracy of eGFR and may be useful as a confirmatory test in patients with solid tumors either by inclusion in multimarker panel equation with creatinine and cystatin C or by substituting for cystatin C in combination with creatinine.

Association of Body Mass Index with Multiple Organ Failure in Hospitalized Patients with COVID-19: A Multicenter Retrospective Cohort Study.

Purpose: This study examines whether excessive adipose tissue, as measured by the body mass index (BMI), is associated with higher systemic markers of inflammation and higher risk of severe acute organ failure among patients with coronavirus disease 2019 (COVID-19). Methods: This was a multicenter retrospective cohort study of 1370 hospitalized adults (18 years or older) with COVID-19 during the first wave of the pandemic. Patient-level variables were extracted from the electronic medical record. The primary predictor variable was the BMI at time of hospital admission, in accordance with the World Health Organization classification. Multivariable logistic regression analyses examined the association of BMI with the composite of acute respiratory distress syndrome (ARDS), as defined by the use of high-flow nasal canula, non-invasive ventilation, or mechanical ventilation, severe acute kidney injury (AKI), as defined by acute dialysis requirement, or in-hospital death. Results: After adjustment for important cofounders, the BMI stratum of > 40 kg/m2 (compared to the BMI < 25 kg/m2 reference group) was associated with higher odds for the composite of ARDS, severe AKI, or in-hospital death (adjusted odds ratio [ORadj] 1.69; 95% confidence interval [CI]1.03, 2.78). As a continuous variable, BMI (per 5-kg/m2 increase) remained independently associated with the composite outcome (ORadj 1.13; 95% CI 1.03, 1.23); patients in higher BMI categories exhibited significantly higher peak levels of C-reactive protein (CRP), a systemic marker of inflammation (P = .01). In a sub-cohort of 889 patients, the association of BMI with the composite outcome was no longer significant after adjustment for the peak level of CRP. Conclusions: Among hospitalized patients with COVID-19, a higher BMI is associated with higher risk of severe organ failure or in-hospital death, which dissipates after adjustment for CRP level. This supports the hypothesis that inflammation is a downstream mediator of adipose tissue on acute organ dysfunction.

Effectiveness of an Intervention to Improve Decision Making for Older Patients With Advanced Chronic Kidney Disease : A Randomized Controlled Trial.

BACKGROUND: Older patients with advanced chronic kidney disease (CKD) face difficult decisions about managing kidney failure, frequently experiencing decisional conflict, regret, and treatment misaligned with preferences. OBJECTIVE: To assess whether a decision aid about kidney replacement therapy improved decisional quality compared with usual care. DESIGN: Multicenter, randomized, controlled trial. (ClinicalTrials.gov: NCT03522740). SETTING: 8 outpatient nephrology clinics associated with 4 U.S. centers. PARTICIPANTS: English-fluent patients, 70 years and older with nondialysis CKD stages 4 to 5 recruited from 2018 to 2020. INTERVENTION: DART (Decision-Aid for Renal Therapy) is an interactive, web-based decision aid for older adults with CKD. Both groups received written education about treatments. MEASUREMENTS: Change in the decisional conflict scale (DCS) score from baseline to 3, 6, 12, and 18 months. Secondary outcomes included change in prognostic and treatment knowledge and change in uncertainty. RESULTS: Among 400 participants, 363 were randomly assigned: 180 to usual care, 183 to DART. Decisional quality improved with DART with mean DCS declining compared with control (mean difference, -8.5 [95% CI, -12.0 to -5.0]; P < 0.001), with similar findings at 6 months, attenuating thereafter. At 3 months, knowledge improved with DART versus usual care (mean difference, 7.2 [CI, 3.7 to 10.7]; P < 0.001); similar findings at 6 months were modestly attenuated at 18 months (mean difference, 5.9 [CI, 1.4 to 10.3]; P = 0.010). Treatment preferences changed from 58% "unsure" at baseline to 28%, 20%, 23%, and 14% at 3, 6, 12, and 18 months, respectively, with DART, versus 51% to 38%, 35%, 32%, and 18% with usual care. LIMITATION: Latinx patients were underrepresented. CONCLUSION: DART improved decision quality and clarified treatment preferences among older adults with advanced CKD for 6 months after the DART intervention. PRIMARY FUNDING SOURCE: Patient-Centered Outcomes Research Institute (PCORI).

Intensive BP Control in Patients with CKD and Risk for Adverse Outcomes.

SIGNIFICANCE STATEMENT: Although most guidelines recommend tightly controlling BP in patients with CKD, individuals with advanced kidney disease or severe albuminuria were not well-represented in trials examining the effect of this intervention on kidney outcomes. To examine the effect of intensive BP control on the risk of kidney outcomes in patients with CKD, the authors pooled individual-level data from seven trials. They found that overall, intensive BP control was associated with a 13% lower, but not significant, risk of a kidney outcome. However, the intervention's effect on the kidney outcome differed depending on baseline eGFR. Data from this pooled analysis suggested a benefit of intensive BP control in delaying KRT onset in patients with stages 4-5 CKD, but not necessarily in those with stage 3 CKD. BACKGROUND: The effect of intensive BP lowering (to systolic BP of <120 mm Hg) on the risk of kidney failure requiring KRT remains unclear in patients with advanced CKD. Such patients were not well represented in trials evaluating intensive BP control. METHODS: To examine the effect of intensive BP lowering on KRT risk-or when not possible, trial-defined kidney outcomes-we pooled individual-level data from seven trials that included patients with eGFR<60 ml/min per 1.73 m 2 . We performed prespecified subgroup analyses to evaluate the effect of intensive BP control by baseline albuminuria and eGFR (CKD stages 4-5 versus stage 3). RESULTS: Of 5823 trial participants, 526 developed the kidney outcome and 382 died. Overall, intensive (versus usual) BP control was associated with a lower risk of kidney outcome and death in unadjusted analyses but these findings did not achieve statistical significance. However, the intervention's effect on the kidney outcome differed depending on baseline eGFR ( P interaction=0.05). By intention-to-treat analysis, intensive (versus usual) BP control was associated with a 20% lower risk of the primary kidney outcome in those with CKD GFR stages 4-5, but not in CKD GFR stage 3. There was no interaction between intensive BP control and the severity of albuminuria for kidney outcomes. CONCLUSIONS: Data from this pooled analysis of seven trials suggest a benefit of intensive BP control in delaying KRT onset in patients with stages 4-5 CKD but not necessarily with stage 3 CKD. These findings suggest no evidence of harm from intensive BP control, but also point to the need for future trials of BP targets focused on populations with advanced kidney disease. PODCAST: This article contains a podcast at https://dts.podtrac.com/redirect.mp3/www.asn-online.org/media/podcast/JASN/2023_02_27_JASN0000000000000060.mp3.

National Projections for Clinical Implications of Race-Free Creatinine-Based GFR Estimating Equations.

BACKGROUND: The National Kidney Foundation and American Society of Nephrology Task Force on Reassessing the Inclusion of Race in Diagnosing Kidney Disease recently recommended a new race-free creatinine-based equation for eGFR. The effect on recommended clinical care across race and ethnicity groups is unknown. METHODS: We analyzed nationally representative cross-sectional questionnaires and medical examinations from 44,360 participants collected between 2001 and 2018 by the National Health and Nutrition Examination Survey. We quantified the number and proportion of Black, White, Hispanic, and Asian/Other adults with guideline-recommended changes in care. RESULTS: The new equation, if applied nationally, could assign new CKD diagnoses to 434,000 (95% confidence interval [CI], 350,000 to 517,000) Black adults, reclassify 584,000 (95% CI, 508,000 to 667,000) to more advanced stages of CKD, restrict kidney donation eligibility for 246,000 (95% CI, 189,000 to 303,000), expand nephrologist referrals for 41,800 (95% CI, 19,800 to 63,800), and reduce medication dosing for 222,000 (95% CI, 169,000 to 275,000). Among non-Black adults, these changes may undo CKD diagnoses for 5.51 million (95% CI, 4.86 million to 6.16 million), reclassify 4.59 million (95% CI, 4.28 million to 4.92 million) to less advanced stages of CKD, expand kidney donation eligibility for 3.96 million (95% CI, 3.46 million to 4.46 million), reverse nephrologist referral for 75,800 (95% CI, 35,400 to 116,000), and reverse medication dose reductions for 1.47 million (95% CI, 1.22 million to 1.73 million). The racial and ethnic mix of the populations used to develop eGFR equations has a substantial effect on potential care changes. CONCLUSION: The newly recommended 2021 CKD-EPI creatinine-based eGFR equation may result in substantial changes to recommended care for US patients of all racial and ethnic groups.

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

SIGNIFICANCE STATEMENT: New eGFR equations from Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) and European Kidney Function Consortium (EKFC) using creatinine (eGFRcr), cystatin C (eGFRcys), and both (eGFRcr-cys) have sufficient accuracy for use in clinical practice, leading to uncertainty in selecting equations for implementation. The authors evaluated performance of equations in an independent population of 4050 adults and evaluated other considerations important for implementation. They found that CKD-EPI and EKFC equations are approaching convergence, with better performance of eGFRcr-cys equations in the overall group and fewer differences among race, sex, and age subgroups than eGFRcr equations. Larger differences among eGFRcr equations reflect regional population differences in creatinine, forcing a trade-off between accuracy and uniformity in global implementation of eGFRcr equations. More widespread use of cystatin C could avoid this trade-off. BACKGROUND: New CKD-EPI and EKFC eGFR equations using eGFRcr, eGFRcys, and both (eGFRcr-cys) have sufficient accuracy for use in clinical practice. A better understanding of the equations, including their performance in race, sex and age subgroups, is important for selection of eGFR equations for global implementation. METHODS: We evaluated performance (bias and P 30 ) of equations and methods used for equation development in an independent study population comprising 4050 adults pooled from 12 studies. The mean (SD) measured GFR was 76.4 (29.6) ml/min per 1.73 m 2 and age 57.0 (17.4) years, with 1557 (38%) women and 579 (14%) Black participants. RESULTS: Coefficients for creatinine, cystatin C, age, and sex in the CKD-EPI and EKFC equations are similar. Performance of the eGFRcr-cys equations in the overall population (bias <±5 ml/min per 1.73 m 2 and P 30 >90%) was better than the eGFRcr or eGFRcys equations, with fewer differences among race, sex, and age subgroups. Differences in performance across subgroups reflected differences in diversity of source populations and use of variables for race and sex for equation development. Larger differences among eGFRcr equations reflected regional population differences in non-GFR determinants of creatinine. CONCLUSION: CKD-EPI and EKFC equations are approaching convergence. It is not possible to maximize both accuracy and uniformity in selecting one of the currently available eGFRcr equations for implementation across regions. Decisions should consider methods for equation development in addition to performance. Wider use of cystatin C with creatinine could maximize both accuracy and uniformity of GFR estimation using currently available equations.

Change in Albuminuria and GFR Slope as Joint Surrogate End Points for Kidney Failure: Implications for Phase 2 Clinical Trials in CKD.

SIGNIFICANCE STATEMENT: Changes in albuminuria and GFR slope are individually used as surrogate end points in clinical trials of CKD progression, and studies have demonstrated that each is associated with treatment effects on clinical end points. In this study, the authors sought to develop a conceptual framework that combines both surrogate end points to better predict treatment effects on clinical end points in Phase 2 trials. The results demonstrate that information from the combined treatment effects on albuminuria and GFR slope improves the prediction of treatment effects on the clinical end point for Phase 2 trials with sample sizes between 100 and 200 patients and duration of follow-up ranging from 1 to 2 years. These findings may help inform design of clinical trials for interventions aimed at slowing CKD progression. BACKGROUND: Changes in log urinary albumin-to-creatinine ratio (UACR) and GFR slope are individually used as surrogate end points in clinical trials of CKD progression. Whether combining these surrogate end points might strengthen inferences about clinical benefit is unknown. METHODS: Using Bayesian meta-regressions across 41 randomized trials of CKD progression, we characterized the combined relationship between the treatment effects on the clinical end point (sustained doubling of serum creatinine, GFR <15 ml/min per 1.73 m 2 , or kidney failure) and treatment effects on UACR change and chronic GFR slope after 3 months. We applied the results to the design of Phase 2 trials on the basis of UACR change and chronic GFR slope in combination. RESULTS: Treatment effects on the clinical end point were strongly associated with the combination of treatment effects on UACR change and chronic slope. The posterior median meta-regression coefficients for treatment effects were -0.41 (95% Bayesian Credible Interval, -0.64 to -0.17) per 1 ml/min per 1.73 m 2 per year for the treatment effect on GFR slope and -0.06 (95% Bayesian Credible Interval, -0.90 to 0.77) for the treatment effect on UACR change. The predicted probability of clinical benefit when considering both surrogates was determined primarily by estimated treatment effects on UACR when sample size was small (approximately 60 patients per treatment arm) and follow-up brief (approximately 1 year), with the importance of GFR slope increasing for larger sample sizes and longer follow-up. CONCLUSIONS: In Phase 2 trials of CKD with sample sizes of 100-200 patients per arm and follow-up between 1 and 2 years, combining information from treatment effects on UACR change and GFR slope improved the prediction of treatment effects on clinical end points.

Acute Declines in Estimated GFR in Blood Pressure Target Trials and Risk of Adverse Outcomes.

RATIONALE & OBJECTIVE: Acute decreases in glomerular filtration rate (GFR) occur commonly during intensive blood pressure (BP) lowering. Our objective was to determine the relationship between acute decreases in estimated GFR and patient outcomes. STUDY DESIGN: Retrospective observational study. SETTING & PARTICIPANTS: Participants from 4 randomized controlled trials of intensive BP lowering in chronic kidney disease (Modification of Diet in Renal Disease study, African American Study of Kidney Disease and Hypertension, Systolic Blood Pressure Intervention Trial, and Action to Control Cardiovascular Risk in Diabetes trial). EXPOSURE: A 4-category exposure defined by the level of acute decrease in estimated GFR (defined as>15% vs≤15% between baseline and month 4) and the randomization to intensive versus usual BP control. OUTCOMES: Risk of kidney replacement therapy (primary outcome), defined as the need for dialysis or transplant except in the Action to Control Cardiovascular Risk in Diabetes trial, which defined its kidney outcome as a composite occurrence of serum creatinine concentration>3.3mg/dL, kidney failure, or kidney replacement therapy. ANALYTICAL APPROACH: Multivariable Cox models. RESULTS: We included 4,473 individuals randomly assigned to intensive versus usual BP control who had a total of 351 kidney outcomes and 304 deaths during median follow-up durations of 22 and 24 months, respectively. Approximately 14% of participants exhibited an acute decrease in eGFR, 11.0% in the usual BP treatment arm and 17.8% in the intensive BP treatment arm. In adjusted models, compared with a≤15% eGFR decrease in the usual BP arm, a≤15% eGFR decrease in the intensive BP control arm was associated with lower risk of the kidney outcome (HR, 0.75; 95% CI, 0.57-0.98). In contrast, a>15% decrease in eGFR was associated with a higher risk of the kidney outcome in the usual (HR, 2.47; 95% CI, 1.80-3.38) and intensive BP treatment arms (HR, 1.99; 95% CI, 1.45-2.73) compared with a≤15% decrease in the usual BP arm. LIMITATIONS: Observational study, residual confounding. CONCLUSIONS: Decreases in eGFR of>15% in the usual and intensive BP treatment arms were associated with a higher risk of kidney outcomes compared with a≤15% decrease in the usual BP arm and may be a harbinger of adverse outcomes.

Association of Longitudinal B-Type Natriuretic Peptide Monitoring With Kidney Failure in Patients With CKD: A Cohort Study.

RATIONALE & OBJECTIVE: Both hypervolemia and hypovolemia are associated with chronic kidney disease (CKD) progression. Although longitudinal monitoring of B-type natriuretic peptide (BNP) may aid physicians' decision making about the optimization of volume status, its clinical benefit remains uncertain in CKD. This study assessed the association between BNP monitoring and the risk of incident kidney replacement therapy (KRT). STUDY DESIGN: Retrospective cohort study. SETTING & PARTICIPANTS: A total of 2,998 outpatients with stages 3-5 of nondialyzed CKD referred to the department of nephrology at an academic hospital. EXPOSURE: BNP monitoring. OUTCOME: KRT, acute kidney injury (AKI), and heart failure hospitalization. ANALYTICAL APPROACH: Marginal structural models, which create a balanced pseudo population at each time point, were applied to account for potential time-dependent confounders. Inverse probability weighted pooled logistic regression models were employed to estimate hazard ratios. RESULTS: At baseline, the median age and estimated glomerular filtration rate were 66 years and 38.1mL/min/1.73m2, respectively. During the follow-up period (median, 5.9 [IQR, 2.8-9.9] years), 449 patients required KRT, 765 had AKI, and 236 were hospitalized for heart failure. After adjustment for time-updated clinical characteristics and physician-specific practice styles, BNP monitoring was associated with lower risks of KRT (HR, 0.44 [95% CI, 0.21-0.92]), AKI (HR, 0.36 [95% CI, 0.18-0.72]), and heart failure hospitalization (HR, 0.37 [95% CI, 0.14-0.95]). The association between BNP monitoring and KRT was attenuated after additional adjustment for AKI or heart failure hospitalization as a time-varying covariate. LIMITATIONS: Residual confounding by measured and unmeasured variables or indications for BNP measurements. CONCLUSIONS: BNP monitoring was associated with a lower risk of KRT among patients with CKD that did not require dialysis. This association is potentially mediated through a reduced risk of AKI or heart failure hospitalization. PLAIN-LANGUAGE SUMMARY: Both volume overload and volume depletion are deleterious to kidney function. B-type natriuretic peptide (BNP) is a biomarker that reflects volume status not only in heart failure but also in nondialysis chronic kidney disease (CKD). Although longitudinal BNP monitoring may aid physicians' decision making about the optimization of volume status, its clinical benefit remains uncertain in CKD. In this cohort study analyzing 2,998 patients with nondialyzed CKD, BNP monitoring was associated with a lower risk of kidney replacement therapy, acute kidney injury, and heart failure hospitalization over the follow-up period. The association with kidney replacement therapy may be mediated through a reduced risk of acute kidney injury or heart failure hospitalization. BNP monitoring may aid physicians in optimal fluid management, potentially conferring better kidney outcomes.

Development and Validation of the Rating of CKD Knowledge Among Older Adults (Know-CKD) With Kidney Failure.

RATIONALE & OBJECTIVE: Few older adults with kidney failure engage in shared decision making (SDM) for kidney replacement therapy. The lack of instruments to assess SDM-relevant knowledge domains may contribute to this. We assessed the reliability and validity of a new instrument, the Rating of CKD Knowledge Older Adults (Know-CKD). STUDY DESIGN: Multistage process, including a stakeholder-engaged development phase, pilot testing, and validation of a knowledge instrument using a cross-sectional survey of older adults with CKD. SETTING & PARTICIPANTS: 363 patients aged 70+years with nondialysis advanced chronic kidney disease (CKD) (estimated glomerular filtration rate [eGFR]<30mL/min/1.73m2) in Boston, Chicago, Portland, ME, and San Diego from June 2018 and January 2020. EXPOSURE: Educational level, higher literacy (Single Item Literacy Screener [SILS]) and numeracy (Subjective Numeracy Scale [SNS]), having participated in clinic-sponsored dialysis education, and self-reported "feeling informed" about options for treatment. OUTCOME: Validity and reliability of the Know-CKD instrument. ANALYTICAL APPROACH: Reliability was assessed with the Kuder-Richardson-20 coefficient. Construct validity was demonstrated by testing a priori hypotheses using t test, analysis of variance (ANOVA) tests, and linear regression analyses. RESULTS: The mean (± SD) participant age was 77.6±5.9 years, and mean eGFR was 22.7±7.2mL/min/1.73m2; 281 participants (78%) self-reported as White. The 12-item Know-CKD assessment had good reliability (Kuder-Richardson-20 reliability coefficient=0.75), and a mean score of 58.2% ± 22.3 SD. The subscales did not attain acceptable reliability. The proportion answering correctly on each item ranged from 20.1% to 91.7%. In examining construct validity, the hypothesized associations held; Know-CKD significantly associated with higher education (ß=6.98 [95% CI, 1.34-12.61], P=0.02), health literacy (ß = -12.67 [95% CI, -19.49 to-5.86], P≤0.001), numeracy per 10% higher (ß=1.85 [95% CI, 1.02-2.69], P≤0.001), and attendance at dialysis class (ß=18.28 [95% CI, 13.30-23.27], P≤0.001). These associations were also observed for the subscales except for prognosis (not associated with literacy or numeracy). LIMITATIONS: Know-CKD is only available in English and has been used only in research settings. CONCLUSIONS: For older adults facing dialysis initiation decisions, Know-CKD is a valid, reliable, and easy to administer measure of knowledge. Further research should examine the relationship of kidney disease knowledge and SDM, patient satisfaction, and clinical outcomes. PLAIN-LANGUAGE SUMMARY: The Rating of CKD Knowledge Among Older Adults (Know-CKD) study measures knowledge of chronic kidney disease (CKD) and is designed for older adults. Most existing knowledge measures for CKD focus on people of all ages and all CKD stages. This measure is useful because it will allow researchers to assess how well patient education efforts are working. Patient education is a way to help patients make decisions about their care. We describe how the measure was developed by a team of doctors, researchers, and patients, and how the measure performed among persons with advanced CKD aged 70 years and older. Know-CKD can inform efforts to improve shared decision-making research and practice for older patients with kidney disease.

Blood Pressure, Incident Cognitive Impairment, and Severity of CKD: Findings From the Chronic Renal Insufficiency Cohort (CRIC) Study.

RATIONALE & OBJECTIVE: Hypertension is a known risk factor for dementia and cognitive impairment. There are limited data on the relation of systolic blood pressure (SBP) and diastolic blood pressure (DBP) with incident cognitive impairment in adults with chronic kidney disease. We sought to identify and characterize the relationship among blood pressure, cognitive impairment, and severity of decreased kidney function in adults with chronic kidney disease. STUDY DESIGN: Longitudinal cohort study. SETTING & PARTICIPANTS: 3,768 participants in the Chronic Renal Insufficiency Cohort (CRIC) Study. EXPOSURE: Baseline SBP and DBP were examined as exposure variables, using continuous (linear, per 10-mm Hg higher), categorical (SBP<120 [reference], 120 to 140,>140mm Hg; DBP<70 (reference), 70 to 80, > 80mm Hg) and nonlinear terms (splines). OUTCOME: Incident cognitive impairment defined as a decline in Modified Mini-Mental State Examination (3MS) score to greater than 1 standard deviation below the cohort mean. ANALYTICAL APPROACH: Cox proportional hazard models adjusted for demographics as well as kidney disease and cardiovascular disease risk factors. RESULTS: The mean age of participants was 58±11 (SD) years, estimated glomerular filtration rate (eGFR) was 44mL/min/1.73m2 ± 15 (SD), and the median follow-up time was 11 (IQR, 7-13) years. In 3,048 participants without cognitive impairment at baseline and with at least 1 follow-up 3MS test, a higher baseline SBP was significantly associated with incident cognitive impairment only in the eGFR>45mL/min/1.73m2 subgroup (adjusted hazard ratio [AHR], 1.13 [95% CI, 1.05-1.22] per 10mm Hg higher SBP]. Spline analyses, aimed at exploring nonlinearity, showed that the relationship between baseline SBP and incident cognitive impairment was J-shaped and significant only in the eGFR>45mL/min/1.73m2 subgroup (P=0.02). Baseline DBP was not associated with incident cognitive impairment in any analyses. LIMITATIONS: 3MS test as the primary measure of cognitive function. CONCLUSIONS: Among patients with chronic kidney disease, higher baseline SBP was associated with higher risk of incident cognitive impairment specifically in those individuals with eGFR>45mL/min/1.73m2. PLAIN-LANGUAGE SUMMARY: High blood pressure is a strong risk factor for dementia and cognitive impairment in studies of adults without kidney disease. High blood pressure and cognitive impairment are common in adults with chronic kidney disease (CKD). The impact of blood pressure on the development of future cognitive impairment in patients with CKD remains unclear. We identified the relationship between blood pressure and cognitive impairment in 3,076 adults with CKD. Baseline blood pressure was measured, after which serial cognitive testing was performed over 11 years. Fourteen percent of participants developed cognitive impairment. We found that a higher baseline systolic blood pressure was associated with an increased risk of cognitive impairment. We found that this association was stronger in adults with mild-to-moderate CKD compared with those with advanced CKD.

Acute Treatment Effects on GFR in Randomized Clinical Trials of Kidney Disease Progression.

BACKGROUND: Acute changes in GFR can occur after initiation of interventions targeting progression of CKD. These acute changes complicate the interpretation of long-term treatment effects. METHODS: To assess the magnitude and consistency of acute effects in randomized clinical trials and explore factors that might affect them, we performed a meta-analysis of 53 randomized clinical trials for CKD progression, enrolling 56,413 participants with at least one estimated GFR measurement by 6 months after randomization. We defined acute treatment effects as the mean difference in GFR slope from baseline to 3 months between randomized groups. We performed univariable and multivariable metaregression to assess the effect of intervention type, disease state, baseline GFR, and albuminuria on the magnitude of acute effects. RESULTS: The mean acute effect across all studies was -0.21 ml/min per 1.73 m2 (95% confidence interval, -0.63 to 0.22) over 3 months, with substantial heterogeneity across interventions (95% coverage interval across studies, -2.50 to +2.08 ml/min per 1.73 m2). We observed negative average acute effects in renin angiotensin system blockade, BP lowering, and sodium-glucose cotransporter 2 inhibitor trials, and positive acute effects in trials of immunosuppressive agents. Larger negative acute effects were observed in trials with a higher mean baseline GFR. CONCLUSION: The magnitude and consistency of acute GFR effects vary across different interventions, and are larger at higher baseline GFR. Understanding the nature and magnitude of acute effects can help inform the optimal design of randomized clinical trials evaluating disease progression in CKD.

A prospective cross-sectional study estimated glomerular filtration rate from creatinine and cystatin C in adults with solid tumors.

Current guidelines recommend estimating glomerular filtration rate (eGFR) using creatinine (eGFRcr) with the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation as the first test for GFR evaluation, but the Cockcroft-Gault (CG) equation is still commonly used in oncology practice and clinical trials despite increasing evidence of its inaccuracy compared to measured GFR (mGFR). Guidelines recommend eGFR using cystatin C (eGFRcys) or both markers (eGFRcr-cys) as a confirmatory test, but neither was carefully evaluated in cancer patients. Therefore, we compared performance of the CKD-EPI equations and others to the CG equation in adults with a variety of solid tumors. The mGFR was determined by plasma clearance of 51Cr-EDTA. Bias was defined as the median of the differences between mGFR and eGFR while accuracy was defined as the percentage of estimates that differed by more than 30% from the measured GFR (1-P30). We prospectively recruited 1,200 patients between April 2015 and September 2017 with a mean age and mGFR of 58.8 years and 78.4 ml/min/1.73m2, respectively. Bias among eGFRcr equations varied from -8.1 to +6.1 ml/min/1.73 m2. CG was the least accurate, 1-P30 (95% confidence interval) was 24.9 (22.4- 27.3)%; CKD-EPI had 1-P30 of 19.1 (16.8-21.2)% while eGFRcr-cys had the best performance: bias -2.0 (-2.6 to -1.1) ml/min/1.73m2 and 1-P30 7.8 (6.3-9.4)%. Thus, the CG equation should not be preferred over CKD-EPI equation, and eGFRcr-cys can be used as a confirmatory test in adults with solid tumors. Hence, a major policy implication would be to adopt general practice guideline-recommended methods for GFR evaluation in oncology practice and clinical trials.

Rates of Reversal of Volume Overload in Hospitalized Acute Heart Failure: Association With Long-term Kidney Function.

RATIONALE & OBJECTIVE: Achievement of decongestion in acute heart failure (AHF) is associated with improved survival and cardiovascular outcomes but can be associated with acute declines in estimated glomerular filtration rate (eGFR). We examined whether the rate of in-hospital decongestion is associated with longer term kidney function decline. STUDY DESIGN: Post hoc analysis of trial data. SETTINGS & PARTICIPANTS: Patients with ≥2 measures of kidney function (n = 3,500) from the Efficacy of Vasopressin Antagonism in Heart Failure Outcome Study With Tolvaptan (EVEREST) trial. EXPOSURE: In-hospital rate of change in assessments of volume overload, including B-type natriuretic peptide (BNP), N-terminal pro-B-type natriuretic peptide (NT-proBNP), and clinical congestion score (0-12); and rate of change in hemoconcentration including measures of hematocrit, albumin, and total protein. OUTCOME: Incident chronic kidney disease GFR category 4 or worse (chronic kidney disease [CKD] categories G4-G5; defined by a new eGFR of <30 mL/min/1.73 m2) and eGFR decline of >40%. ANALYTICAL APPROACH: Multivariable cause-specific hazards models. RESULTS: Over median 10-month follow-up period, faster decreases in volume overload and more rapid increases in hemoconcentration were associated with a decreased risk of incident CKD G4-G5 and eGFR decline of >40%. In adjusted analyses, for every 6% faster decline in BNP per week, there was a 32% lower risk of both incident CKD G4-G5 (HR, 0.68 [95% CI, 0.58-0.79]) and eGFR decline of >40% (HR, 0.68 [95% CI, 0.57-0.80]). For every 1% faster increase per week in absolute hematocrit, there was a lower risk for both incident CKD G4-G5 (HR, 0.73 [95% CI, 0.64-0.84]) and eGFR decline of >40% (HR, 0.82 [95% CI, 0.71-0.95]), with results consistent for other biomarkers. LIMITATIONS: Possibility of residual confounding. CONCLUSIONS: These results provide reassurance that more rapid decongestion in patients with AHF does not increase the risk of adverse kidney outcomes in patients with heart failure.

Shared Decision Making Among Older Adults With Advanced CKD.

RATIONALE & OBJECTIVE: Older adults with advanced chronic kidney disease (CKD) face difficult decisions about dialysis initiation. Although shared decision making (SDM) can help align patient preferences and values with treatment options, the extent to which older patients with CKD experience SDM remains unknown. STUDY DESIGN: A cross-sectional analysis of patient surveys examining decisional readiness, treatment options education, care partner support, and SDM. SETTING & PARTICIPANTS: Adults aged 70 years or older from Boston, Chicago, San Diego, or Portland (Maine) with nondialysis advanced CKD. PREDICTORS: Decisional readiness factors, treatment options education, and care partner support. OUTCOMES: Primary: SDM measured by the 9-item Shared Decision Making Questionnaire (SDM-Q-9) instrument, with higher scores reflecting greater SDM. Exploratory: Factors associated with SDM. ANALYTICAL APPROACH: We used multivariable linear regression models to examine the associations between SDM and predictors, controlling for demographic and health factors. RESULTS: Among 350 participants, mean age was 78 ± 6 years, 58% were male, 13% identified as Black, and 48% had diabetes. Mean SDM-Q-9 score was 52 ± 28. SDM item agreement ranged from 41% of participants agreeing that "my doctor and I selected a treatment option together" to 73% agreeing that "my doctor told me that there are different options for treating my medical condition." In multivariable analysis adjusted for demographic characteristics, lower estimated glomerular filtration rate, and diabetes, being "well informed" and "very well informed" about kidney treatment options, having higher decisional certainty, and attendance at a kidney treatment options class were independently associated with higher SDM-Q-9 scores. LIMITATIONS: The cross-sectional study design limits the ability to make temporal associations between SDM and the predictors. CONCLUSIONS: Many older patients with CKD do not experience SDM when making dialysis decisions, emphasizing the need for greater access to and delivery of education for individuals with advanced CKD.

Kidney Recovery and Death in Critically Ill Patients With COVID-19-Associated Acute Kidney Injury Treated With Dialysis: The STOP-COVID Cohort Study.

RATIONALE & OBJECTIVE: Acute kidney injury treated with kidney replacement therapy (AKI-KRT) occurs frequently in critically ill patients with coronavirus disease 2019 (COVID-19). We examined the clinical factors that determine kidney recovery in this population. STUDY DESIGN: Multicenter cohort study. SETTING & PARTICIPANTS: 4,221 adults not receiving KRT who were admitted to intensive care units at 68 US hospitals with COVID-19 from March 1 to June 22, 2020 (the "ICU cohort"). Among these, 876 developed AKI-KRT after admission to the ICU (the "AKI-KRT subcohort"). EXPOSURE: The ICU cohort was analyzed using AKI severity as the exposure. For the AKI-KRT subcohort, exposures included demographics, comorbidities, initial mode of KRT, and markers of illness severity at the time of KRT initiation. OUTCOME: The outcome for the ICU cohort was estimated glomerular filtration rate (eGFR) at hospital discharge. A 3-level outcome (death, kidney nonrecovery, and kidney recovery at discharge) was analyzed for the AKI-KRT subcohort. ANALYTICAL APPROACH: The ICU cohort was characterized using descriptive analyses. The AKI-KRT subcohort was characterized with both descriptive analyses and multinomial logistic regression to assess factors associated with kidney nonrecovery while accounting for death. RESULTS: Among a total of 4,221 patients in the ICU cohort, 2,361 (56%) developed AKI, including 876 (21%) who received KRT. More severe AKI was associated with higher mortality. Among survivors, more severe AKI was associated with an increased rate of kidney nonrecovery and lower kidney function at discharge. Among the 876 patients with AKI-KRT, 588 (67%) died, 95 (11%) had kidney nonrecovery, and 193 (22%) had kidney recovery by the time of discharge. The odds of kidney nonrecovery was greater for lower baseline eGFR, with ORs of 2.09 (95% CI, 1.09-4.04), 4.27 (95% CI, 1.99-9.17), and 8.69 (95% CI, 3.07-24.55) for baseline eGFR 31-60, 16-30, ≤15 mL/min/1.73 m2, respectively, compared with eGFR > 60 mL/min/1.73 m2. Oliguria at the time of KRT initiation was also associated with nonrecovery (ORs of 2.10 [95% CI, 1.14-3.88] and 4.02 [95% CI, 1.72-9.39] for patients with 50-499 and <50 mL/d of urine, respectively, compared to ≥500 mL/d of urine). LIMITATIONS: Later recovery events may not have been captured due to lack of postdischarge follow-up. CONCLUSIONS: Lower baseline eGFR and reduced urine output at the time of KRT initiation are each strongly and independently associated with kidney nonrecovery among critically ill patients with COVID-19.

Association of Treatment Effects on Early Change in Urine Protein and Treatment Effects on GFR Slope in IgA Nephropathy: An Individual Participant Meta-analysis.

RATIONALE & OBJECTIVE: An early change in proteinuria is considered a reasonably likely surrogate end point in immunoglobulin A nephropathy (IgAN) and can be used as a basis for accelerated approval of therapies, with verification in a postmarketing confirmatory trial. Glomerular filtration rate (GFR) slope is a recently validated surrogate end point for chronic kidney disease progression and may be considered as the end point used for verification. We undertook a meta-analysis of clinical trials in IgAN to compare treatment effects on change in proteinuria versus change in estimated GFR (eGFR) slope. STUDY DESIGN: Individual patient-level meta-analysis. SETTING & STUDY POPULATIONS: Individual data of 1,037 patients from 12 randomized trials. SELECTION CRITERIA FOR STUDIES: Randomized trials of IgAN with proteinuria measurements at baseline and 6 (range, 2.5-14) months and at least a further 1 year of follow-up for the clinical outcome. ANALYTICAL APPROACH: For each trial, we estimated the treatment effects on proteinuria and on the eGFR slope, computed as the total slope starting at baseline or the chronic slope starting 3 months after randomization. We used a Bayesian mixed-effects analysis to relate the treatment effects on proteinuria to effects on GFR slope across these studies and developed a prediction model for the treatment effect on the GFR slope based on the effect on proteinuria. RESULTS: Across all studies, treatment effects on proteinuria accurately predicted treatment effects on the total slope at 3 years (median R2 = 0.88; 95% Bayesian credible interval [BCI], 0.06-1) and on the chronic slope (R2 = 0.98; 95% BCI, 0.29-1). For future trials, an observed treatment effect of approximately 30% reduction in proteinuria would confer probabilities of at least 90% for nonzero treatment benefits on the total and chronic slopes of eGFR. We obtained similar results for proteinuria at 9 and 12 months and total slope at 2 years. LIMITATIONS: Study population restricted to 12 trials of small sample size, leading to wide BCIs. There was heterogeneity among trials with respect to study design and interventions. CONCLUSIONS: These results provide new evidence supporting that early reduction in proteinuria can be used as a surrogate end point for studies of chronic kidney disease progression in IgAN.

A New Panel-Estimated GFR, Including ß2-Microglobulin and ß-Trace Protein and Not Including Race, Developed in a Diverse Population.

RATIONALE AND OBJECTIVE: Glomerular filtration rate (GFR) estimation based on creatinine and cystatin C (eGFRcr-cys) is more accurate than estimated GFR (eGFR) based on creatinine or cystatin C alone (eGFRcr or eGFRcys, respectively), but the inclusion of creatinine in eGFRcr-cys requires specification of a person's race. ß2-Microglobulin (B2M) and ß-trace protein (BTP) are alternative filtration markers that appear to be less influenced by race than creatinine is. STUDY DESIGN: Study of diagnostic test accuracy. SETTING AND PARTICIPANTS: Development in a pooled population of 7 studies with 5,017 participants with and without chronic kidney disease. External validation in a pooled population of 7 other studies with 2,245 participants. TESTS COMPARED: Panel eGFR using B2M and BTP in addition to cystatin C (3-marker panel) or creatinine and cystatin C (4-marker panel) with and without age and sex or race. OUTCOMES: GFR measured as the urinary clearance of iothalamate, plasma clearance of iohexol, or plasma clearance of [51Cr]EDTA. RESULTS: Mean measured GFRs were 58.1 and 83.2 mL/min/1.73 m2, and the proportions of Black participants were 38.6% and 24.0%, in the development and validation populations, respectively. In development, addition of age and sex improved the performance of all equations compared with equations without age and sex, but addition of race did not further improve the performance. In validation, the 4-marker panels were more accurate than the 3-marker panels (P < 0.001). The 3-marker panel without race was more accurate than eGFRcys (percentage of estimates greater than 30% different from measured GFR [1 - P30] of 15.6% vs 17.4%; P = 0.01), and the 4-marker panel without race was as accurate as eGFRcr-cys (1 - P30 of 8.6% vs 9.4%; P = 0.2). Results were generally consistent across subgroups. LIMITATIONS: No representation of participants with severe comorbid illness and from geographic areas outside of North America and Europe. CONCLUSIONS: The 4-marker panel eGFR is as accurate as eGFRcr-cys without requiring specification of race. A more accurate race-free eGFR could be an important advance.