Creatinine-versus cystatin C-based renal function assessment in the Northern Manhattan Study

Background: Accurate glomerular filtration rate estimation informs drug dosing and risk stratification. Body composition heterogeneity influences creatinine production and the precision of creatinine-based estimated glomerular filtration rate (eGFR_cr) in the elderly. We compared chronic kidney disease (CKD) categorization using eGFR_crand cystatin C-based estimated GFR (eGFR_cys) in an elderly, racially/ethnically diverse cohort to determine their concordance. Methods: The Northern Manhattan Study (NOMAS) is a predominantly elderly, multi-ethnic cohort with a primary aim to study cardiovascular disease epidemiology. We included participants with concurrently measured creatinine and cystatin C. eGFR_cr was calculated using the CKD-EPI2009 equation. eGFR_cys was calculated using the CKD-EPI 2012 equation. Logistic regression was used to estimate odds ratios and 95% confidence intervals of factors associated with reclassification from eGFR_cr≥60ml/min/1.73m² to eGFR_cys<60ml/min/1.73m². Results: Participants (n = 2988, mean age 69±10yrs) were predominantly Hispanic, female, and overweight/obese. eGFR_cys was lower than eGFR_cr by mean 23mL/min/1.73m².51% of participants' CKD status was discordant, and only 28% maintained the same CKD stage by both measures. Most participants (78%) had eGFR_cr≥60mL/min/1.73m²; among these, 64% had eGFR_cys<60mL/min/1.73m². Among participants with eGFR_cr≥60mL/min/1.73m², eGFR_cys-based reclassification was more likely in those with age >65 years, obesity, current smoking, white race, and female sex. Conclusions: In a large, multiethnic, elderly cohort, we found a highly discrepant prevalence of CKD with eGFR_cys versus eGFR_cr. Determining the optimal method to estimate GFR in elderly populations needs urgent further study to improve risk stratification and drug dosing.