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(cr) and 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-EPI 2009 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/1.73m(2) to eGFR(cys) >= 60ml/min/1.73m(2). 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/1.73m(2). 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/1.73m(2); among these, 64% had eGFR(cys) <60mL/min/1.73m(2). Among participants with eGFR(cr) >= 60mL/min/1.73m(2), 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.