Serum cystatin C is an alternative to serum creatinine for estimating glomerular filtration rate (GFR), since cystatin C is less influenced by age and muscle mass. Among persons with diabetes, we compared the performance of GFR estimated using cystatin C (eGFR cys) with that using creatinine (eGFR cr) for the identification of reduced kidney function and its association with diabetes complications.
We analyzed data from adult participants from the 1999–2002 National Health and Nutrition Examination Survey with available cystatin C ( N = 4,457). Kidney function was dichotomized as preserved (eGFR ≥60 mL/min/1.73 m 2) or reduced (eGFR <60 mL/min/1.73 m 2) using the 2012 Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) cystatin C and the 2009 CKD-EPI creatinine equations.
Among 778 persons with diabetes, the prevalence of reduced kidney function was 16.5% using eGFR cr and 22.0% using eGFR cys. More persons with diabetes were reclassified from preserved kidney function by eGFR cr to reduced kidney function by eGFR cys than persons without diabetes (odds ratio 3.1 [95% CI 1.9–4.9], P < 0.001). The associations between lower eGFR and higher prevalence of albuminuria, retinopathy, peripheral arterial disease, and coronary artery disease were robust regardless of filtration marker. Similarly, the risk of all-cause mortality increased with lower eGFR cr and eGFR cys. Only lower eGFR cys was significantly associated with cardiovascular mortality.