OBJECTIVE 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 (eGFRcys) with that using
creatinine (eGFRcr) for the identification of reduced kidney function and its association with
diabetes complications. RESEARCH DESIGN AND METHODS 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. RESULTS Among 778 persons with diabetes, the prevalence of reduced kidney function was 16.5% using eGFRcr and 22.0% using eGFRcys. More persons with diabetes were reclassified from preserved kidney function by eGFRcr to reduced kidney function by eGFRcys 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 eGFRcr and eGFRcys. Only lower eGFRcys was significantly associated with cardiovascular mortality. CONCLUSIONS More persons with diabetes had reduced kidney function by eGFRcys than by eGFRcr, and lower eGFRcys was strongly associated with
diabetes complications. Whether eGFRcys is superior to eGFRcr in approximating true kidney function in a diabetic population requires additional study.