Serum cystatin C as a marker for early detection of chronic kidney disease and grade 2 nephropathy in Japanese patients with type 2 diabetes.

ABSTRACT

BACKGROUND: Diabetic nephropathy (DN) is a significant cause of hemodialysis, and its early detection is extremely important to prevent or delay end-stage renal disease. The significance of the renal function marker serum cystatin C (sCysC) and its relationship with glomerular filtration rate in chronic kidney disease (CKD) and DN in Japanese patients with type 2 diabetes remains uncertain. In this study, we examined the effectiveness of sCysC as a marker of early DN and CKD in Japanese subjects. METHODS: A total of 325 Japanese patients with type 2 diabetes and 88 healthy subjects were studied retrospectively. sCysC concentration (mg/L) was determined by a latex turbidmetric immunoassay using a BioMajesty 8040 analyzer. The renal function of the diabetic patients was evaluated using the albumin-creatinine ratio (ACR) and Kidney Disease Outcome Quality Initiative-Kidney Disease Improving Global Outcomes (K/DOQI-KDIGO) classification. RESULTS: There was a significant increase in sCysC but not in serum creatinine (sCr) or serum ß2-microglobulin (sß2M) in patients with grade 2 DN (ACR 30-300 mg/g) compared to grade 1 patients. Receiver operating characteristic analysis in grade 2 and 3 DN patients showed that sCysC had superior sensitivity and specificity than sCr and sß2M for early detection of DN. In addition, sCysC showed particularly high sensitivity and specificity in DN patients with stage 2 CKD. CONCLUSIONS: sCysC was effective for detection of grade 2 DN and would be especially useful for screening stage 2 CKD patients (K/DOQI-KDIGO).