Glomerular filtration rate-based cystatin C compared to microalbuminuria to detect early stage of diabetic nephropathy in children with type 1 diabetes mellitus

Microalbuminuria is a sensitive marker to detect early nephropathy in diabetes mellitus. Cystatin C correlates better than serum creatinine with microalbuminuria in type 1 diabetes mellitus (T1D). We evaluated the correlation between microalbuminuria, serum cystatin C (Cyc-C), and serum creatinine (SCr) in diabetic children. A hundred patients with stable T1D and 66 sex-matched healthy children were entered in the study between September 2008 and February 2011. Fasting blood sample was drawn for HbA(1)C, creatinine, and cystatin C. A. 24-h urine aliquot was collected to measure microalbumin, creatinine, and volume. Glomerular filtration rate estimated based on creatinine (eGFR(cr)), cystatin C (eGFR(Cyst) C), and creatinine + cystatin C (eGFR(Cyst C + Cr)). Binary logistic regression analysis, chi- square, ANOVA, Students t test, and nonparametric median tests were used to analyze data. P<0.05 was considered significant. Medians serum creatinine and cystatin C of T1D group were significantly different from controls (P<0.05). Overall, medians eGFR(Cyst C) were higher than eGFR(cr), or eGFR(Cyst C + Cr). Thirty-six children with T1D had microalbuminuria. There was a correlation between microalbuminuria and eGFR(Cyst C) (<60 and >130 ml/min/1.73 m(2)) (P<0.05). Medians eGFR(cr) were significantly lower than medians eGFR(Cyst C) in T1D, regardless of microalbuminuria (P<0.05). Chronic kidney disease classification according to eGFR(cr) and eGFR(Cyst C) were not matched (P<0.05). GFR in healthy children was overestimated by eGFR(Cyst C) and underestimated by eGFR(cr). There was higher correlation between abnormal eGFR(Cyst C) and microalbuminuria in diabetic children. eGFR(Cr) detected higher rate of GFR less than 60 ml/min/1.73 m(2).