CYSTATIN C BASED FORMULA HAS A HIGHER DIAGNOSTIC ACCURACY THAN CREATININE BASED FORMULA IN EGYPTIAN TYPE 2 DIABETIC PATIENTS WITH EARLY NEPHROPATHY

Background: Diabetic nephropathy is difficult to be detected by traditional methods like serum creatinine and creatinine clearance rate. Cystatin C is sensitive to changes in creatinine blind glomerular filtration rate (GFR) range (40-90 ml/min/1.73m2). The aim of this study was to assess cystatin C and to compare between cystatin C-based GFR and creatinine based GFR estimates in patients with type 2 diabetes mellitus (T2DM) either nephropathic or non-nephropathic.

Methods: The study comprised 75 patients with T2DM and 15 age- and sex-matched controls. Patients were categorized into three groups according to albuminuria status; group 1 included 25 T2DM patients with normoalbuminuria, group 2 included 25 T2DM patients with microalbuminuria and group 3 included 25 T2DM patients with macroalbuminuria or protienuria. Anthropometric measurements, cystatin C, eGFR-cystatin C, creatinine and eGFR-creatinine were assessed.

Results: Cystatin C was higher in patients with T2DM than in controls. Cystatin C was positively correlated with creatinine and urinary albumin -creatinine ratio (UACR) and negatively correlated with albumin, GFR-creatinine and GFR-cystatin. eGFR-creatinine was significantly lower in T2DM patients with macroalbuminuria than normoalbuminuria and microalbuminuria, but there was insignificant difference between patients with normoalbuminuria and microalbuminuria. eGFR-cystatin was significantly lower in T2DM patients with macroalbuminuria than in microalbuminuria and normoalbuminuria and also was significantly lower in patients with microalbuminuria than in normoalbuminuria.

Conclusion: Serum cystatin C is elevated in patients with T2DM along with progression of albuminuria. Cystatin C based formula (eGFR-cystatin C) has a higher diagnostic accuracy than that of creatinine based formula (eGFR-creatinine) in early diabetic nephropathy.