Evaluation of the estimation of glomerular filtration rate assessment in diabetic patients using equations based on creatinine and cystatin C

Abstract

Diabetic nephropathy (DN) is the most frequent pathology in hemodialysis admission (in Argentina, almost 4 out of 10 hemodialysis patients are diabetic). To detect DN at early stages, it is recommended to measure albumin excretion. However, the glomerular filtration rate (GFR) can decrease without albuminuria and DN can only present a reduced GFR (as occurs in patients with type-2 diabetes). Thus, the GFR should be estimated at least once a year. The KDIGO 2012 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease (CKD) recommends 2009 CKD-EPI formulas to estimate GFR, using Cystatin C-based formulas whenever a confirmatory test is required, or when creatinine measurement is not reliable. At present, Cystatin C measurement has been standardized, and traceable immunological methods are available; however, these methods are not routinely used in Argentina. The aims of the present study were to verify significant differences in GFR estimated with 2009 CKD-EPI, CKD-EPI Cystatin C and CKD-EPI creatinine-cystatin C formulas, comparing them with the MDRD4-IDMS formula, and to classify patients into CKD risk groups following the recommendations of KDIGO 2012.
Materials and Methods: 156 diabetic patients (age range 40-70 years) with glycated hemoglobin HbA1c ≥ 6.5 % and first morning urine. Using Cystatin C as a confirmatory test when GFR values were slightly and/or moderately decreased, 10 patients were confirmed to have CKD and other 5 patients with GFRCREA on stage 2 were reclassified to stage 3A with GFRCYS, showing CKD.