Glomerular hyperfiltration and metabolic syndrome: results from the FIrenze-BAgno A Ripoli (FIBAR) Study

Metabolic syndrome (MS) has been associated with microalbuminuria and kidney disease. In the present cohort study, different methods for the estimation of glomerular filtration rate (GFR) on the basis of serum creatinine were compared with respect to their association with MS and their predictive value for incident diabetes mellitus. The present analysis was performed on the cohort of subjects enrolled in the FIBAR study, a screening program for diabetes. GFR was estimated (eGFR) using three different methods: Cockroft-Gault (CG) formula, using actual body weight (CAW), CG formula using ideal body weight (CIW), and Modification of Diet in Renal Disease formula (M). The study was performed on 2,694 nondiabetic subjects, without history of renal insufficiency or serum creatinine at baseline >1.5 mg/dl. Mean follow-up was 27.8 +/- 11.5 months. Elevated eGFR, estimated with different methods, was associated with increased prevalence of most components of MS; however, an association between elevated clearance and MS was observed only when using CAW, which overestimates filtration in obese subjects. During follow-up, 40 new cases of diabetes were recorded (0.5/100 patient*years). After adjusting for age and sex, the HR (with 95% confidence intervals) for diabetes for patients in the highest quintile of eGFR was 1.14 [0.44-2.99], 0.89 [0.31-2.51], and 1.01 [0.42-2.41] for formula CAW, CIW, and M, respectively (all p > 0.7). Elevated eGFR, estimated through methods which do not produce a systematic overestimate in obese subjects, is not associated with the diagnosis of MS, and does not predict diabetes.