Factors associated with diabetic nephropathy in subjects with proliferative retinopathy

The purpose was to compare the phenotype of subjects with type 2 diabetes mellitus having both retinopathy and nephropathy with that of subjects having retinopathy but no nephropathy.

We recruited 196 subjects; 85 were normoalbuminuric (controls), whilst cases consisted of patients with micro- (n = 66) or macroalbuminuria (n = 45). Both groups underwent 24-h blood pressure (BP) monitoring and were analysed regarding markers of the metabolic syndrome, inflammation (erythrocyte sedimentation rate [ESR] and high-sensitivity CRP [hsCRP]) and insulin resistance (HOMA-IR).

Cases had significantly higher white cell count (P = 0.02), ESR (P < 0.001), platelets (P = 0.02), triglycerides (P = 0.001), uric acid (P < 0.001), daytime and night-time systolic BP (P = 0.001 & P = 0.001, respectively), diastolic BP (P = 0.007 & P = 0.001), pulse pressure (P = 0.02 & 0.055) and mean arterial pressure (P = 0.001 & P < 0.001) in univariate analysis. Cases had a lower haemoglobin level (P = 0.01) and estimated glomerular filtration rate (eGFR) (P = 0.002) in comparison with controls. Multivariate analysis showed that night-time diastolic BP (P = 0.002, B = 1.057), platelet count (P = 0.018, B = 1.007) and eGFR (P < 0.001, B = 0.097) are independent predictors of diabetic nephropathy. Platelet count (P = 0.045, B = 1.006), night-time mean diastolic BP (P = 0.029, B = 1.042) and eGFR (P = 0.001, B = 0.975) were also found to be independent predictors of the occurrence of microalbuminuria.

By analysing factors associated with diabetic nephropathy rather than microvascular disease in general, this study provides evidence that night-time diastolic BP and a relative increase in platelet count are associated with incipient diabetic nephropathy.