Retinopathy is independently related to microalbuminuria in type 2 diabetes mellitus

Aim, subjects and methods: To evaluate whether microalbuminuria is related to retinopathy in type 2 diabetes, we studied a sample of 125 known diabetic subjects with a mean disease duration of II years (range 5-22 years), aged 46-71 years, by ophthalmoscopy, fundus photography and fluoresceine angiography. Urinary albumin excretion rate (UAER) was measured by nephelometry and the fractional clearance of albumin, i.e. in relation to creatinine was calculated from spot samples. The subjects were classified into groups based on the UAER/24 h. Results: Microalbuminuria was present if UAER was 30-300 mg/24 h and overt nephropathy when UAER greater than or equal to 300 mg/24 h. Background (greater than or equal to 2 microaneurysms or greater than or equal to 2 hemorrhages or greater than or equal to 1 more advanced lesions, except proliferative changes) and proliferative retinopathies were found in 21% and in 3%, respectively. Subjects with microalbuminuria (p = 0.026) and overt nephropathy (p = 0.002) had more frequently background retinopathy than their counterparts with a normal UAER (chi(2)-test). A multivariate logistic regression model was obtained for background retinopathy (chi(2) = 37.5, p = 0.0000039, OR 14.9, correct prediction of negative outcome in 97% and of positive outcome in 30.4%) including the following variables. The fractional clearance of albumin independently explained background retinopathy (OR 3.9, 95% CI 1.3-12, p = 0.028). Insulin therapy (p = 0.0017), diabetes duration (p = 0.048), blood glucose at 2 h in standard oral glucose tolerance test (p = 0.009) and low fasting serum HDL cholesterol (p = 0.023) also independently explained retinopathy. Age, gender, BMI, systolic blood pressure, ACE inhibitor therapy, fasting serum total cholesterol and triglyceride, blood glucose or insulin, hemoglobin A(1c), glucagon-stimulated C peptide response, glomerular filtration rate or smoking habits did not independently explain retinopathy. Conclusion: We conclude that microalbuminuria is related to background retinopathy in type 2 diabetes.