A simple approach to screening for microalbuminuria in a type 1 (insulin-dependent) diabetic population

The reproducibility of albumin concentration in first-morning samples of urine was assessed in 334 insulin-dependent diabetic patients aged 18-60 years. The albumin excretion rate was determined immunoturbidimetrically in three sterile, Albustix-negative, first-morning urine samples submitted over a week. An abnormally high mean value, greater than or equal to 2.5 mg albumin per mmol creatinine (Ua/Uc), was found in 33 patients (9.9%). These patients were older (mean 42 vs 34 years, P less than 0.01), had longer disease duration (18 vs 14 years, P less than 0.01) and higher HbA1c values (6.8 vs 6.3%, P less than 0.05) than those without microalbuminuria. Although triplicate samples were collected within 7 days, Ua/Uc showed considerable intraindividual variation, with a mean coefficient of variation of 49%. Despite this it was found that Ua/Uc values greater than 1 mg/mmol on the first specimen had a sensitivity of 97% and a specificity of 82% for detecting those with a three-sample mean value greater than 2.5 mg/mmol. Thus virtually all those with microalbuminuria (32/33) had a single first-morning result greater than 1 mg/mmol, and in those with a lower ratio microalbuminuria was excluded with more than 99% certainty.