Rapid screening test evaluation for microalbuminuria in diabetes mellitus

Microalbuminuria predicts clinical nephropathy and cardiovascular disease in diabetes mellitus. This study was undertaken to evaluate a screening microalbuminuria test with the Micral test II dipstick in a general practice setting and compare whether, if three urine samples are tested, any advantage is offered over a testing single sample. Two hundred and eighty diabetic patients attending a primary health care centre were studied. The first morning urine albumin concentration was determined by dipstick over 3 consecutive days. We studied two valuation methods: Method 1. Three-sample method: the test was considered positive if albumin was equal to or above 20 mg/l in at least two of three tests; Method 2. Single-sample method: we selected the third test, i.e. the most recent urine sample; if albumin was equal to or above 20 mg/l it was considered positive. The gold standard was the albumin excretion rate measured by a nephelometric method in a 24-h urine collection. Sensitivity, specificity, predictive values and Kappa coefficient were calculated. The diagnostic performance was assessed by a receiver operating characteristic curve. Microalbuminuria was defined for different thresholds of albumin excretion rate, 15, 20, 25 and 30 microg/min: their frequency was 38, 29, 23 and 18%, respectively. For method 1, the sensitivity of Micral test II oscillated between 70-94% and the specificity between 93-83%. For method 2, the sensitivity oscillated between 64-86%, and the specificity between 88-80%. Both methods had a high diagnostic performance. The Kappa coefficient was 84 and 60% for method 1 and 2, respectively. The Micral test II is a rapid, valid and reliable method for microalbuminuria screening in diabetic patients. It constitutes an important tool for diabetic surveillance in general practice. Although the use of three samples provides better results, the use of a single sample produces acceptable results at a low cost.