ACCURACY OF THE URINARY ALBUMIN TITRATOR STICK MICRAL-TEST IN KIDNEY-DISEASE PATIENTS

Background. A quick, accurate, and easy measurement of microalbuminuri a can be useful for the management of many patients. The Micral-Test(R ) stick (Boehringer Mannheim, Germany) gives a semiquantitative estima tion of urinary albumin concentration at discrete readings of 0, 10, 2 0, 50 or 100 mg/l. The purpose of this study was to test its accuracy. Methods. From 46 non-diabetic patients, 491 urinary samples were anal ysed both with Micral-Test(R) and with immunochemical nephelometry. Re sults. Of 491 samples, 308 were from non-proteinuric patients (urinary albumin <300 mg/day). In these patients the correlation coefficient o f nephelometric values versus the stick readings was 0.79; 120/123 sam ples from non-microalbuminuric (less than or equal to 30 mg/24 h) and 164/185 from microalbuminuric patients were correctly identified by th e stick, giving an 89% sensitivity and a 98% specificity. The readings around the threshold for microalbuminuria (20 and 50 mg/l patches) we re the most reliable ones. Analysis of the correct/uncorrect readings' ratio for every patch in the 245 samples in the 0-150mgll range shows a relative uniformity (chi(2) = 8.5, P = 0.07), while analysis of the over/correct/underreadings for the 10, 20 and 50 patches, shows that incorrect responses tend to be underestimations for the 10 patch and o verestimations for the 20 and 50 mg/l patches (chi(2) = 10.5: P = 0.03 ). Conclusions The Micral-Test(R) stick is useful for screening, but l ess reliable for follow-up, unless considerable changes in albumin exc retion are expected.