Accuracy of the urinary albumin titrator stick 'Micral-Test' in kidney-disease patients

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Abstract
BACKGROUND: A quick, accurate, and easy measurement of microalbuminuria can be useful for the management of many patients. The Micral-Test stick (Boehringer Mannheim, Germany) gives a semiquantitative estimation of urinary albumin concentration at discrete readings of 0, 10, 20, 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 analysed both with Micral-Test and with immunochemical nephelometry. RESULTS: Of 491 samples, 308 were from non-proteinuric patients (urinary albumin < 300 mg/day). In these patients the correlation coefficient of nephelometric values versus the stick readings was 0.79: 120/123 samples from non-microalbuminuric (< or = 30 mg/24 h) and 164/185 from microalbuminuric patients were correctly identified by the stick, giving an 89% sensitivity and a 98% specificity. The readings around the threshold for microalbuminuria (20 and 50 mg/l patches) were the most reliable ones. Analysis of the correct/uncorrect readings' ratio for every patch in the 245 samples in the 0-150 mg/l range shows a relative uniformity (chi2 = 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 overestimations for the 20 and 50 mg/l patches (chi2 = 10.5, P = 0.03). CONCLUSIONS: The Micral-Test stick is useful for screening, but less reliable for follow-up, unless considerable changes in albumin excretion are expected.

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