THE RECEIVER OPERATING CHARACTERISTICS CURVE IN THE EVALUATION OF A RANDOM URINE SPECIMEN AS A SCREENING-TEST FOR DIABETIC NEPHROPATHY

OBJECTIVE - To assess the performance of measurements of urinary album in concentration (UAC) and urinary albumin:creatinine ratio (UACR) in a diurnal random urine specimen (RUS) for the screening of diabetic ne phropathy. RESEARCH DESIGN AND METHODS - A total of 95 ambulatory NIDD M patients (49 women, ages 40-75 years) collected 123 RUSs during the morning after completing a timed 24-h urine collection. Albumin was me asured by immunoturbidimetry. According to timed urinary albumin excre tion rate (UAER) measured in the 24-h collection (criterion standard), samples were classified as normalbuminuric (UAER <20 mu g/min; n = 54 ), microalbuminuric (UAER 20-200 mu g/min; n = 44), and macroalbuminur ic (UAER >200 mu g/min; n = 25). The receiver operating characteristic s (ROC) curve approach was used. The ROC curves of UAC and UACR in RUS for screening of microalbuminuria (normo- and microalbuminuric sample s; n = 98) and macroalbuminuria (micro- and macroalbuminuric samples; n = 69) were plotted.RESULTS - Spearman's coefficients of correlation of 24-h UAER vs. UAC and UACR were 0.91 and 0.92, respectively (P < 0. 001). The calculated areas (+/- SE) under the ROC curves to screen mic roalbuminuria for UAC (0.9766 +/- 0.015) and UACR (0.9689 +/- 0.014) w ere similar (P > 0.05) as were the corresponding areas for macroalbumi nuria (0.9868 +/- 0.0094 and 0.9614 +/- 0.0241, respectively; P > 0.05 ). The first point with 100% sensitivity and the point of intersection with a 100%-to-100% diagonal for microalbuminuria were as follows: 16 .9 and 33.6 mg/l for UAC and 15.0 and 26.8 mg/g for UACR; for macroalb uminuria 174.0 and 296.2 mg/l for UAC and 116.0 and 334.3 mg/g for UAC R, respectively. CONCLUSIONS - Albumin measurements (UAC and UACR) in an RUS presented almost perfect accuracy for the screening of micro- a nd macroalbuminuria and UAC measured in an RUS is simpler and less exp ensive than UACR and UAER. It is suggested as a valid test for use in screening for diabetic nephropathy.