The Receiver Operating Characteristics Curve in the Evaluation of a Random Urine Specimen as a Screening Test for Diabetic Nephropathy

Themis Zelmanovitz; Jorge L Gross; Jarbas R Oliveira; Alexandre Paggi; Mariana Tatsch; Mirela J Azevedo

doi:10.2337/diacare.20.4.516

Original Articles

The Receiver Operating Characteristics Curve in the Evaluation of a Random Urine Specimen as a Screening Test for Diabetic Nephropathy

Themis Zelmanovitz, MD,
Jorge L Gross, MD,
Jarbas R Oliveira, PHD,
Alexandre Paggi,
Mariana Tatsch and
Mirela J Azevedo, MD

Endocrine Unit, Hospital de Clínicas de Porto Alegre, Federal University of Rio Grande do Sul Porto Alegre, Brazil

Address correspondence and reprint requests to Mirela J. de Azevedo, MD, Serviço de Endocrinologia, Hospital de Clínicas de Porto Alegre, Rua Ramiro Barcellos 2350/635, 90035-003, Porto Alegre, RS, Brazil.

Diabetes Care 1997 Apr; 20(4): 516-519. https://doi.org/10.2337/diacare.20.4.516

Abstract

OBJECTIVE To assess the performance of measurements of urinary albumin concentration (UAC) and urinary albumin:creatinine ratio (UACR) in a diurnal random urine specimen (RUS) for the screening of diabetic nephropathy.

RESEARCH DESIGN AND METHODS A total of 95 ambulatory NIDDM patients (49 women, ages 40–75 years) collected 123 RUSs during the morning after completing a timed 24-h urine collection. Albumin was measured by immunoturbidimetry. According to timed urinary albumin excretion rate (UAER) measured in the 24-h collection (criterion standard), samples were classified as normoalbuminuric (UAER < 20 μg/min; n = 54), microalbuminuric (UAER 20–200 μg/min; n = 44), and macroalbuminuric (UAER > 200 μg/min; n = 25). The receiver operating characteristics (ROC) curve approach was used. The ROC curves of UAC and UACR in RUS for screening of microalbuminuria (normo- and microalbuminuric samples; 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 microalbuminuria for UAC (0.9766 ± 0.015) and UACR (0.9689 ± 0.014) were similar (P > 0.05) as were the corresponding areas for macroalbuminuria (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 macroalbuminuria 174.0 and 296.2 mg/l for UAC and 116.0 and 334.3 mg/g for UACR, respectively.

CONCLUSIONS Albumin measurements (UAC and UACR) in an RUS presented almost perfect accuracy for the screening of micro- and macroalbuminuria and UAC measured in an RUS is simpler and less expensive than UACR and UAER. It is suggested as a valid test for use in screening for diabetic nephropathy.