Diagnostic accuracy of urine dipstick for proteinuria in older outpatients

Abstract

BackgroundThe urine dipstick is widely used as an initial screening tool for the evaluation of proteinuria; however, its diagnostic accuracy has not yet been sufficiently evaluated. Therefore, we evaluated its diagnostic accuracy using spot urine albumin/creatinine ratio (ACR) and total protein/creatinine ratio (PCR) in proteinuria. MethodsUsing PCR ≥0.2g/g or ≥0.5g/g and ACR ≥300mg/g or ≥30mg/g as the reference standard, we calculated the diagnostic accuracy profile: sensitivity, specificity, positive and negative predictive value, and the area under the curve (AUC) of the receiver operating characteristic curve. ResultsPCR and ACR were available for 10,348 and 3,873 instances of dipstick testing. The proportions with PCR ≥0.2g/g, ≥0.5g/g and ACR ≥300mg/g, ≥30mg/g were 38.2%, 24.6% and 8.9%, 31.7%, respectively. The AUCs for PCR ≥0.2g/g, ≥0.5g/g, and ACR ≥300mg/g were 0.935 (trace: closest to ideal point), 0.968 (1+), and 0.983 (1+), respectively. Both sensitivity and specificity were >80% except for PCR ≥0.5g/g with trace cutoff. For the reference standard of ACR ≥30mg/g, the AUC was 0.797 (trace) and the sensitivity was 63.5%. ConclusionUrine dipstick test can be used for screening in older outpatients with ACR ≥300mg/g or PCR as the reference standard for proteinuria. However, we cannot recommend the test as a screening tool with ACR ≥30mg/g as the reference owing to its low sensitivity.