Author(s): White SL, Yu R, Craig JC, Polkinghorne KR, Atkins RC,
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Abstract BACKGROUND: Urine dipsticks, an inexpensive accessible test for proteinuria, are widely advocated for mass screening; however, their diagnostic accuracy in the general community is largely unknown. STUDY DESIGN: Evaluation of diagnostic test accuracy in a cross-sectional cohort. SETTING & PARTICIPANTS: AusDiab, a representative survey of Australian adults 25 years and older (conducted in 1999/2000). Stratified cluster random sampling from 11,247 individuals participating in the biomedical examination; complete urinalysis data available for 10,944. INDEX TEST: Urine dipsticks (Bayer Multistix), with a positive result defined as ≥1+ or trace or higher protein. REFERENCE TEST: Albumin-creatinine ratio (ACR), measured on a random spot urine sample. Reference test positivity was defined as ACR ≥30 mg/g or ACR ≥300 mg/g. RESULTS: Numbers of participants with ACR <30, 30-300, and ≥300 mg/g were 10,219 (93.4\%), 634 (5.8\%), and 91 (0.8\%), respectively. The area under the receiver operating characteristic curve (AUC) for dipstick detection of ACR ≥30 mg/g was 0.8451 ± 0.0129 (SE) in men and 0.7775 ± 0.0131 in women (P < 0.001). The AUROC for dipstick detection of ACR ≥300 mg/g was 0.9904 ± 0.0030 in men and 0.9950 ± 0.0016 in women (P = 0.02). Dipstick result ≥1+ identified ACR ≥30 mg/g with 57.8\% sensitivity (95\% CI, 54.1\%-61.4\%) and 95.4\% specificity (95\% CI, 95.0\%-95.8\%) and identified ACR ≥300 mg/g with 98.9\% sensitivity (99\% CI, 92.1\%-100\%) and 92.6\% specificity (99\% CI, 92.0\%-93.3\%). A dipstick result of trace or higher identified ACR ≥30 mg/g with 69.4\% sensitivity (95\% CI, 65.9\%-72.7\%) and 86.8\% specificity (95\% CI, 86.1\%-87.4\%) and identified ACR ≥300 mg/g with 100\% sensitivity (99\% CI, 94.3\%-100\%) and 83.7\% specificity (99\% CI, 82.8\%-84.6\%). A negative dipstick result (less than trace) had a negative predictive value of 97.6\% (95\% CI, 97.2\%-97.9\%) for ACR ≥30 mg/g and a negative predictive value of 100\% (99\% CI, 99.9\%-100\%) for ACR ≥300 mg/g. The probability of an ACR ≥30 mg/g confirmed on laboratory investigation was 47.2\% (95\% CI, 43.9\%-50.5\%) based on a dipstick result ≥1+ and 27.1\% (95\% CI, 25.1\%-29.2\%) based on a trace or higher result. LIMITATIONS: Isolated urine samples precluded assessment of test reproducibility. Urine specific gravity and pH were not recorded; therefore, the effect of urine concentration on test performance was not assessed. CONCLUSIONS: A dipstick test result <1+ or less than trace has a high negative predictive value in the general community setting, with minimal risk of a missed diagnosis of macroalbuminuria. High false-positive rates emphasize the need for laboratory confirmation of positive results. Copyright © 2011 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.
This article was published in Am J Kidney Dis
and referenced in Journal of Clinical & Experimental Ophthalmology