Comparison of urine protein–creatinine ratio and urine dipstick test for significant proteinuria in preeclamptic women

Abstract

Background: Assessing for significant proteinuria in pregnancy (SPIP) stands as a key indicator for diagnosing preeclampsia. However, the initial method typically employed for this assessment, the urine dipstick test, often yields inaccurate results. While a 24-h urine collection is considered the most reliable test, its implementation can lead to delays in diagnosis, potentially affecting both maternal and fetal well-being. The urine protein–creatinine (P/Cr) ratio can be used as an alternative to 24-h urine protein analysis, but its diagnostic accuracy has remained uncertain. There is a need to compare the diagnostic accuracy of urine P/Cr ratio and dipstick urinalysis for SPIP, especially in resource-poor settings. Objectives: To determine and compare the diagnostic accuracy of urine P/Cr ratio and dipstick urinalysis in a spot urine specimen for the diagnosis of SPIP among women evaluated for preeclampsia using 24-h urine protein excretions as a gold standard. Design: This is a comparative cross-sectional study. Methods: The study involved 82 singleton pregnant women evaluated for preeclampsia from 20 weeks of gestation who underwent dipstick and P/Cr ratio tests in the same urine sample. Women at risk of preeclampsia were given a specimen container for the collection of urine samples on an outpatient basis. Participants were trained and told to collect the urine sample 24 h prior to their next antenatal appointment. However, those on admission and evaluated for preeclampsia had their 24-h urine collected in the hospital. The outcome measures included sensitivity, specificity, positive predictive value, negative predictive value, likelihood ratio and accuracy for the two tests. Significant proteinuria was defined as a P/Cr ratio >0.27 or ⩾2+ of proteinuria on the dipstick test. Preeclampsia was confirmed in women with both high blood pressure and SPIP. Results: The mean age of participants was 28.65 ± 5.76 years. Comparatively, the diagnostic accuracy (91.46% (95% CI = 83.29–96.59) vs 59.76% (95% CI = 48.34–70.44), p = 0.001), sensitivity (94.74% vs 70.00%, p = 0.021), specificity (84.00% vs 43.75%, p = 0.001), negative predictive value (87.50% vs 48.28%, p = 0.003) and positive predictive value (93.10% vs 66.04%, p = 0.001), respectively, were higher for the spot urine P/Cr ratio than dipstick test. In addition, the positive likelihood ratio and the negative likelihood ratio for spot urine P/Cr ratio versus dipstick test were (1.93 vs 1.24) and (0.07 vs 0.69), respectively. Conclusion: The spot urine P/Cr has superior diagnostic accuracy in the determination of significant proteinuria in pregnant women being evaluated for preeclampsia than the widely used dipstick test. A more robust multicenter study is needed to compare the diagnostic accuracy of spot urine PCR with the standard 24-h urine protein in low-income settings.