Abstract
BackgroundThe dipstick test is widely used as a primary screening test for detection of significant proteinuria in pregnancy (SPIP). However, it often shows a false positive test result. This study was performed to determine which pregnant women should be recommended to undergo determination of urinary protein-to-creatinine ratio (mg/mg, P/Cr test) after dipstick test for confirmation of SPIP.MethodsThis was a multicenter, prospective, and observational study of 2212 urine specimens from 1033 pregnant women who underwent simultaneous dipstick and P/Cr tests in the same spot urine samples at least once. SPIP was defined as P/Cr > 0.27. Preeclampsia was diagnosed in women with both hypertension and SPIP.ResultsPreeclampsia, hypertension alone, and SPIP alone developed in 202 (20 %), 73 (7.1 %), and 120 (12 %) women, respectively. Creatinine concentration [Cr] varied greatly, ranging from 8.1 to 831 mg/dL in the 2212 urine samples. Rate of positive dipstick test results increased with increasing [Cr], while SPIP prevalence rate was lower in urine samples with higher [Cr], yielding higher false positive rates in samples with higher [Cr]. Postpartum urine samples had significantly lower [Cr] compared to those obtained antepartum (60 [8.7–297] vs. 100 [10–401] mg/dL, respectively). At the first P/Cr test among women with similar dipstick test results, the risk of having SPIP was consistently and significantly higher for hypertensive women than for normotensive women at any dipstick test result: 18 % (14/77) vs. 3.2 % (8/251), 47 % (26/55) vs. 8.7 % (37/425), 91 % (82/90) vs. 59 % (44/75) for negative/equivocal, 1+, and ≥ 2+ test results, respectively. The risk of SPIP was 16 % (9/55) for normotensive women when two successive antenatal urine samples showed a dipstick test result of 1 + .ConclusionsFor prediction of SPIP, the dipstick test was more likely to show a false positive result in concentrated urine samples with higher [Cr]. Hypertensive women with ≥ 1+ as well as normotensive women with ≥ 2+ on dipstick test should be advised to undergo the P/Cr test.
Highlights
The dipstick test is widely used as a primary screening test for detection of significant proteinuria in pregnancy (SPIP)
As PE is usually diagnosed in women that developed both hypertension and significant proteinuria in pregnancy (SPIP), assessment of proteinuria is an important constituent of antenatal care for pregnant women
The dipstick test is designed to reflect urinary protein concentration [P] at a certain cutoff level not corrected by urinary creatinine concentration [Cr]; dipsticks with ≥ 1+ on visual judgment for urinary protein concentration ≥ 30 mg/dL are widely used in Japan [9]
Summary
This prospective observational study was conducted after receiving approval from the Institutional Review Board of Hokkaido University Hospital (013–0399, April 30, 2014). Participants A total of 6984 women gave birth at gestational week (GW) ≥ 22 during the one-year study period between April 1, 2014, and March 31, 2015, in the 12 facilities. Of the 6984 women, 1033 (15 %) underwent simultaneous dipstick test and P/Cr test in the same spot urine specimens at least once, and were enrolled in this study. SPIP was defined as a P/Cr (mg/mg) test result of > 0.27. PE was diagnosed in women with chronic hypertension when SPIP occurred on and after GW 20. The attending physicians at each facility ordered the P/Cr test in the same spot urine specimen with a dipstick test result at their discretion when it was considered helpful for patient care. P < 0.05 was taken to indicate statistical significance
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