Objective: To evaluate the accuracy of a 12-hour urine collection to diagnose preeclampsia and to determine whether time of collection influences the performance of this test.Methods: A prospective observational study was conducted in a tertiary obstetric center in Portugal between November 1, 2015, and November 30, 2016. Pregnant women (≥20 weeks) admitted for observation with suspected pre-eclampsia were eligible for inclusion. Two consecutive 12-hour urine samples were collected (07:00-19:00 hours vs 19:00-07:00 hours). Protein levels were measured in each 12-hour sample, as well as in a pooled sample (07:00-07:00 hours). The diagnostic cut-off values for pre-eclampsia were 150 mg (12-hour samples) and 300 mg (24-hour sample).
Results:The study included 99 patients and diagnoses of pre-eclampsia were confirmed among 42 (42%) patients. In all, 456 12-hour urine samples were analyzed (equivalent to 228 24-hour samples). Qualitative analysis (pre-eclampsia vs no preeclampsia) indicated substantial agreement between the 12-and 24-hour samples (Cohen κ 0.779). The sensitivity was 85.9% (95% confidence interval [CI] 81%-90%) and the specificity was 91.7% (95% CI 88%-95%). No statistically significant difference was found between the two 12-hour collections.
Conclusion:The 12-hour test showed acceptable accuracy for detecting pre-eclampsia, regardless of the time of collection.
K E Y W O R D S24-hour urine collection; Hypertensive disorders of pregnancy; Non-inferiority; Pre-eclampsia; Proteinuria
| INTRODUCTIONPre-eclampsia and other hypertensive disorders of pregnancy account for 10.3%-22.1% of all maternal deaths worldwide.1 The current diagnostic criteria indicate that proteinuria should no longer be considered an obligatory component of pre-eclampsia 2,3 ; however, quantification of urinary protein levels is still routine practice.A 24-hour urine collection, with a 300 mg cut-off level for proteinuria, remains the gold standard to diagnose the presence of substantial proteinuria. Nonetheless, alternative methods-including the urine spot protein-to-creatinine ratio with a cut-off of 0.3-are considered equivalent by many obstetric societies. 2,3 The protein-to-creatinine ratio test is undoubtedly more practical and convenient to perform than the 24-hour urine collection test but some controversy remains given the wide range of sensitivity (65%-96%), specificity (49%-100%), and clinical heterogeneity reported.
4-6A systematic review and meta-analysis by Stout et al. 7 found that 12-hour urine collection, with a 150 mg cut-off level for proteinuria, performed well among women with hypertension during pregnancy.However, the main limitations were the small sample sizes of the studies included in the analysis, the heterogeneous methods used for urine collection, and the lack of information on time of collection.