Accuracy of 12-hour urine collection in the diagnosis of pre-eclampsia

A meta-analysis on diagnostic accuracy of spot urinary protein to creatinine ratio versus 12-h proteinuria in preeclampsia

To systematically review the diagnostic accuracy of spot urinary protein to creatinine ratio (PCR) and 12-h proteinuria in preeclampsia and to estimate which is a preferred alternative method for 24-h proteinuria, we carried out this meta-analysis. 25 primary studies were included based on searching strategy. For spot urinary PCR, our results showed pooled sensitivity of 87% (95% confidence interval [CI] 83%-91%) and specificity of 86% (95% CI 79%-91%), with an area under curve (AUC) of 0.93 (0.90-0.95). For 12-h proteinuria, pooled sensitivity and specificity were 92% (95% CI 87%-96%) and 99% (95% CI 75%-100%), respectively, with an AUC of 0.97 (0.95-0.98). Fagan plot and likelihood ratio scattergram showed that 12-h proteinuria yielded a better discriminatory performance on diagnosis of proteinuria (≥0.3 g/24 h). These results indicated that 12-h proteinuria estimation shows better clinical value than spot urine PCR for diagnosis of preeclampsia. However, due to the severity of condition and the fact that preeclampsia patients cannot wait for 12 h, spot urine PCR can be used as one of the diagnostic indicators.

Proteinuria during pregnancy: definition, pathophysiology, methodology, and clinical significance

Qualitative and quantitative measurement of urine protein excretion is one of the most common tests performed during pregnancy. For more than 100 years, proteinuria was necessary for the diagnosis of preeclampsia, but recent guidelines recommend that proteinuria is sufficient but not necessary for the diagnosis. Still, in clinical practice, most patients with gestational hypertension will be diagnosed as having preeclampsia based on the presence of proteinuria. Although the reference standard for measuring urinary protein excretion is a 24-hour urine collection, spot urine protein-to-creatinine ratio is a reasonable "rule-out" test for proteinuria. Urine dipstick screening for proteinuria does not provide any clinical benefit and should not be used to diagnose proteinuria. The classic cutoff cited to define proteinuria during pregnancy is a value of >300 mg/24 hours or a urine protein-to-creatinine ratio of at least 0.3. Using this cutoff, the rate of isolated proteinuria in pregnancy may reach 8%, whereas preeclampsia occurs among 3% to 8% of pregnancies. Although this threshold is widely accepted, its origin is not based on evidence on adverse pregnancy outcomes but rather on expert opinion and results of small studies. After reviewing the available data, the most important factor that influences maternal and neonatal outcome is the severity of blood pressures and presence of end organ damage, rather than the excess protein excretion. Because the management of gestational hypertension and preeclampsia without severe features is almost identical in frequency of surveillance and timing of delivery, the separation into 2 disorders is unnecessary. If the management of women with gestational hypertension with a positive assessment of proteinuria will not change, we believe that urine assessment for proteinuria is unnecessary in women who develop new-onset blood pressure at or after 20 weeks' gestation. Furthermore, we do not recommend repeated measurement of proteinuria for women with preeclampsia, the amount of proteinuria does not seem to be related to poor maternal and neonatal outcomes, and monitoring proteinuria may lead to unindicated preterm deliveries and related neonatal complications. Our current diagnosis of preeclampsia in women with chronic kidney disease may be based on a change in protein excretion, a baseline protein excretion evaluation is critical in certain conditions such as chronic hypertension, diabetes, and autoimmune or other renal disorders. The current definition of superimposed preeclampsia possesses a diagnostic dilemma, and it is unclear whether a change in the baseline proteinuria reflects another systemic disease such as preeclampsia or whether women with chronic disease such as chronic hypertension or diabetes will experience a different "normal" pattern of protein excretion during pregnancy. Finally, limited data are available regarding angiogenic and other biomarkers in women with chronic kidney disease as a potential aid in distinguishing the worsening of baseline chronic kidney disease and chronic hypertension from superimposed preeclampsia.

Management of pregnancies with suspected preeclampsia based on 6-hour vs 24-hour urine protein collection-a randomized double-blind controlled pilot trial

BACKGROUND

Traditionally, the diagnosis of preeclampsia requires elevated blood pressure measurements and proteinuria demonstrated in a 24-hour urine collection. This prolonged urine collection is associated with patient discomfort, a delay in diagnosis, and in some cases, hospitalization for further management of outcomes.

OBJECTIVE

We aimed to assess the feasibility, reliability, and association between maternal and neonatal outcomes of pregnancies managed according to a 6-hour vs 24-hour urine protein collection for suspected preeclampsia.

STUDY DESIGN

This was a randomized controlled trial conducted at a tertiary university hospital between January 2019 and January 2021 (ClinicalTrials.gov Identifier: NCT03724786). Patients who were hospitalized for preeclampsia workup were asked to participate and randomized at a 1:1 ratio to 6- and 24-hour urine protein collection groups. Both groups collected urine for 24 hours, during which the collection was also tested after 6-hours. After 24 hours, both results were reviewed by one of the research staff, and either the 6- or 24-hour collection result was reported to the patient's managing physician and was documented in the patient's medical record. Both patient and the managing physician were blinded to group allocation. Unblinding was undertaken in cases of a discrepancy between the results (1 of 2 results of >300 mg protein), and the results were analyzed by intention to treat. The primary study outcome was defined as a composite of adverse maternal outcomes. The sample size was set empirically as per proof on concept design.

RESULTS

During the study period, 115 patients participated in the trial, 101 of whom completed the follow-up and were analyzed-51 in the 6-hour group and 50 in the 24-hour group. Patient demographics were similar between the study groups. Unblinding occurred in 7 cases in the 6-hour group, in which the initial 6-hour result ranged from 168 to 475 mg. The rates of composite adverse maternal outcomes were 15.6% and 12.0% in the 6- and 24-hour groups, respectively (P=.59). No significant difference was demonstrated in the rate of adverse neonatal outcomes, cesarean delivery, induction of labor, gestational age at delivery, betamethasone treatment, or neonatal birthweight.

CONCLUSION

Managing pregnancies suspected of preeclampsia with a 6-hour urine protein collection is feasible and associated with similar maternal and neonatal outcomes. In cases where the 6-hour result is in the 168 to 475 mg range, we propose completing a 24-hour collection.