Spot urine protein-to-creatinine ratio as a diagnostic test in pre-eclampsia: A gold standard?

OBJECTIVE: To determine the diagnostic accuracy and optimal threshold of the spot protein-to-creatinine ratio (PCR) compared to the gold standard, 24-hour proteinuria (24HP) in patients with suspected pre-eclampsia. METHODS: A prospective observational study was performed from June 2015 to May 2017 consisting of patients hospitalized for suspected pre-eclampsia in a tertiary care referral center. To compare the two diagnostic tests, a spot urine sample was obtained to perform the PCR before starting the collection of the 24HP. Only patients who had both tests were analyzed. RESULTS: In total, 148 patients (216 samples) were included. The two tests were highly correlated (r=0.80, P<0.001). The receiver operating characteristic curve analysis and the area under the curve (AUC=0.92) highlighted the accuracy of PCR in diagnosing significant proteinuria and thus pre-eclampsia. The optimal cut-off using the Liu method was 56.9 mg/mmol (sensitivity=79.3%, specificity=91.5%). CONCLUSION: The results suggest that PCR could replace 24HP when diagnosing proteinuria in pre-eclampsia. Moreover, it is a simple test, easy to realize and standardize, and cheap with no need for systematic hospitalization. The best cut-off should be chosen by thinking about the risks for adverse maternal and/or fetal outcomes. The test may help to optimize medical care in pre-eclampsia worldwide.