A Two-hour Urinary Protein-creatinine Ratio for Predicting Significant Proteinuria in Preeclampsia

Abstract

Objective: To determine an optimal cutoff level of urinary protein-creatinine ratio (PCR) obtaining from 2 hours urine collection from women admitted with suspected preeclampsia for predicting significant proteinuria.

Study design: Diagnostic test.

Subject:  Pregnant women with gestational age > 20 weeks who were admitted at Bangkok Metropolitan Administration Medical College and Vajira Hospital for evaluation of preeclampsia were studied prospectively. They were instructed to collect a 24-hour urine in two separate containers: one for the first 2 hours urine and the other for the following 22 hours urine specimens.  Each sample was measured for volume, protein, and creatinine values. The first 2-hour urinary PCR and total 24-hour proteinuria were calculated. A receiver operating characteristic curve (ROC) of the 2-hour urinary PCR was constructed in order to determine the optimal cutoff level for estimate the degree of proteinuria.

Results:  A total of 182 out of 187 women completed the study; 137 (75%) had significant proteinuria. This study demonstrated moderate correlation between 2-hour urine protein and 24-hour urine protein(r=0.451). By using a 2-hour urinary PCR, the optimal cutoff level to predict significant proteinuria was ≥ 0.30 which yielded sensitivity, specificity, PPV, NPV and area under the ROC curve of 71.5%, 71.1%, 88.3%, 45.1% and 0.801 respectively. On the other hand, a cutoff level of ≥ 0.05 had a sensitivity of 100%, while the cutoff level of ≥ 2.0 offered 100% specificity. 

Conclusions:  The 2-hour urinary PCR is not a good test to predict significant proteinuria due to its high false negative rate.