Protein-to-creatinine (P:C) ratio is a rapid test that is used to estimate the quantity of proteinuria in pregnant women being evaluated for pre-eclampsia. Few published articles have focused on how a P:C ratio cutoff value predictive of 300 mg of protein may change in women with pre-pregnancy medical issues or non-preeclampsia pregnancy diagnoses.METHODS:
We performed a retrospective observational study of all women evaluated at >20 weeks gestation with a P:C ratio and follow up 24 hour-urine protein at Hartford Hospital between January 1, 2009 and August 31, 2012. The primary outcome was to define an optimal cutoff for a P:C ratio that predicts 300 mg of protein in a 24-hour urine collection. The secondary outcomes were to define optimal P:C ratio cutoffs for patients with medical conditions that may increase proteinuria. Pearson correlation coefficients and Receiver Operator Characteristic curves were calculated.RESULTS:
Data analysis confirmed the high correlation between P:C ratio and 24-hour urine protein results (R=0.64, P<.001). For the total population (n=112), the ideal cutoff P:C ratio was 0.285 (sensitivity 80%, specificity 83%). In patients with no medical conditions (n=50), the ideal cutoff was 0.285 (sensitivity 94%, specificity 83%). In patients with pre-pregnancy medical issues (n=30), the cutoff was 0.265 (sensitivity 75%, specificity 92%). In patients who developed a medical condition in pregnancy (n=32), the cutoff was 0.420 (sensitivity 60%, specificity 95%).CONCLUSION:
The P:C ratio cutoff that correlates with a 24-hour urine protein result of 300 mg may vary in women with either pre-pregnancy or pregnancy-induced medical conditions.