This study aimed to evaluate the agreement between the proteinuria/creatinuria (P/C) ratio and the traditional 24-hour proteinuria measurement for proteinuria levels above 3g/24h in pregnant patients with preeclampsia. Additionally, we assessed whether high levels of each measurement are predictive of adverse maternal and neonatal outcomes.

We conducted a monocentric retrospective study of pregnant patients hospitalized for preeclampsia between January 1, 2019, and November 11, 2020. The primary outcome was a composite measure of adverse maternal outcomes associated with preeclampsia, and the secondary outcome focused on adverse neonatal outcomes. Agreement between high levels of 24-hour proteinuria and the P/C ratio was evaluated using Cohen's Kappa. Maternal and neonatal outcomes were compared across three groups: those with neither, one, or both high proteinuria levels (24-hour proteinuria ≥ 3g/24h and/or P/C ratio ≥ 300 mg/mmol). Logistic regression, adjusted for confounders, analyzed associations between measures and outcomes, with ROC curves and AUC calculated for predictive models.

We found a strong correlation between 24-hour proteinuria and P/C ratio, with 95.1% agreement at the threshold of 3 g/24h and 300 mg/mmol, respectively (Kappa = 0.87, p < 0.01). Both measurements were associated with an increased risk of adverse maternal (aOR 6.78 [2.47–18.63]) and neonatal (aOR 7.00 [1.56–31.31]) outcomes.

This study demonstrated a strong agreement between the P/C ratio ≥ 300 mg/mmol and 24-hour proteinuria ≥ 3g/24h, both associated with an increased risk of adverse perinatal outcomes, with the P/C ratio offering a quicker, simpler alternative for managing preeclampsia.