Evaluación del índice proteína-creatinina en orina aislada para la predicción de proteinuria significativa durante la gestación

Introduction

Diagnosis and follow-up of preeclampsia requires measurement of proteinuria and the gold standard for this evaluation is the 24-hour collection. However, this collection is cumbersome, time consuming and delays clinical diagnosis. The purpose of this study is assess the diagnostic performance of the spot urine protein/creatinine (P/C) ratio to predict the absence or presence of significant proteinuria (≥ 300 mg per 24 hours) among outpatient pregnant women with suspected or previous diagnosis of preeclampsia.

Material and methods

The P/C ratio was calculated in 106 single voided urine samples, obtained after the completion of the 24-hour collection, from 66 outpatient pregnant women admitted to the Maternal Fetal Care Unit at our Hospital to follow-up of hypertension gestational. Correlation between the spot urine P/C ratio with the 24-hour urine protein excretion was calculated. Receiver operator characteristic (ROC) curves analysis was used to evaluate the diagnostic performance and to determinate the best cutoff to predict the absence or presence of significant proteinuria.

Results

Significant proteinuria on 24 hour collection urine was identified in 31 urines from 22 pregnant women. There was a significant correlation between the spot urine P/C and 24-hour urine protein excretion (r_Spearman = 0,658, p = 0,01). ROC curves analysis revealed an area under the curve for spot P/C ratio of 0,838, greater than urine dipstick (0,629). No single P/C ratio cutoff was appropriate to rule-out or predict significant proteinuria; however, use of dipstick and spot urine P/C ratio, with two cutoffs, 120 mg/g to predict the absence of significant proteinuria and 240 mg/g to confirm it, clasiffied correctly 44,3% of urines and avoided the collection of 24 hours urine in 51% of the cases.

Conclusions

Spot urine P/C ratio, in conjunction with dipstick urianalysis, is a useful test in the initial screen for rule-out and predict significant proteinuria in outpatient pregnant women with hypertensive pregnancy or preeclampsia, but it should not be used as an alternative to 24-hour total protein evaluation in midrange P/C ratio, requiring a full 24-hour urine for accurate results.