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The effect of amniotomy on urine protein creatinine ratio test accuracy

Authors Herrera Gonzalez A, Quinn S, Lennon J, Zabo J, Dierking E, Anasti J

Received 11 January 2019

Accepted for publication 23 April 2019

Published 10 June 2019 Volume 2019:11 Pages 371—375

DOI https://doi.org/10.2147/IJWH.S201210

Checked for plagiarism Yes

Review by Single-blind

Peer reviewers approved by Dr Amy Norman

Peer reviewer comments 2

Editor who approved publication: Professor Elie Al-Chaer


Aaron Herrera Gonzalez, Sara Quinn, Jessica Lennon, Jordan Zabo, Elizabeth Dierking, James Anasti

St. Luke’s University Health Network, Department of Obstetrics and Gynecology, Bethlehem, PA, USA

Introduction: While the gold standard for evaluation of maternal urinary protein is a 24-hr urine collection, spot urine protein/creatinine ratio has been instituted as an alternative for quantification proteinuria. Though it seems intuitive to obtain a catheterized urine sample on patients with ruptured amniotic membranes, it is a common practice to forgo this step under the argument that there is no data to show its necessity. Data on the effect of amniotomy, spontaneous or artificial, on the accuracy of the protein/creatinine ratio are scant. The present study was designed to address this issue and objectively compare protein/creatinine ratio values on samples obtained from the same patient before and after amniotomy.
Methods: We conducted a prospective non-interventional study. Women presenting in active labor or for labor induction with intact amnion were enrolled. Separate random catch urines for the protein/creatinine ratio were obtained prior to and immediately after spontaneous or assisted amniotomy. The urine samples were analyzed in the hospital chemistry department, and the results were compared.
Results: Of the 137 patients consented, 63 had pre- and post-amniotomy protein/creatinine ratios collected. The mean age was 28.5±5.6 y, Gravidity 2.7±1.6, Gestational age 39.2±1.8 wks, and BMI 31.6±6.4 kg/m2. Comorbidities included gestational diabetes (5/63, 7.9%), chronic hypertension (3/63, 4.7%), and pre-eclampsia (5/63, 7.9%). Post-amniotomy protein/creatinine ratio was significantly higher than pre-amniotomy ratio (1.3±2.5 vs 0.34±0.83, p<0.001). In addition, the number of patients with protein/creatinine ratio greater than 0.3 was higher post-amniotomy than pre-amniotomy (41/63 vs 14/63, p<0.001).
Conclusion: Amniotomy results in a false elevation of the protein/creatinine ratio in term patients. Urine samples should be obtained by catheterization in the setting of ruptured membranes to reduce falsely elevated results. Although the same can be assumed for other gestational ages, further studies including this population need to be conducted.

Keywords: amniotic fluid, protein creatinine ratio, preeclampsia, urine protein, pregnancy, gestational hypertension

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