Comparative diagnosis of premature rupture of membrane by nitrazine test, urea, and creatinine estimation

Abstract

Objective: The study compared the reliability of nitrazine, urea, and creatinine in the diagnosis of premature rupture of membrane (PROM). Nitrazine strip measures pH levels while urea and creatinine are produced mainly in amniotic fluid and not in the maternal vagina.
Methods: Sixty-four pregnant women with demonstrable passage or pooling of liquor par vaginum on speculum examination and 64 with no liquor drainage at 28–42 weeks gestation were studied. Vaginal fluid aspirates from both groups of patient were tested for urea, creatinine, and pH levels using nitrazine strip. Receiver Operating Characteristic (ROC) curves were plotted to determine cutoff values for urea and creatinine. Statistical analysis was done using SPSS version 23.0 and setting statistical significance at P ≤ 0.05.
Results: Nitrazine test showed high level of specificity (100%) but a sensitivity of 87.5%. Predictive ability of urea at >12.7 mg/dl obtained as cutoff value from the ROC curve showed a sensitivity of 19.64% and specificity of 94.44% while for creatinine the cutoff value was at >0.8 mg/dl with sensitivity of 48.21% and specificity of 65.28%.
Conclusion: Nitrazine strip was the most reliable of the three in the diagnosis of PROM. This was followed by creatinine and then urea. In view of the gaps in sensitivity and accuracy and the importance of precise diagnosis to prevent maternal and fetal complications, there is still the need to find other affordable, more sensitive and more accurate biochemical marker/s that will help in diagnosing PROM especially in difficult cases.