The sensitivity, specificity, and accuracy of Creatinine test and human chorionic gonadotropin (HCG) test of cervical mucus discharge to diagnose preterm premature rupture of membranes (PPROM)

Premature Rupture of Membranes (PROM) is one of the common problems of midwifery, which its early diagnosis is essential in the process of treatment and prevention of pregnancy adverse outcomes. Therefore, this study was performed with aim to evaluate the diagnostic accuracy of Creatinine and human chorionic Gonadotropin (HCG) test of cervical mucusdischarge to diagnose PROM in pregnant women.

This prospective study was conducted in 2017-2018 on 150 pregnant women with gestational age of 24 to 37 weeks and suspected to PROM. The subjects were divided into two groups of Rupture Membranes (Pooling and Fern test both of them were positive) and control group (Pooling and Fern test both of them were negative and AFI was normal). Creatinine was measured with Automated Analyzer method (Prestige device) and βHCG with Chemi-luminescence Signal Band method (Abbott device). Cut-off point and diagnostic accuracy were measured for two tests by rock curve. P-value<0.05 was considered statistically significant.

The highest sensitivity and specificity for creatinine in the diagnosis of PPROM was obtained at cut-off point 0.135 and for βHCG at cut-off point 26.78, with sensitivity of 91.7% and specificity 56.1%, and positive predictive value of 39.75% and negative predictive value of 95.52% and overall accuracy was 64.66% and the agreement rate was 0.33 (P <0.001). For βHCG, the sensitivity 58.3% and specificity 63.2%, and positive predictive value 33.33%, and negative predictive value of 82.75% and overall accuracy was 62% and the agreement rate was 0.171 (P=0.023).

The sensitivity and diagnostic power of Creatinine in preterm women was higher than βHCG. Reasonable price, simplicity, and safety are the advantages of both methods. The diagnostic accuracy obtained in this study was low, but due to the limited studies in preterm patients, the clinical use of these markers cannot be recommended or rejected; therefore, more studies are suggested.