Vaginal fluid creatinine, human chorionic gonadotropin and alpha-fetoprotein levels for detecting premature rupture of membranes.

Background: Diagnosis of premature rupture of membranes (PROM) is difficult in equivocal cases. The concentrations of human chorionic gonadotropin (hCG), alpha-fetoprotein (AFP) and creatinine are high in amniotic fluid. The purpose of this study was to determine the usefulness of vaginal fluid hCG, AFP and creatinine measurements in the detection of PROM.

Methods: About 3 ml of normal saline was used to irrigate the posterior vaginal fornix and was collected for the measurement of hCG, AFP and creatinine. The control group included 10 normal pregnant women in the third trimester (> 28 weeks of gestational age). Levels of hCG, AFP and creatinine were compared with those of 10 women with confirmed PROM.

Results: The median levels of vaginal fluid hCG of normal pregnant women and pregnant women with confirmed PROM were 35.0 mIU/ml and 478.0 mIU/ml (p = 0.0046), respectively. For AFP, the corresponding values were 0.80 ng/ml and 54.24 ng/ml (p < 0.0001), respectively, and for creatinine, the values were 0.05 mg/dl and 0.95 mg/dl (p < 0.0001), respectively. All three markers were significantly higher in the experimental group than in the control group. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy for hCG were 80%, 70%, 72.7%, 77.8% and 75%, respectively. For AFP, these values were 90%, 100%, 100%, 90.9%, and 95.0%, respectively, and for creatinine, they were 90%, 100%, 100%, 90.9%, and 95%, respectively. The diagnostic value of AFP or creatinine level in vaginal washing may be better than that of hCG, though the difference was not statistically significant, probably due to the limited case number.

Conclusions: Creatinine in vaginal fluid washings is a useful marker for PROM. It was less expensive and easier to measure than hCG and AFP, and appears to be more accurate than hCG.