Human chorionic gonadotropin assay in cervical secretions for accurate diagnosis of preterm labor

We planned to determine whether the concentration of human chorionic gonadotropin (hCG) in cervical secretions could be a useful marker for accurate diagnosis of preterm labor, and whether the use of cervical hCG assay in combination with the Bishop score would improve the prediction of delivery within 7 days, and to determine the cut-off values for hCG in prediction of delivery within 100 h, 7 and 14 days, as well as before 35 and 37 weeks of gestation in a group of women at high risk for preterm delivery.

The study was conducted in the perinatology department of Zeynep Kamil Women and Children Diseases Education and Research Hospital between February 2002 and February 2003. One hundred and two subjects with a diagnosis of threatened preterm labor with intact membranes were included in the study. For hCG measurements, a cotton swab was rolled intracervically for 10 s to absorb fluid. Bishop scores were assessed. The correlation test was employed for the variables influencing hCG values. The ROC curve analysis was used to establish an optimal cut-off concentration for cervical hCG and an optimal cut-off level for Bishop score. The continuous variables were analyzed by the unpaired, independent, two-tailed t-test and categorical data were analyzed by the chi-square test.

A significant positive correlation was present between the cervical hCG concentrations and Bishop scores (r=0.72, P<0.0001), and a highly negative correlation between the cervical hCG concentrations and the time interval from sampling time until delivery (r=-0.80, P<0.0001) was detected. The cut-off value for cervical hCG concentration and its sensitivity, specificity, positive and negative predictive values, accuracy, relative risk and likelihood ratio for accurate determination of delivery within 100 h were > or =32 mIU/ml, 98%, 55%, 70%, 96%, 77%, 19.68 and 2.18, respectively. However, these values were > or =32 mIU/ml, 97%, 84%, 89%, 95%, 92%, 17.37 and 6.06, respectively, for prediction of delivery within 7 days; > or =30 mIU/ml, 97%, 79%, 87%, 94%, 89%, 15.15 and 4.62, respectively, for prediction of delivery within 14 days; > or =33 mIU/ml, 89%, 92%, 94%, 83%, 90%, 5.83 and, 11.55, respectively, for prediction of delivery before 35 weeks; and finally > or =27 mIU/ml, 76%, 50%, 85%, 37%, 71%, 1.34 and 1.52, respectively, for prediction of delivery before 37 weeks.

Cervical hCG expression seems to be rewarding in accurate diagnosis of preterm labor. This test has the advantage of low cost and wide availability.