New rapid bed-side test to predict preterm delivery: phosphorylated insulin-like growth factor binding protein-1 in cervical secretions

Background: Phosphorylated insulin-like growth factor binding protein-1 (phIGFBP-1) is secreted by decidual cells and leaks into cervical secretions when fetal membranes detach from decidua. Our aim was to assess whether detection of phIGFBP-1 in cervical secretions by a rapid bed-side test could be used to predict preterm delivery in patients with regular uterine contractions. Study design: In our prospective study, 36 women between 20 and 36 weeks of gestation with regular, persistent contractions (> 10/h) and 18 women between 20 and 36 weeks gestation without symptoms of preterm labor were assessed for the presence of cervical phIGFBP-1. Dacron swabs were applied to the cervix and assayed in 5 min by using immunochromotography, a new rapid bed-side test (actim partus test, Medix Biochemica, Kauniainen, Finland). Data analysis included one-way variance analysis (ANOVA), Student's t-test, chi-square and Fisher's exact test. Results: Of the 36 patients with regular uterine contractions, 18 had a positive actim partus test and 18 had a negative test. Among the 18 patients with a positive test, only one delivered term and the other 17 patients delivered preterm (< 37 weeks). Among the 18 women with a negative test, only two delivered preterm (p < 0.05). Mean gestational age at delivery for patients with a positive and a negative test was 34.4 +/- 3.0 and 37.9 +/- 2.3 weeks, respectively (p < 0.05). Sensitivity, specificity, positive and negative predictive values of the rapid phIGFBP-1 test for preterm delivery was 89.5, 94.1, 94.4 and 88.9%, respectively. For delivery < 37 weeks, positive likelihood ratio was 15.2 (+/- 95% CI; range 2.6-102.5). When cervical phIGBP-1 assay was used to predict delivery within 7 days, sensitivity, specificity, positive and negative predictive values were 93.8, 85%, 83.3 and 94.1%, respectively. Positive likelihood ratio with +/- 95% CI was 6.25 (range 2.2-17.8). When patients were categorized according to cervical dilatation, the positive likelihood ratio of the test when the cervix was closed at less than or equal to 1, less than or equal to 2 and > 2 cm were 8.3 (1.3-55.3), 13.6 (2-91.4), 15.8 (2.3-106.3) and 1.5 (0.2-11.5), respectively, Conclusion: The presence of cervical phIGFBP-1 is predictive of preterm delivery < 37 weeks of gestation. Our study shows that cervical detection of phIGFBP-1 by immunochromotography is a rapid and easily applicable test that highly anticipates preterm delivery in patients at risk.