Comparison of rapid bedside tests for phosphorylated insulin-like growth factor-binding protein 1 and fetal fibronectin to predict preterm birth

Objective: To compare the accuracy of rapid bedside tests for phosphorylated insulin-like growth factor-binding protein 1 (phIGFBP-1) and fetal fibronectin (fFN) to predict preterm delivery among women with threatened preterm labor.

Methods: A prospective observational study was conducted among women with a singleton pregnancy of 28-36 weeks, intact membranes, and symptoms suggestive of preterm labor who attended a center in New Delhi, India, between April 1, 2011, and March 31, 2014. Rapid bedside tests were performed at presentation to measure the levels of phIGFBP-1 and fFN in cervicovaginal secretions. All patients were managed as per the standard hospital protocol and followed up until delivery.

Results: Data were available for 468 participants. For delivery before 37 weeks, the phIGFBP-1 test exhibited a sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of 81.1%, 97.1%, 95.2% and 87.7%, respectively. The sensitivity, specificity, PPV, and NPV for the fFN test were 19.4%, 99.4%, 97.4%, and 63.2%, respectively. The phIGFBP-1 test displayed higher sensitivity and NPV than did the fFN test for delivery before 34 weeks and within 7 days of testing (P<0.05 for all).

Conclusion: The rapid bedside test for phIGFBP-1 was more reliable in the prediction of preterm delivery than was the equivalent test for fFN.