Cervical length measurement and cervical phosphorylated insulin-like growth factor binding protein-1 testing in prediction of preterm birth in patients reporting uterine contractions

Abstract

Objectives: To evaluate the performance of cervical phosphorylated insulin-like growth factor binding protein-1 (phIGFBP-1) testing and cervical length measurement separately and in combination with physician's clinical judgment in prediction of preterm birth among patients with self-reported uterine contractions and intact membranes.

Design: We enrolled a total of 246 women between 22 and 34 weeks of gestation.

Methods: The initial evaluation included cervical length measurement using transvaginal ultrasonography. Short cervix was defined as <25 mm. A swab sample was obtained from the cervix for phIGFBP-1. Admission was used as a clinical marker of an increased risk of preterm delivery <or=34 weeks. The diagnostic performances of the tests and clinician's judgment, as well as likelihood ratios (LRs) were calculated.

Main outcome measures: Delivery <or=34 weeks and within 14 days.

Results: The overall rate of spontaneous preterm delivery <or=34 weeks was 4.1% (10/246). Short cervix, positive phIGFBP-1 test, combination of both, and clinician's judgment were all associated with preterm delivery <or=34 weeks or within 14 days (p<0.01). The negative predictive values for delivery <or=34 weeks were 97.4, 97.6, 97.1, and 98.7%, respectively, and within 14 days 98.7, 99.0, 98.3, and 99.6%, respectively. The corresponding positive LRs for delivery <or=34 weeks were 6.8, 3.8, 75.0, 14.9, and within 14 days 9.7, 5.5, 107.3, 17.1. The negative LRs were 0.6, 0.6, 0.7, 0.3 and 0.5, 0.3, 0.6, 0.2.

Conclusion: The rapid phIGFBP-1-test has a high negative predictive value for preterm delivery, comparable to that of ultrasonographic cervical length measurement.