Comparison of bedside test kits for prediction of preterm delivery: phosphorylated insulin-like growth factor binding protein-1 (pIGFBP-1) test and fetal fibronectin test.

OBJECTIVE: The objective of the study was to compare the effectiveness of bedside test kits for pIGFBP-1 and fetal fibronectin test in predicting preterm delivery. MATERIALS AND METHODS: Patients presenting with symptoms of preterm labour between 24 and 34 weeks of gestation were recruited. Both pIGFBP-1 and fetal fibronectin bedside tests were performed. Managing obstetricians and patients were blinded to the pIGFBP-1 and fetal fibronectin results. Tocolysis and steroid therapy were administered to all the recruited patients. Outcome data were collected after delivery. RESULTS: One hundred and eight patients were recruited into the study. Fourteen patients had to be excluded from the final analysis due to incomplete data and failure to meet inclusion criteria. Ninety-four patients had complete data for analysis. Among those with negative pIGFBP-1 and fetal fibronectin results, the median [+/-standard deviation (SD)] gestational age at delivery was 37.4 weeks (+/-2.8 weeks) and 37.4 weeks (+/-2.1 weeks), respectively. Among those with positive pIGFBP-1 and fetal fibronectin results, the median (+/-SD) gestational age at delivery was 32.9 weeks (+/-4.0 weeks) and 34.2 weeks (+/-4.2 weeks), respectively (P <0.001 for both pIGFBP-1 and fetal fibronectin). A positive result with either test was associated with a significantly reduced admission-to-delivery interval. The median admission-to-delivery interval was 2.8 weeks shorter in the group with positive pIGFBP-1 results compared to those with a negative pIGFBP-1 result (2.3 weeks compared with 5.1 weeks) (P <0.001). This is 1.8 weeks shorter in the group with positive fibronectin results, compared to those with a negative result (3.3 weeks compared with 5.1 weeks) (P=0.002). Both pIGFBP-1 and fetal fibronectin tests have high negative predictive value (NPV) in predicting risk of delivery within 48 hours, 7, or 14 days (1.00; 0.92; 0.92 and 0.97; 0.89; 0.89, respectively). CONCLUSIONS: Both pIGFBP-1 and fetal fibronectin tests are effective adjuvant bedside test kits for the prediction of preterm delivery in patients presenting with signs or symptoms of preterm labour. pIGFBP-1 has the higher NPV of 1.00 in predicting risk of delivery within 48 hours.