Fetal fibronectin detection in preterm labor: Evaluation of a prototype bedside dipstick technique and cervical assessment

OBJECTIVE: The aims of this study were to evaluate a prototype bedside test for fetal fibronectin detection in women with symptoms of preterm labor, t o compare the efficacy of obtaining fetal fibronectin swabs with and withou t a speculum, and to assess the value of combining the fetal fibronectin te st with cervical dilatation for predicting delivery within 10 days. STUDY DESIGN:This investigation prospectively studied a cohort of women wit h symptoms of preterm labor (n = 121), gestational age between 24 and 33% w eeks, and cervical dilatation less than or equal to 3 cm. Vaginal swabs for fibronectin testing with the bedside dipstick Fetal Fibronectin Membrane I mmunoassay test (Adeza Biomedical, Sunnyvale, Calif) were obtained with and without a speculum. Results were not available to the clinicians. RESULTS: Twenty-two percent of the fetal fibronectin samples collected with a speculum (27/121) yielded positive results. The incidence of delivery wi thin 10 days of testing was 14% (17/121). Fetal fibronectin detection predi cted delivery within 10 days with sensitivity, specificity, and positive an d negative predictive values of 65%, 85%, 41%, and 94%, respectively. The p ositive and negative likelihood ratios were 4.3 and 0.41, respectively. The re was substantial association between samples obtained with and without a speculum (Cohen kappa statistic 0.65, 95% confidence interval 0.44-0.87). C ervical dilatation tl cm predicted delivery within 10 days with sensitivity , specificity, and positive and negative predictive Values of 71%, 87%, 46% , and 95%, respectively, with positive and negative likelihood ratios of 5. 5 and 0.33, respectively. Combination of fetal fibronectin testing with cer vical dilatation greater than or equal to 1 cm did not significantly improv e the fetal fibronectin test characteristics. After exclusion of women with slight vaginal bleeding, cervical dilatation greater than or equal to 1 cm and fetal fibronectin status remained the only independent variables assoc iated with delivery within 10 days. CONCLUSION: Fetal fibronectin testing according to this prototype may have a limited role in clinical decision analysis. In this study a cervical dila tation greater than or equal to 1 cm had predictive values equivalent to th ose of the fetal fibronectin test, and it should be evaluated further in a clinical setting.