Fetal fibronectin as a short-term predictor of preterm birth in symptomatic patients: a meta-analysis

To appraise critically the diagnostic accuracy of cervicovaginal fetal fibronectin as a short-term predictor of preterm birth in patients with signs and symptoms of preterm labor.

We searched MEDLINE, Current Contents, Index Medicus, EMBASE, the Cochrane Library, and syllabi from scientific meetings, and we performed manual searches of references from textbooks and of known primary and systematic review articles. We also contacted authors, experts on this subject, and the manufacturer.

We targeted cohort studies reporting data on the diagnostic accuracy of fetal fibronectin for the prediction of preterm birth within 7 days in symptomatic patients before 37 weeks of gestation. Case-control studies were excluded. The total analysis included 32 trials with 5,355 overall participants.

Two authors independently assessed methodological quality and constructed 2x2 tables for assessment of diagnostic measures. Pooled estimates of sensitivity, specificity, and likelihood ratios were obtained using a bivariate random effects model. Tests for publication bias and meta-regression were performed. Sensitivity analyses were performed for studies using different fetal fibronectin assays. The overall pooled estimates for sensitivity and specificity were 76.1% (95% confidence interval [CI] 69.1-81.9) and 81.9% (95% CI 78.9-84.5), respectively. Likelihood ratios for a positive and negative fetal fibronectin test were 4.20 (95% CI 3.53-4.99) and 0.29 (95% CI 0.22-0.38), respectively. Meta-regression analyses found that test accuracy was affected by prevalence, publication year, and blinding of studies. When subgroup analyses were performed for studies using the same assay, the results were similar.

The cervicovaginal fetal fibronectin assay has limited accuracy in predicting preterm birth within 7 days of sampling in symptomatic pregnant women.