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Fetal fibronectin detection in preterm labor: evaluation of a prototype bedside dipstick technique and cervical
M A Coleman1, L M McCowan, N S Pattison
1Departments of Obstetrics and Gynaecology and Pharmacology and Clinical Pharmacology, National Women's Hospital, Auckland, New Zealand.
Objective:
The aims of this study were to evaluate a prototype bedside test for fetal fibronectin detection in women with symptoms of preterm labor, to compare the efficacy of obtaining fetal fibronectin swabs with and without a speculum, and to assess the value of combining the fetal fibronectin test with cervical dilatation for predicting delivery within 10 days.
Study Design:
This investigation prospectively studied a cohort of women with symptoms of preterm labor (n = 121), gestational age between 24 and 33 6/7 weeks, and cervical dilatation
Results:
Twenty-two percent of the fetal fibronectin samples collected with a speculum (27/121) yielded positive results. The incidence of delivery within 10 days of testing was 14% (17/121). Fetal fibronectin detection predicted delivery within 10 days with sensitivity, specificity, and positive and negative predictive values of 65%, 85%, 41%, and 94%, respectively. The positive and negative likelihood ratios were 4.3 and 0.41, respectively. There was substantial association between samples obtained with and without a speculum (Cohen kappa statistic 0.65, 95% confidence interval 0.44-0.87). Cervical dilatation >/=1 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 cervical dilatation >/=1 cm did not significantly improve the fetal fibronectin test characteristics. After exclusion of women with slight vaginal bleeding, cervical dilatation >/=1 cm and fetal fibronectin status remained the only independent variables associated 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 dilatation >/=1 cm had predictive values equivalent to those of the fetal fibronectin test, and it should be evaluated further in a clinical setting.