Clinical Application of Quantitative Foetal Fibronectin for the Prediction of Preterm Birth in Symptomatic Women.

AIM: To evaluate the clinical application of the new Hologic quantitative foetal fibronectin (qfFN) bedside test for the prediction of spontaneous preterm birth (sPTB) in patients with symptoms suggestive of spontaneous threatened preterm labour (sPTL). METHODS: A prospective observational study with 154 pregnant women presenting signs and symptoms of sPTL was conducted. These women were subjected to a qfFN test between 22 and 35 weeks of gestation For each cut-off threshold, the ability to predict sPTB at within 14 days of conducting the test and <37 weeks was assessed by calculating the positive predictive value (PPV), negative predictive value (NPV), likelihood ratios, odds ratios, sensitivity, and specificity. RESULTS: For the outcome of delivery within 14 days of the test, qfFN <10 ng/mL had a 100% NPV and >200 ng/mL produced a 50.0% PPV; thus, qfFN added enhanced discrimination between high- and low-risk patients. The overall rate of sPTB (<37) was 13.3% (16/120), which increased progressively with increasing levels of fFN, with rates of 9.8% (8/81), 11.5% (3/26), 14.2% (1/7), 50% (3/6) within the 4 categories (fFN 0-9, 10-49, 50-200, 200+) respectively. CONCLUSIONS: The use of the qfFN testing in symptomatic patients allowed for more accurate identification of women at risk of sPTB and thus more directed management.

Evaluation of a quantitative fetal fibronectin test for spontaneous preterm birth in symptomatic women.

OBJECTIVE: The purpose of this study was to determine whether quantification of cervicovaginal fluid fetal fibronectin (fFN) improves diagnostic accuracy of spontaneous preterm birth (sPTB) in symptomatic women. STUDY DESIGN: A prospective blinded predefined secondary analysis of a larger study of cervicovaginal fluid fFN concentration (nanograms per milliliter) in women symptomatic of preterm labor (n =300 women; 22-35 weeks' gestation) with a Hologic 10Q system (Hologic, Marlborough, MA). Clinicians were blinded to the result until after the delivery, but the qualitative Hologic TLI(IQ) fFN result was made available. RESULTS: The positive predictive value for sPTB (<34 weeks' gestation) increased from 19%, 32%, 61%, and 75% with increasing thresholds (10, 50, 200, and 500 ng/mL, respectively). Compared with <10 ng/mL fFN, the relative risk of delivery was 5.6 (95% confidence interval [CI], 1.05-29.57), 7.9 (95% CI, 1.38-45.0), 22.8 (95% CI, 3.84-135.5), and 51.3 (95% CI, 12.49-211.2; P < .01). CONCLUSION: Quantitative fFN provides thresholds (10 and 200 ng/mL) in addition to the qualitative method (50 ng/mL) to discriminate the risk of sPTB in symptomatic women.

Quantitative Fetal Fibronectin at 18 Weeks of Gestation to Predict Preterm Birth in Asymptomatic High-Risk Women.

OBJECTIVE: To compare quantitative fetal fibronectin measurement from 18 to 21 weeks of gestation to measurement at 22-27 weeks of gestation for the prediction of spontaneous preterm birth. METHODS: In a prospective cohort study, we studied the accuracy of cervicovaginal fluid quantitative fetal fibronectin concentrations measured between 18 0/7 weeks of gestation and 21 6/7 weeks of gestation in high-risk asymptomatic women to predict spontaneous preterm birth before 34 weeks of gestation. Predefined fibronectin thresholds were 10 or greater, 50 or greater, and 200 ng/mL or greater. Diagnostic accuracy of the early test (n=898) was compared with the standard test performed between 22 0/7 and 27 6/7 weeks of gestation (n=691) in the same cohort. Subgroup analysis was performed according to cervical length measurement. RESULTS: Of 898 women, 8.7% delivered spontaneously before 34 weeks of gestation. Only 3.8% of the women with concentrations less than 10 ng/mL (65% of test results) delivered before 34 weeks of gestation. A concentration threshold of 10 ng/mL measured at 18 and 22 weeks of gestation had comparably high sensitivity (early 0.71, 95% confidence interval 0.60-0.81; standard 0.76, 0.63-0.87) and negative predictive value (early 0.96, 0.94-0.98; standard 0.97, 0.95-0.99) for delivery before 34 weeks of gestation. Specificity was also comparable (early 0.69, 0.65-0.72; standard 0.70, 0.66-0.74). A threshold of 200 ng/mL had high specificity (early 0.96, 0.94-0.98; standard 0.96, 0.94-0.97) with lower sensitivity (early 0.26, 0.17-0.37; standard 0.35, 0.22-0.49). Consideration of cervical length strengthened prediction. CONCLUSION: Quantitative cervicovaginal fetal fibronectin measured from 18 to 21 weeks of gestation has similar predictive value as measurement at 22-27 weeks of gestation for prediction of spontaneous preterm birth. Low fibronectin concentrations are associated with spontaneous preterm birthrates approaching population background levels.