• Mmc Bruijn, J Y Vis, F F Wilms, M A Oudijk, A Kwee, M M Porath, G Oei, Hcj Scheepers, Mea Spaanderman, Kwm Bloemenkamp, M C Haak, A C Bolte, Fpha Vandenbussche, M D Woiski, C J Bax, Jmj Cornette, J J Duvekot, Bwa Nij Bijvanck, J van Eyck, Mtm Franssen, K M Sollie, Jam van der Post, Pmm Bossuyt, B C Opmeer, M Kok, Bwj Mol, and G-J van Baaren.
• Obstetrics and Gynaecology, Academic Medical Centre, Amsterdam, the Netherlands. m.m.bruijn@amc.uva.nl.
• BJOG. 2016 Nov 1; 123 (12): 1965-1971.

ObjectiveTo evaluate whether in symptomatic women, the combination of quantitative fetal fibronectin (fFN) testing and cervical length (CL) improves the prediction of preterm delivery (PTD) within 7 days compared with qualitative fFN and CL.DesignPost hoc analysis of frozen fFN samples of a nationwide cohort study.SettingTen perinatal centres in the Netherlands.PopulationSymptomatic women between 24 and 34 weeks of gestation.MethodsThe risk of PTD <7 days was estimated in predefined CL and fFN strata. We used logistic regression to develop a model including quantitative fFN and CL, and one including qualitative fFN (threshold 50 ng/ml) and CL. We compared the models' capacity to identify women at low risk (<5%) for delivery within 7 days using a reclassification table.Main Outcome MeasuresSpontaneous delivery within 7 days after study entry.ResultsWe studied 350 women, of whom 69 (20%) delivered within 7 days. The risk of PTD in <7 days ranged from 2% in the lowest fFN group (<10 ng/ml) to 71% in the highest group (>500 ng/ml). Multivariable logistic regression showed an increasing risk of PTD in <7 days with rising fFN concentration [10-49 ng/ml: odds ratio (OR) 1.3, 95% confidence interval (95% CI) 0.23-7.0; 50-199 ng/ml: OR 3.2, 95% CI 0.79-13; 200-499 ng/ml: OR 9.0, 95% CI 2.3-35; >500 ng/ml: OR 39, 95% CI 9.4-164] and shortening of the CL (OR 0.86 per mm, 95% CI 0.82-0.90). Use of quantitative fFN instead of qualitative fFN resulted in reclassification of 18 (5%) women from high to low risk, of whom one (6%) woman delivered within 7 days.ConclusionIn symptomatic women, quantitative fFN testing does not improve the prediction of PTD within 7 days compared with qualitative fFN testing in combination with CL measurement in terms of reclassification from high to low (<5%) risk, but it adds value across the risk range.Tweetable AbstractQuantitative fFN testing adds value to qualitative fFN testing with CL measurement in the prediction of PTD.© 2015 Royal College of Obstetricians and Gynaecologists.

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