793: A new prediction model for birth within 48 hours in women with preterm labour symptoms

To develop and internally validate a prognostic model using quantitative fetal fibronectin concentration, in combination with clinical risk factors, for the prediction of birth within 48 hours. Data from an individual participant data (IPD) meta-analysis of 5 European studies were combined with data from a recently-ended large UK prospective cohort study (QUIDS study ISRCTN 41598423). Inclusion criteria were women 22+0-34+6weeks gestation with signs and symptoms of preterm labour. We developed the model from quantitative fFN and clinical risk factors chosen from a set of pre-defined potential predictors, with multivariable logistic regression with backward stepwise selection (threshold of p-value< 0.1). Multiple imputation was used for predictor values considered missing at random, and non-linear trends allowed for continuous predictors. Clustering and between-study heterogeneity of outcome incidence was accounted for by a separate intercept term per study. The performance of the model was assessed by overall fit (Nagelkerke R2) and discrimination (AUC). Bootstrap re-sampling techniques were used for internal validation and optimism-adjustment using shrinkage. Net benefit was calculated and plotted across a range of thresholds for which a woman would be designated at high risk of preterm birth within 48 hours. A risk calculator was developed in conjunction with clinicians and women. The joint IPD meta-analysis and prospective cohort study included 4707 women, with 113 (2.4%) events of spontaneous preterm birth within 48 hours. The model included quantitative fFN, Age, Smoking, Nulliparity, Multiple pregnancy, Previous spontaneous preterm delivery within 48 hours and Gestational age at assessment. After applying a uniform shrinkage factor of 0.927, the model showed an R2 of 0.27 and an AUC of 0.90 (95% CI 0.87 – 0.93). A prognostic model including qfFN and clinical risk factors showed excellent performance in the prediction of spontaneous preterm birth within 48 hours, which is likely to be of clinical benefit.