External validation of a simple risk score based on the ASPRE trial algorithm for preterm pre-eclampsia considering maternal characteristics in nulliparous pregnant women: a multicentre retrospective cohort study.

OBJECTIVE: To validate the performance of a first-trimester simple risk score based on the ASPRE trial algorithm for pre-eclampsia.

DESIGN: Multicentre retrospective cohort analysis.

SETTING: Four Italian hospitals.

POPULATION: Unselected nulliparous women at 11-13 weeks of gestation from January 2014 through to January 2018.

METHODS: Model performance was evaluated based on discrimination and calibration.

MAIN OUTCOME MEASURES: Delivery before 37 weeks of gestation with a diagnosis of pre-eclampsia.

RESULTS: Based on 73 preterm pre-eclampsia cases and 7546 controls (including 101 cases of late pre-eclampsia), the area under the receiver operating characteristics curve was 0.659 (95% CI 0.579-0.726). The sensitivity was 32.9% (95% CI 22.1-43.7) at a false-positive rate of 8.8%. The positive likelihood ratio was 3.74 (95% CI 2.67-5.23), the positive predictive value was 3.49% (95% CI 2.12-4.86%) and the negative predictive value was 99.3% (95% CI 99.1-99.5%). The sensitivity and positive likelihood ratio were approximately 40% lower than in the original study. The calibration analysis showed a good agreement between observed and expected risks (P = 0.037). Comparison with the Fetal Medicine Foundation (FMF) algorithm yielded a difference in the area under the curve of 0.084 (P = 0.007).

CONCLUSIONS: In our Italian population, the simple risk score had a lower performance than expected for the prediction of preterm pre-eclampsia in nulliparous women. The FMF algorithm applied to the same data set resulted in a better prediction.

TWEETABLE ABSTRACT: Simple risk score predicts preterm pre-eclampsia in Italy.