Assessment of NICE and USPSTF guidelines for identifying women at high risk of pre-eclampsia for tailoring aspirin prophylaxis in pregnancy

Objective: To assess the accuracy of the National Institute of Health and Care Excellence (NICE) and United States Preventive Services Task Force (USPSTF) guidelines for predicting pre-eclampsia in pregnancy to guide aspirin prophylaxis. Study design: We conducted an individual participant data meta-analysis using the Perinatal Antiplatelet Review of International Studies (PARIS) dataset. This dataset includes randomised controlled trials (RCTs) of antiplatelet therapy for primary prevention of pre-eclampsia conducted in international antenatal care settings. RCTs were eligible if they enrolled pregnant women up to 28 weeks'gestation, reported risk factors, and assessed pre-eclampsia. Women assigned to the control arm (no antiplatelet agent) were included. Both guidelines recommend aspirin if ≥1 high-risk factors or ≥2 moderate-risk factors. Two moderate-risk factors (body mass index and pregnancy interval) were unavailable. Pre-eclampsia was the primary outcome. The secondary outcomes were pre-eclampsia defined by gestational age at delivery (<37 weeks versus ≥37 weeks; <34 weeks versus ≥34 weeks). We assessed the performance of the NICE and USPSTF approaches for parous and nulliparous women by estimating sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for predicting pre-eclampsia, the number-needed-to-screen (NNS) and the number-needed-to-treat (NNT) to prevent one pre-eclampsia event. Results: Three RCTs were eligible (4524 women, 221 pre-eclampsia cases). Using the NICE guidelines, 9.4% of 1020 parous women were classified as screen-positive with a sensitivity of 26.4% (95% confidence interval 16.4–39.6%), specificity 91.5% (89.6–93.1%), PPV 14.6% (8.9–23.0%) and NPV 95.8% (94.3–96.9%). The NNS was 729 and NNT 69. For 3504 nulliparous women, 3% were classified as screen-positive with a sensitivity of 8.9% (5.5–14.4%), specificity 97.2% (96.6–97.8%), PPV 14.2% (8.7–21.9%), NPV 95.5% (94.8–96.1%). The NNS was 2336 and NNT 71. The USPSTF approach demonstrated similar performance. Conclusion: The NICE and USPSTF guidelines offer a simple and specific approach for recommending aspirin prophylaxis for women at high-risk of pre-eclampsia where more advanced screening methods are not available. However, the low detection rate limits its value in clinical practice, in particular for nulliparous women, and raises the need for development of an improved simple risk prediction tool.