Competing risks model for prediction of preeclampsia

Abstract

We are grateful to Drs Guerby and Bujold for raising an important question.1Guerby P. Bujold E. How to calculate the risk of preeclampsia in women with a history of positive screening.Am J Obstet Gynecol. 2020; 223: 299-300Abstract Full Text Full Text PDF PubMed Scopus (3) Google Scholar The competing risks model uses data on maternal demographic characteristics and medical history along with biomarker measurements to produce risks of delivery with preeclampsia (PE) before any specified gestational age.2Wright D. Wright A. Nicolaides K.H. The competing risk approach for prediction of preeclampsia.Am J Obstet Gynecol. 2020; 223: 12-23.e7Abstract Full Text Full Text PDF PubMed Scopus (48) Google Scholar Compared with the risk of PE in nulliparous pregnant women, the risk is substantially increased in parous women with history of PE in their previous pregnancy and the risk is decreased in parous women with no history of PE. As shown in the Figure, the increase in risk in a woman with a history of previous PE is not constant but depends on the gestational age at delivery; similarly, the risk of PE in a woman with no previous history of PE is also dependent on the gestation at delivery. For example, compared with a nulliparous woman with a profile resulting in a risk for preterm PE of 1 in 100, a parous woman with the same characteristics and history of delivery with PE at 30 weeks’ gestation would have a risk of about 1 in 10, and if the delivery was at 41 weeks’ gestation, the risk would be 1 in 90. In a parous woman with the same characteristics as the nulliparous woman and previous delivery without PE at 30 weeks’ gestation, the risk would be about 1 in 110, and if the delivery was at 41 weeks’ gestation, the risk would be 1 in 700. Longitudinal data on aspirin treatment and outcomes in successive pregnancies are needed to determine whether risks in the index pregnancy should be modified to account for treatment with aspirin in previous pregnancies. In the absence of such data, we carried out a sensitivity analysis: changing the previous pregnancy history in the screening program for preeclampsia trial3Tan M.Y. Wright D. Syngelaki A. et al.Comparison of diagnostic accuracy of early screening for pre-eclampsia by NICE guidelines and a method combining maternal factors and biomarkers: results of SPREE.Ultrasound Obstet Gynecol. 2018; 51: 743-750Crossref PubMed Scopus (131) Google Scholar data to reflect the effect of aspirin. We examined the following 3 policies:1.Ignore aspirin prophylaxis in the previous pregnancy. This could result in a decrease in overall detection rate of 5% to 10% and a reduction in screen-positive rate of around 1%; in the subgroup that had received aspirin in their previous pregnancy, the decrease in detection rate could be as high as 40%.2.Continue treatment with aspirin. All women treated with aspirin in their previous pregnancy because of increased risk of preterm PE, irrespective of whether they developed PE or not, should also be treated with aspirin in their current pregnancy; such a policy could result in doubling of women taking aspirin.3.Consider women who received aspirin in their previous pregnancy as nulliparous. This may be the preferred option because it would result in only a small decrease (2%–3%) in overall detection rate and small increase (<1%) in screen-positive rate; in the subgroup that had received aspirin in their previous pregnancy, the decrease in detection rate could be as high as 10%. How to calculate the risk of preeclampsia in women with a history of positive screeningAmerican Journal of Obstetrics & GynecologyVol. 223Issue 2PreviewWith the current demonstration of the benefits of aspirin initiated in early pregnancy to prevent the most severe and preterm forms of preeclampsia, there is a growing interest for the prediction of preterm preeclampsia in the first trimester of pregnancy.1 In the review by Wright et al,2 the authors reported that approximately 90% of women who will develop early preeclampsia could be identified using a competing risks approach in the first trimester of pregnancy, with a false-positive rate of 10%. Full-Text PDF Competing risks model for prediction of preeclampsia in women who took aspirin prophylaxis in a previous pregnancyAmerican Journal of Obstetrics & GynecologyVol. 225Issue 2PreviewWe thank Professors Wright and Nicolaides for their detailed comment concerning our recent question about preeclampsia screening in parous women.1,2 Full-Text PDF