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When to give aspirin to prevent preeclampsia: application of Bayesian decision theory
David Wright1, Alan Wright1, Min Yi Tan2
1Institute of Health Research, University of Exeter Medical School, Exeter, United Kingdom.
Insights
Targeted aspirin treatment for high-risk pregnancies effectively prevents preterm preeclampsia, outperforming universal aspirin use. Risk-based screening is recommended to balance aspirin
Area of Science:
- Obstetrics and Gynecology
- Maternal-Fetal Medicine
- Clinical Pharmacology
Background:
- First-trimester screening can identify women at high risk for preterm preeclampsia.
- Aspirin treatment in high-risk pregnancies reduces preterm preeclampsia incidence but carries risks of hemorrhagic complications.
- Debate exists on universal versus risk-stratified aspirin prophylaxis for preeclampsia prevention.
Purpose of the Study:
- To compare the effectiveness and safety of universal aspirin treatment, stratified (risk-based) treatment, and no aspirin treatment for preventing preterm preeclampsia.
- To evaluate different aspirin prophylaxis policies using Bayesian decision theory.
Main Methods:
- Bayesian decision theory was employed to analyze risks and benefits of aspirin prophylaxis.
- Data from the Screening programme for pre-eclampsia study (prediction) and the Aspirin for Evidence-Based Preeclampsia Prevention trial (intervention) were utilized.
- Policies were compared across a range of 'exchange rates' (women treated per case prevented) to assess trade-offs between aspirin's benefits and harms.
Main Results:
- Risk-based screening and targeted aspirin treatment demonstrated greater net benefit compared to no treatment or universal treatment across various exchange rates (10-1000 women treated per case prevented).
Conclusions:
- Universal aspirin treatment for preterm preeclampsia prevention should be avoided.
- Risk-based screening is the preferred strategy for identifying women who would benefit from aspirin.
- The optimal cutoff for initiating aspirin should balance the trade-offs between treatment benefits, harms, and screening performance metrics (detection, false-positive, and screen-positive rates).
Background:
There is good evidence that first-trimester assessment of the risk for preterm preeclampsia and treatment of the high-risk group with aspirin reduces the incidence of preterm preeclampsia. Furthermore, there is evidence that aspirin is associated with an increased risk of maternal and neonatal hemorrhagic complications. Against this background, there are ongoing debates whether aspirin should be recommended for all women or to a subpopulation of women predicted to be at increased risk of developing preeclampsia. Moreover, if a strategy of the prediction and prevention of preterm preeclampsia is to be used, what method should be used for the prediction, and what risk cutoff should be used to decide on who to treat?
Objective:
This study aimed to compare the policies of universal treatment, stratified treatment, and no treatment with aspirin.
Study Design:
Decisions about aspirin prophylaxis were considered from the perspective of the Bayesian decision theory. Using this approach, the treatment policies were evaluated for risks of preterm preeclampsia, effects of aspirin, and trade-offs between the harms and benefits of the treatment. Evidence on the risk of preterm preeclampsia was taken from the Screening programme for pre-eclampsia study, which was a first-trimester screening study for the prediction of preeclampsia. Evidence of the effect of aspirin was taken from the Aspirin for Evidence-Based Preeclampsia Prevention trial, which was a trial of aspirin vs placebo in the prevention of preterm preeclampsia. The trade-off between the benefits and harms of aspirin was specified by addressing the question, "What is the maximum number of women that should be treated to prevent 1 case of preterm preeclampsia?" The number can be considered as an exchange rate between the harms and benefits of using aspirin to prevent preterm PE. Given the uncertainty about the harms associated with aspirin, the treatment policies were compared across a wide range of exchange rates.
Results:
For exchange rates between 10 and 1000 women treated with aspirin to prevent 1 case of preterm preeclampsia, the net benefit achieved from the risk assessment and targeted treatment of women at high risk of preterm preeclampsia was higher than that from women with no treatment or women with universal treatment with aspirin.
Conclusion:
Universal treatment with aspirin should be avoided. Risk-based screening should be used, and the cutoff for taking aspirin should be determined from the consideration of the trade-off between the benefits and harms and detection, false-positive, and screen-positive rates.
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