Aspirin primary prophylaxis: how to identify patients with net benefit


By Mardi Chapman

19 Sep 2019

The net benefit of using aspirin for primary prevention of cardiovascular disease (CVD) is quite variable, emphasising the importance of shared decision-making, New Zealand researchers say.

An Auckland Univeristy study conducted a benefit-harm analysis on 245,028 adults without established CVD but in whom CVD risk had previously been calculated using the PREDICT web-based decision support program.

Published in Annals of Internal Medicine, the study calculated participants’ absolute CVD risk of events such as MI and major bleeding risks for non-trauma bleeds causing hospitalisation or death over five years.

The net benefit of aspirin was calculated by subtracting the predicted reduction in CVD events from the predicted increase in major bleeds among 1,000 persons receiving aspirin for five years.

The study found when CVD and major bleeding events were assumed to be equivalent, 2.5% of women and 12.1% of men were likely to derive a net benefit from aspirin.

The proportion of participants deriving net benefit ranged widely from 0.0% to 28.5% among women and 0.1% to 50.0% among men.

More people in the net benefit group were current smokers, had diabetes or were on antihypertensive or lipid-lowering drugs.

When one CVD event was considered equivalent to two major bleeds, the net benefit of aspirin increased to 21.4% of women and 40.7% of men.

Again, there was a considerable range in the proportion of people deriving a net benefit  – from 0.1% to 60.0% among women and 1.9% to 77.9% among men.

“This indicates the difficulty of recommending thresholds of CVD risk above which net benefit from aspirin is likely, or thresholds of bleeding risk above which net harm from aspirin is likely,” the study said.

The study did not consider any potential benefits of aspirin on cancer outcomes.

“In the end, however, patients are the ones who must decide, in consultation with their physician, whether to take aspirin.”

They said a stand-alone web-based calculator of personalised risk could however be incorporated into the consultation and decision-making.

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