Aspirin benefit harm calculator

Aspirin benefit harm calculator guides individualised decision-making for CVD primary prevention

University of Auckland researchers have developed a calculator that provides clinicians with an individualised estimate of the CVD benefit and bleeding harms of aspirin for their patients without established CVD.

Link to the Calculator(1)

The tool is based on NZ’s CVD risk equation(2) and a NZ bleeding risk equation developed in the same cohort for this tool.(3)

The latest meta-analysis(4) of primary prevention aspirin trials, including the results of three major trials published last year, confirmed that aspirin reduces the relative risk of CVD and increases the relative risk of bleeding. The key clinical question is whether there are individuals without established CVD in whom the absolute benefits of aspirin outweigh its absolute harms. The calculator addresses this question by providing an individualised estimate of the number of CVD events avoided and number of major bleeds caused by aspirin.

For further information please contact lead researcher Vanessa Selak (


1. Selak  V, Jackson R, Poppe K, Wu B, Harwood M, Grey G, et al. Personalized prediction of cardiovascular benefits and bleeding harms from aspirin for primary prevention: a benefit–harm analysis. Ann Int Med. 2019;171:529-39.

2. Pylypchuk R, Wells S, Kerr A, Poppe K, Riddell T, Harwood M, et al. Cardiovascular disease risk prediction equations in 400 000 primary care patients in New Zealand: a derivation and validation study. Lancet 2018;391:1897-907.

3. Selak  V, Jackson R, Poppe K, Wu B, Harwood M, Grey C, et al. Predicting bleeding risk to guide aspirin use for the primary prevention of cardiovascular disease. A cohort study. Ann Int Med. 2019;doi:10.7326/M18-2808.

4. Zheng SL, Roddick AJ. Association of aspirin use for primary prevention with cardiovascular events and bleeding events. A systematic review and meta-analysis. JAMA. 2019;321:277-87.