Reply to the letter to the editor 'the harms of low-dose aspirin prophylaxis are overstated' by P. Elwood and G. Morgan

Individualised benefit-harm balance of aspirin as primary prevention measure - a good proof-of-concept, but could have been better…

Guidelines from different organisations regarding the use of aspirin for primary prevention vary despite being based on similar evidence. Translating these in practice presents a further major challenge. The benefit-harm balance tool developed by Puhan et al. (BMC Med 13:250, 2015) for aspirin can overcome some of these difficulties and is therefore an important step towards personalised medicine. Although a good proof-of-concept, this tool has some important limitations that presently preclude its use in practice or for further research. One of the major benefits of aspirin that has become apparent in the last decade or so is its effect in preventing cancer and cancer-related deaths. However, this benefit is clear and consistent in randomised as well as observational evidence only for specific cancers. Additionally, it has long lag-time and carry-over periods. These nuances of aspirin's effects demand a specific and a more sophisticated model such as a time-varying model. Further refinement of this tool with respect to these aspects is merited to make it ready for evaluation in qualitative and quantitative studies with the goal of clinical utility.Please see related article: http://bmcmedicine.biomedcentral.com/articles/10.1186/s12916-015-0493-2.