Estimates of risks and benefits, should be set out in a straightforward way for patients

Proponents of breast cancer screening make powerful claims for its role in reducing mortality.1 The evidence is, however, disputed.2 Critics argue that the presentation of information about the benefits of screening in terms of the relative reduction in the risk of dying from breast cancer is misleading and that the absolute reduction in overall mortality should be used.3 Another criticism is that women are given insufficient information about possible harmful consequences.4 In this issue, Barratt et al present a balance sheet of risks and benefits to help patients make informed choices about screening (p 936).5

The figures on the balance sheet are generated by using a mathematical technique known as Markov modelling. A disease is represented as a process with several states (for example, healthy, diagnosed, treated) and the probabilities of possible transitions between them. The model employed by …