| Net Benefit = | Risk Level x Risk Reduction - Adverse Effects |
| (External Data) (Trial Data) |
The model suggests potential patient benefit increases with risk - those most at risk have most to gain - but that harm will remain relatively fixed. Thus at low levels of risk, the benefits will not outweigh the harm and we should refrain from treatment, but at higher levels the benefit will outweigh the harm. To complete this model generally requires several sources of data: the relative risk reduction should come from randomised trials, the adverse event rates may come from both randomized trials and epidemiological studies; the individualised patient risk level will usually come from multivariate risk equations derived from large cohort studies, thus allowing individualised predictions of net benefit from the above equation. Before making firm conclusions, the model assumptions, of fixed adverse effects and constant relative risk reduction, need to be checked. In addition, it will be useful to search for modifiers of either the benefit and harm by a subgroup analysis. We illustrate these methods with the use of examples and compare this model to how authors approach generalisation in recently published trials and meta-analyses.