Clinicians know that individual patients may respond differently to a given treatment and that the overall treatment effect reported in a randomized trial of the treatment may not be directly applicable to all patients in clinical practice. Determining the treatment effect for an individual patient involves a comparison of the outcome when that patient is exposed to the treatment vs the outcome of the same patient exposed to a control treatment at the same time, a comparison impossible to make in conventional parallel-group trial designs. A practical alternative is to examine heterogeneity of (variation in) treatment effects across groups of patients, categorized by baseline demographic or clinical characteristics, such as age or risk factors for the outcome.
Source: JAMA Online First