Subset Analysis: Insights and Pitfalls

Subset analysis, also called subgroup analysis, is the statistical analysis of the effect of treatment intervention within subsets of the subjects in clinical trials. The subsets are usually defined by baseline characteristics of the subject population such as age groups, gender, or pretreatment comorbidity. As a supplement to the primary analysis of the clinical trial, which compares the randomized groups as a whole and ignores the potential heterogeneity within each subset, the subset analysis is widely used to explore whether the treatment effect is consistent across various subsets and, if different, which patient subsets might benefit more from the treatment under study. While the subset analysis provides valuable insights to the heterogeneity of subject population, it can be easily mismanaged or misinterpreted. The following sections ...