Subgroup Analysis
An analysis examining treatment effects in specific patient subsets (e.g. by age, sex, baseline BMI, or ethnicity). Pre-specified subgroup analyses are more reliable than post hoc subgroup analyses. They help identify whether a drug's effect varies across different patient populations.
Technical Context
Pre-specified subgroup analyses (defined in the protocol before unblinding) are more reliable than post hoc subgroup analyses. Standard subgroups in peptide drug trials include: age (<65 vs ≥65), sex, race/ethnicity, baseline disease severity (HbA1c <8.5% vs ≥8.5%, BMI categories), background therapy, and geographic region. Interaction tests assess whether the treatment effect genuinely differs across subgroups (significant interaction p-value <0.05) rather than simply testing significance within each subgroup. Important principle: even pre-specified subgroup analyses have reduced statistical power (smaller sample sizes) and increased false positive risk from multiple comparisons. Treatment guidelines generally do not vary recommendations based on subgroup analyses unless the interaction is strong, biologically plausible, and replicated.