Per-Protocol Analysis
A statistical method that includes only participants who completed the trial as prescribed, excluding dropouts and non-adherent patients. Per-protocol analysis shows efficacy under ideal conditions and typically shows larger treatment effects than intention-to-treat analysis.
Technical Context
The PP population typically excludes: participants with major protocol violations (wrong drug, wrong dose), participants who discontinued treatment before a minimum exposure duration, participants who took prohibited concomitant medications, and participants with inadequate compliance (<80% of prescribed doses). PP results typically show larger treatment effects because the compliant, tolerant subpopulation benefits most. The difference between ITT and PP results (the ITT-PP gap) is clinically informative: a large gap suggests issues with tolerability or adherence. For non-inferiority trials, PP analysis is considered the primary analysis (because ITT can bias toward finding non-inferiority by including non-compliant patients in both groups).