Protocol Deviation
Any departure from the approved clinical trial protocol, whether intentional or accidental. Protocol deviations may include wrong dose administered, missed visits, or inclusion of ineligible participants. Significant deviations can affect data quality and are reported to ethics committees and sponsors.
Technical Context
Deviations are categorised as: minor (not expected to affect participant safety or data integrity — e.g. visit window slightly exceeded), major (may affect safety or data integrity — e.g. wrong dose administered, prohibited medication used), and critical (directly compromises participant safety — e.g. enrolled participant who met exclusion criteria for a safety reason). Major and critical deviations must be reported to the IRB/REC and sponsor. Systematic deviations (patterns affecting multiple sites) may indicate training deficiencies or protocol design problems. In regulatory submissions, deviation rates and types are reviewed as indicators of trial quality. Participants with critical deviations may be excluded from the PP analysis population.