Samenvatting

OBJECTIVE: PRECIS - 2 is a tool that could improve design insight for trialists. Our aim was to validate the PRECIS - 2 tool, unlike its predecessor, testing the discriminant validity and inter-rater reliability. STUDY DESIGN AND SETTING: Over 80 international trialists, methodologists, clinicians and policymakers created PRECIS - 2 helping to ensure face and content validity. The inter-rater reliability of PREC IS - 2 was measured using 19 experienced trialists who used PRECIS - 2 to score a diverse sample of 15 RCT protocols. Discriminant validity was tested with two raters to independently determine if the trial protocols were more pragmatic or more explanatory, with scores from the 19 raters for the 15 trials as predictors of pragmatism. RESULTS: Inter-rater reliability was generally good, with seven out of nine domains having an ICC over 0.65. Flexibility (Adherence) and Recruitment had wide confidence intervals but raters found these difficult to rate and wanted more information. Each of the nine PRECIS - 2 domains could be used to differentiate between trials taking more pragmatic or more explanatory approaches with better than chance discrimination for all domains. CONCLUSION: We have assessed the validity and reliability of PRECIS - 2. An elaboration paper and website provide guidance to help future users of the tool which is continuing to be tested by trial teams, systematic reviewers and funders.