Three week compared to seven week run-in period length and the assessment of pre-randomization adherence: A study within a trial

To examine how measuring adherence at 3 weeks by self-report and pill counts compares to measurements 7 in a pre-randomization run-in period. Study within trial of an international parallel group randomized controlled (RCT) that spironolactone placebo. Adults receiving dialysis enter 8-week active period with spironolactone. Adherence was assessed both subgroup participants weeks. 332 entered the which 166 had complete data. By self-report, 146/166 (94.0%) 153/166 (92.2%) least 80% respectively (kappa = 0.27 (95% C.I. 0.16 0.38). counts, mean (SD) 96.5% (16.1%) 92.4% (18.2%) ( r 0.32) difference 3.1% (17.8%) 95% limit agreement from −31.7% +37.9%. The proportion adherent agreed 87.4% (McNemar's p -value 0.58, kappa 0.11, 0.02) 92.2% p-value 0.82, 0.47, < 0.001). Three seven-week periods self-reported count assessments performed similarly. Trial registration: ClinicalTrials.gov Identifier: NCT03020303