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Three week compared to seven week run-in period length and the assessment of pre-randomization adherence: A study
David Collister1, Lawrence Mbuagbaw2, Gordon Guyatt3
1Population Health Research Institute, Hamilton, Canada; Department of Health Research Methods, Evidence and Impact, McMaster University, Canada; Department of Medicine, McMaster University, Canada.
Background/Aims:
To examine how measuring adherence at 3 weeks by self-report and pill counts compares to measurements at 7 weeks in a pre-randomization run-in period.
Methods:
Study within a trial of an international parallel group randomized controlled trial (RCT) that compares spironolactone to placebo. Adults receiving dialysis enter an 8-week active run-in period with spironolactone. Adherence was assessed by both self-report and pill counts in a subgroup of participants at both 3 weeks and 7 weeks.
Results:
332 participants entered the run-in period of which 166 had complete data. By self-report, 146/166 (94.0%) and 153/166 (92.2%) had at least 80% adherence at 3 and 7 weeks respectively (kappa = 0.27 (95% C.I. 0.16 to 0.38). By pill counts, the mean (SD) adherence was 96.5% (16.1%) and 92.4% (18.2%) at 3 and 7 weeks respectively (r = 0.32) with a mean (SD) difference of 3.1% (17.8%) and a 95% limit of agreement from -31.7% to +37.9%. The proportion of adherent participants by self-report and pill counts at 3 weeks agreed in 87.4% of participants (McNemar's p-value 0.58, kappa 0.11, p = 0.02) and at 7 weeks agreed in 92.2% (McNemar's p-value 0.82, kappa 0.47, p < 0.001).
Conclusions:
Three and seven-week run-in periods and both self-reported and pill count assessments performed similarly.
Trial Registration:
ClinicalTrials.gov Identifier: NCT03020303.
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