Association of study visit interval length with follow-up completeness and adherence to assigned study drug dose: A randomized comparison of participants in the ADAPTABLE trial.

Abstract

Background: Little is known of the frequency of follow-up visits impact on completion of scheduled study visits, adherence to randomized treatment assignment, and completion of the study.

Methods: In ADAPTABLE, participants with ASCVD were randomized to 81 mg or 325 mg of aspirin and to follow-up at 3- or 6-month intervals. At follow-up, participants answered questions about aspirin dose, adherence, and outcome measures via internet patient portal or telephone. Differences in visit adherence and study completion were compared using logistic regression. Proportional hazard models were used to compare time to study drop out, stopping aspirin, or changing aspirin dose between the 3-and 6-month groups.

Results: When compared with 6-month follow-up, participants assigned to 3-month follow-up were less likely to attend any study visit (OR 0.69, 95 % CI 0.65-0.73), but 3-month follow-up had more total visits (8 vs 5, p < 0.0001). The likelihood of completing the end-of-study visit were similar (OR 0.94, 95 % CI 0.87-1.03). Assignment to 3- vs 6-month follow-up was not associated with rates of aspirin dose switching (HR 1.02, 95 % CI = 0.94-1.09), aspirin discontinuation (HR 1.00, 95 % CI 0.88-1.14), or study drop out (HR 0.95, 95 % CI 0.88-1.03).

Conclusions: More frequent study visits led to higher total visits but lower visit adherence. There were no significant differences in visit and medication adherence between 3 v. 6 months follow up. As we continue to refine approaches to designing pragmatic clinical trials, more work is needed to understand the factors that may impact adherence to randomized assignments.

Clinicaltrials: govIdentifier:NCT02697916.