This one is part of the Methods Matter series that we co-host in the British Journal of Sports Medicine. In randomised controlled trials (RCTs) of interventions that aim to prevent sports injuries, the intention-to-treat principle is a recommended analysis method and one emphasised in the Consolidated Standards of Reporting Trials (CONSORT) statement that guides quality reporting of such trials. However, an important element of injury prevention trials-compliance with the intervention-is not always well-reported. Therefore, to highlight the importance of reporting compliance, in this study we carefully evaluated eight of the author’s previous trials with the purpose to describe the compliance during follow-up and address compliance issues that surfaced. Based on these observations, we discussed how results from ITT analyses can be interpreted according to the observed compliance.
Methods
Data from seven different randomised trials and one experimental study were included in the present educational review. In the trials that used training programme as an intervention, we defined full compliance as having completed the programme within +/-10% of the prescribed running distance (ProjectRun21 (PR21), RUNCLEVER, Start 2 Run) or time-spent-running in minutes (Groningen Novice Running (GRONORUN)) for each planned training session. In the trials using running shoes as the intervention, full compliance was defined as wearing the prescribed running shoe in all running sessions the participants completed during follow-up.
Results
In the trials that used a running programme intervention, the number of participants who had been fully compliant was 0 of 839 (0%) at 24-week follow-up in RUNCLEVER, 0 of 612 (0%) at 14-week follow-up in PR21, 12 of 56 (21%) at 4-week follow-up in Start 2 Run and 8 of 532 (1%) at 8-week follow-up in GRONORUN. In the trials using a shoe-related intervention, the numbers of participants who had been fully compliant at the end of follow-up were 207 of 304 (68%) in the 21 week trial, and 322 of 423 (76%), 521 of 577 (90%), 753 of 874 (86%) after 24-week follow-up in the other three trials, respectively.
Conclusion
The proportion of runners compliant at the end of follow-up ranged from 0% to 21% in the trials using running programme as intervention and from 68% to 90% in the trials using running shoes as intervention. We encourage sports injury researchers to carefully assess and report the compliance with intervention in their articles, use appropriate analytical approaches and take compliance into account when drawing study conclusions. In studies with low compliance, G-estimation may be a useful analytical tool provided certain assumptions are met.
To take home ..
As low compliance may exist in many trials in our field, we encourage sports injury researchers and readers of sports injury literature to carefully consider if it is fair to conclude that one intervention/treatment is better than the other if the intention-to-treat principle is applied.
We recommend authors to (i) think about strategies that will improve compliance during study planning; (ii) define compliance a priori, calculate and report it, and define an ‘acceptable threshold’; and (iii) analyse data according to the intention-to-treat and/or per protocol principle, report observed compliance and formulate conclusions appropriately.
We also recommend sports injury researchers explore the method of G-estimation. This is now a standard analytical approach (provided assumptions are fulfilled) in trials with low compliance. Inverse probability weighting is important in trials with large drop-out (censoring) before the end of follow-up.
Nielsen RO, Bertelsen ML, Ramskov D, Damsted C, Verhagen E, Bredeweg SW, et al. Randomised controlled trials (RCTs) in sports injury research: authors-please report the compliance with the intervention. Br J Sports Med. 2019.
The full article can be accessed here (open access)