Association between interactive voice response adherence and subject retention in a randomized controlled trial

Introduction: Interactive voice response (IVR) technology uses the telephone to collect patient reports. This study examined whether IVR adherence during a year-long clinical trial was related to subject retention in the trial.

Methods: As part of a randomized, double-blind, placebo-controlled study of daily multivitamin supplementation for recurrent aphthous stomatitis, 160 study participants were asked to make 1 weekly IVR call for the one-year study duration.

Results: The 114 subjects who completed the study made 90.5% of their expected number of IVR calls, as compared to 55.7% of expected calls made by the 46 subjects who withdrew prematurely (p<0.001). Subjects who successfully completed the study were also more likely to initiate their IVR calls as compared to subjects who withdrew from the study (p<0.001). A multivariable model incorporating different adherence variables was able to successfully predict retention status of more than 80% of subjects. IVR adherence during the first few weeks of study participation was strongly predictive of subsequent retention and successful completion of this one-year study.

Discussion: Subjects who withdrew prematurely had more missing data than study completers, even after accounting for period of study participation, potentially introducing bias into IVR results. Sub-optimal adherence to weekly IVR might provide an early signal of subsequent premature withdrawal in clinical trials. IVR adherence could be used as a screening tool during a trial period, to identify subjects most likely to stay on long clinical trials.

Conclusion: IVR adherence may be useful in anticipating retention in long-term clinical studies.