Leave me out: Patients' characteristics and reasons for opting out of a pragmatic clinical trial involving medication adherence.

Opt-out procedures are sometimes used instead of standard consent practices to enable patients to exercise their autonomous preferences regarding research participation while reducing patient and researcher burden. However, little is known about the characteristics of patients who opt-out of research and their reasons for doing so. We gathered such information in a large pragmatic clinical trial (PCT) evaluating the effect of theory informed text messages on medication adherence.Eligible patients, identified through electronic health records, were sent information about the study and provided with an opportunity to opt-out. Those opting out were asked to complete a voluntary survey regarding their reasons for doing so. Demographic data were compared among patients opting-out vs those included in the study using chi-squared tests and a log binomial regression model.Of 9046 patients receiving study packets, 906 (10.0%) patients returned opt-out forms. Of those, 451 (49.8%) returned the opt-out survey. Patients who opted out were more likely to be older, white, and nonHispanic than those who were included in the PCT. Survey respondents expressed high levels of trust in their health care providers, research, and system. Nearly half (46.6%) reported concerns about time as a reason to opt-out.In this PCT, 10% of patients receiving packets opted out, with significant differences in age, race, gender, and ethnicity compared to those included. Future trials should further investigate representativeness and reasons patients choose to opt-out of participating in research.