Clinical Trials and Gold Standard Patient Response

All 18 clinical trials that recruited patients in the ED and required patients’ (and/or parents’) consent/assent before enrollment were included in the study. The trials covered a variety of clinical areas, interventions, observations, randomized trials, and trials requiring long-term follow-ups. Trial descriptions are presented in Table A1, Supplementary Appendix.

In current practice, patient recruitment in the ED is performed on a per visit basis. A clinical research coordinator (CRC) matches patients with the actively enrolling trials open on the patients’ date of visit and approaches the eligible patients if consent is required. Therefore, in this study we treated each patient visit (referred to as “encounter”) as the unit of analysis. During the study period, patients in 3444 encounters were eligible for at least one of the trials and were approached for enrollment. Patients in 99 encounters (2.87%) were excluded due to lack of documentation in the Electronic Health Record (EHR) (ie, no patient response documented or unidentified home addresses), resulting in a set of 3345 encounters for the study. We retrospectively collected the patients’ actual response (ie, agree or decline) to the trial invitations from the CRC study database, which served as a gold standard set to train and evaluate the predictive models. To use these data, we labeled the consent and decline response as {+1, −1}, respectively.