A series of randomized trials of behavioral economic interventions to increase racial and ethnic diversity of research participants: Rationale and design of ITERATE

ITERATE (NCT05827718) is a series of 4 randomized clinical trials (RCTs) designed to rigorously, systematically, and iteratively test the effects of different messaging strategies informed by behavioral economic theory on the enrollment of Black and Hispanic individuals into the Penn Medicine BioBank (PMBB), a prospective registry. For all 4 RCTs, we will identify patients eligible for enrollment in the PMBB (those with ≥ 1 encounter with the University of Pennsylvania Health System in the past 3 months, a phone number able to receive text messages or a valid email address on file, no history of consenting to or declining enrollment in the PMBB, and able to provide their own consent) and randomly assign them to receive different outreach messages. RCT 1 will test the method of outreach (email vs. text message vs. email + text message); RCT 2, source of outreach (research team vs. clinical team); RCT 3, message framing (appeal to altruism vs. appeal to social proof vs. control); and RCT 4, financial incentive (none vs. medium guarantee vs. small guarantee + small lottery vs. medium lottery vs. large lottery). In each RCT, at least 50% of the participants will be Black or Hispanic. The primary outcome of each RCT is enrollment fraction, defined as the number of participants who enroll in the PMBB divided by the total number of participants who received an outreach message, compared between arms among both Black and Hispanic patients. Secondary outcomes will include overall enrollment fraction and enrollment fraction among White patients. The "winning" strategies in earlier RCTs will be incorporated as the "standard of care" in the subsequent RCTs.