Conducting the Study - Retention of subjects

One of the keys to the success of a research study is the recruitment and retention of the study subjects in sufficient numbers to preserve the necessary sample size that will yield a certain statistical power, expressed as the probability of a β or Type 2 error. Typically, the investigator aims for a statistical power of 80 percent, which means that the probability of missing a “true” difference is 20 percent.

The primary strategy for subject retention lies with one of the tenets of subject recruitment, namely, the ongoing process of informed consent. Subjects who are well-informed and understand the expectations of the investigator with respect to study participation are more likely to complete the research study or trial. Additional recommendations for subject retention include respecting the needs of subjects by providing flexible and reliable appointment times for calls and visits, meeting subjects in convenient locations or providing transportation to visits where appropriate, and providing consistent study personnel. Consistency in study personnel staffing helps subjects feel comfortable and builds trust with investigators, especially if study procedures require interviews or the gathering of sensitive data. Investigators should also keep updated contact information on subjects and contact subjects using the subject’s preferred method. Regular and frequent contacts with subjects via the sending of visit reminders, study newsletters, or birthday/holiday cards (especially for longitudinal studies) assists with retention. Where possible, the investigator or study team may also assist subjects in navigating the health care system with regard to other needed clinical services.

When faced with low accrual, the investigator must take care to avoid recruitment methods that might be considered coercive or as representing undue inducement. For example, lotteries in which subjects may win large sums of money are not acceptable.

If involved in a large multicenter trial, investigators should be aware of their IRB policies with regard to the acceptance of enrollment bonuses and incentives as well as referral fees. Large amounts of money or gifts from sponsors or referral fees (“finder’s fees”) may unduly influence health care practitioners to influence a potential subject’s decision to participate. The Yale University Policy on Conflict of Interest and Conflict of Commitment contains additional information about the propriety of investigator incentives. Finder’s fees are monetary rewards given to practicing health care professionals for referring a patient into a trial. Finder’s fees are forbidden at Yale University. The HHS Inspector General finds that this practice is questionable, but no regulatory requirement exists.