Challenges to Recruitment
Challenges to recruitment are multifaceted and include a lack of planning or knowledge on the part of the research team; factors related to the study design and resources allocated to recruitment; and characteristics of the target population and contextual/environmental factors. In this section, we provide a summary review of these challenges.
Lack of Planning
A common problem with recruitment is investigators’ overestimation of the pool of individuals who conform to the study inclusion criteria and be willing to enroll in a trial. This is commonly known as the recruitment “funnel effect” (Spilker & Cramer, 1992). It generally results from a lack of knowledge of the characteristics of a community or recruitment site, relevant data on prevalence of a population characteristic (e.g., Internet access), or a chronic condition in the catchment area. Relaxing the inclusion criteria (assuming that it does not negatively impact on the study or outcomes), enhancing the catchment area, and increasing canvassing efforts are potentially effective ways to rectify this problem. For example, in a recent trial examining the efficacy of a software application to enhance the well-being and quality of life of older adults at risk for social isolation (Czaja et al., 2015), the original study inclusion criteria stipulated that participants could not have prior exposure to computers or the Internet. However, this criterion had to be modified as it quickly became obvious that it was not reasonable given the ubiquitous dispersion of computer technology. Participants may have had exposure by completing an online form at a doctor’s office or through a relative. Therefore, the criterion was changed to the inclusion of persons who did not have a computer at home and only minimal computer and Internet use in the past 3 months.
Investigators may also place too much reliance on surrogate sources of recruitment such as referrals from a health care provider or contacts within an agency or organization. It is important to recognize that, although people within these organizations have the best intentions, they are typically busy with their own workplace demands. A research project that they are not actively involved in may not be a priority or be forgotten with increased work demands.