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Planning for a Participant Recruitment Phase

Set a realistic timeframe for recruitment by thinking through the opportunities and barriers for participation.

CREd Library and Floris Singletary

DOI: 10.1044/cred-sprs-tth-003

Investigators often underestimate the time and effort required for recruiting a sufficient number of participants, or don’t fully consider the impacts of inclusion/exclusion criteria when making study population and enrollment estimates. A few suggestions for improving study recruitment include seeking out opportunities for engagement within the institution and community, developing systems to streamline referrals, and considering the perspective of potential participants in emphasizing benefits and addressing barriers for enrollment or participation.

Video: Planning for a Participant Recruitment Phase

Floris Singletary, Brooks Rehabilitation Clinical Research Center

Many researchers have these great ideas. Their science is perfect. But they fail to look at their recruitment piece. They may think they’ll be able to get a certain population, but when they put all of the inclusion/exclusion criteria as an overlay — that number of 25 or 30 may have been reduced to 2 or 3.

You want to allow for a recruitment phase. So, someone says, “I have a year.” Or, “I’m hoping to get this in a year.” Well, it takes them six months to get their design honed, maybe they had some IRB issues. Then the deadline is starting to close in and they need to get their clinical trial started — and they really haven’t allowed for what I call a “recruitment phase.” You have to allow for that. You have to allow for a recruitment phase, especially if there is a screening process involved.

I work in an area where we’re working with people with disabilities. If you’re a speech-language pathologist, you’re working with people who have disabilities in communication. So the recruitment is going to be a little bit harder because of the very nature of the fact that they may have some disability in communication and understanding, and you may be working with a family member.

When you’re recruiting for clinical trials in a population that has disabilities, some people have comorbidities. Or sometimes researchers will say, you need to wait until you’re six months post-onset — of stroke, that that for instance. Maybe you’ve met this person during the admission process, and you maybe have talked to them, but then you have to connect that dot, waiting during that time period.

Also sometimes recruiting when people have just gone through something very traumatic, like a brain injury, they have a terrible brain injury, or a stroke, or a spinal cord injury. Well, you have to let them get through that process and that time, and you have to learn the skills of being able to contact at the right moment, not push too hard, and have the mechanisms for following up.

How much time should researchers build in for recruitment?

A lot of it has to do with what number you are hoping to recruit for your trial. A lot of your funding is based on someone giving you money because you’re saying, I’m going to recruit 50 participants.

Another thing to think about is what size you want your waiting list to be. If you’re going to recruit people, some researchers may want two or three people in queue. It also depends on the specificity. Let me use an example. I worked with a lot of neuroscientists. They want to do brain imaging. So, one of the screening exclusions is metal. In your recruitment phase, if you’re going to require that you’re going to do fMRI, and you know that metal is going to be an exclusion, you know that is going to knock out a certain percentage of the folks you’re going to work with.

To answer your question on a recruitment phase. I would say — and this is just by the seat of my pants — you need to allow a good two to three months for a recruitment phase, if there’s really a solid plan. And people fail to have a plan and build that in. And they’re so excited about their science and their work they don’t realize what it’s going to take.

The poster presentation with samples and further details is available under the “Supplemental” tab on this page.

Points to Consider

Excerpted from Points to Consider about Recruitment and Retention While Preparing a Clinical Research Study, National Institute of Mental Health.

Community Engagement

  • Have you identified the communities that you would like to engage?
  • What relationships have you established with communities in order to facilitate your study? What relationships will you need to establish?
  • How will you maintain these relationships?
  • What strategies will you use to engage different communities before and during your study?
  • What efforts has your University/Research Institution made in the past to engage these communities? Are there any ongoing collaborations/partnerships at your institution?
  • What will the participating communities receive in return for their involvement in the study?

Examples of communities: Potential participants and their family members, referring physicians, community-based organization directors, state mental health directors, civic organizations, advocacy organizations, faith-based organizations, churches, community centers, health clinics, and the media.

Benefits to Participation

  • What are the benefits to enrolling in this clinical research study, from the perspective of potential participants? How will you determine these benefits?
  • Does the study design include assessment/treatment strategies that are likely to foster enrollment and retention?

Suggestions: Work with communities through focus groups, interviews, and surveys to develop a list of benefits to participating in the research study. The list of benefits can be communicated to potential participants, and specific benefits can be emphasized when speaking to different audiences.

Barriers to Participation

  • What are the barriers to participation?
  • How will you prepare to address each of these barriers?
  • Will all study costs be covered for the participant? Is there a way to reduce any costs?
  • Have you considered the language requirements and literacy of proposed participants?
  • Are you familiar with how English is used by different racial and ethnic groups?

Participant barriers: time off work, transportation costs, childcare, care for an elderly relative, language differences, out-of-pocket expenses, not wanting to change current treatment, concerns about side-effects, limited health insurance reimbursement, mistrust of medical research, fear of stigma associated with a disorder/disease, etc.

Investigator barriers: lack of diversity on the research team, research teams lacking knowledge about the communities chosen for inclusion, ineffective guidance to study staff, recruitment based on convenience, ineffective informed consent processes, limited knowledge about methods to promote a study, limited knowledge of appropriate retention methods, etc.

Planning and Timeline

  • What is a realistic recruitment timeline?
  • What is your timeline for protocol finalization, IRB approvals, development of treatment materials or experimental methods, piloting, staff training and certification, development of data collection instruments and systems, tools for quality control, acquisition of treatment products and matching placebo, etc.?
  • Do you plan to match resources to recruitment over the lifespan of the grant (i.e. funds, personnel)?
  • What resources will be required to retain participants after the recruitment phase is completed?
  • Have you considered using available local data to generate enrollment/retention estimates that are as accurate as possible?

Suggestions: Rebounding from recruitment shortfalls can be difficult as a study progresses. Thus, detailed planning of all aspects of study design and implementation is critical to the success of the study. Personnel effort should be adjusted accordingly during periods of high/low recruitment. Prior local studies may provide parameter estimates of the percent of eligible participants.

A Recruitment timeline considers the following critical time points: Enrollment start date; Enrollment end date; Intervention completion date (date last person will complete study intervention if patient completes the full protocol); Data lock date (date when all data have been entered, queries resolved, data ready for analysis); Paper Finalization date (date when outcome manuscript is ready for journal submission)SeeNational Institute of Mental Health (2005) for additional considerations and suggestions.

Recruitment Opportunities to Explore

Digested from Clinical Trials Recruitment Best Practices Manual, Michael J. Fox Foundation Clinical Trial Strategies Team.

Your Clinic

Because individuals in your clinic are the easiest to recruit, it is important to be thorough and strategic in your efforts. Develop systems to make it easy for colleagues to refer participants, and make sure participant recruitment materials are visible in high traffic areas such as waiting rooms.


Provide opportunities for enrolled subjects, family members, or others who want to engage and help to promote your study to their networks.
Your Institution

Reach out to colleagues in other departments and/or satellite locations for help cultivating leads. Look for opportunities to post flyers, host a meeting or participate in events, post to an organization’s email list, or write a newsletter article in order to share key information about the study.

Your Community

Connect with support groups or other organizations that may be willing to have you speak at a meeting, publish an article about your study, or help distribute recruitment materials. Remember that your “local” community may cover a very large area, as participants may be willing to travel several hours to get to your site depending on the nature of your study.
See Michael J. Fox Foundation (2011) for more details and additional ideas.

See Michael J. Fox Foundation (2011)  for more details and additional ideas.

Further Reading: Online Resources of Interest

Agency for Healthcare Research and Quality (AHRQ). (2012). Participant Recruitment for Research. AHRQ-Funded Projects: Emerging Lessons (Available from the AHRQ Website at

Michael J. Fox Foundation (MJFF). (2014). Clinical Trials Recruitment Best Practices Manual [PDF]. For Researchers: Trial Resources (Available from the MJFF Website at

National Institute of Mental Health (NIMH). (2005). Points to Consider about Recruitment and Retention While Preparing a Clinical Research Study [PDF]. NIMH Policy for the Recruitment of Participants in Clinical Research (Available from the NIMH Website at

NIH Workshop on the Enrollment and Retention of Participants in NIH-Funded Clinical Trials. (2014, July). Workshop on Clinical Trial Patient Enrollment and Retention [Streaming Video, .F4V Download, and/or Caption File]. NIH VideoCasting and Podcasting (Available from the NIH Website at

U.S. Food and Drug Administration (FDA). (2014). Recruiting Study Subjects Information Sheet: Guidance for Institutional Review Boards and Clinical Investigators. Regulatory Information: FDA Guidance Documents (Available from the FDA Website at

Further Reading: Strategies to Improve Participant Recruitment

Blanton, S., Morris, D. M., Prettyman, M. G., Mcculloch, K., Redmond, S., Light, K. E. & Wolf, S. L. (2006). Lessons learned in participant recruitment and retention: The EXCITE trial. Physical Therapy, 86(11), 1520–1533 [Article] [PubMed]

Campbell, M., Snowdon, C., Francis, D., Elbourne, D. & Mcdonald, A. (2007). Recruitment to randomised trials: strategies for trial enrolment and participation study. The STEPS study. Health Technology Assessment, 11(48), 126 [Article]

Kernan, W. N., Viscoli, C. M., Demarco, D., Mendes, B., Shrauger, K., Schindler, J. L., Mcveety, J. C., Sicklick, A., Moalli, D., Greco, P., Bravata, D. M., Eisen, S., Resor, L., Sena, K., Story, D., Brass, L. M., Furie, K. L., Gutmann, L., Hinnau, E., Gorman, M., Lovejoy, A. M., Inzucchi, S., Young, L., Horwitz, R. & on behalf of the IRIS Trial Investigators. (2009). Boosting enrollment in neurology trials with local identification and outreach networks (LIONS). Neurology, 72(15), 1345–1351 [Article] [PubMed]

Lovato, L. C., Hill, K., Hertert, S., Hunninghake, D. B. & Probstfield, J. L.. (1997). Recruitment for controlled clinical trials: Literature summary and annotated bibliography. Controlled Clinical Trials, 18(4), 328–352 [Article] [PubMed]

Treweek, S., Mitchell, E., Pitkethly, M., Cook, J., Kjeldstrøm, M., Johansen, M., Taskila, T.K., Sullivan, F., Wilson, S., Jackson, C., Jones, R., & Lockhart, P. (2010). Strategies to improve recruitment to randomised controlled trials. Cochrane Database of Systematic Reviews, 4. 10.1002/14651858.MR000013.pub5

Watson, J. & Torgerson, D. (2006). Increasing recruitment to randomised trials: a review of randomised controlled trials. BMC Medical Research Methodology, 6(1), 34. 10.1186/1471-2288-6-34 [Article] [PubMed]

The content of this page is based on selected clips from a video interview conducted at the ASHA Convention.

Additional digested resources and references for further reading were selected and implemented by CREd Library staff.

Copyright © 2015 American Speech-Language-Hearing Association