Finding the Right Participants

Part of Clinical Research Coordinator (CRC) Training: Recruitment, Screening and Enrollment.

About 5 minutes. Free, in your language, no account needed.

Why this matters

Most trials that fail do not fail because the treatment did not work. They fail because not enough people joined, or the people who joined did not represent the patients the treatment is meant for.

Recruitment is therefore not marketing. It is the part of the study where science, ethics and operations meet most directly.

Start from your own patients

The most productive source is almost always the population your service already sees.

• Chart or database review. Searching your own records for people who may be eligible. This must be approved: your ethics committee and your data protection rules govern who may look and how people may be contacted.
• Clinician referral. Colleagues who see suitable patients. This works when they understand the study in one sentence and know exactly how to refer.
• Point-of-care identification. A flag in the clinic system, or a poster in the waiting room, that prompts a conversation during a normal appointment.

Internal sources produce better-qualified candidates, faster, at lower cost, and with an existing relationship of trust.

External sources

• Registries and listing services, such as ClinicalTrials.gov and national registers, where people search for studies themselves.
• Community outreach: health fairs, patient advocacy groups, community and faith organizations. Slow to build, durable once built, and often the only route to communities that research has neglected.
• Digital advertising on search and social platforms, which reaches large numbers quickly and can target specific groups.
• Traditional advertising: local press, radio, posters, leaflets.
• Recruitment vendors who run campaigns or supply pre-screened candidates.
• Former participants who agreed to be contacted about future research. Check that the consent they gave actually covers this.

The rules that apply to all of it

Four requirements apply regardless of the method.

1. Everything participant-facing needs approval before use. Advertisements, posters, leaflets, social media text, telephone scripts, pre-screening questions and referral letters. Approval attaches to a version. Using an unapproved or superseded version is a reportable deviation.
2. Privacy law governs who you may contact and how. Do not access health records for recruitment without the approval and the legal basis to do so, and do not pass identifiable details to a sponsor or vendor.
3. No coercion and no undue influence. Material must be truthful and neutral. It must not promise benefit, imply that the new treatment is better, or present study participation as the only option. Payment must be described accurately and must compensate rather than tempt.
4. No misleading simplification of eligibility. "Do you have high blood pressure? You may qualify" is acceptable. Wording that leads people to believe they will definitely qualify wastes their time and yours.

Representative recruitment

A trial that enrolls only the people who are easiest to reach produces evidence about those people only. Practical steps that widen reach:

• Provide materials in the languages your community actually speaks, approved in each language.
• Offer appointment times outside working hours where the protocol allows it.
• Use the reimbursement the ethics committee approved for travel, parking and time.
• Ask about barriers directly rather than assuming: transport, childcare, work, mobility, literacy.
• Build relationships with community organizations before you need them.

Track who is being screened and who is being enrolled. If a group is disappearing between the two steps, that is a finding about your process, not about them.

Managing the pipeline

Recruitment is a funnel, and each stage loses people.

Identified → contacted → pre-screened → screening visit → eligible → consented → enrolled.

Measure each stage. The stage where you lose most people tells you what to fix, and the fixes are different:

• Losing people between identified and contacted usually means nobody has time to make the calls.
• Losing people at pre-screening usually means the eligibility criteria are stricter than the advertisement suggested.
• Losing people between screening and enrollment usually means the visit burden became clear and the study asks more than they expected.

Keep the logs your protocol requires, and keep pre-screening logs de-identified where required.

In practice

Northside Clinic has enrolled 4 participants in VT-201 in three months against a plan of 2 a month. Dr. Osei suggests a newspaper advertisement.

Nadia looks at the funnel first. The practice identified 140 potentially eligible patients. Thirty were contacted. Of those, 18 attended screening and 4 enrolled.

The bottleneck is not awareness. It is that 110 identified patients were never contacted, because calls were being made in leftover time. Nadia proposes two protected hours twice a week for recruitment calls, and a short referral card for the practice's other clinicians.

She also looks at the 14 who attended screening and did not enroll. Nine were ineligible for the same exclusion criterion, which the referral card had not mentioned. She adds it.

Enrollment reaches plan the following quarter, with no advertisement and no new budget.

Before you spend money on reach, find out where you are losing the people you already have.

Key takeaways

• Your own patient population is usually the most productive recruitment source, provided the chart review and contact method are approved and lawful.
• Every participant-facing recruitment material needs ethics approval before use, and approval attaches to a specific version.
• Recruitment material must be truthful and neutral, must not promise benefit, and must describe payment as compensation rather than as an inducement.
• A trial that enrolls only the easiest-to-reach people produces evidence only about those people, so language, timing, reimbursement and community relationships are scientific issues.
• Measure the recruitment funnel stage by stage, because the stage with the largest loss identifies which fix will actually work.