Screening and Eligibility

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

About 6 minutes. Free, in your language, no account needed.

Why this matters

Enrolling an ineligible participant is one of the most damaging errors a site can make. It exposes a person to risk the protocol did not assess for them, and it puts data into the study that may have to be excluded or explained.

It is also one of the easiest errors to make, because it usually happens through small, reasonable steps: a value close to the threshold, a test done a day late, a history nobody checked.

Pre-screening and screening

Pre-screening is the assessment done before consent, using information you already lawfully hold or that a person volunteers. It filters out people who obviously cannot take part. Keep it limited: until a person has consented, you may not perform study-specific procedures on them.

Screening is the formal assessment after consent, against the protocol's criteria. It happens within a defined screening window and produces a documented decision.

The order is fixed. Consent first, then any study-specific procedure. If a test is done only because of the study, it may not happen before consent. If a test would have been done anyway as part of routine care, the protocol will say whether its result may be used.

Inclusion and exclusion criteria

Inclusion criteria are the conditions a person must meet. Every one of them must be satisfied.

Exclusion criteria are the conditions that disqualify. Every one of them must be absent.

Both are absolute. There is no such thing as being nearly eligible, and there is no such thing as an eligibility criterion an investigator may waive. If a criterion appears wrong for a particular person, the route is to ask the sponsor, not to interpret it locally.

Criteria commonly exist to:

How eligibility errors happen

Learn this list; it is the origin of most eligibility deviations.

Working the eligibility checklist

  1. Use the checklist for the current protocol version, and check the version number on it.
  2. Work through every criterion in order. Do not skip criteria you believe you already know.
  3. For each one, record the source of the answer: which laboratory report, which clinic note, which measurement, on which date.
  4. Where a criterion depends on a value, write the value down, not just "met".
  5. Where a criterion depends on clinical judgment, the investigator decides and signs. This is a medical decision.
  6. Have a second person check the completed checklist before randomization. Two-person verification before randomization prevents more errors than any other single practice.
  7. The investigator signs and dates the eligibility confirmation before randomization.

Screen failures

A person who is screened and found ineligible is a screen failure. This is a normal outcome, not a mistake.

If an ineligible person is enrolled

It happens. What matters is what you do next.

  1. Tell the investigator immediately.
  2. Assess safety first. Does this person face a risk that the protocol did not anticipate?
  3. Notify the sponsor, and the ethics committee where local rules require it.
  4. Record it as a protocol deviation, with the facts and the date of discovery.
  5. Follow the sponsor's decision on whether the participant continues.
  6. Find the cause and fix it, rather than treating it as one person's mistake.

Never quietly correct a record to make an ineligible person look eligible. That is falsification, and it is a different category of problem entirely.

In practice

Nadia screens a woman for VT-201 whose eGFR is 44. The protocol excludes anyone below 45.

She is one unit outside, she is keen, and she would be an excellent participant. Dr. Osei is comfortable clinically. Everyone would like to enroll her.

Nadia records her as a screen failure with the specific reason and the laboratory report reference. She does not ask for a repeat test in the hope of a better number, because the protocol does not provide for that and the intention would be visible in the record.

She does raise the criterion with Marcus, the monitor, noting that several candidates have failed on the same threshold. That feedback goes to the sponsor and contributes to a later amendment. The amendment changes the criterion prospectively, for people screened afterwards.

The woman who was 44 is not enrolled retrospectively. Nadia calls her to explain, and passes the kidney result to her general practitioner.

An eligibility criterion is a boundary, not a target to be negotiated toward.

Key takeaways