Inclusion criteria are the characteristics a person must have to join a clinical trial. Exclusion criteria are the characteristics that rule a person out. Together they define the eligible study population.
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Inclusion and exclusion criteria
noun · clinical research
Protocol-defined conditions that a person must meet (inclusion) and must not meet (exclusion) to be enrolled in a clinical trial.
Related terms
In short
Explained
Every protocol lists the conditions for enrolment. Inclusion criteria describe the people the study is designed to learn about: an age range, a diagnosis, a disease stage, a lab value within range, the ability to give consent. Exclusion criteria remove people for whom taking part would be unsafe, whose data would be hard to interpret, or who could not complete the study: pregnancy in some studies, a competing treatment, an organ function threshold, a recent participation in another trial.
The lists serve three purposes at once. They protect participants from foreseeable harm. They make the enrolled group similar enough that a difference between arms can be attributed to the treatment. And they define external validity: results apply most directly to people who look like those who were eligible. That is why regulators and ethics committees look closely at them, and why overly narrow criteria can make a trial hard to enrol and its results hard to generalise. FDA has published guidance encouraging sponsors to broaden eligibility criteria where it is scientifically justified; check the current version on FDA.gov for the exact title and recommendations.
Eligibility is the decision. Screening is the process of collecting the information needed to make it, which may take several visits and tests. A person who consents and then fails a criterion is a screen failure. Screen failures are usually logged with the reason, because the reasons show whether the criteria are workable and feed enrolment reporting such as a CONSORT flow diagram.
A criterion is testable when two different coordinators would reach the same answer for the same participant. "Adequate renal function" fails that test; "eGFR 60 mL/min/1.73 m2 or higher at screening, by CKD-EPI 2021" passes it, and a calculator such as the eGFR CKD-EPI tool removes arithmetic errors. Specify the time window ("within 28 days before randomization"), the source (central lab or local lab) and what happens if a value is borderline or repeated.
Examples
Illustrative wording for a hypothetical adult study. Real criteria must come from your protocol.
| Type | Weak wording | Testable wording |
|---|---|---|
| Inclusion | Adult with type 2 diabetes | Age 18 to 75 years; documented type 2 diabetes for at least 6 months |
| Inclusion | Stable on current medication | No change in dose of metformin in the 8 weeks before screening |
| Inclusion | Able to consent | Has signed the approved consent form before any study procedure |
| Exclusion | Significant kidney problems | eGFR below 45 mL/min/1.73 m2 at screening |
| Exclusion | Recent clinical trial | Received another investigational product within 30 days or 5 half-lives, whichever is longer |
| Exclusion | Pregnant | Positive pregnancy test at screening, or pregnant or breastfeeding |
Numbers above are illustrative demo values, not clinical recommendations.
Build the screening form in the free sandbox, add range checks and test it with dummy participants before enrolment opens. No credit card.
Practice
Most studies record eligibility on a dedicated screening form with one question per criterion: yes or no, plus the value and date behind it. A final field records the investigator decision. Good practice is to keep the evidence next to the answer, so a monitor can verify it later through source data verification, and to make the form refuse an inconsistent answer set rather than rely on someone noticing.
The eligibility screening eCRF template shows this pattern. If criteria change through a protocol amendment, the form version and the date of the change should be traceable so you can show which participants were screened under which criteria. The protocol template has a section for the lists, and our patient eligibility screening guide covers pre-screening for recruitment.
Inclusion met
4 of 4
Exclusion met
0 of 5
Decision
Eligible
In Capture
Build the screening form with skip logic, edit checks and calculated fields such as eGFR (CKD-EPI 2021) and age from date of birth. Forms move from draft to approved, only approved forms reach the casebook, and every change to an answer is recorded with who changed it, the old value, the new value and the reason. Start from the screening template and adapt it to your protocol.
Start screening
Screen new subject
Not screened before
Rescreen subject
Needs a new screening number
ICF date
14-Sep-2026
Year of birth
1971
Sex
Female
Inclusion criteria are the characteristics a person must have to join a trial; exclusion criteria are the characteristics that rule a person out. A participant must meet all inclusion criteria and none of the exclusion criteria.
Age 18 to 75 years with a documented diagnosis of the condition under study for at least six months. Real criteria come from each protocol.
A lab value outside a safety limit, such as kidney function below a protocol threshold, or participation in another investigational study within a stated period.
Yes, through a protocol amendment, which needs ethics committee or IRB approval before it is applied. Records should show which version of the criteria each participant was screened against.
It is normally documented as a protocol deviation and assessed, often with the medical monitor and sponsor, for participant safety and impact on the analysis.
A person who signed consent and began screening but was not enrolled, usually because a criterion was not met. Teams log the reason.
Keep exploring
Eligibility screening eCRF
Criteria as checkable questions.
Patient eligibility screening
Pre-screening and recruitment.
Informed consent
Comes before screening procedures.
Randomization
Allocation after eligibility.
Protocol template
Where criteria are written.
CONSORT flow diagram generator
Reporting screened and excluded.
Free sandbox with every feature. Try your criteria on dummy participants. No credit card.