Eligibility Criteria

Key facts

Set in

The trial protocol, approved by the IRB

Structured ClinicalTrials.gov fields

Sex, minimum age, maximum age, accepts healthy volunteers

Detailed criteria on ClinicalTrials.gov

Free text, usually split into inclusion and exclusion lists

What are eligibility criteria?

Inclusion criteria describe characteristics a participant must have, such as a confirmed diagnosis or a minimum age. Exclusion criteria describe characteristics that rule a person out, such as pregnancy, kidney impairment, a recent heart attack or use of a conflicting medication.

Criteria serve two purposes: protecting people who could be harmed by the intervention, and creating a population in which the effect can be measured clearly. Tight criteria make results easier to interpret but can make the trial population less representative of the patients who will use the product.

How eligibility criteria are structured

Criteria typically cover:

• Demographics: age range and sex.
• Disease definition: diagnosis, stage, severity, and biomarker or genetic status.
• Treatment history: prior therapies that are required or excluded, and washout periods.
• Laboratory values and organ function thresholds.
• Other conditions, concurrent medications, pregnancy and the ability to complete study visits.

Why eligibility criteria matter

Criteria drive recruitment feasibility. Before placing a trial, sponsors estimate how many patients near each site meet the criteria, often using claims and electronic health record data coded with ICD-10-CM diagnoses and drug codes. Overly restrictive criteria are a common reason enrollment falls behind.

FDA has issued guidance encouraging sponsors to broaden eligibility where scientifically appropriate, for example by avoiding unnecessary exclusion of older adults or people with organ dysfunction. Criteria also shape the label, because approval generally reflects the population that was studied.

Limitations of eligibility data

On ClinicalTrials.gov, only sex, age limits and healthy volunteer status are structured. The detailed criteria are free text with inconsistent formats, units and terminology, so matching patients to trials or comparing criteria across studies requires parsing that text, and conclusions should be checked against the full protocol.