Every clinical trial has a set of eligibility criteria — specific requirements that determine who can and cannot participate. These criteria exist to protect participant safety and to ensure the study can produce meaningful scientific results. Understanding how to read these criteria can help you quickly identify which trials may be relevant to your situation.
Inclusion Criteria vs. Exclusion Criteria
Inclusion criteria describe the characteristics you must have to be eligible. Common inclusion criteria include a specific diagnosis, age range, disease stage, or previous treatment history. For example, a trial might require participants to have "histologically confirmed Stage III non-small cell lung cancer" and be "aged 18 years or older."
Exclusion criteria describe characteristics that would disqualify you from participating. These often relate to other medical conditions, medications you are currently taking, or prior treatments that could interfere with the study. For example, a trial might exclude people who have "uncontrolled diabetes," "active autoimmune disease," or who have "received chemotherapy within the past 4 weeks."
Common Eligibility Requirements
Age: Most adult trials require participants to be 18 or older. Some trials have upper age limits, while others are specifically designed for older adults or children.
Performance status: Many trials use the ECOG scale (0–5) to measure how well you can carry out daily activities. An ECOG score of 0 means fully active; a score of 1 means restricted in physically strenuous activity but able to carry out light work. Most trials require an ECOG score of 0–2.
Prior treatments: Trials may require that you have tried (and not responded to) certain standard treatments before enrolling. Others may require that you have not received specific treatments.
Organ function: Trials often require adequate kidney, liver, and blood cell function, verified through blood tests. This ensures your body can safely process the study treatment.
Washout periods: If you are switching from another treatment, trials may require a waiting period (washout) before starting the study drug to clear the previous treatment from your system.
How to Evaluate Whether You Might Qualify
Start by reading the inclusion criteria. If you clearly do not meet one or more required criteria (for example, the trial is for a different condition than yours), you can rule it out.
Next, review the exclusion criteria. These are deal-breakers — if any exclusion criterion applies to you, you would not be eligible.
Keep in mind that eligibility criteria as listed on public registries are summaries. The full protocol may have additional details. If you are unsure whether you qualify, the study team can do a formal screening assessment. Do not rule yourself out based on ambiguous wording — many criteria have nuances that only the research team can evaluate.
Frequently Asked Questions
What does "histologically confirmed" mean?
It means your diagnosis has been confirmed by examining tissue samples under a microscope (a biopsy). This is the standard way cancers and many other conditions are definitively diagnosed.
What is an ECOG performance status?
ECOG (Eastern Cooperative Oncology Group) performance status is a scale from 0 to 5 that describes your level of daily functioning. 0 = fully active, 1 = restricted in strenuous activity, 2 = ambulatory and capable of self-care but unable to work, 3 = limited self-care, 4 = completely disabled, 5 = deceased. Most trials require 0–2.
What does "treatment-naive" mean?
It means you have not yet received any treatment for the condition being studied. Some trials specifically seek treatment-naive patients to test a new therapy as a first-line treatment.
Can I still qualify if I do not meet every criterion?
Sometimes. Eligibility criteria listed on registries are summaries and may not capture all nuances. If you are close to meeting the criteria, it is worth contacting the study team. In some cases, principal investigators can request protocol exceptions (waivers) for specific criteria, though this is not guaranteed.
What is a washout period?
A washout period is a required gap between stopping a previous treatment and starting the study treatment. This ensures the previous drug has cleared your system and will not interfere with the study results. Washout periods typically range from 2 to 6 weeks depending on the drug.