Every clinical trial has a study protocol, or? list of guidelines? that describes the characteristics that all patients in a study must have.? These guidelines, called eligibility criteria, vary from study to study depending on the research purpose.? ? They may include age, gender, medical history, and current health status. Some eligibility criteria? often require that patients have a particular type and stage of cancer.

Enrolling participants with similar characteristics ensures that the results will be due to the new treatment being studied and? not other factors.? As a result,? eligibility criteria help researchers achieve accurate and meaningful results.? ? During a study, they help protect patient safety, so that people who are likely to be harmed by study drugs or other treatments are not exposed to the risk.