The University of Iowa

Who Can Participate in a Trial?

Clinical trials enroll people who are alike in certain ways depending on the study's purpose. Every protocol identifies some specific characteristics that the people should have in order to participate in the study. These characteristics are called eligibility criteria. They may include the type of disease or condition and its stage, as well as the age and general health of the participants.

Eligibility criteria are a key part of medical research. They help assure that the study results answer the research question. They also help doctors identify who will benefit in the future from the approach being studied. For example, in cancer prevention studies, a new medication may work for people with one type of risk factor but not for those with another.

Eligibility criteria also help assure the safety of participants by protecting them from known risks. For example, some medications can only be given safely if a person has normal kidneys or liver. So, persons with kidney or liver problems may be excluded from participating.

Those who are interested in participating in a clinical trial should visit our list of open clinical trials.