All clinical trials have guidelines about who can participate. Using inclusion/exclusion criteria is an important principle of medical research that helps to produce reliable results. The factors that allow someone to participate in a clinical trial are called "inclusion criteria" and those that disallow someone from participating are called "exclusion criteria". These criteria are based on such factors as age, gender, the type and stage of a disease, previous treatment history, and other medical conditions.

Before joining a clinical trial, a participant must qualify for the study. Some research studies seek participants with illnesses or conditions to be studied in the clinical trial, while others need healthy participants. It is important to note that inclusion and exclusion criteria are not used to reject people personally. Instead, the criteria are used to identify appropriate participants and keep them safe. The criteria help ensure that researchers will be able to answer the questions they plan to study.

When thinking about participating in a clinical trial, you will face the issue of how to cover the costs of care. Even if you have health insurance, your plan may not cover all of the costs related to receiving treatment in a clinical trial. This is because some health insurance companies define clinical trials as "experimental." There are two types of costs associated with a clinical trial, the patient care costs and the research costs. The routine care costs for the patient, like doctor visits and scans, are those related to treating your disease, whether you are in a trial or receiving standard therapy. These costs are often covered by health insurance, whereas extra costs are not always covered. Research costs are those related to conducting the trial and those are often covered by the organization sponsoring the trial.

More information can also be found at ClinicalTrials.gov The U.S. National Institutes of Health has developed ClinicalTrials.gov to provide patients, family members and members of the public current information about clinical research studies. The database is a registry of federally and privately supported clinical trials conducted in the United States and around the world. ClinicalTrials.gov gives you information about a trial's purpose, who may participate, locations, and phone numbers for more details.