Although there are many types of clinical trials, they are generally considered to be biomedical or health-related research studies in human beings that are based on a study plan called a protocol. This plan is carefully designed to safeguard the health of the participants as well as answer specific research questions. The protocol describes who may participate in the trial; the schedule of tests, procedures, medications and dosages; and the length of the study. While in a clinical trial, participants following a protocol are seen regularly by the research staff to monitor their health and to determine the safety and effectiveness of their treatment. In the United States all clinical trials are approved by the U.S. Food and Drug Administration and then are reviewed and approved by each hospital's Internal Review Board to ensure patient safety.

Besides the process and phases of clinical trials involved in experimental drugs and devices, there are different types of clinical trials:

• Prevention trials look for better ways to prevent disease in people who have never had the disease or to prevent a disease from returning, and may include medicines, vaccines, vitamins, minerals or lifestyle changes.
• Diagnostic trials are geared to develop better tests or procedures for diagnosing a particular disease or condition and usually include people who have signs or symptoms of the disease or condition being studied.
• Screening trials test the methods for detecting certain diseases or health conditions.
• Quality of Life trials (or Supportive Care trials) explore ways to improve comfort and the quality of life for individuals with a chronic illness.

Clinical trials are often randomized. Randomization minimizes the differences among groups by equally distributing people with particular characteristics among the trial arms. A randomized trial is "blind" if the participant is not told whether he or she is on the experimental or control arm of the study. In a "single-blind study," one group, either the investigator or participant, is unaware of what therapy the participant is taking. In a "double-blind study," neither the participating individuals nor the study's staff knows which participants are receiving the experimental drug and which are receiving a placebo or another therapy. Double-blind trials are thought to produce objective results by eliminating the possibility that the expectations of the doctor and the participant about the experimental drug will affect the outcome.

Clinical Trial Sponsors & Funders

Clinical trials are sponsored or funded by a variety of organizations or individuals such as physicians, medical institutions, foundations, voluntary groups, and pharmaceutical or medical device companies, in addition to federal agencies such as the National Institutes of Health (NIH), the Department of Defense (DOD) and the Department of Veterans Affairs (VA). Trials can take place in a variety of locations, such as hospitals, universities, doctors' offices or community clinics.

Ask Questions Before Enrolling in a Clinical Trial

Before choosing to participate in a clinical trial, it is often helpful to talk to a physician, family members or friends. Click here for some questions to consider, in addition to your own, about joining a clinical trial.