How Clinical Trials Work

A clinical trial is generally designed to answer a specific research question about a disease process's diagnosis, course, or treatment. Every clinical trial is based on a study plan called a protocol. This plan is carefully designed to safeguard the health of the participants and describes the steps involved in trial participation. In the U.S., all clinical trials are approved by the U.S. Food and Drug Administration (FDA) and reviewed and approved by each hospital's Institutional Review Board (IRB) 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 – These trials look for better ways to prevent disease in people who have never had the disease or to prevent a disease from returning. 
  • Diagnostic trials – These trials are geared to develop better tests or procedures for diagnosing a particular disease or condition and usually include people with signs or symptoms of the disease or condition being studied.
  • Screening trials – These trials test the methods for detecting certain diseases or health conditions.
  • Quality of life trials (or supportive care trials) – These trials explore ways to improve comfort and the quality of life for individuals with a chronic illness.

Clinical trials are often randomized. Randomization minimizes group differences by equally distributing people with particular characteristics among the trial arms. A randomized trial is "blind" if participants aren’t told whether they are 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 participants about the experimental drug will affect the outcome.

Clinical trial sponsors and funders

Clinical trials are sponsored or funded by a variety of organizations or individuals such as doctors, 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 U.S. Department of Defense (DOD), and the U.S. Department of Veterans Affairs (VA). Trials can take place in a variety of locations, such as hospitals, universities, doctor's offices, or community clinics.

Additional resources on clinical trials

For more information on clinical trials, visit these reputable resources:

Doctor explaining condition to patient with heart diagram

Questions to ask before you participate in a clinical trial

Before choosing to participate in a clinical trial, it’s often helpful to talk to a doctor, family members, or friends.