Clinical Trials

A clinical trial is a research study in which one or more human subjects are prospectively assigned to one or more interventions (which may include placebo or other control) to evaluate the effects of the interventions on biomedical or behavioral health-related outcomes. These studies may include drugs, biologics, devices, or behavioral interventions. Types of clinical trials may include:

  • Prevention trials look for better ways to prevent a disease in people who have never had the disease or to prevent the disease from returning. Approaches may include medicines, vaccines, or lifestyle changes.
  • Screening trials test new ways for detecting diseases or health conditions.
  • Diagnostic trials study or compare tests or procedures for diagnosing a particular disease or condition.
  • Treatment trials test new treatments, new combinations of drugs, or new approaches to surgery or radiation therapy.
  • Behavioral trials evaluate or compare ways to promote behavioral changes designed to improve health.
  • Quality of life trials (or supportive care trials) explore and measure ways to improve the comfort and quality of life of people with conditions or illnesses.

A link to the NIH decision tree for Clinical Trial Definition can be found here.

Phases of Clinical Trials

Clinical trials may proceed through several phases as defined by federal guidelines. Click here for detailed information about each phase.

Other Definitions

A placebo is a pill or liquid that looks like the new treatment but does not have any treatment value from active ingredients. In clinical trials that compare a new product or therapy with another that already exists, researchers try to determine if the new one is as good, or better than, the existing one. In some studies, a participant may be assigned to receive a placebo. Comparing a new product with a placebo can be the fastest and most reliable way to show the new product’s effectiveness. However, placebos are not used if they will put the participant at risk — particularly in the study of treatments for serious illnesses — by not having effective therapy. Participants will be told if placebos are used in the study before entering a trial.

Randomization is the process by which treatments are assigned to participants by chance rather than by choice. This is done to avoid any bias in assigning volunteers to get one treatment or another. The effects of each treatment are compared at specific points during a trial. If one treatment is found superior, the trial is stopped so that the most volunteers receive the more beneficial treatment.

“Blinded” (or “masked”) studies are designed to prevent members of the research team and study participants from influencing the results. Blinding allows the collection of scientifically accurate data. In single-blind (“single-masked”) studies, participants are not told what is being given, but the research team knows. In a double-blind study, neither the participant nor the research team are told what the participant is given; only the pharmacist knows. Members of the research team are not told which participants are receiving which treatment, in order to reduce bias. If medically necessary, however, it is always possible to find out which treatment the participants are receiving.

Page last updated 11:10 AM, May 8, 2024