Glossary A-H

Below is a glossary of clinical trial terms that are meant to help you to better understand the language of clinical trials.

Adverse Event (AE)

Any untoward or unfavorable medical occurrence in a clinical research study participant, including any abnormal sign (e.g. abnormal physical exam or laboratory finding), symptom, or disease. A serious adverse event is any adverse event that results in death, is life-threatening, requires or prolongs hospitalization, causes disability or incapacity, results in birth defects, or is any other hazardous condition. An adverse reaction refers to an effect that is caused by the study drug.

Blinded Study

A clinical trial is called a blinded study if the participant is not told which arm of the trial he or she is on. Double-blind trials are designed so that neither the participant nor the study team knows whether the participant is receiving the experimental drug or the placebo.

Clinical Trial

A clinical trial is a research study in human volunteers that Definitions specific health questions. Clinical trials can be interventional (involving a study drug or treatment) or observational (recording data with no intervention) research studies. Clinical trials usually progress through four phases: Phase I, Phase II, Phase III, and Phase IV to determine if a new drug or treatment is safe and effective. Carefully conducted clinical trials are the safest and fastest way to discover treatments that work in people to improve their health.


Refers to making sure that only those involved in the study have access to the participant’s personal identity and all personal medical information. The participant’s consent to the use of records should be obtained prior to the trial and assurance must be given that confidentiality will be maintained.

Control Group

Given either a standard treatment for the condition or a placebo. Since this group will not be given the experimental treatment, it will be used as a comparison against those in the experimental group.

Eligibility Criteria

Specific criteria that a participant must meet in order to take part in a clinical trial. These criteria could include age, gender, type of disease, previous treatment history, and other medical conditions.

Food and Drug Administration (FDA)

An agency of the U.S. Department of Health and Human Services responsible for protecting and promoting public health by ensuring the safety and effectiveness of all drugs, biologics, vaccines, and medical devices. The FDA also regulates and supervises other industries such as blood banks, food, veterinary products and cosmetics.

Good Clinical Practice (GCP)

A standard for clinical trials that provides assurance that the data and reported results are credible and accurate and that the rights, integrity, and confidentiality of research participants are protected.

Health Insurance Portability and Accountability Act (HIPAA) Privacy Rule

The first Federal regulation that establishes the private use of personal health information for research purposes. The Privacy Rule is a set of national standards for the protection of individually identifiable health information known as protected health information (PHI).