Study Definitions

Clinical Study Definitions

Below are definitions of frequently used clinical study terms.

A group of people in a clinical study who receive the same intervention. Clinical studies may have two or more research arms. For example, often in a Phase III study people in one arm receive the standard treatment and people in another arm receive the investigational, or new, treatment.

Blinded study
A clinical study in which participants do not know which intervention (standard of care or investigational) they are receiving until the study is complete. In a double-blind study, the researchers also do not know which intervention the participant is receiving until the study ends.

Clinical trial
Research to test an intervention in human subjects. Also known as a clinical study. Clinical trials are carefully designed studies that closely monitor people as they undergo an investigational intervention. Before reaching clinical trials, the intervention typically will have been studied in a laboratory (nonclinical studies) and in animals (pre-clinical studies). Clinical trials are designed to answer questions about the safety and effectiveness of a new intervention or the long-term effects of an approved intervention.

Controlled study
A study involving one group that receives the investigational intervention and another group (the control group) for comparison. Depending on the reason for the study, the control group may get the standard treatment (this is typically true in cancer treatment studies), a placebo, or no intervention at all.

Data and safety monitoring board (DSMB)
An independent committee typically made up of clinical research experts—scientists, doctors, and statisticians—who review information from the study to make sure the study is being done safely. Similar to institutional review boards, DSMBs review the ongoing progress of the study. The DSMB may recommend stopping the study early if it finds that the intervention is harmful, has no benefit, or is significantly better than standard treatment. Also known as a data monitoring committee.

Double-blind study
A clinical study in which two or more parties, usually the researchers and the participants, do not know until the study is complete which participants are receiving the standard intervention and which are receiving the investigational intervention.

Eligibility criteria
Standards people must meet or characteristics they must have to participate in a clinical study. Studies typically have inclusion criteria (which define who can participate) and exclusion criteria (which define who cannot participate).

Informed consent
Agreement from participants to take part in a clinical study after they receive detailed information about the study. Before people decide to participate in a study, they are given details such as the interventions that will be tested, the possible risks and side effects, and the time commitment required. Participants must review this information and agree in writing to enroll in the study before they undergo any procedures that are part of the study.

A process, action, or treatment that is the focus of a clinical study. Depending on the type of study, interventions can include drugs, vaccines, medical devices, procedures (such as surgery or radiation therapy), behavior changes (such as diet and exercise changes), educational programs, counseling, and more.

Describes an intervention approved by the U.S. Food and Drug Administration to be tested in clinical studies with people who have a certain disease or condition. The intervention may be approved for use outside of studies for a different disease, such as a different type of cancer.

Institutional review board (IRB)
An independent committee made up of at least five people, including scientists, doctors, and laypeople. An IRB is responsible for reviewing the clinical study protocol to protect the rights and welfare of participants and ensure the study is carried out in a safe and ethical manner. The IRB monitors the progress of the study and must review it at least once a year.

A pill or other intervention that looks like the one being tested; it is given in the same way but does not contain any known active ingredient. Placebos are used in research to control for what is called the placebo effect—an effect attributed solely to the power of suggestion, or to the expectation that an intervention will work. In pill form, a placebo is sometimes called a sugar pill.

The formal written description of the clinical study. It includes the study objectives, design, and methods as well as relevant background and statistical information.

Pre-clinical trials
Studies done in animals before interventions are tested on humans in clinical studies.

Randomized trial
A study in which participants are randomly assigned to the different arms, or intervention groups, usually by computer, in order to ensure the validity of the results. A randomized clinical study typically compares an investigational, or new, treatment to the standard treatment.

Standard of care
The most widely accepted treatment for a certain condition. Also known as standard treatment.

The organization responsible for the study. It may be a health care provider or research facility (such as University of Washington), a government entity (such as the National Cancer Institute), a drug company, a nonprofit organization, or a combination. The sponsor oversees the study and analyzes the data collected.