If you’re considering participating in a clinical trial, you’ll likely hear a lot of new—and complex—terminology. Read on for a helpful glossary of some of the most commonly used clinical trials terms.
Adverse reaction (or adverse event)—an unwanted effect brought on by the administration of drugs. The onset of an adverse reaction may be sudden or prolonged.
Approved drugs—refers to medications that have received approval from the US Food and Drug Administration (FDA) or other governmental bodies around the world. In the United States, FDA approval is necessary before a new drug can be marketed; the approval process involves a number of steps, including pre-clinical studies, clinical trials, and the filing and review of a New Drug Application.
Arm—the name for a treatment group in a randomized trial; most trials have two arms, but some can have three or more.
Baseline—refers either to information obtained at the start of a study against which variations found in the study are measured; to a known quantity or value used for comparison with the results of an unknown measurement or assessment; or to a clinical trial’s initial time point, just before the treatment being tested is first given to participants.
Blind—in a blind randomized trial, participants are not aware of which arm of the trial they are on; in a blind clinical trial, participants are not aware if they are in the study’s experimental arm or its control arm.
Clinical trial—a research study designed to answer specific questions about new medications or therapies, or new ways of using existing treatments.
Compassionate use—under compassionate use, very sick individuals who may have no other treatment options are permitted to use experimental therapeutics (which have not yet received FDA approval). Permission for compassionate use of a drug or therapy is typically granted by the FDA on a case-by-case basis.
Control group—the standard against which experimental results may be evaluated. In clinical trials, the control group receives either a placebo or a standard treatment for the condition in question, while the experimental group receives the experimental drug being tested.
Double-blind study—a type of clinical trial in which neither the participants nor the trial staff know which participants are receiving a placebo and which are receiving the experimental drug. The idea behind this trial design is that it can yield more objective results, since no expectations, either from participants or from the study team, can affect the outcome.
Efficacy—the degree to which an intervention (such as a drug, vaccine, device, behavior, or procedure, etc.) produces the expected result under ideal conditions.
Empirical—based on proven experimental data rather than on a theory.
Epidemiology—the field of medical science concerned with studying disease incidence, distribution, and control in a population.
Experimental drug—a drug that has not yet received FDA approval for use in humans or to treat a particular condition.
Food and Drug Administration (FDA)—the agency of the US Department of Health and Human Services which ensures the safety and effectiveness of all drugs, vaccines, biologics, and medical devices (including those used to diagnose, treat, and prevent HIV infection, AIDS, and AIDS-related infections). The FDA also helps safeguard the country’s blood supply by working together with the blood banking industry.
Inclusion/exclusion criteria—the medical or social factors which determine an individual’s eligibility to enter a clinical trial. Typical factors include age, gender, the type and stage of the disease being studied in the trial, and other medical conditions. These criteria are used only to identify appropriate trial participants and ensure their safety, not to reject people personally.
Interventions—an intervention can be a drug, vaccine, device, behavior, procedure, or gene transfer.
New Drug Application (NDA)—after clinical trials have been completed successfully, a drug manufacturer submits this application to the FDA for a license to make the drug commercially available.
Open-label trial—a clinical trial in which the drug or vaccine being administered is known by both participants and doctors.
Orphan drugs—an FDA term for medications that treat infrequently occurring diseases and conditions.
Peer review—the process by which chosen experts (“peers”) review a clinical trial for scientific merit, ethical considerations, and participant safety.
Pharmacokinetics—refers to the processes of absorption, distribution, metabolism, and excretion of a vaccine or drug that occur in a living organism.
Placebo—an inactive pill, powder, or liquid with no treatment value. Placebos are often used as a basis for comparison alongside experimental treatments in a clinical trial to better assess the treatment’s effectiveness.
Preclinical—the stage of experimental drug testing that occurs in the test tube or in animals before human trials may be carried out.
Randomized trial—a study in which the process of assigning participants to the different treatment arms of a clinical trial is done completely at random.
Risk-benefit ratio—the risk to an individual patient versus the possible benefits of a particular drug or treatment.
Statistical significance—the likelihood, or probability, that a particular event or difference resulted from chance alone. The level of statistical significance in clinical trials depends on factors such as the number of participants, the observations made, and the magnitude of the differences observed.
Therapeutic index—typically, the ratio between the dosage of a drug that causes toxicity, and the dosage that produces the desired therapeutic effect.