July 17, 2001
The language used to talk about clinical trials and research can be unfamiliar and perhaps confusing. To help you understand more about the trial(s) you are considering, here is a list of terms that researchers commonly use.
Researchers may also use other terms to describe a trial you or a loved one is considering. If you do not understand what a researcher or health care professional tells you, be sure to ask him or her to explain it in simpler terms.
If you decide to join a trial but do not understand the written information or informed consent form, ask your doctor to explain it to you before you sign it. You should not feel pressured to do anything that you are not sure you want to do.
Adverse event. Any change in a participant's health that occurs after a person enrolls in a trial. Even though not every adverse event is related to the treatment given, the investigators must report all adverse events to the Food and Drug Administration.
Analysis. Accepted methods of mathematics that determine whether a difference in treatment outcomes is statistically significant. A statistically significant difference means that the result is very unlikely to be due to chance alone.
Arm. A treatment group in a study. Trials that offer more than one treatment are said to have multiple arms.
Baseline. A person's health status before he or she begins a trial.
Blinding. Keeping patients unaware of which treatment they receive. This process helps prevent bias in reporting or evaluating results. Double blinding means that during treatment, both the study participants and the caregivers do not know who is assigned to each group.
Clinical trial. A carefully planned study to evaluate the benefits and risks of treatments on humans. Often, similar groups of people receive different forms of treatments or a standard treatment so researchers can compare outcomes.
Contract research organization (CRO). A company that contracts with the agency funding research to manage the study. CROs are often used when pharmaceutical companies sponsor clinical trials that take place in medical centers.
Control group. The group of participants that receives the standard treatment for a condition.
Dose-limiting toxicity. The amount of experimental drug that causes an unacceptable adverse event, and thereby stops any increase in the dose given.
Efficacy. The ability of a drug or therapy to relieve symptoms or halt disease progression. A treatment is said to have efficacy if certain positive outcomes — for example, shrinking of a tumor — chosen before the start of a trial occur.
Exclusion criteria. Guidelines that specify who may not participate in a clinical trial.
Generalizability of results. The ability to obtain the trial results in a different group of patients. The results and conclusions of a study on one group of people (for example, men) may not apply equally to another (women). Researchers must take care not to generalize their results too broadly. Often they do more studies to see how the treatment works in different groups of people.
Inclusion criteria. Guidelines that specify who may participate in a clinical trial.
Informed consent. An agreement to participate in a trial that is given after a potential participant has reviewed all available information about the treatment. To be fair, participants in a clinical trial must be fully informed of potential risks and benefits as well as other treatment options. There must not be any penalties for declining to participate or withdrawing at any time.
Institutional review board (IRB). A group that reviews studies proposed by investigators. Each institution that conducts research has an IRB made up of researchers and members of the public. The IRB must be sure that the study is managed in a way that protects those who participate in it.
Investigational new drug (IND). An experimental drug or biological drug to be tested in a clinical trial.
Investigator. The person in charge of a research study. If there is more than one investigator, one person may be named as the principal investigator.
Maximum dose. The largest dose that can be given to trial participants without causing unacceptable adverse effects.
Monitoring. Oversight and administrative efforts that ensure a trial proceeds as outlined in the protocol. The government and other funding agencies require data and safety monitoring boards to oversee clinical trials. They also want to be certain that safety measures are in place to protect participants.
Multicenter research trial. A trial to be conducted at more than one medical center or clinic. Most large clinical trials are conducted at several research centers. The benefits of multicenter trials include larger numbers of participants, different geographic locations, various ethnic groups and the ability to compare results among centers.
Peer review. Review of trial reports by scientists not involved with a study. The findings of a trial usually are reviewed before being accepted for publication. When the work is either published or presented at a conference, the researchers open both their study protocol and results up to critical review by the scientific community at large.
Placebo (control) group. A group that receives an inactive treatment for comparison with the active treatment(s) being tested. Placebos are generally used only when they can be given for short periods and when the disease is not life-threatening. It is unethical to give placebos to people in some circumstances, such as when a medical condition requires some form of therapy that is already approved.
Preclinical studies. Studies that are done before an experimental therapy is tested in humans — for example, testing done with mice.
Protocol. The specific set(s) of goals and procedures that define what will happen in a trial. Protocols are developed before a trial so that participants can know what will happen and other researchers can replicate the studies.
Randomization. A process that reduces the likelihood of bias by assigning people to treatment groups by chance alone (randomly). When groups are created by random assignment, individual characteristics are less likely to make the results inaccurate.
Sample. The group of people who participate in a trial. Generally, having more participants decreases the likelihood of reaching a wrong conclusion. However, when a drug shows effectiveness against a life-threatening condition, researchers may need only a small sample of people to determine if the treatment is effective. They still, however, must test another group to learn about the risks associated with the treatment.
Serious adverse event. A reaction to a treatment that results in death, a life-threatening situation, a need for admittance to a hospital — or having to stay in a hospital longer than if the treatment had not been given — a temporary or permanent disability, or a birth defect in a study participant's child.
Sponsor. The organization that develops the treatment, designs the study, and pays for the trial(s).
Standard treatment. The treatment that is normally provided to people with a given condition. In many studies, a control group receives the standard treatment and a treatment group receives the experimental treatment. After the trial, researchers compare the outcomes of the two groups to see if the experimental treatment is better than, as good as or not as beneficial as the standard treatment.
Study coordinator. The person at a medical center or research facility who manages the daily activities
Toxicity. An adverse effect of a treatment.
Treatment group. The group
of participants that receives an experimental treatment.
© 2001 Mayo Foundation for Medical
Education and Research (MFMER).
© 2001 Mayo Foundation for Medical Education and Research (MFMER).