Glossary of Clinical Trial Terms
Glossary of Clinical Trial Terms
The following glossary was prepared by ClinicalTrials.gov to help
the consumer become familiar with the most common terms used in
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Reaction: (Adverse Event.) An
unwanted effect caused by the administration of drugs. Onset may be sudden
or develop over time. (See
and Support Groups: Organizations and
groups that actively support participants and their families with valuable
resources, including self-empowerment and survival tools.
In the U.S., the Food and Drug Administration (FDA) must approve a
substance as a drug before it can be marketed. The approval process
involves several steps including pre-clinical laboratory and animal
studies, clinical trials for safety and efficacy, filing of a New Drug
Application by the manufacturer of the drug, FDA review of the
application, and FDA approval/rejection of application. (See
Arm: Any of the
treatment groups in a randomized trial. Most randomized trials have two
"arms," but some have three "arms," or even more. (See
Information gathered at the beginning of a study from which variations
found in the study are measured. 2) A known value or quantity with which
an unknown is compared when measured or assessed. 3) The initial time
point in a clinical trial, just before a participant starts to receive the
experimental treatment which is being tested. At this reference point,
measurable values such as CD4 count are recorded. Safety and efficacy of a
drug are often determined by monitoring changes from the baseline values.
When a point of view prevents impartial judgment on issues relating to the
subject of that point of view. In clinical studies, bias is controlled by
blinding and randomization. (See
randomized trial is "Blind" if the participant is not told which arm of
the trial he is on. A clinical trial is "Blind" if participants are
unaware on whether they are in the experimental or control arm of the
study; also called masked. (See
Blind Study and
Clinical: Pertaining to or founded on
observation and treatment of participants, as distinguished from
theoretical or basic science.
Investigator: A medical researcher in
charge of carrying out a clinical trial's protocol.
A clinical trial is a research study to answer specific questions about
vaccines or new therapies or new ways of using known treatments. Clinical
trials (also called medical research and research studies) are used to
determine whether new drugs or treatments are both safe and effective.
Carefully conducted clinical trials are the fastest and safest way to find
treatments that work in people. Trials are in four phases: Phase I tests a
new drug or treatment in a small group; Phase II expands the study to a
larger group of people; Phase III expands the study to an even larger
group of people; and Phase IV takes place after the drug or treatment has
been licensed and marketed. (See
III Trials, and
Community-Based Clinical Trial
A clinical trial conducted primarily through primary-care physicians
rather than academic research facilities.
Use: A method of providing
experimental therapeutics prior to final FDA approval for use in humans.
This procedure is used with very sick individuals who have no other
treatment options. Often, case-by-case approval must be obtained from the
FDA for "compassionate use" of a drug or therapy.
Complementary and Alternative Therapy:
Broad range of healing philosophies, approaches, and therapies that
Western (conventional) medicine does not commonly use to promote
well-being or treat health conditions. Examples include acupuncture,
herbs, etc. (Internet Address:
Confidentiality Regarding Trial Participants:
Refers to maintaining the confidentiality of
trial participants including their personal identity and all personal
medical information. The trial participants' consent to the use of records
for data verification purposes should be obtained prior to the trial and
assurance must be given that confidentiality will be maintained.
Contraindication: A specific
circumstance when the use of certain treatments could be harmful.
control is the nature of the intervention control.
The standard by which experimental observations are evaluated. In many
clinical trials, one group of patients will be given an experimental drug
or treatment, while the control group is given either a standard treatment
for the illness or a placebo. (See
Trials: Control is a standard against
which experimental observations may be evaluated. In clinical trials, one
group of participants is given an experimental drug, while another group
(i.e., the control group) is given either a standard treatment for the
disease or a placebo.
Safety and Monitoring Board (DSMB):
An independent committee, composed of community representatives and
clinical research experts, that reviews data while a clinical trial is in
progress to ensure that participants are not exposed to undue risk. A DSMB
may recommend that a trial be stopped if there are safety concerns or if
the trial objectives have been achieved.
Trials: Refers to trials that are are
conducted to find better tests or procedures for diagnosing a particular
disease or condition. Diagnostic trials usually include people who have
signs or symptoms of the disease or condition being studied.
Study: A clinical trial in which two
or more doses of an agent (such as a drug) are tested against each other
to determine which dose works best and is least harmful.
Study: A clinical trial design in
which neither the participating individuals nor the study staff knows
which participants are receiving the experimental drug and which are
receiving a placebo (or another therapy). Double-blind trials are thought
to produce objective results, since the expectations of the doctor and the
participant about the experimental drug do not affect the outcome; also
called double-masked study. (See
Single-Blind Study, and
Double-Masked Study: See
Interaction: A modification of the
effect of a drug when administered with another drug. The effect may be an
increase or a decrease in the action of either substance, or it may be an
adverse effect that is not normally associated with either drug.
Data Safety and Monitoring Board.
Efficacy: (Of a
drug or treatment). The maximum ability of a drug or treatment to produce
a result regardless of dosage. A drug passes efficacy trials if it is
effective at the dose tested and against the illness for which it is
prescribed. In the procedure mandated by the FDA, Phase II clinical trials
gauge efficacy, and Phase III trials confirm it (See
Food and Drug
Phase II Trials
Phase III Trials.)
Eligibility Criteria: Summary
criteria for participant selection; includes Inclusion and Exclusion
Based on experimental data, not on a theory.
Overall outcome that the protocol is designed to evaluate. Common
endpoints are severe toxicity, disease progression, or death.
The branch of medical science that deals with the study of incidence and
distribution and control of a disease in a population.
Exclusion/Exclusion Criteria: See
Refers to any of the FDA procedures, such as compassionate use, parallel
track, and treatment IND that distribute experimental drugs to
participants who are failing on currently available treatments for their
condition and also are unable to participate in ongoing clinical trials.
Drug: A drug that is not FDA licensed
for use in humans, or as a treatment for a particular condition. (See
Food and Drug Administration.
and Drug Administration (FDA): The
U.S. Department of Health and Human Services agency responsible for
ensuring the safety and effectiveness of all drugs, biologics, vaccines,
and medical devices, including those used in the diagnosis, treatment, and
prevention of HIV infection, AIDS, and AIDS-related opportunistic
infections. The FDA also works with the blood banking industry to
safeguard the nation's blood supply. (Internet address:
Food and Drug Administration.)
supposition or assumption advanced as a basis for reasoning or argument,
or as a guide to experimental investigation.
medical or social standards determining whether a person may or may not be
allowed to enter a clinical trial. These criteria are based on such
factors as age, gender, the type and stage of a disease, previous
treatment history, and other medical conditions. It is important to note
that inclusion and exclusion criteria are not used to reject people
personally, but rather to identify appropriate participants and keep them
Investigational New Drug.
Consent: The process of learning the
key facts about a clinical trial before deciding whether or not to
participate. It is also a continuing process throughout the study to
provide information for participants. To help someone decide whether or
not to participate, the doctors and nurses involved in the trial explain
the details of the study.
Informed Consent Document:
that describes the rights of the study participants, and includes details
about the study, such as its purpose, duration, required procedures, and
key contacts. Risks and potential benefits are explained in the informed
consent document. The participant then decides whether or not to sign the
document. Informed consent is not a contract, and the participant may
withdraw from the trial at any time.
Institutional Review Board (IRB): 1)
A committee of physicians, statisticians, researchers, community
advocates, and others that ensures that a clinical trial is ethical and
that the rights of study participants are protected. All clinical trials
in the U.S. must be approved by an IRB before they begin. 2) Every
institution that conducts or supports biomedical or behavioral research
involving human participants must, by federal regulation, have an IRB that
initially approves and periodically reviews the research in order to
protect the rights of human participants.
Intent To Treat:
Analysis of clinical trial results that includes all data from
participants in the groups to which they were randomized even if they
never received the treatment. (See
Drug: The generic name of the precise
intervention being studied.
Primary interventions being studied: types of interventions are Drug, Gene
Transfer, Vaccine, Behavior, Device, or Procedure.
Investigational New Drug:
A new drug,
antibiotic drug, or biological drug that is used in a clinical
investigation. It also includes a biological product used in vitro
for diagnostic purposes.
Institutional Review Board.
knowledge of intervention assignment. (See
History Study: Study of the natural
development of something (such as an organism or a disease) over a period
Application (NDA): An application
submitted by the manufacturer of a drug to the FDA - after clinical trials
have been completed - for a license to market the drug for a specified
A drug prescribed for conditions other than those approved by the FDA.
Trials: A clinical trial in which
doctors and participants know which drug or vaccine is being administered.
An FDA category that refers to medications used to treat diseases and
conditions that occur rarely. There is little financial incentive for the
pharmaceutical industry to develop medications for these diseases or
conditions. Orphan drug status, however, gives a manufacturer specific
financial incentives to develop and provide such medications.
Review of a clinical trial by experts chosen by the study sponsor. These
experts review the trials for scientific merit, participant safety, and
Pharmaconkinetics: The processes (in a living organism) of
absorption, distribution, metabolism, and excretion of a drug or vaccine.
Phase I Trials:
Initial studies to determine the metabolism and pharmacologic actions of
drugs in humans, the side effects associated with increasing doses, and to
gain early evidence of effectiveness; may include healthy participants
Phase II Trials:
Controlled clinical studies conducted to
evaluate the effectiveness of the drug for a particular indication or
indications in patients with the disease or condition under study and to
determine the common short-term side effects and risks.
Phase III Trials:
Expanded controlled and uncontrolled trials after preliminary evidence
suggesting effectiveness of the drug has been obtained, and are intended
to gather additional information to evaluate the overall benefit-risk
relationship of the drug and provide and adequate basis for physician
Phase IV Trials:
Post-marketing studies to delineate additional information including the
drug's risks, benefits, and optimal use.
placebo is an inactive pill, liquid, or powder that has no treatment
value. In clinical trials, experimental treatments are often compared with
placebos to assess the treatment's effectiveness. In some studies, the
participants in the control group will receive a placebo instead of an
active drug or treatment. No sick participant receives a placebo if there
is a known beneficial treatment. (See
Placebo Controlled Study)
Controlled Study: A method of
investigation of drugs in which an inactive substance (the placebo) is
given to one group of participants, while the drug being tested is given
to another group. The results obtained in the two groups are then compared
to see if the investigational treatment is more effective in treating the
A physical or emotional change, occurring after a substance is taken or
administered, that is not the result of any special property of the
substance. The change may be beneficial, reflecting the expectations of
the participant and, often, the expectations of the person giving the
Refers to the testing of experimental drugs in the test tube or in animals
- the testing that occurs before trials in humans may be carried out.
Trials: Refers to trials to find
better ways to prevent disease in people who have never had the disease or
to prevent a disease from returning. These approaches may include
medicines, vitamins, vaccines, minerals, or lifestyle changes.
Protocol: A study plan on which all clinical trials are based. The plan is carefully designed to safeguard the health of the participants as well as answer specific research questions. A protocol describes what types of people may participate in the trial; the schedule of tests, procedures, medications, and dosages; and the length of the study. While in a clinical trial, participants following a protocol are seen regularly by the research staff to monitor their health and to determine the safety and effectiveness of their treatment (See
Life Trials (or Supportive Care trials):
Refers to trials that explore ways to improve comfort and
quality of life for individuals with a chronic illness.
A method based on chance by which study
participants are assigned to a treatment group. Randomization minimizes
the differences among groups by equally distributing people with
particular characteristics among all the trial arms. The researchers do
not know which treatment is better. From what is known at the time, any
one of the treatments chosen could be of benefit to the participant (See
Trial: A study in which participants
are randomly (i.e., by chance) assigned to one of two or more treatment
arms of a clinical trial. Occasionally placebos are utilized. (See
Ratio: The risk to individual
participants versus the potential benefits. The risk/benefit ratio may
differ depending on the condition being treated.
Trials: Refers to trials which test
the best way to detect certain diseases or health conditions.
Any undesired actions or effects of a drug or treatment. Negative or
adverse effects may include headache, nausea, hair loss, skin irritation,
or other physical problems. Experimental drugs must be evaluated for both
immediate and long-term side effects. (See
Study: A study in which one party,
either the investigator or participant, is unaware of what medication the
participant is taking; also called single-masked study. (See
Single-Masked Study: See
Treatment: A treatment currently in
wide use and approved by the FDA, considered to be effective in the
treatment of a specific disease or condition.
Care: Treatment regimen or medical
management based on state of the art participant care.
Statistical Significance: The
probability that an event or difference occurred by chance alone. In
clinical trials, the level of statistical significance depends on the
number of participants studied and the observations made, as well as the
magnitude of differences observed.
A primary or secondary outcome used to judge the effectiveness of a
Study Type: The
primary investigative techniques used in an observational protocol; types
are Purpose, Duration, Selection, and Timing.
Supportive Care Trials: See
Quality of Life
adverse effect produced by a drug that is detrimental to the participant's
health. The level of toxicity associated with a drug will vary depending
on the condition which the drug is used to treat.
IND stands for Investigational New Drug application, which is part of the
process to get approval from the FDA for marketing a new prescription drug
in the U.S. It makes promising new drugs available to desperately ill
participants as early in the drug development process as possible.
Treatment INDs are made available to participants before general marketing
begins, typically during Phase III studies. To be considered for a
treatment IND a participant cannot be eligible to be in the definitive
Trials: Refers to trials which test
new treatments, new combinations of drugs, or new approaches to surgery or