GLOSSARY

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

ACCEPTS HEALTHY VOLUNTEERS

Indicates whether a clinical study allows people who do not have the condition or related conditions or symptoms being studied to participate in that study.

ACTIVE COMPARATOR ARM

A group of participants that receives an intervention that is considered to be effective. One of several Arm Types.

ACTIVE, NOT RECRUITING

The clinical study is ongoing (that is, participants are receiving an intervention or being examined), but potential participants are not currently being recruited or enrolled. A type of Recruitment Status.

ADVERSE EVENT

An unfavorable change in the health of a participant, including abnormal laboratory findings, that happens during a clinical study or within a certain time period after the study has ended. This change may or may not be caused by the intervention being studied.

ALLOCATION

A clinical trial design strategy used to assign participants to an arm of a study. Types of Allocations include randomized and nonrandomized

ARM

A group or subgroup of participants in a clinical trial that receives specific interventions, or no intervention, according to the study protocol. This is decided before the trial begins.

ARM TYPE

A general description of the clinical study arm. It identifies the role of the intervention that participants will receive. Types of arms includeExperimental, Active Comparator, Placebo Comparator, Sham Comparator, and No Intervention.

BASELINE CHARACTERISTICS

Data collected at the beginning of a clinical study for all participants and for each arm or comparison group. These data include demographics, such as age and gender, and study-specific measures (for example, systolic blood pressure, prior antidepressant treatment).

BLINDING (or Masking)

See Masking (or Blinding).

CERTAIN AGREEMENTS

As required by Section 801 of the Food and Drug Administration Amendments Act, in general, a description of any agreement between the Sponsor of a clinical study and the Principal Investigator (PI) that does not allow the PI to discuss the results of the study or publish the study results in a scientific or academic journal after the trial is completed. (This does not apply if the PI is an employee of the Sponsor.)

CLINICAL STUDY

A research study using human subjects to evaluate biomedical or health-related outcomes. Two types of clinical studies are Interventional studies (or clinical trials) and Observational studies.

CLINICAL TRIAL (or Interventional Study)

See Interventional Study.

CLINICALTRIALS.GOV IDENTIFIER (NCT NUMBER)

A unique identification code is given to each clinical study registered on ClinicalTrials.gov. Because the format is "NCT" followed by an 8-digit number (for example, NCT00000419), this identifier is also known as the NCT Number.

CLOSED STUDIES

Clinical studies that are no longer recruiting participants because they have enough participants already, have ended, or have been stopped for some reason. This term also describes studies with very specific Eligibility Criteria that recruit participants by invitation only.

COLLABORATOR

A Collaborator is an organization other than the Sponsor that provides support for a clinical study. This support may include funding, design, implementation, data analysis, or reporting.

COMPLETED

The clinical study has ended normally, and participants are no longer being examined or treated (that is, the "last subject, last visit" has occurred). A type of Recruitment Status.

CONDITION

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

CONTROLLED TRIAL

A type of clinical trial in which observations made during the trial are compared to a standard, called the control. The control may be observations of a group of participants in the same trial or observations from outside the trial (for example, from an earlier trial, which is called a historical control).

CROSS-OVER DESIGN

Describes a clinical trial in which groups of participants receive two or more interventions in a particular order. For example, a two-by-two cross-over design involves two groups of participants. One group receives drug A during the initial phase of the trial, followed by drug B during a later phase. The other group receives drug B during the initial phase, followed by drug A. So during the trial, participants "cross over" to the other drug. All participants receive drug A and drug B at some point during the trial but in a different order, depending on the group to which they are assigned. One type of Intervention Model (design).

DATA MONITORING COMMITTEE (DMC)

A group of independent scientists who monitor the safety and scientific integrity of a clinical trial. The group can recommend to the study sponsor that the study be stopped if it is not effective, is harming participants, or is unlikely to serve its scientific purpose. Members are chosen based on the scientific skills and knowledge needed to monitor the particular trial. Also referred to as a data safety and monitoring board (DSMB).

DOUBLE BLIND MASKING

A type of Masking in which two or more parties involved in the clinical trial do not know which participants have been assigned which interventions. Typically, the parties include the investigator and participants.

ELIGIBILITY CRITERIA

The key standards that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility Criteria include both inclusion criteria and exclusion criteria. For example, a study might only accept participants who are above or below certain ages. (See also Eligibility Criteria data element on ClinicalTrials.gov.)

ENROLLING BY INVITATION

A clinical study that selects its participants from a population, or group of people, decided on in advance by the researchers. These studies are not open to everyone who meets the Eligibility Criteria but only to people in that particular population, who are specifically invited to participate. A type of Recruitment Status.

ENROLLMENT

The number of participants in a clinical study. The "estimated enrollment" is the number of participants that the researchers need for the study.

EXCLUSION CRITERIA

The factors, or reasons, that prevent a person from participating in a clinical study.

EXPANDED ACCESS

A process regulated by the Food and Drug Administration (FDA) that allows manufacturers to provide investigational new drugs to patients with serious diseases or conditions who cannot participate in a clinical trial. One of several Study Types.

For more information on Expanded Access programs, visit the Expanded Access: Information for Patients page on the FDA Web site.

EXPERIMENTAL ARM

A group of participants that receives the intervention that is the focus of the study. One of several Arm Types.

FACTORIAL DESIGN

Describes a clinical study in which groups of participants receive one of several combinations of interventions. For example, a two-by-two factorial design involves four groups of participants. Each group receives one of the following pairs of interventions: 1) drug A and drug B, 2) drug A and a placebo, 3) a placebo and drug B, or 4) a placebo and a placebo. So during the trial, all possible combinations of the two drugs (A and B) and the placebos are given to different groups of participants. One type of Intervention Model (design).

FDA

Food and Drug Administration. See also Food and Drug Administration (FDA).

FDAAA 801

Section 801 of the Food and Drug Administration Amendments Act of 2007 (U.S. Public Law 110-85). See also Section 801 of the Food and Drug Administration Amendments Act (FDAAA 801).

FIRST RECEIVED DATE

The First Received date is the date on which summary clinical study protocol information was first submitted to the ClinicalTrials.govregistry.

FOOD AND DRUG ADMINISTRATION (FDA)

An agency within the U.S. Department of Health and Human Services. FDA is responsible for protecting the public health by making sure that human and veterinary drugs, vaccines and other biological products, medical devices, the Nation's food supply, cosmetics, dietary supplements, and products that give off radiation are safe, effective, and secure.

FUNDER TYPE

Describes the organization that provides funding or support for a clinical study. Support may include providing facilities, expertise, or financial resources. Organizations listed as Sponsors and Collaborators for a study are considered the funders of the study. There are four types of funders:

National Institutes of Health
Other U.S. Federal agencies (for example, the Food and Drug Administration, Centers for Disease Control and Prevention, U.S. Department of Veterans Affairs)
Industry (pharmaceutical and device companies)
All others (including individuals, universities, and community-based organizations)

GENDERS ELIGIBLE FOR STUDY

The physical gender of people who may participate in a clinical study (Female, Male, or Both). (See also Gender data element on ClinicalTrials.gov.)

HEALTH AUTHORITY

A national or international health organization that has authority over a clinical study.

HUMAN SUBJECTS REVIEW BOARD

A group of people who review, approve, and monitor the clinical study protocol. Their role is to protect the rights and welfare of human research subjects participating in a study. The group typically includes people with varying backgrounds, including a community member, to make sure that research activities conducted by an organization are completely and adequately reviewed. Also known as an institutional review board (IRB) or ethics committee.

INCLUSION CRITERIA

The factors, or reasons, that allow a person to participate in a clinical study.

INFORMED CONSENT

A process used by researchers to communicate with potential and enrolled participants about a clinical study. As part of the informed consent process, researchers:

Provide all the important information about the study, so potential participants can decide whether to enroll or, if they are already enrolled, whether to continue to participate
Make sure that potential participants understand the risks and potential benefits of participating in the study and the alternatives to the research being conducted
Stress that enrolling in, and staying in, a clinical study is completely voluntary. Because giving consent to participate in research is not a contract, participants may leave a study at any time.

The goal of the informed consent process is to protect participants. It begins when a potential participant first asks for information about a study and continues throughout the study until the study ends. The researcher and potential participant have discussions that include answering the participant's questions about the research. All the important information about the study must also be given to the potential participant in a written document that is clear and easy to understand. The informed consent document is reviewed and approved by the human subjects review board before the document is given to potential participants. Generally, a person must sign an informed consent document to enroll in a clinical study.

INTERVENTION

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as surveys, education, and interviews.

INTERVENTION MODEL (Design)

The general design of the strategy for assigning interventions to participants in a clinical study. Types of Intervention Models includeSingle Group design, Parallel design, Cross-over design, and Factorial design.

INTERVENTION NAME

The intervention being studied.

INTERVENTION TYPE

The general category of the intervention being studied. Intervention Types include Drug, Device, Biological/Vaccine, and Procedure/Surgery, among others.

INTERVENTIONAL STUDY (or Clinical Trial)

A clinical study in which participants are assigned to receive one or more interventions (or no intervention) so that researchers can evaluate the effects of the interventions on biomedical or health-related outcomes. The assignments are determined by the study protocol. Participants may receive diagnostic, therapeutic, or other types of interventions. A Study Type.

INVESTIGATIONAL NEW DRUG

A drug or biological product that is used in a clinical trial but has not been approved by the Food and Drug Administration (FDA) (the drug is either not available for a doctor to prescribe or is available but has not been approved by FDA for the use being studied).

INVESTIGATOR

A researcher involved in a clinical study. Related terms include Site Principal Investigator, Site Sub-Investigator, Study Chair, Study Director, and Study Principal Investigator.

MASKING (or Blinding)

A clinical trial design strategy in which one or more parties involved in the trial, such as the investigator or participants, do not know which participants have been assigned which interventions. Types of Masking include Open Label, Single Blind Masking, and Double Blind Masking.

NO INTERVENTION ARM

A group of participants that does not receive any interventions during a clinical study. One of several Arm Types.

OBSERVATIONAL STUDY

A clinical study in which participants identified as belonging to study groups are assessed for biomedical or health outcomes. Participants may receive diagnostic, therapeutic, or other types of interventions, but the investigator does not assign participants to specific interventions (as in an Interventional study). A Study Type.

OBSERVATIONAL STUDY MODEL (Design)

The general design of the strategy for identifying and following up with participants during Observational studies. Types of Observational Study Models include Cohort, Case-control, Case-only, Case-cross-over, Ecologic or community studies, Family-based, and Other.

OPEN LABEL

Describes a clinical trial in which masking is not used. This means that all parties involved in the trial know which participants have been assigned which interventions.

OTHER ADVERSE EVENT

An adverse event that is not a serious adverse event, meaning that it does not result in death, is not life-threatening, does not require inpatient hospitalization or extend a current hospital stay, does not result in an ongoing or significant incapacity or interfere substantially with normal life functions, and does not cause a congenital anomaly or birth defect; it also does not put the participant in danger and does not require medical or surgical intervention to prevent one of the results listed above.

OTHER STUDY ID NUMBERS

Identification numbers assigned to the clinical study protocol by the study sponsor, funders, or others. These numbers include unique identifiers from other registries and National Institutes of Health grant numbers.

OUTCOME MEASURE

A planned measurement described in the protocol that is used to determine the effect of interventions on participants in a clinical trial. For Observational studies, a measurement or observation that is used to describe patterns of diseases or traits, or associations with exposures, risk factors, or treatment. Types of Outcome Measures include Primary Outcome Measure and Secondary Outcome Measure.

PARALLEL DESIGN

Describes a clinical trial in which two or more groups of participants receive different interventions. For example, a two-arm parallel design involves two groups of participants. One group receives drug A, and the other group receives drug B. So during the trial, participants in one group receive drug A "in parallel" to participants in the other group, who receive drug B. One type of Intervention Model (design).

PARTICIPANT FLOW

A summary of the progress of participants through each stage of a clinical study, by study arm. This includes the number of participants who started, completed, and dropped out of the study

PHASE

Food and Drug Administration (FDA) descriptions of the clinical trial of a drug based on the study's characteristics, such as the objective and number of participants. There are five phases:

Phase 0: Exploratory study involving very limited human exposure to the drug, with no therapeutic or diagnostic goals (for example, screening studies, microdose studies)
Phase 1: Studies that are usually conducted with healthy volunteers and that emphasize safety. The goal is to find out what the drug's most frequent and serious adverse events are and, often, how the drug is metabolized and excreted.
Phase 2: Studies that gather preliminary data on effectiveness (whether the drug works in people who have a certain disease or condition). For example, participants receiving the drug may be compared to similar participants receiving a different treatment, usually an inactive substance, called a placebo, or a different drug. Safety continues to be evaluated, and short-term adverse events are studied.
Phase 3: Studies that gather more information about safety and effectiveness by studying different populations and different dosages and by using the drug in combination with other drugs.
Phase 4: Studies occurring after FDA has approved a drug for marketing. These including postmarket requirement and commitment studies that are required of or agreed to by the study sponsor. These studies gather additional information about a drug's safety, efficacy, or optimal use.

PLACEBO

A substance that does not contain active ingredients and is made to be physically indistinguishable (that is, it looks and tastes identical) from the actual drug being studied.

PLACEBO COMPARATOR ARM

A group of participants that receives a placebo during a clinical study. One of several Arm Types.

PRIMARY COMPLETION DATE

The date on which the last participant in a clinical study was examined or received an intervention and that data for the Primary Outcome Measure were collected. Whether the clinical study ended according to the protocol or was terminated does not affect this date. The "estimated primary completion date" is the date that the researchers think will be the Primary Completion Date for the study.

PRIMARY OUTCOME MEASURE

The planned Outcome Measure in the protocol that is the most important for evaluating the effect of an intervention. Most clinical studies have one Primary Outcome Measure, but some may have more than one.

PRIMARY PURPOSE

The main reason for the clinical trial. The types of Primary Purposes are Treatment, Prevention, Diagnostic, Supportive Care, Screening, Health Services Research, Basic Science, and Other.

PRINCIPAL INVESTIGATOR (PI)

The person who is responsible for the scientific and technical direction of the entire clinical study (for example, for all sites of a multisite study).

PROTOCOL

The written description of a clinical study. It includes the study's objectives, design, and methods. It may also include relevant scientific background and statistical information.

RANDOMIZED ALLOCATION

A strategy in which participants are assigned to arms of a clinical trial by chance. A type of Allocation.

RANK

Indicates the order in which studies appear on the Search Results list. The studies most relevant to the search terms appear higher on the list.

RECORD

See Study Record.

RECRUITING

The clinical study is currently recruiting participants. A type of Recruitment Status.

REGISTRATION

The process of submitting and updating summary information about a clinical study protocol, from its beginning to end, to a structured, Web-based registry that is accessible to the public, such as ClinicalTrials.gov.

REGISTRY

A structured online system, such as ClinicalTrials.gov, that provides the public with access to summary information about ongoing and completed clinical studies.

REPORTING (OR COMPARISON) GROUP

A grouping of participants in a clinical study that is used in summarizing the data collected during the study. This grouping may be the same as or different from a study arm.

RESPONSIBLE PARTY

The Sponsor, Sponsor-Investigator, or Sponsor-designated Principal Investigator who is responsible for submitting information about a clinical study to ClinicalTrials.gov and updating that information.

RESULTS DATABASE

A structured online system, such as the ClinicalTrials.gov results database, that provides the public with access to registration and summary results information for completed or terminated clinical studies.

RESULTS FIRST RECEIVED DATE

The date on which summary information about the results of a clinical study was first submitted to the ClinicalTrials.gov results database.

RESULTS SUBMISSION

The process of submitting and updating summary information about the results of a clinical study to a structured, publicly accessible, Web-based results database, such as the ClinicalTrials.gov results database.

SECONDARY OUTCOME MEASURE

A planned Outcome Measure in the protocol that is not as important as the Primary Outcome Measure but is still of interest in evaluating the effect of an intervention. Most clinical studies have more than one Secondary Outcome Measure.

SERIOUS ADVERSE EVENT

An adverse event that results in death, is life-threatening, requires inpatient hospitalization or extends a current hospital stay, results in an ongoing or significant incapacity or interferes substantially with normal life functions, or causes a congenital anomaly or birth defect. Medical events that do not result in death, are not life-threatening, or do not require hospitalization may be considered serious adverse events if they put the participant in danger or require medical or surgical intervention to prevent one of the results listed above.

SHAM COMPARATOR ARM

A group of participants that receives a procedure or device that is made to be indistinguishable from the actual procedure or device being studied but does not contain active processes or components. One of several Arm Types.

SINGLE BLIND MASKING

A type of Masking in which one party involved in the clinical trial, either the investigator or participants, does not know which participants have been assigned which interventions.

SINGLE GROUP DESIGN

Describes a clinical trial in which all participants receive the same intervention. One type of Intervention Model (design).

SPONSOR (LEAD)

The Sponsor is the organization or person (see also Sponsor-Investigator) who oversees the clinical study and is responsible for analyzing the study data.

SPONSOR-INVESTIGATOR

The person who both initiates and conducts the clinical study.

STATUS

See Recruitment Status.

STUDY COMPLETION DATE

The date on which the final data for a clinical study were collected because the last study participant made the final visit to the study location (that is, "last subject, last visit"). The "estimated study completion date" is the date that the researchers think will be the completion date for the study.

STUDY DESIGN

The investigative methods used in the clinical study. For Interventional studies, these include Primary Purpose, Intervention Model (design), Masking (or blinding), and Allocation.

STUDY START DATE

The date on which the enrollment of participants for a clinical study began.

STUDY TYPE

Describes the nature of a clinical study. Study Types include Interventional studies (or clinical trials), Observational studies, andExpanded Access.

SUSPENDED

The clinical study has stopped recruiting or enrolling participants early, but it may start again. A type of Recruitment Status.

TERMINATED

The clinical study has stopped recruiting or enrolling participants early and will not start again. Participants are no longer being examined or treated.

TIME FRAME, OUTCOME MEASURE

The points in time at which an Outcome Measure is assessed. These times are planned before the clinical study starts and are listed in the protocol.

WITHDRAWN

The clinical study stopped before enrolling its first participant. A type of Recruitment Status.