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Glossary of Common Site Terms

This glossary will help you understand words or phrases frequently used on ClinicalTrials.gov. Many of these words are also used by clinical researchers and others in the same or similar manner. But the definitions below are provided to explain content on ClinicalTrials.gov only.

For help with medical terms, see the MedlinePlus® Medical Dictionary.

Study record managers should refer to the Protocol Data Element Definitions and the Basic Results Data Element Definitions for help with the data items required to register a study or submit results.

• A
• B
• C
• D
• E
• F
• G
• H
• I
• J
• K
• L
• M
• N
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• Q
• R
• S
• T
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• W
• XYZ

A

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. (See also Accepts Healthy Volunteers data element on ClinicalTrials.gov.)

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 is over. This may or may not be caused by the intervention being studied. (See also Adverse Events basic results data element on ClinicalTrials.gov.)

ALLOCATION

A clinical trial design strategy used to assign participants to an arm of a study. Types of Allocation include Randomized, and Nonrandomized. (See also Allocation data element on ClinicalTrials.gov.)

ARM

A group or subgroup of participants in a clinical trial who 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 include Experimental, Active comparator, Placebo comparator, Sham comparator, and No intervention. (See also Arm Type data element on ClinicalTrials.gov.)

B

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). (See also Baseline Characteristics results data element on ClinicalTrials.gov.)

BLINDING (or Masking)

See MASKING (or Blinding).

C

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 to 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.) (See also Certain Agreements basic results data element.)

CLINICAL STUDY

A research study using human subjects to evaluate the effect of interventions or exposures on 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 given to each clinical study registered on ClinicalTrials.gov. The format is the letters "NCT" followed by an 8-digit number (for example, NCT00000419).

CLOSED STUDIES

Clinical studies that are no longer recruiting participants because they have enough participants already, because they are completed, or because they have been stopped for some reason. This also describes studies with very specific eligibility criteria that recruit participants by invitation only. Recruitment statuses for closed studies appear in red text in ClinicalTrials.gov search results and study records. These are:

Active, not recruiting
Completed
Terminated
Suspended
Withdrawn
Enrolling by invitation
Temporarily not available for expanded access
No longer available for expanded access
Approved for marketing

Note: For closed studies, the word "Unknown," in brown text, means that a study record with an Active, not recruiting status has not been verified in ClinicalTrials.gov within the past 2 years. (See LAST VERIFIED DATE.)

COLLABORATOR

A collaborator is an organization other than the sponsor that provides support for a clinical study. This may include funding, design, implementation, data analysis, or reporting. (See also Collaborators data element on ClinicalTrials.gov.)

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

A disease, disorder, syndrome, illness, or injury that is being studied. In ClinicalTrials.gov, conditions may also include other health-related issues such as lifespan, quality of life, and health risks. (See also Conditions or Focus of Study data element on ClinicalTrials.gov.)

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 from a group of participants in the same trial or observations from outside the trial (for example, from an earlier trial, called a "historical control").

CROSSOVER 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 crossover 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 during a later phase. So during the study, participants "cross over" to the other drug. All participants receive drug A and drug B at some point during the study, but in a different order, depending on the group to which they are assigned. One type of Intervention Model (Design).

D

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, if it is causing harm to participants, or if it is not likely to serve its scientific purpose. Committee members are chosen based on the scientific skills and knowledge needed to monitor the particular study. Also referred to as a data safety and monitoring board (DSMB). (See also Data Monitoring Committee data element on ClinicalTrials.gov.)

DMC

See DATA MONITORING COMMITTEE (DMC).

DOUBLE BLIND MASKING

A type of masking in which two or more parties involved with the clinical trial do not know which participants have been assigned which interventions. Typically, this includes the investigator and participant.

E

ELIGIBILITY CRITERIA

The key standards that people who want to participate in a clinical study must meet or the characteristics that they must have. These include 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. (See also Enrollment data element on ClinicalTrials.gov.)

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, please visit the FDA Web site at http://www.fda.gov/ForConsumers/ByAudience/ForPatientAdvocates/AccesstoInvestigationalDrugs/default.htm.

EXPERIMENTAL ARM

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

F

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 placebos are given to different groups of participants. One type of Intervention Model (Design).

FDA

Food and Drug Administration. See 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 FOOD AND DRUG ADMINISTRATION AMENDMENTS ACT, SECTION 801 (FDAAA 801).

FIRST RECEIVED DATE

The first received date is the date that summary clinical study protocol information was first submitted to the ClinicalTrials.gov registry. There may be a delay of a few days before the study information is available on ClinicalTrials.gov.

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.

FOOD AND DRUG ADMINISTRATION AMENDMENTS ACT, SECTION 801 (FDAAA 801)

Section 801 of U.S. Public Law 110-85, which was enacted on September 27, 2007. It amends Section 402 of the U.S. Public Health Service Act to expand the clinical study registry known as ClinicalTrials.gov and create a clinical study results database.

For more information on FDAAA 801, see the History, Policies, and Laws page on this site.

FUNDER TYPE

Describes the organization that provides funding or support for the 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 agency (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)

G

GENDERS ELIGIBLE FOR STUDY

The physical gender of persons who may participate in the clinical study (female, male, or both). (See also Gender data element on ClinicalTrials.gov.)

H

HAS DATA MONITORING COMMITTEE (DMC)

Indicates whether the clinical study has a data monitoring committee (DMC) or data safety and monitoring board (DSMB). (See also Data Monitoring Committee data element on ClinicalTrials.gov.)

HAS RESULTS

Indicates that summary information about the results for a clinical study registered on ClinicalTrials.gov. is available in the ClinicalTrials.gov results database and can be viewed in the study record.

HEALTH AUTHORITY

A national or international health organization that has authority over the clinical study. (See also Oversight Authorities data element on ClinicalTrials.gov.)

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. (See also Human Subjects Review data element on ClinicalTrials.gov.)

I

INCLUSION CRITERIA

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

INFORMED CONSENT

A process in which researchers communicate with potential and enrolled participants about a clinical study. This is when researchers:

1. provide all the important information about the study, so that potential participants can decide whether to enroll (or if enrolled, to continue participating);
2. ensure that potential participants understand the risks and potential benefits of participating in the study, and the alternatives to the research being conducted; and
3. 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 can 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. This informed consent document is reviewed and approved by the human subjects review board for a study before it is given to potential participants. Generally, a person must sign an informed consent document to enroll in a study.

INTERVENTION

A process or action that is the focus of a clinical study. This can include giving participants 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 describing the strategy in which interventions will be assigned to participants in a clinical study. Types of intervention models include Single group design, Parallel design, Crossover design, and Factorial design. (See also Intervention Model data element on ClinicalTrials.gov.)

INTERVENTION NAME

The intervention being studied. (See also Intervention Name data element on ClinicalTrials.gov.)

INTERVENTION TYPE

The general category for the intervention being studied. Intervention types include Drug, Device, Biological, and Procedure. (See also Intervention Type data element on ClinicalTrials.gov.)

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 FDA (the drug is either not available for a doctor to prescribe or, is available, but not approved by the 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. (See also Investigators data element on ClinicalTrials.gov.)

L

LAST UPDATED DATE

The last updated date is the most recent date that changes to study information were submitted to ClinicalTrials.gov. There may be a delay of a few days to a few weeks before the updated study information is available on ClinicalTrials.gov. This date may be different from the last verified date.

LAST VERIFIED DATE

The last verified date is the most recent date that all of a clinical study's information on ClinicalTrials.gov was confirmed as accurate and up to date. This date may be different from the last updated date. If a study with a status of Recruiting; Not yet recruiting; or Active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as Unknown (See also Record Verification Date data element on ClinicalTrials.gov.)

M

MASKING (or Blinding)

A clinical trial design strategy in which one or more parties involved with the trial, such as the investigator or participant, do not know which participants have been assigned which interventions. Types of masking include none Open label, Single blind masking, and Double blind masking.

N

NCT NUMBER (or ClinicalTrials.gov Identifier)

See CLINICALTRIALS.GOV IDENTIFIER (NCT NUMBER).

NO INTERVENTION ARM

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

NOT YET RECRUITING

The clinical study has not started recruiting participants. A type of Recruitment Status.

O

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, describing the strategy for identifying and following up with participants during observational studies. Types of observational study models include Cohort, Case-control, Case-only, Case-crossover, Ecologic or community studies, Family-based, and Other. (See also Observational Study Model data element on ClinicalTrials.gov.)

OPEN LABEL

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

OPEN STUDIES

Studies that are currently recruiting participants, will be recruiting participants in the future, or involve drugs that are available for expanded access. Recruitment statuses for open studies appear in green text in ClinicalTrials.gov search results and study records. These are:

Recruiting
Not yet recruiting
Available for expanded access

Note: For open studies, the word "Unknown," in brown text, means that a study record with a Recruiting or Not yet recruiting status has not been verified in ClinicalTrials.gov within the past 2 years. (See LAST VERIFIED DATE.)

OTHER ADVERSE EVENT

An adverse event that is not a serious adverse event. (See also Adverse Events basic results data element on ClinicalTrials.gov.)

OTHER IDs

See OTHER STUDY ID NUMBERS.

OTHER STUDY ID NUMBERS

Identification numbers assigned to the clinical study protocol by the sponsor, funders, or others. These include unique identifiers from other registries and National Institutes of Health grant numbers. (See also Secondary IDs data element on ClinicalTrials.gov.)

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. (See also Primary and Secondary Outcome Measures data element and Outcome Measure basic results data element on ClinicalTrials.gov.)

P

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 receiving 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. (See also Participant Flow basic results data element on ClinicalTrials.gov.)

PHASE

Food and Drug Administration (FDA) categories (http://www.fda.gov/drugs/resourcesforyou/consumers/ucm143534.htm) for describing 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 with 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 sponsor. These studies gather additional information about a drug's safety, efficacy, or optimal use.

(See also Study Phase data element on ClinicalTrials.gov.)

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 that 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. The primary completion date is the term used in ClinicalTrials.gov for "completion date" defined in Section 801 of the Food and Drug Administration Amendments Act of 2007. (See also Primary Completion Date data element on ClinicalTrials.gov.)

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. (See also Primary Outcome Measure data element on ClinicalTrials.gov.)

PRIMARY PURPOSE

The one main reason for the clinical trial. Types of primary purposes include treatment, prevention, diagnostic, supportive care, screening, health services research, and basic science. (See also Primary Purpose data element on ClinicalTrials.gov.)

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.

PUBLICATIONS

Published scientific articles or abstracts about a clinical study. A publication reference, also called a citation, may be submitted to ClinicalTrials.gov at any time. It can also be automatically identified by the NCT Number, which is indexed in MEDLINE®, a database of biomedical and life sciences journal citations.

R

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 in the Search Results list. The studies most relevant to your search terms appear higher in the list.

RECORD

See STUDY RECORD.

RECRUITING

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

RECRUITMENT STATUS

Indicates the current stage of a clinical study and whether it is or will be open for enrollment. The possible recruitment statuses are:

Possible recruiting statuses

Open Studies	Not yet recruiting	The study has not started recruiting participants.
	Recruiting	The study is currently recruiting participants.
	Available for expanded access	An Expanded Access program is currently available for this study intervention.
Closed Studies	Active, not recruiting	The study is ongoing (that is, participants are receiving an intervention or being examined), but potential participants are not currently being recruited or enrolled.
	Completed	The study has ended normally, and participants are no longer being examined or treated (that is, the "last subject, last visit" has occurred).
	Terminated	The study has stopped recruiting or enrolling participants early and will not start again. Participants are no longer being examined or treated.
	Suspended	The study has stopped recruiting or enrolling participants early, but may start again.
	Withdrawn	The study stopped early, before enrolling its first participant.
	Enrolling by invitation	A 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.
	Temporarily not available for expanded access	An Expanded Access program is not currently available for this intervention but is expected to be available in the future.
	Temporarily not available for expanded access	An Expanded Access program is not currently available for this intervention but is expected to be available in the future.
	No longer available for expanded access	An Expanded Access program was available for this study intervention previously but is not currently available and will not be available in the future.
	Approved for marketing	Applies to an Expanded Access program. The intervention has been approved for sale to the public.
Open or Closed Studies	Unknown	A study in ClinicalTrials.gov with a status of Recruiting; Not yet recruiting; or Active, not recruiting and whose status has not been verified within the past 2 years. Studies with an Unknown recruitment status are considered open studies or closed studies, depending on their last known recruitment status

(See also Overall Recruitment Status data element and Recruitment Status data element on ClinicalTrials.gov on ClinicalTrials.gov.)

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. (See also Responsible Party data element on ClinicalTrials.gov.)

RESULTS DATABASE

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

Note: The ClinicalTrials.gov results database became available in September 2008. Older studies are unlikely to have results in the database.

RESULTS FIRST RECEIVED DATE

The date that 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, public Web-based results database, such as the ClinicalTrials.gov results database.

S

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. (See also Secondary Outcome Measures data element on ClinicalTrials.gov.)

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. (See also Adverse Events basic results data element on ClinicalTrials.gov.)

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 with the clinical trial, either the investigator or participant, 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 organization or person (see Sponsor-Investigator) who oversees the clinical study and is responsible for analyzing the study data. (See also Sponsor data element on ClinicalTrials.gov.)

SPONSOR-INVESTIGATOR

The person who both initiates and conducts the clinical study.

STATUS

See Recruitment Status.

STUDY COMPLETION DATE

The date that the final data for a clinical study were collected because the last study participant has made the final visit to the study location (that is, "last subject, last visit"). The "estimated study completion date" is the date that researchers think will be the completion date for the study. (See also Study Completion Date data element on ClinicalTrials.gov.)

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. (See also Study Design data element on ClinicalTrials.gov.)

STUDY RECORD

An entry in ClinicalTrials.gov that contains summary protocol information about a clinical study, such as recruitment status, eligibility criteria, contact information, and in some cases summary results. Each study record is assigned a ClinicalTrials.gov Identifier (NCT Number).

STUDY START DATE

The date that the enrollment of participants for a clinical study begins. (See also Study Start Date data element on ClinicalTrials.gov.)

STUDY TYPE

Describes the nature of a clinical study. Study types include Interventional Studies (or Clinical Trials), Observational Studies, and Expanded Access. (See also Study Type data element on ClinicalTrials.gov.)

SUSPENDED

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

T

TERMINATED

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

TIME FRAME, OUTCOME MEASURE

The points in time at which the outcome measure is assessed. These are planned before the clinical study starts and listed in the protocol. (See also Primary and Secondary Outcome Measures data element and Outcome Measure Time Frame basic results data element on ClinicalTrials.gov.)

TITLE ACRONYM

The acronym or initials used to identify a clinical study, if provided. For example, the title acronym for the Women's Health Initiative is "WHI." (See also Acronym data element on ClinicalTrials.gov.)

U

UNKNOWN (RECRUITMENT STATUS)

A clinical study in ClinicalTrials.gov with a status of Recruiting; Not yet recruiting; or Active, not recruiting and whose status has not been confirmed within the past 2 years. Studies with an Unknown recruitment status are considered open studies or closed studies, depending on their last recorded recruitment status.

V

VERIFICATION DATE

See LAST VERIFIED DATE.

W

WITHDRAWN

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