Glossary of common clinical research terms

Return to CTV home

Accepts healthy volunteers

An eligibility criteria that indicates whether people without the condition/disease being studied can participate in the clinical trial.

Active comparator arm

An arm type in which a group of participants receives an intervention/treatment considered to be effective (or active) by health care providers.

Age or age group

An eligibility criteria that specifies the age a person must be to participate in a clinical study.


A group of participants in a clinical trial that receives a specific treatment, or no treatment, according to the trial's design.

Arm type

A classification of the clinical trial arm. Types of arms include experimental, active comparator, placebo comparator, sham comparator, and no intervention.

Clinical study

A research study involving participants that is intended to add to medical knowledge. There are two types of clinical studies: interventional studies (also called clinical trials) and observational studies.

Clinical trial

Clinical trials, sometimes called interventional studies, are research studies that test a medical, surgical, or behavioral treatment in people to determine its effectiveness.


An organization other than the sponsor that provides support for a clinical trial.


The disease, condition, illness, injury, or health related issue that is being studied.


The name and contact information for the person who can answer enrollment questions for a clinical trial. Each location where a trial is being conducted may also have a site-specific contact.


CTV stands for ClinicalTrials.Veeva, a clinical trial search provided by Veeva Systems as part of its public benefit mission.

Early phase 1

A phase of research used to describe exploratory trials used to investigate how or whether a drug affects the body. They involve very limited human exposure to the drug and are not intended to assess a drug’s effectiveness in treating disease.

Eligibility criteria

The requirements that participants in a clinical trial must meet, consisting of both inclusion criteria (which are required for a person to participate) and exclusion criteria (which prevent a person from participating).


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

Exclusion criteria

These are criteria that, if met, would exclude a person from participating in a clinical trial.

Expanded access

A way for patients with serious diseases or conditions who cannot participate in a clinical trial to gain access to a medical product that has not been approved by the U.S. Food and Drug Administration (FDA). For more information, see FDA Expanded Access: Information for Patients.

Experimental arm

An arm type in which a group of participants receives the treatment that is the focus of the clinical trial.

First posted

The date on which the study record was first available on

Funder type

Describes the type of organization that provides funding or support for a clinical trial:

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

Requirements that a person must meet to participate in a clinical trial.


A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and noninvasive approaches, such as education or modifying diet and exercise.

Interventional study (clinical trial)

A type of clinical study in which participants are assigned to groups that receive one or more treatments (or no intervention) so that researchers can evaluate the effects of the treatment on a person’s health. Interventional studies are commonly referred to as clinical trials.

Last update posted

The most recent date on which changes to a study record were made available on

NCT number

A unique identification code given to each clinical study record registered on

No intervention arm

An arm type in which a group of participants does not receive any treatment during the clinical trial.

Observational study

A type of study where patients are monitored over time rather than being assigned a treatment/intervention.


The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4.

Phase 1

A phase of research to describe clinical trials that focus on the safety of a drug. They are usually conducted with healthy volunteers, and the goal is to determine the drug's most frequent and serious adverse events. These trials usually involve a small number of participants.

Phase 2

A phase of research to describe clinical trials that gather preliminary data on a drug's effectiveness. For example, participants receiving the drug may be compared to similar participants receiving a different treatment.

Phase 3

A phase of research to describe clinical trials that gather more information about a drug's safety and effectiveness by studying different populations and different dosages and by using the drug in combination with other drugs. These studies typically involve more participants.

Phase 4

A phase of research to describe clinical trials occurring after FDA has approved a drug for marketing. These trials gather additional information about a drug's safety, efficacy, or optimal use.

Phase not applicable

Describes trials without FDA-defined phases, including trials of devices or behavioral treatments.


An inactive substance or treatment that looks the same as, and is given in the same way as, an active drug or treatment being studied.

Placebo comparator arm

An arm type in which a group of participants receives a placebo during a clinical trial.

Primary completion date (end date)

The date on which the last participant in a clinical study was examined or received treatment in order to assess the trial’s primary goal. The "estimated" primary completion date is the date that the researchers think will be the primary completion date for the study.

Principal investigator (PI)

The research professional who is responsible for the scientific and technical direction of a clinical trial.

Results first posted

The date on which summary results information was first available on


A type of eligibility criteria that indicates the sex of people who may participate in a clinical study (all, female, male). Sex is a person's classification as female or male based on biological distinctions.

Sham comparator arm

An arm type in which a group of participants receives a procedure or device that appears to be the same as the actual procedure or device being studied but does not contain active processes or components.


The organization or person who initiates the study and who has authority and control over the study.


Describes the status of a clinical trial:

  • Not yet enrolling: The study has not started enrolling participants
  • Enrolling: The study is currently enrolling participants
  • Invitation-only: The study is selecting its participants from a population, or group of people, decided on by the researchers in advance
  • Active, not recruiting: The study is ongoing, but potential participants are not currently being enrolled
  • Completed: The study has ended normally, and participants are no longer being examined or treated (that is, the last participant's last visit has occurred)
  • Terminated: The study has stopped early and will not start again. Participants are no longer being examined or treated
  • Withdrawn: The study stopped early, before enrolling its first participant
  • Unknown: A study on that has passed its completion date, and the status has not been last verified within the past 2 years.
Study IDs

Identifiers that are assigned to a clinical study by the study's sponsor, funders, or others.

Study results

A study record that includes the summary results posted in the database.

Study start date

The date on which the first participant was enrolled in a clinical study.

Study type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies, and expanded access.

Veeva-enabled site

A research site that is a member of SiteVault, which is part of Veeva’s Digital Trials Platform. SiteVault connects sites, sponsors, and patients on a single technology ecosystem to make clinical trials more efficient and improve patient participation.

Clinical trials

Find clinical trialsTrials by location
© Copyright 2024 Veeva Systems