Advanced Search Field Definitions

The following search fields are available on the Advanced Search page. They are listed in the order in which they appear on the form. To view information on a search field, click on its name below. You can also click on the field label on the Advanced Search form to access information for that field.


Recruitment—Use this field to specify whether you want to search for studies that are open (recruiting participants) or closed (not recruiting participants). You can select one of the following search options:

  • All Studies: All studies, whether or not they are recruiting new participants
  • 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: Open studies marked with the word "Unknown" in brown text have a Recruiting or Not yet recruiting status that has not been verified on ClinicalTrials.gov by the sponsor of the study or responsible party within the past 2 years.
  • 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. They 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    Withdrawn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: Closed studies marked with the word "Unknown" in brown text have an Active, not recruiting status that has not been verified on ClinicalTrials.gov by the sponsor of the study or responsible party within the past 2 years.
  • Exclude Unknown Status: Use this checkbox to remove studies with a recruitment status of Unknown from the search results. A status of Unknown identifies a study on ClinicalTrials.gov with a status of Recruiting; Not yet recruiting; or Active, not recruiting and whose status has not been confirmed by the sponsor of the study or responsible party within the past 2 years. Marking this checkbox on the Advanced Search form is the same as marking the Exclude studies with Unknown status checkbox at the top of the search results list.

See Recruitment Status in the glossary for the definitions of each status.

Study Results—Use this field to search based on whether a study has results posted in the ClinicalTrials.gov results database. You can select one of the following search options:

  • All Studies
  • Studies With Results
  • Studies Without Results
The ClinicalTrials.gov results database provides the public with access to summary results and registration information for completed or terminated clinical studies. Further, study results are often published in medical journals. On ClinicalTrials.gov, publication citations are displayed at the bottom of the Full Text View tab of a study record, under the More Information heading. See the How to Find Results of Studies page to learn more.

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

Study Type—Use this field to limit your search to one of the following clinical study types:

  • All Studies
  • Interventional Studies (or Clinical Trials): Clinical studies 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.
  • Observational Studies: Clinical studies 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).
    • Patient Registries: A type of Observational Study that collects uniform data prospectively for a population defined by a particular disorder/disease, condition, or exposure and that serves a predetermined scientific, clinical, or policy purpose.
  • Expanded Access Studies: 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.

    For more information on Expanded Access programs, visit the FDA Web site

Conditions—Use this field to specify 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.

Interventions—Use this field to specify 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.

  • Examples: clofibrate, cyclosporine, vitamin E, pacemaker, PET scan

Outcome Measures—Use this field to specify a measurement, decided on in advance, that is used to determine the effect of interventions on participants in a clinical trial. For observational studies, specify 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

  • Examples: weight loss, ejection fraction, muscle strength

Sponsor/Collaborators—Use this field to specify the Sponsor (Lead) or Collaborator. A sponsor is the organization or person (a Sponsor-Investigator) who oversees the clinical study and is responsible for analyzing the study data. 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.

  • Examples: National Cancer Institute, Mayo Clinic, Bristol-Myers Squibb
  • Exact match: Use this checkbox to indicate that the sponsor name listed in the study must exactly match the sponsor name entered in the search field. For example, if this checkbox is not marked, a search with "Merck" in the Sponsor (Lead) field will find studies with Merck, Merck KGaA, Dupont Merck, and Merck Sharp & Dohme listed as the sponsor. If the checkbox is marked, only studies with Merck listed as the lead sponsor (with no other words in the name) will be included in the search results.

  • Examples: National Cancer Institute, Mayo Clinic, Bristol-Myers Squibb
  • Exact match: Use this checkbox to indicate that the sponsor name listed in the study must exactly match the sponsor name entered in the search field. For example, if this checkbox is not marked, a search with "Merck" in the Sponsor (Lead) field will find studies with Merck, Merck KGaA, Dupont Merck, and Merck Sharp & Dohme listed as the sponsor. If the checkbox is marked, only studies with Merck listed as the lead sponsor (with no other words in the name) will be included in the search results.

Study IDs—Use this field to search for a clinical study by an identification number.

Every clinical study is associated with 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. In addition, ClinicalTrials.gov assigns a ClinicalTrials.gov Identifier, or NCT Number, a unique identification code is given to each clinical study registered on ClinicalTrials.gov. Because the format is the letters "NCT" followed by an 8-digit number (for example, NCT00000419), this identifier is also known as the NCT Number.

Country/State—Studies are often conducted in many locations around the world. Use this field to select up to three locations to search for studies. For some countries, you can narrow your search by selecting a state or province. This feature is currently available for the United States, Canada, and Australia only.

  • Examples:
    State: United States, Alabama
    Country: United States

Location Terms—If you are interested in a specific city (such as Los Angeles) or facility (such as the Mayo Clinic), enter it in the Location Terms field.

Note: Not all studies include this level of detail.

Gender—Use this field to search by the physical gender of persons who may participate in a study. You can select one of the following search options:

  • All Studies
  • Studies With Female Participants
  • Studies With Male Participants

Age Group—Use this field to limit your search to studies that accept participants from selected age groups. You can select more than one age group. If more than one age group is selected, the search results will include studies that accept at least one of the age groups you indicated. If you do not select any age group, all age groups will be included in your search.

The age groups are:
  • Child (birth–17)
  • Adult (18–65)
  • Senior (66+)

Phase—Use this field to select the study phase you want to include in your search. You can select more than one study phase. If you do not select any study phase, all study phases, including Phase 0, will be included in your search results.

Phases are Food and Drug Administration (FDA) categories for describing the study 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 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 include 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 Learn About Clinical Studies to learn more about the phases of drug trials.

Funder Type—Use this field to select the funder type you want to include in your search. You can select more than one funder type. If you do not select any funder type, all funder types will be included in your search results.

Funder type describes the organization that provides funding or support for the 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 (NIH)
  • 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 (individuals, universities, and organizations)

Safety Issue—Use this checkbox to limit your search to studies that have an Outcome Measure that is designated by the sponsor of the study or responsible party as a safety issue.

First Received—Specify a From date to find studies submitted to ClinicalTrials.gov on or after that date. Specify a To date to find studies submitted on or before that date. Specify both From and To dates to find studies submitted during a certain time period. If no dates are entered, all studies will be included in your search results.

Dates should be entered in MM/DD/YYYY format. For example, March 1, 2010, is entered as "03/01/2010."
The First Received date is the date that summary clinical study protocol information was first submitted to the ClinicalTrials.gov registry. There is typically a delay of a few days between the First Received date and when the study information is available on ClinicalTrials.gov.

Last Updated—Specify a From date to find studies updated on ClinicalTrials.gov on or after that date. Specify a To date to find studies updated on or before that date. Specify both From and To dates to find studies that were updated during a certain time period. If no dates are entered, all studies will be included in your search results.

Dates should be entered in MM/DD/YYYY format. For example, March 1, 2010, is entered as "03/01/2010."
The Last Updated date is the most recent date that changes to a study record were submitted to ClinicalTrials.gov. There may be a delay between the Last Updated date and when the updated study information is available on ClinicalTrials.gov. This date may be different from the last verified date.

This page last reviewed in May 2015