Clinical Trials - Definitions
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Definitions and Acronyms
Definitions and Acronyms
Adverse event

Unfavorable changes in health, including abnormal laboratory findings, that occur in trial participants during the clinical trial or within a specified period following the trial.  Two types of adverse event data are to be reported: "Serious" and "Other (Not Including Serious)" adverse events.

  • Serious Adverse Events include adverse events that result in death, require either inpatient hospitalization or the prolongation of hospitalization, are life-threatening, result in a persistent or significant disability/incapacity or result in a congenital anomaly/birth defect. Other important medical events, based upon appropriate medical judgment, may also be considered Serious Adverse Events if a trial participant's health is at risk and intervention is required to prevent an outcome mentioned.
  • Other (Not Including Serious) Adverse Events are those that are not Serious Adverse Events that exceed a frequency threshold.

For further information, please see the ClinicalTrials.gov “Basic Results” Data Element Definitions.

Applicable clinical trial Under the statute, “applicable clinical trials” generally include: 

(1) Trials of Drugs and Biologics:  Controlled, clinical investigations, other than Phase 1 investigations, of a product subject to FDA regulation;

(2) Trials of Devices:  Controlled trials with health outcomes, other than small feasibility studies, and pediatric postmarket surveillance.
Complete statutory definitions and more detailed information on the NIH’s current thinking about the meaning of “applicable clinical trials” may be found in the “Elaboration of Definitions of Responsible Party and Applicable Clinical Trial”.
Brief title Protocol title intended for the lay public.  This is a required data element in ClinicalTrials.gov.  For further information on this and other ClinicalTrials.gov protocol data elements may be accessed at: http://prsinfo.clinicaltrials.gov/definitions.html
FDAAA Food and Drug Administration Amendments Act of 2007
IDE Investigational device exemption; allows an investigational device to be used in a clinical study in order to collect safety and effectiveness data required to support a Premarket Approval (PMA) application or a Premarket Notification [510(k)] submission to Food and Drug Administration (FDA).
IND Investigational new drug application; a request for authorization from the FDA to administer an investigational drug or biological product to humans.
NCT number National Clinical Trial (NCT) number, another term for the ClinicalTrials.gov registry number unique to each record.  The format for the ClinicalTrials.gov registry number is “NCT” followed by an 8-digit number, e.g.: NCT00000419.
Official title Official name of the protocol provided by the study principal investigator or sponsor. This is a required data element in ClinicalTrials.gov.  For further information on this and other ClinicalTrials.gov protocol data elements may be accessed at: http://prsinfo.clinicaltrials.gov/definitions.html
Ongoing “Ongoing” in the context of FDAAA means a trial had one or more patients enrolled, but had not examined the final subject or provided the final subject an intervention for the purposes of final collection of data for the primary outcome.
Primary completion date As specified in P.L. 110-85, Title VIII, Section 801, with respect to an applicable clinical trial, the date that the final subject was examined or received an intervention for the purposes of final collection of data for the primary outcome, whether the clinical trial concluded according to the prespecified protocol or was terminated.  This is a required data element in ClinicalTrials.gov.  For further information on this and other ClinicalTrials.gov protocol data elements may be accessed at: http://prsinfo.clinicaltrials.gov/definitions.html
Principal Investigator

For the purposes of defining the responsible party, the principal investigator means “the individual who is responsible and accountable for conducting the clinical trial. The PI assumes full responsibility for the treatment and evaluation of human subjects, and for the integrity of the research data and results.”  The Elaboration of the Definition of Responsible Party and Applicable Clinical Trial explains that “the PI can serve as a responsible party only if he or she ‘is responsible for conducting the trial, has access to and control over the data from the clinical trial, has the right to publish the results of the trial, and has the ability to meet all of the requirements FDAAA for the submission of clinical trial information’ to the Clinical Trial Registry Data Bank. Accordingly, if the PI does not meet the specified conditions for serving as the responsible party, the sponsor must be the responsible party.”

Responsible party The entity responsible for registering the trial is the “responsible party.”  The statute defines the responsible party as:

(1) the sponsor of the clinical trial (as defined in 21 C.F.R. 50.3), or

(2) the principal investigator of such clinical trial if so designated by a sponsor, grantee, contractor, or awardee (provided that “the principal investigator is responsible for conducting the trial, has access to and control over the data from the clinical trial, has the right to publish the results of the trial, and has the ability to meet all of the requirements” for submitting information under the law.)  See PL 110-85, Section 801(a) (PDF - 549 KB), (adding new 42 U.S.C. 282(j)(1)(A)(ix)). 

Complete statutory definitions and more detailed information on the NIH’s current thinking about the meaning of responsible party may be found in the “Elaboration of Definitions of Responsible Party and Applicable Clinical Trial”.
Serious or life threatening disease or condition

Consistent with current FDA and ClinicalTrials.gov guidance, the NIH interprets “serious and life-threatening disease or condition” to mean: (1) diseases or conditions where the likelihood of death is high unless the course of the disease is interrupted and (2) diseases or conditions with potentially fatal outcomes, where the endpoint of clinical trial analysis is survival.

Any investigational drug that has received fast track designation by the FDA is considered a drug to treat a serious disease or condition.

The seriousness of a disease is a matter of judgment, but generally is based on such factors as survival, day-to-day functioning, and the likelihood that the disease, if left untreated, will progress from a less severe condition to a more serious one.  For further elaboration of the NIH’s interpretation of “serious or life threatening disease or condition”, please access the “Fact Sheet: Registration at ClinicalTrials.gov”.

Sponsor FDAAA utilizes the definition of “sponsor” that is found in section 50.3 of title 21, Code of Federal Regulations (or any successor regulation).  Complete statutory definitions and more detailed information on the NIH’s current thinking about the meaning of sponsor may be found in the “Elaboration of Definitions of Responsible Party and Applicable Clinical Trial”.
Study completion date Final date on which data were (or are expected to be) collected. This is a required data element in ClinicalTrials.gov.  For further information on this and other ClinicalTrials.gov protocol data elements may be accessed at: http://prsinfo.clinicaltrials.gov/definitions.html


The NIH encourages registration and results reporting for all NIH-supported clinical trials, regardless of whether or not they are subject to FDAAA.

This page last updated on May 26, 2011
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