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About Clinical Trials

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What is a clinical trial?

Clinical trials are one form of clinical research that involves a researcher or researchers who directly observe a person or people, and/or who collect data to answer a scientific or medical question about the safety or potential benefit of an intervention such as a medication, device, teaching concept, training method, or behavioral change. There are several definitions of clinical trial, some of which are explained below.

  • The NIH defines a clinical trial as a prospective biomedical or behavioral research study of human subjects that is designed to answer specific questions about biomedical or behavioral interventions (such as drugs, treatments, devices, or new ways of using known drugs, treatments, or devices).
    • Clinical trials are used to determine whether new biomedical or behavioral interventions are safe, efficacious, and effective.
    • Behavioral human subjects research involving an intervention to modify behavior (such as diet, physical activity, cognitive therapy, etc.) fits this definition.
    • Research with human subjects to develop or evaluate clinical laboratory tests (imaging or molecular diagnostic tests) might be considered as a clinical trial if the test will be used for medical decision making, or if the test itself imposes more than minimal risk for subjects.
  • The Department of Health and Human Services (DHHS) defines a clinical trial as a controlled study involving human subjects that is designed to prospectively evaluate the safety and effectiveness of new drugs or devices or of behavioral interventions (from the Institutional Review Board [IRB] Handbook).
  • The DHHS Office for Human Research Protection refers to the Code of Federal Regulations, Title 46, Part 102 and defines a clinical trial as follows:
    • Research is a systematic investigation, including research development, testing, and evaluation, that is designed to develop or contribute to generalizable knowledge.
    • A human subject is a living individual about whom an investigator (whether professional or student) conducting research obtains: (1) Data through intervention or interaction with the individual; or (2) Identifiable private information.
    • Intervention includes both physical procedures by which data are gathered (for example, collection of blood) and manipulations of the subject or the subject's environment that are performed for research purposes.
    • Interaction means communication or interpersonal contact between the investigator and participant. This contact includes private information: Data about behavior that occurs in a context in which an individual can reasonably expect that no observation or recording is taking place; data provided for specific purposes by an individual; data that the individual can reasonably expect will not be made public (for example, a medical record).

What outcomes do clinical trials provide?

Clinical trials are designed to provide information about different types of outcomes.

  • Some studies, particularly those involving pharmaceutical products, are designed to determine what the body does to the product. These are usually called pharmacokinetic (PK) studies. PK studies are usually the first phase of study and are performed to determine proper dosing. Dosing may be different for different populations based on age and genetics (which includes sex, race, and differences in metabolism).
  • Another type of outcome is to examine what the product does to the body. These studies are called pharmacodynamic (PD) studies. PD studies are used to examine the ability, safety, and clinical activity of a drug or device.

Some studies combine a PK component and a PD component.

An additional category of clinical trials—called efficacy studies—establish the overall risks and benefits of any intervention. These studies must be of large enough size and must incorporate the proper design to allow the results to be analyzed and generalized, or applied to the general population.

Where can I get more information on clinical trials?


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Last Updated Date: 02/09/2011
Last Reviewed Date: 02/09/2011
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