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Is my study observational or interventional?

Observational Study:
A biomedical or behavioral research study of human subjects designed to assess risk factors for disease development or progression, assess natural history of risk factors or disease, identify variations based on geographic or personal characteristics (such as race/ethnicity or gender), track temporal trends, or describe patterns of clinical care and treatment in absence of specific study-mandated interventions.

Interventional Study:
For purposes of reviewing grant applications and contract proposals submitted to the NIH, a clinical trial is operationally defined as a prospective biomedical or behavioral research study of human subjects that is designed to answer specific questions about biomedical (drugs, treatments, devices, or new ways of using known drugs, treatments, or devices) or behavioral interventions.

Clinical trials are used to determine whether new biomedical or behavioral interventions are safe, efficacious and effective. Clinical trials of experimental drug, treatment, device or behavioral intervention may proceed through four phases:

  • Phase I
  • Phase II
  • Phase III (see also NIH-Defined Phase III Clinical Trial )
  • Phase IV

Page Last Updated: February 2011
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