TABLE 3-1The Evidence Rating System of the U.S. Preventive Services Task Force

Overall rating
  • Good
  • Fair
  • Poor
Definition of “good”
  • Consistent results
  • Well designed, well conducted
  • Representative populations
  • Directly assesses effects on health outcomes
Definition of “fair”
  • Evidence adequate to determine effects on health outcomes but limited by

    Number, quality, or consistency of studies

    Generalizability to routine practice

    Indirect character of the effect on health outcomes

Definition of “poor”
  • Evidence is insufficient to assess effects on health outcomes because

    Limited number of studies

    Limited power of studies (a wide 95 percent confidence interval that leads to inconclusive results)

    Important flaws in study design or conduct

    Gaps in the chain of evidence

    Lack of information on health outcomes

From: 3, Contemporary Approaches to Evidence of Treatment Effectiveness: A Context for CAM Research

Cover of Complementary and Alternative Medicine in the United States
Complementary and Alternative Medicine in the United States.
Institute of Medicine (US) Committee on the Use of Complementary and Alternative Medicine by the American Public.
Washington (DC): National Academies Press (US); 2005.
Copyright © 2005, National Academy of Sciences.

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