Evidence-Based Concepts

Levels of Evidence

EBDM is about solving clinical problems. In solving these problems, there are two principles:*

  1. Evidence alone is never sufficient to make a clinical decision. Evidence is just 1 component of the decision-making process.
  2. A hierarchy of evidence is available to guide clinical decision-making and as a hierarchy implies, not all evidence is equally useful for making patient care decisions.

As you progress up the hierarchy, the research designs allow more control so that intervention or treatment outcome differences are not due to chance. Also, as you progress up the hierarchy, the number of published studies decreases, and yet these are more clinically relevant studies.

*Guyatt G, et al, EBM Working Group. Users’ guides to the literature, 2008. JAMA and Archives Journals, Chicago: McGraw Hill Medical.

© 2009 Forrest JL, Miller SA. National Center for DH Research & Practice