Different types of studies are considered to have different levels of quality of evidence. The pyramid below shows the general ranking of studies by the quality of evidence they are anticipated to contain.
Adapted from Walden University's Evidence-Based Practice Research: Levels of Evidence Pyramid
The phrase "Evidence Based Medicine" was first used by Dr. David M. Eddy, an American physician, mathematician, and healthcare analyst. In 1974 as he prepared an example for his lecture on how physicians make decisions, much to his amazement, he found very little strong evidence in the published literature to support the use of diagnostic mammography. He then searched for the evidence behind the customary treatment for ocular hypertension. He found that six out of eight trials showed that patients got worse with the treatment, plus all of the studies were of poor design. He asked himself "What in the world are physicians basing their decisions on?"1
He submitted a paper to JAMA about this lack of evidence in clinical practice, but ultimately pulled it when there was outrage over the paper. He began using the term "evidence-based" in speeches, and the concept got a supportive push when the Evidence-Based Medicine Working Group of the American Medical Association published an article in JAMA in 1992 stating:
"A new paradigm for medical practice is emerging. Evidence-based medicine de-emphasizes intuition, unsystematic clinical experience, and pathophysiologic rationale as sufficient grounds for clinical decision making and stresses the examination of evidence from clinical research. Evidence-based medicine requires new skills of the physician, including efficient literature searching and the application of formal rules of evidence evaluating the clinical literature."2
Evidence Based Practice is informed by three important components, and all three play a part toward good clinical decision making, as illustrated in the image below.
1. Eddy DM. The origins of evidence-based medicine - A personal perspective. AMA Journal of Ethics. 2011;13(1):55-60. https://www.ncbi.nlm.nih.gov/pubmed/23134763.
2. Evidence-Based Medicine Working Group. Evidence-based medicine. A new approach to teaching the practice of medicine. JAMA. 1992;268(17):2420-2425. https://www.ncbi.nlm.nih.gov/pubmed/1404801.
The evidence-based practice cycle consists of 5 steps:
Some sources also reference an additional step in the cycle. According to Melynk et al., step zero is "cultivating a spirit of inquiry."1 Whether you are seeking answers to a particular patient problem or questioning a common practice in the clinical setting, ongoing curiosity and a desire to improve care are attitudes that propel practitioners along the evidence-based cycle.
1. Melnyk BM, Fineout-Overholt E, Stillwell SB, Williamson KM. Igniting a spirit of inquiry: An essential foundation for evidence-based practice. 2009;109(11):49-52. https://www.ncbi.nlm.nih.gov/pubmed/19858857
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