• About the Program
  • Specific Aims
  • Contributors
  • What is EBM?
  • What is EBCAM?

What is Evidence-based Medicine?

The terms "Evidence-based Medicine" (EBM) and "Evidence-based Practice" have been defined by several groups (see Netting the Evidence, "Definitions of Evidence Based Practice." These definitions can be summarized in the following statement: EBM is the process through which health care is delivered, based on the best available evidence that is applicable to the individual patient being treated.

What is "Evidence"?

This question can be the topic of an entire textbook, but put briefly, evidence in the allopathic or western medicine model is established from the results of peer-reviewed, clinical and epidemiologic studies. The field of evidence-based medicine has established a "gold standard" by which evidence is judged. This basically consists of proof through the scientific method, demonstration through the use of repeated randomized, controlled clinical trials (RCTs). However, not every intervention in all patient populations can be studied in this manner. In allopathic medicine there are many examples of this. In an uncommon disease it is very difficult to get enough patients to perform an RCT to evaluate an intervention. Ethics are also a consideration in conducting an RCT. Therefore, a less rigorous standard based on the "best available evidence" often drives clinical decisions.

Evidence has a hierarchy where some types of studies carry more weight to support a medical intervention than others. A general maxim is that studies looking at a broader population carry more weight than anecdotal reports of single or a few patients. In order of "weight" from highest to lowest, the studies are as follows:

1. Epidemiologic studies - including cohort and case-control studies
2. Case series ­ from one or multiple centers
3. Case reports ­ from individual patients at a single site
4. Physiologic data ­ human > animal: provides a rationale for an intervention

There are many web sites (see Resources and Links below) devoted to guiding healthcare providers through the process of using evidence to make decisions about patient care. The process involves six steps, but is often described in five steps. Each step has its own unique skill set. Practice is needed before one becomes proficient in them. The steps are in order:

1. Identify a problem or question arising from the care of a patient
2. Form an answerable (or well-built) question. Using the PICO technique (see links for further details) can help to formulate a question and define search terms.
3. Search for the best evidence. Need to know which resources are appropriate, how to search efficiently and effectively and the limitations of resources.
4. Critically appraise the evidence ­ both for quality and applicability to the patient.
5. Apply the evidence to the patient taking into account both patient preference and clinical experience and judgement.
6. Evaluate your performance in each of the previous steps.

Resources and Links

• EBM What it is and what it isn't, Sackett, D. L., Rosenberg,W.M.C., Muir Gray, J.A., Haynes,R. B., Richardson, W.S. (1996), BMJ ; 312: 71-2.
• Glossary of EBM Terms
  Oxford Centre for Evidence-Based Medicine (UK)
• Glossary of EBM Terms
  Center for Evidence-Based Medicine, University of Toronto
• Study Design
  Oxford Centre for Evidence-Based Medicine (UK). This page gives a brief comparison of the advantages and disadvantages of different study types.
• Practising EBM
  Center for Evidence-Based Medicine, University of Toronto. Tips on practising the five steps of EBM:
  1. Formulating Answerable Clinical Questions
  2. Searching for the Best Evidence
  3. Appraising the Evidence
  4. Applying the Evidence to the Patient
  5. Evaluation
• Tufts Hirsh Health Sciences Library EBM Resources
  For links to EBM resources including tools, databases, calculators, clinical guidelines collections, tutorials, PDA resources, journals, print and online textbooks.
• Epidemiology and Biostatistics Lectures(Tufts Access only via TUSK).
  Tufts University School of Medicine