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Module 1: Introduction to Evidence Based Medicine (EBM)

Evidence Based Medicine - Click each tab in the box below to know more!

Evidence-based medicine (EBM) is also known as evidence-based health care (EBHC) and evidence-based practice (EBP). In the 1990s, a team of medical professionals from Oxford, McMaster, Duke and other medical universities, led by David Sackett of McMaster University published an article. In the article, they defined "Evidence based medicine is the conscientious, explicit and judicious use of current best evidence in making decisions about the care of individual patients.” - Sackett et al., 1996. 

As the area has evolved, a new definition was given, “Evidence-based medicine (EBM) requires the integration of the best research evidence with our clinical expertise and our patient’s unique values and circumstances.” - Straus et al., 2019

To find current best evidence and appraise the evidence are important steps in EBM. In the original EBM article written by Dr. Sackett (1996), he stated that “studies show that busy clinicians who devote their scarce reading time to selective, efficient, patient driven searching, appraisal, and incorporation of the best available evidence can practice evidence based medicine”. Masic et al. (2008) wrote "the key difference between evidence-based medicine and traditional medicine is not that EBM considers the evidence while the latter does not. Both take evidence into account; however, EBM demands better evidence than has traditionally been used". 

Sackett, D. L., Rosenberg, W. M., Gray, J. A., Haynes, R. B., & Richardson, W. S. (1996). Evidence based medicine: what it is and what it isn't. BMJ (Clinical research ed.), 312(7023), 71–72. https://doi.org/10.1136/bmj.312.7023.71

Masic, I., Miokovic, M., & Muhamedagic, B. (2008). Evidence based medicine - new approaches and challenges. Acta informatica medica : AIM : journal of the Society for Medical Informatics of Bosnia & Herzegovina : casopis Drustva za medicinsku informatiku BiH, 16(4), 219–225. https://doi.org/10.5455/aim.2008.16.219-225

Straus, Glasziou, P., Richardson, W., & Haynes, R. (2019). Evidence-Based Medicine : How to Practice and Teach EBM (5th ed.). Elsevier Health Sciences.

The evidence based medicine process is also known as the EBM cycle or the 5 A's of Information. 

The process of conducting evidence based medicine typically includes the following steps:

1. Assess the patient and identify the clinical problem -- be sure to assess and acknowledge your own knowledge gaps
2. Ask a well-built clinical question that relates to the current case/situation 
3. Acquire the evidence by searching an appropriate resource 
4. Appraise the evidence for its quality and relevance 
5. Apply what you have learned -- integrate the evidence with your expertise and your patient's preferences

Bonus stage: Assess how you executed the EBM process -- would you do anything differently? 

 

Sources of Evidence

Case Series and Case Reports

  • Collections of reports on the treatment of individual patients OR a report for a singular patient
  • Do not include groups with which to compare outcomes
  • Limited statistical validity

Case Control Studies

  • Compares patient who already have specific condition with those without said condition
  • Researchers look back to identify factors or exposures that may be associated with the condition, typically relying on medical records or patient recall
  • Has varying reliability since showing a statistical relationship does not mean that one factor necessarily caused the other
  • This type of study is particularly helpful for ascertaining the cause of rare conditions/diseases

Cohort Studies

  • Follows a group of people and studies at how events (treatment or exposure) differs among people within the group
  • Observational and not as reliable as randomized controlled studies since the groups may differ in ways other than the variable under study
  • A study that examines a cohort, which differs in respect to exposure to some suspected risk factor is useful for trying to ascertain whether exposure is likely to cause specified conditions/diseases
  • Prospective cohort studies, which track participants forward in time, are more reliable than retrospective cohort studies. The latter studies groups after the outcome has been reached
  • Click here to learn more about the difference between prospective and retrospective cohort studies

Controlled Clinical Trials

  • Does not include randomization; the treatment is assigned by a method other than random allocation
  • Participants are assigned to two or more different treatment groups
  • More likely to suffer from bias than randomized controlled trials

Randomized, Controlled Clinical Trials

  • A carefully planned trial in which participants are assigned to two or more groups through random selection
  • At least one group is the experimental group that receives the intervention while the other, the comparison or control group, receives an alternative treatment or placebo
  • Includes methodologies that reduce the potential for bias (randomization and blinding) and allows for assessment of the relative effects the intervention

Critically Appraised Topics

  • Authors evaluate and synthesize multiple research studies
  • Findings are typically presented as a review article on a particular topic
  • Follows a similar process to a systematic review although they do not have to be as comprehensive

Systematic Review 

  • Typically focus on a clinical topic and answer a specific question
  • Features a specified methodology that is followed to identify, appraise, and summarize studies
  • It can but does not always involve a meta-analysis

Meta-Analysis

  • Thoroughly examines a number of valid studies on a topic and combines the results using an accepted statistical methodology to report the results as if it were one large study

Adapted from https://hslguides.med.nyu.edu/EBM/Levels

What are practice guidelines?

"A set of recommendations defining conditions for using or not using available interventions in clinical or public health practice. Practice guidelines may be evidence-based and referred to as evidence-based guidelines or evidence-based recommendations." (Riegelman, R.K. (2005). Studying a study & testing a test: How to read the medical evidence. Philadelphia: Lippincott Williams & Wilkins.)

In other words, practice guidelines are sets of evidence-based, systematically developed recommendations for health care.