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What is evidence based medicine?

What is EBM?

Evidence Based Medicine (EBM) is an approach to forming medical knowledge, based on systematic and unbiased methods of appraising scientific evidence (Source: BestBETs).

The Key Steps in Evidence Based Practice (EBP)

Evidence-based practice (EBP) is the inclusive term which the principles of EBM are founded; primarily EBP is based on five well defined steps.

  • Step One: Asking Focused Questions: translation of uncertainty to an answerable question
  • Step Two: Finding the Evidence: systematic retrieval of best evidence available
  • Step Three: Critical Appraisal: testing evidence for validity, clinical relevance, and applicability
  • Step Four: Applying the Evidence: application of results in practice
  • Step Five: Evaluating Performance: auditing evidence-based decisions

Step One: Asking Focused Questions

One of the fundamental skills required for practising EBM is the asking of well-built clinical questions. To benefit patients and clinicians, such questions need to be both directly relevant to patients' problems and phrased in ways that direct your search to relevant and precise answers. In practice, well-built clinical questions usually contain the four PICO elements (Source: Centre for Evidence Based Medicine). For more information on PICO visit our PICO guide.

Step Two: Finding the Evidence

It is important when searching for evidence that search terms are referred back to your original PICO question. The type of evidence located may include:

  • Systematic reviews
  • Meta-analysis
  • Randomised controlled clinical trials
  • Cohort studies
  • Longitudinal follow-up studies
  • Case-controlled studies
  • Case series and case reports
  • Cross-sectional studies
  • Qualitative evidence                    

When forming your question think of alternate keywords, including alternate spelling and terms for example:

  • Teenagers: teenager, adolescents, adolescent, adolescence, youth, youths, young people
  • Acupuncture: acupressure
  • Hypnosis: hypnoses, hypnotism, hypnotise, hypnotize, hypnotherapy
  • Smoking: smokes, tobacco, cigarette, cigarettes, stop (smoking), quit, quitting, cease...

You also need to think about the following:

  • Are there other words that mean the same thing (synonyms)? e.g. adolescents, adolescence, youth, young people
  • Are there alternative spellings? e.g. pediatrics/paediatrics, randomised/randomized
  • Are any of the important words singular and plural? e.g. family, families, child/children
  • Are words used differently in different countries? e.g. operation/surgery, physiotherapy/physical therapy
  • Are any of the words commonly used as abbreviations? e.g. CHF or congestive heart failure

Step Three: Appraising the Evidence

The purpose of critical appraisal is to determine the relevance of the material collected in relation to the clinical question raised. In other words, does the evidence provide the answer to the question raised and how confidently can the evidence be applied to practice? (Source: Cleary- Holdforth J, Leufer T, 2008 ‘Essential elements in developing evidence-based practice' Nursing Standard. 23, 2, 42-46)

Step Four: Applying the Evidence

Once the evidence has been appraised, and the best available evidence selected, it must be applied to your local situation. How it is applied will depend on its relevance to local conditions. Below is a list of questions you may ask to help determine how evidence applies:

  • Is the test affordable, accurate and available in my hospital?
  • Can I estimate the pre-test probability of the disease in question?
  • Will the post-test probability affect my management?
  • Is my patient so different from those in the study group that the results can not be applied?
  • According to the study results, how much would my patient benefit from the treatment?
  • Can the study results be applied to my patient?
  • What is my patient's risk for adverse affects?
  • Are there alternative therapies?
  • Is my patient similar to the patients in the study group?
  • How will the evidence influence my choice of treatment?

Applicability may be determined by the following variables listed in the checklists below:

User Group

  • Is the user group similar to mine?
  • Did the research measure outcomes important to my situation and users?
  • What is the impact of the age of the user group?
  • Does the service/product fit with values, needs and preferences of my user group?


  • Has the situation changed since the evidence was gathered?
  • Is there a potentially newer technical solution that should be explored?


  • Are the benefits worth the cost in my situation?
  • How big an impact will be achieved and is it worth the cost?
  • Are there any negative side affects for users that may be costly in the long run?
  • Are there other less costly things that can be done instead or prior to implementation to control costs?


  • Is there support within the institution and who do I need to partner/target to become my champion?
  • What will be the positive and negative effects of this initiative in my environment?
  • Will my employer/users embrace the different way of doing things?


  • What is the level of severity of the issue?
  • Will implementation make a difference? If so, how much, and is it worth the effort?
  • Are there other remedies for this situation?
  • Are the potential consequences so severe that any solution will only work in the short term?

Step Five: Evaluating Performance

To complete the cycle of practising evidence based medicine clinicians should evaluate their own performance, and this fifth step of self evaluation allows clinicians to focus on earlier steps that may need improvement in the future. Clinicians can evaluate their progress at each stage by asking some or all of the following questions:

  • Was the question answerable?
  • Was the diagnosis and treatment successful?
  • How quickly was good evidence located?
  • Is there new information/data in the literature?
  • How can I improve/update my clinical decision?
  • How effectively appraised was the evidence?
  • Was the application of the new information or procedure effective?
  • Should this new information and/or clinical practice procedure continue to be included in day to day applications?
  • How could any of the 5 steps improve the next time a question is asked?

(Source: Straus, E and Sackett D L 1998, ‘Getting research findings into practice Using research findings in clinical practice' BMJ Vol.317 p.339-342; Johnson, C 2008, ‘Evidence-based practice in 5 simple steps' Journal of Manipulative and Physiological Therapeutics Vol. 31 p.169-170).