Epidemiology: Evidence Based Medicine

Evidence based medicine (EBM) has been defined as the a process of turning clinical problems into questions and then systematically locating, appraising, and using contemporaneous research findings as the basis for clinical decisions.'¹ The term ‘evidence based medicine’ was coined at McMaster Medical School in Canada in the 1980s to label this clinical learning strategy.

It marks a shift from basing clinical decisions on out of date teaching or experiences with individual patients, to bring in the results of the most recent knowledge from rigorous clinical studies. At worst, gaps between research evidence and clinical practice can mean patients receive expensive, ineffective, or even harmful treatments. Recognition of this has been one of the driving forces behind the development of evidence based medicine.^1,3

The practice of evidence-based medicine means integrating individual expertise with the best available external clinical evidence from systematic research. This means clinically relevant research, often from the basic sciences of medicine, but especially from patient centred clinical research into the accuracy and precision of diagnostic tests, the power of prognostic markers, and the efficacy and safety of therapeutic, rehabilitative, and preventative regimens. Additionally it is not restricted to randomised trials and meta-analyses, but should involve tracking down the best external evidence available with which to answer the clinical questions.²

Research literature is constantly changing and the volume of health information has increased rapidly. The growth of health care information has been particularly rapid in diagnostic and therapeutic technologies.^1,3 However, the development of computer-based bibliographies has made it easier for busy clinicians to make use of the published literature, simply and relatively cheaply.

EBM is now widely taught in medical schools, and British centres for evidence based practice have been established in many specialities. Groups such as the Cochrane Collaboration and the Centre for Review and Dissemination in York provide systematic reviews of the effects of health care and a variety of evidence based practice journals have being launched.2

The practice of evidence based medicine involves five essential steps ^{3, 4}

1. Formulating answerable clinical questions – this may relate to diagnosis, prognosis, treatment, iatrogenic harm, quality of care, or health economics
2. Systematic retrieval of best evidence available.
3. 'Critically appraising' the evidence (determining the validity and applicability).
4. Applying the evidence (directly in patient care, development of protocols, guidelines).
5. Evaluating performance.

Advantages of EBM¹

• EBM allows the patient access to the most recent clinical knowledge
• Evidence based medicine can be learnt by people from different backgrounds and at any stage in their careers.
• EBM has the potential to improve continuity and uniformity of care through the development of common approaches and guidelines
• It can help providers make better use of limited resources by enabling them to evaluate clinical effectiveness of treatments and services

Disadvantages of EBM¹

• Evidence based medicine takes time both to learn and to practice
• Establishing the infrastructure for practising evidence based medicine costs money, for example buying and maintaining suitable computer systems
• EBM exposes gaps in the evidence. However, this can also be helpful in generating local and national research projects
• Medline and the other electronic databases are not comprehensive and are not always well indexed

References

1. Rosenberg W, Donald A. Evidence based medicine: an approach to clinical problem-solving. BMJ 1995;310:1122-1126.
2. Sackett, DL, Rosenberg W, Muir Gray JA et al. Evidence-Based Medicine: What it is and what it isn't. BMJ 1996:312:71-72.
3. Dawes M, Summerskill W, Glasziou P et al. Sicily statement on evidence based practice. BMC Medical Education 2005, 5:1.
4. Porzsolt F, Ohletz A, Thim A et al. Evidence-based decision making - the six step approach. Evidence Based Medicine 2003;8:165-166.
5. Muir Gray JA. Evidence-based healthcare: how to make health policy and management decisions. London: Churchill Livingstone, 1997.
6. Akobeng AK. Principles of evidence based medicine. Archives of Disease in Childhood 2005;90:837-840

Further Resources

Evidence based medicine on the web

• The Cochrane Collaboration: www.cochrane.org
• The Cochrane Collaboration Handbook for Systematic Reviews of Interventions: http://www.cochrane.org/resources/handbook/
• The Centre for Evidence-Based Medicine (University of Oxford): www.cebm.net
• The NHS Centre for Reviews and Dissemination (CRD) University of York: www.york.ac.uk/inst/crd
• Core Library for Evidence Based Practice (University of Sheffield): http://www.shef.ac.uk/scharr/ir/core.html
• European Observatory on Health Care Systems and Policies: http://www.euro.who.int/observatory
• Clinical Evidence: http://www.clinicalevidence.com/ceweb/about/index.jsp
• Clinical Practice Guidelines Infobase (Canada): http://mdm.ca/cpgsnew/cpgs/index.asp

Evidence Based Medicine Journals

• Effectiveness Matters: http://www.york.ac.uk/inst/crd/em.htm
• ACP Journal Club: http://www.acpjc.org
• British Medical Journal - Evidence Based Medicine: http://ebm.bmjjournals.com
• Bandolier: http://www.jr2.ox.ac.uk/Bandolier
• Effective Health Care: http://www.york.ac.uk/inst/crd/ehcb.htm
• Evidence Based Healthcare and Public Health: http://www.harcourt-international.com
• The NHS Health Technology Assessment Programme: http://www.ncchta.org/

© Helen Barratt, Maria Kirwan 2009