Introduction to Evidence Based Medicine

Introduction to Evidence Based Medicine


What is Evidence Based Medicine?

    Evidence Based Medicine (EBM), a term that did not exist a decade ago, has captured the imagination of clinicians and health policy makers. We now have journals exclusively devoted to EBM, databases on systematic reviews (like the Cochrane Collaboration), workshops, courses and books on EBM. In the 1980s and 1990s, clinicians (primarily from the McMaster University) who introduced the concept of EBM argued for health care and clinical decisions to be made on the basis of strong evidence generated by well done controlled trials and research studies (EBM Working Group 1992). They felt that this approach was better than traditional decision-making approaches which they saw as being far more open to bias and error.

    EBM arose out of the need to make well-informed decisions in a setting of limited resources. How can one get the best deal given limited resources? It became obvious that those who need to make decisions should evaluate the benefits and risks of competing options on the basis of the best available evidence [which can be reproduced and described] rather than on an unsystematic or haphazard evaluation.

    EBM has been defined as a process of “integrating individual clinical expertise with the best available external clinical evidence from systematic research” (Sackett et al. 1996, Sackett et al. 1997). All expert recommendations should be based on a systematic appraisal of the best evidence available; to accomplish this, the best evidence available relating to a particular decision must be found. Good evidence is usually derived from strong epidemiological study designs [like a randomized controlled clinical trial]. Evidence derived from poorly done observational study designs is weak and therefore not very useful in decision making.

    The EBM approach to health care practice is one in which the clinician is aware of the evidence that bears on her clinical practice, and the strength of that evidence. The EBM process of decision-making involves the following sequence [Sibbald 1998]:

  • Identifying a clear, focused clinical question.
  • Undertaking a systematic search of the medical literature to identify trials and research done on the question.
  • Assessing the validity of the studies identified by critically reviewing them.
  • Applying the results of the search to the decision-making process.
  • Evaluating performance of the above.

    A busy clinician who sees many patients is likely to confront several clinical questions for which an evidence-based approach may be needed. Given the vast number of such problems, the following points are often raised as barriers to implementing EBM in daily practice (Dawes MG 1998):

  1. The quality of the evidence is limited for many decisions.
  2. Even when there is high quality evidence, busy clinicians do not find the time to track it down.
  3. Even if the evidence is tracked down, clinicians lack the necessary skills and experience to critically review the evidence and make a judgment about it

1. Not enough high quality evidence:

Over the years an impressive number of randomised clinical trials have been performed and numerous meta-analyses based on such trials are now available as systematic reviews. By using resources like Best Evidence, the Cochrane database, MEDLINE and Up to Date, it is possible to find trials on many clinical questions.

2. Not enough time to track down evidence:

A busy clinician does not have to track down and critically evaluate evidence by herself. Much of the evidence that answers common questions have already been tracked down and critically appraised. Many of the resources for finding the information also includes packaging in easily accessible formats [either directly online or through CDs]. Best Evidence and the Cochrane Database of Systematic Reviews (CDSR) are great examples. The Cochrane Collaboration is already being compared to the Human Genome Project in its potential implications for modern medicine.

    There are many more such resources: the ACP (American College of Physicians) Journal Club is another example [access through:]. The University of Sheffield’s School of Health and Related Research (ScHARR) produces an excellent bibliography of EBM related websites called “Netting the Evidence: A ScHARR Introduction to Evidence Based Practice on the Internet. This website is a fantastic collection of EBM related sources.

    Thus, quite a lot of good EBM related material could be easily accessed and used even by busy clinicians. Those who do not have access to computers and the internet can buy books on these topics. The book titled “Evidence Based Cardiology” by Yusuf et al is a good example of a book that a busy cardiologist can read. The other example is “Effective Care in Pregnancy and Childbirth” by Chalmers et al. This book is considered one of the best evidence based resources in the field of Obstetrics. Another publication called “Clinical Evidence” is published every 6 months by the British Medical Journal.3. Clinicians lack the skills and experience to critically review evidence

    This is a genuine problem and needs to be urgently addressed. Since critical review of journals and basic epidemiology is not taught at all, or not taught well in medical colleges, most clinicians find it difficult to read journals. If clinicians could do short courses or workshops on epidemiology or on critical appraisal skills, part of the problem could be solved. Medical colleges could organise workshops on this theme for postgraduate students and residents. At the very least, doctors should read medical literature with the help of very useful resources like the Users’ Guides to the Medical Literature (Guyatt GH, 1993). 

    Another approach is to form journal clubs where clinicians get together regularly and critically review papers. This will enhance their ability to critically review papers. Unfortunately, most journal clubs do not sustain themselves after an initial phase of interest and enthusiasm.

    Whatever the methods used, the individual clinician, ultimately, has to put in the effort and allocate time for reviewing evidence and using them in his/her practice. The next few articles in this series in we will present articles on basic epidemiology, statistics and critical appraisal of journal articles.

Can EBM improve quality of health care?

    Good clinicians use both clinical expertise and scientific evidence; neither alone is enough. With just clinical expertise alone, practice might become out dated very soon and therapies based on new scientific evidence is not offered to the patient. Thus, the patient does not get the best quality of care. On the other hand, scientific evidence alone takes away the strong individual element in the art of medicine. Even the best external scientific evidence may not be applicable to all people in all settings.

    While it is impossible to do a randomised trial of the impact of EBM on quality of medical care, the final assumption of EBM is that doctors whose practice is based on an understanding of the underlying evidence will provide superior patient care. Work done at the McMaster University has shown that the teaching of EBM may help medical graduates stay up-to-date in their practice (Shin et al. 1991). Doctors who are up-to-date as a function of their ability to critically read current medical literature will be able to distinguish strong from weaker evidence. This will, in turn, enable them to be more judicious in the therapy they recommend and the tests they use for diagnosis.

    Doctors are increasingly faced with the problem of exploding volume of new medical literature, rapid introduction of new therapies and technologies, rising health care costs, and increasing attention to the quality and outcomes of medical care. EBM could help ameliorate these problems and therefore deserve to be widely disseminated.

The need for EBM training in India

    In India, irrational medical practice is common. For example, despite attempts to promote rational drug use, irrational drug therapy is widespread (Phadke 1998). Another example is the failure of the National Tuberculosis Control Programme due to non-adherence to practice guidelines in anti-tuberculous therapy by physicians (Uplekar et al. 1991). Even a simple, easy to use evidence-based practice guidelines like the use of oral rehydration therapy (ORT) for diarrhoea is not widely practiced.

    Research and publishing in India also suffers from problems. There is a paucity of good medical research (Reddy et al. 1991) and only a few Indian journals are indexed (in Index Medicus) and only 3 are indexed by the Science Citation Index. Many Indian papers go unnoticed and have a very small impact on the global research scene (Arunachalam 1997). Much of the Indian medical research is largely irrelevant to the health problems of the country (Arunachalam 1997). Another survey on which are the best medical colleges in India demonstrated a startling fact: there are many medical colleges in India which do not contribute even one peer reviewed publication in a year (Arora et al. 1996).

    In India, there are hardly any training programs on EBM. Very few centers in India offer training in epidemiology and biostatistics. But no programs are offered exclusively on Evidence Based Medicine. EBM, epidemiology and biostatistics are grossly neglected areas of undergraduate and postgraduate medical education. As one author wrote, “a large part of the poverty in medical publishing in India arises from a lack of a publishing and research culture in Indian medical schools… medical trainees have virtually no exposure to the basics of scientific methodology, study design, and biostatistics. Almost all their publishing exposure is to mindless articles of the ‘show and tell’ variety… virtually none of the publishing in clinical medicine is of the prospective, randomized, controlled trial variety… when there is so little medical publishing in India – good or bad – there is even less exposure of the young to the proper techniques and joys of scientific research.” (Rajagopalan 1997).

    Thus, there is a real need for clinicians in India to get trained in EBM. Professional bodies and medical associations (irrespective of the speciality) could incorporate this as a part of their conferences and scientific meetings.

    At the end of this paper, a list of Institutions in south India which offer training in epidemiology and statistics is appended. Several other useful resources for epidemiology training are also included.

Limits to EBM

    Though EBM is here to stay, there has been a lot of discussion on the limitations of EBM (Naylor 1995, Sibbald 1998, Grahame-Smith 1995, Lancet 1995). Many clinicians fear that EBM limits clinical freedom to practice medicine as they see fit in the best interests of their patients. They also fear that the art of clinical medicine will be threatened if they are expected to follow evidence based protocols and not allowed to do what they want. As Naylor points out, there are many grey zones in clinical medicine where EBM offers little help. There are many clinical situations when evidence is either lacking or simply confusing!

    Some authors have pointed out that EBM itself should be put to the test: is there evidence to show that EBM is better than what is hopes to replace? There is also this fear that EBM is being hijacked by those who want to cut health care costs at the expense of clinical freedom.

References & further reading

  1. Arora M, Banerjee JK, Sahni P, Pande GK, Nundy S. Which are the best undergraduate medical colleges in India. Natl Med J India 1996;9(3):135-140.
  2. Arunachalam S. How relevant is medical research done in India? A study based on Medline. Current Science 1997:72:912-922.
  3. Chalmers I, Enkin M, Kierse MJNC. Effective care in pregnancy and childbirth. New York: Oxford University Press.
  4. Dawes MG. On the need for evidence-based general and family practice. ACP Journal Club., 1998.
  5. Evidence-Based Medicine Working Group: Evidence-based medicine: A new approach to teaching the practice of medicine. JAMA 1992;268:2420-2425.
  6. Grahame-Smith D. Evidence based medicine: Socratic dissent. BMJ 1995;310:1126-7.
  7. Guyatt GH. Users’ guides to the medical literature. JAMA 1993; 270 (17) : 2096-2097.
  8. Evidence based medicine; in its place [editorial]. Lancet 1995;346:785.
  9. Naylor DC. Grey zones of clinical practice: some limits to evidence based medicine. Lancet 1995;345:840-42.9.
  10. Phadke A. Drug supply and use. Towards a rational policy in India. Sage Publications, New Delhi, 1998.
  11. Rajagopalan A. Medical research in India. Current Science 1997;73:397.
  12. Reddy KS, Sahni P, Pande GK, Nundy S. Research in Indian medical institutes. Natl Med J India 1991;4:90-92.
  13. Sackett DL, Haynes RB, Guyatt GH, Tugwell P. Clinical Epidemiology: a basic science for clinical medicine. Boston, Little, Brown & Co, 1991.
  14. Sackett DL, Rosenburg WMC, Grey JAM, et al. Evidence Based Medicine: What it is and what it isn’t. BMJ 1996;312:71-72.
  15. Sackett DL, Richardson WS, Rosenberg W, Haynes RB. Evidence-Based Medicine: How to Practice and Teach EBM. London: Churchill Livingstone, 1997.
  16. Shin J, Haynes RB. Does a problem-based, self-directed undergraduate medical curriculum promote continuing clinical competence? Clin Res 39. 143A (1991).
  17. Sibbald WJ. Some opinions on the future of evidence-based medicine. Critical Care Clinics 1998;14(3):549-559.
  18. Uplekar MW, Shephard DH. The private GP and treatment of tuberculosis: a study. Foundation for Research in Community Health, Mumbai, 1991.
  19. Yusuf S, et al. Evidence Based Cardiology. BMJ, 1998.



    • CDC, Atlanta: The Centers for Disease Control, Atlanta, website, offers a lot of epidemiology training modules (DOEPI) and free statistical software (Epi Info, Epi Map, Epi Meta, etc.).
    • Evidence Based Medicine:

(1) EBM is a new journal for learning to practice evidence based medicine. The journal can be accessed through

    (2) The University of Sheffield’s School of Health and Related Research (ScHARR) produces a bibliography of EBM related websites called “Netting the Evidence: A ScHARR Introduction to Evidence Based Practice on the Internet.

      (3) The Cochrane Collaboration produces the Cochrane Database of Systematic Reviews.

        • Journal Clubs: These are good resources for learning to critique journal articles.

      (1) The American College of Physicians (ACP) run a good journal club in their website

        (2) Another journal club can be accessed at:

          (3) CASP, a Critical Appraisal Skills Programme is a UK project on critical appraisal and EBM:
          (4) The Centre for Evidence Based Medicine in the UK runs regular courses

          Dr. Madhukar Pai MD, DNB
          Consultant, Community Medicine & Epidemiology
          Email: [email protected]