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Evidence Based Medicine (EBM) is the name given to a relatively new direction in medical thinking and action. EBM has as its mainstay the principle that health care providers actively investigate which of the various diagnostic and therapeutic measures they apply actually work. They should do this by reviewing claims of efficacy through critical analysis of the biological rationale and experimental justification (”the evidence”) of whatever intervention is under consideration. The “evidence” is to be found in the clinical research literature, so the practice of EBM requires a certain facility in retrieving this material. It also presupposes the ability to evaluate clinical research literature effectively, and to separate stronger studies from weak ones. In turn, this skill requires some degree of mathematical competence, especially in basic statistics. It also implies a working knowledge of the elements constituting a strong study, and something that perhaps is best called “practical logic”, that is, the ability to ask the right questions at the right time.

To say that EBM is “new” and is based on evidence, implies that the bulk of what came before it was based on something else: tradition, authority, convention, the persuasive power of pharmaceutical marketing, etc. Some physicians resented the suggestion. Others dismissed EBM as just another bandwagon, or as a pretentious description of their actual practices. EBM was also labeled as some kind of Ivory Tower exercise, unsuitable for busy MDs in the real world. And, it was also alleged that EBM resulted in “cook-book” medicine, something favored by bean counters and administrators, but not at all conducive to patient interests. Despite all these expressions of hostility, EBM has gathered momentum sufficient to overcome or at least silence most doubters. In fact, the movement has attracted converts in nursing, physical therapy, midwifery, and other health sciences, where the drive to establish a specific Evidence Based Practice (EBP) is becoming quite strong. Fields outside the health sciences are also flirting with the concept. To some extent, this imitation is simply a reflected glory phenomenon. If Medicine, the premier profession, adopts a fashion the temptation for other professions, real or merely soi disantes, to do the the same is hard to resist. Then too, how can anyone resist what seems such an obviously good idea? Still, one can be excused for thinking that the sudden appearance of “evidence based” everything is taking on comic and even ridiculous dimensions.

EBM advocates are at pains to point out that much of what they are suggesting has a venerable pedigree, dating back at least to Pierre Louis (1787-1872), who kept detailed records of the usefulness or futility of various therapeutic measures, such as bleeding for tuberculosis. A mathematico-critical approach to the evaluation of medical practice has continued since Louis’s time, but never attained “mainstream” status. The name Evidence Based Medicine, and the current form of the method, resulted from the work of a group at the McMaster University School of Medicine, in Hamilton, Ontario, Canada. Gordon Guyatt, MD and David Sackett, MD are closely associated with the origins and first steps of EBM, but there were many other contributors. Recent years have seen a steady growth in the advance of EBM in schools of medicine around the world, and in publications, both monograph and serial, devoted to EBM concepts and tenets.

Texts explaining EBM typically list these topics as main areas of concern:
Diagnosis
Prognosis
Therapy
Harm

They also list these steps in the process:

Form an answerable question, based on patient needs and clinician’s state of knowledge.
Retrieve the relevant literature.
Evaluate this material for validity, utility and application in the current case.
Use the information gained, respecting patients’ values and needs.
Evaluate one’s own performance of these steps, with a view to improvement next time.

EBM benefits from the formation and growth of another powerful critical movement, the Cochrane Collaboration(CC), which grew out of the work of British epidemiologist Archie Cochrane, and also seeks to determine which diagnostic or therapeutic interventions are effective. Cochrane studies are very elaborate and detailed analyses of the published literaure, often described as “systematic reviews”. Reviewers attempt to gather all reports on the matter at hand, not contenting themselves with the results of computer based literature searches, but using the printed indexes and even by detailed examination of journal articles, their lists of references, and then those referenced articles, in a very painstaking cycling operation. Systematic Reviews prefer the randomized controlled trial as the evidentiary gold standard, but consider other less rigorous designs.

Those interested in reading further about EBM can consult any of several textbooks on the subject. Since attention to the literature is the backbone of EBM, a number of works have been written on the topic of the best methods to read clinical journal articles. The MEDLINE database introduced EVIDENCE BASED MEDICINE as a searchable subject heading in 1997, and as of August, 2006 there were over 20,000 references indexed with that term in the system. This suggests that the articles are about EBM, not that they themselves should be used for clinical decision making. It is interesting to note the “linguistic spread” of the publications. EBM started out in North America and the UK, but physicians and educators all over the world seem interested in the idea, as manifested in publications in many languages. A search on AMAZON.COM in the Advanced search mode yielded several hundred entries with titles containing the worlds “evidence based”

Further Reading:
Evidence-based Medicine: how to practice and teach EBM is the name of a text that appeared over the last several years in different editions, with various co-authors. The newest edition is the Third, by Sharon E. Strauss, MD and co-authors, published by Elsevier in 2005. MML Reserve: WB 102 E93 2005
A web site with important supplementary information is available for review at:
http://www.cebm.utoronto.ca/
The second edition of this work, which some readers prefer, by David L Sackett and co-authors appeared in 2000 and was published by Churchill Livingstone. The supplementary web site to this edition can be linked to from the web page noted above.

How to Read a Paper, by Trisha Greenhalgh, Blackwell Publishing, 2006. Dr. Greenhalgh is a British physician and this is the Thrird Edtition of her book, which has been translated into six European languages in addition to Chinese and Japanese. She notes: “I am neither an epidemiologist nor a statistician, but a person who reads papers and who has developed a pragmatic (and at times uncoventional) system for testing their merits”. MML Reserve:W 20.5 G813h 2006

The American Medical Association published:
Evidence-Based Practice: Logic and Critical Thinking in Medicine by Milos Jenicek and David L. Hitchcock, AMA Press, 2005. This book is a guide to applying logical methods and critical analysis of argument (a paper is an argument) to clinical cases. MML Reserve: WB 102 J51e 2005

Users’ Guides to the Medical Literature: a manual for evidence-based clinical practice edited by Gordon Guyatt MD and Drummond Rennie MD, Chicago,AMA Press, 2002. Guyatt was one of the McMaster pioneers in EBM and Rennie’s long editorship of JAMA and his interest in the movement give this text a certain weight and authority. The book’s title comes from a series of the same name which ran in JAMA, and which was important in introducing EBM concepts to the American medical audience. MML Reserve WB 102 U84 2002

The Users’ Guides is a rather hefty 700 page item, so the AMA press has also released, confusingly, under the same title a precis of the larger work, with a subtitle explaining that this book offers the “Essentials of Clinical Practice”, while the tubby other volume is a full fledged “manual”. MML Reserve: WB 102 U841 2002

Statistical Evidence in Medical Trials; what do the data really tell us? by Stephen D. Simon is an introduction to research design and to understanding what the numbers reported in clinical trials mean for practice decisions.
MML W 20.5 S596s 2006.

The Logic of Medicine by Edmond A. Murphy is a very thorough discussion, with numerous historical examples, of the roles played in diagnosis and treatment by logical thinking, mathematical analysis and statistical interpretation. The book is less a manual on evidence-based medicine, which does not even occur in the subject index, and more a treatise on medical philosophy. It’s not an easy read, but the effort of dealing with it is well rewarded.
MML W61 M978L 1997