Jun 2, 2017

The original evidence-based medicine

In a 1991 ACP Journal Club editorial Gordon Guyatt writes what appears to be the first time the term evidence-based medicine (EBM) is defined:

The way of the future described above depicts an important advance in the inclusion of new evidence into clinical practice. Clinicians were formerly taught to look to authority (whether a textbook, an expert lecturer, or a local senior physician) to resolve issues of patient management. Evidence-based medicine uses additional strategies, including quickly tracking down publications of studies that are directly relevant to the clinical problem, critically appraising these studies, and applying the results of the best studies to the clinical problem at hand. It may also involve applying the scientific method in determining the optimal management of the individual patient (3).

For the clinician, evidence-based medicine requires skills of literature retrieval, critical appraisal, and information synthesis. It also requires judgment of the applicability of evidence to the patient at hand and systematic approaches to make decisions when direct evidence is not available. The primary purpose of ACP Journal Club is to help make evidence-based medicine more feasible for internists by extracting new, sound clinical evidence from the morass of the biomedical literature so that practitioners can get at it.

In 1992 article titled Evidence-Based Medicine A New Approach to Teaching the Practice of Medicine (PMID: 1404801) Guyatt further develops the concept of EBM and calls it a new paradigm. The article starts:

A NEW paradigm for medical practice is emerging. Evidence-based medicine de-emphasizes intuition, unsystematic clinical experience, and pathophysiologic rationale as sufficient grounds for clinical decision making and stresses the examination of evidence from clinical research. Evidence-based medicine requires new skills of the physician, including efficient literature searching and the application of formal rules of evidence evaluating the clinical literature. [My emphasis]

On the rationale behind the shift in medical practice he writes:

Thomas Kuhn has described scientific paradigms as ways of looking at the world that define both the problems that can legitimately be addressed and the range of admissible evidence that may bear on their solution.4 When defects in an existing paradigm accumulate to the extent that the paradigm is no longer tenable, the paradigm is challenged and replaced by a new way of looking at the world. Medical practice is changing, and the change, which involves using the medical literature more effectively in guiding medical practice, is profound enough that it can appropriately be called a paradigm shift.

As for what influences this new paradigm Guyatt finds support in how the medical research can inform the day-to-day clinical practice. He also adds which assumptions from the former paradigm are not sufficient for practicing medicine:

  1. Unsystematic observations from clinical experience are a valid way of building and maintaining one's knowledge about patient prognosis, the value of diagnostic tests, and the efficacy of treatment.
  2. The study and understanding of basic mechanisms of disease and pathophysiologic principles are a sufficient guide for clinical practice.
  3. A combination of thorough traditional medical training and common sense is sufficient to allow one to evaluate new tests and treatments.
  4. Content expertise and clinical experience are a sufficient base from which to generate valid guidelines for clinical practice.

The assumptions under which the new paradigm functions includes:

  1. Clinical experience and the development of clinical instincts (particularly with respect to diagnosis) are a crucial and necessary part of becoming a competent physician. Many aspects of clinical practice cannot, or will not, ever be adequately tested. Clinical experience and its lessons are particularly important in these situations. At the same time, systematic attempts to record observations in a reproducible and unbiased fashion markedly increase the confidence one can have in knowledge about patient prognosis, the value of diagnostic tests, and the efficacy of treatment. In the absence of systematic observation one must be cautious in the interpretation of information derived from clinical experience and intuition, for it may at times be misleading. [My emphasis]
  2. The study and understanding of basic mechanisms of disease are necessary but insufficient guides for clinical practice. The rationales for diagnosis and treatment, which follow from basic pathophysiologic principles, may in fact be incorrect, leading to inaccurate predictions about the performance of diagnostic tests and the efficacy of treatments.
  3. Understanding certain rules of evidence is necessary to correctly interpret literature on causation, prognosis, diagnostic tests, and treatment strategy.

It is also interesting that Guyatt lists and implies skepticism, uncertainty, independent critical thinking, and inquiry as part of this new paradigm. Of note these concepts are also emphasized in the scientific method. He writes:

It follows that clinicians should regularly consult the original literature (and be able to critically appraise the methods and results sections) in solving clinical problems and providing optimal patient care. It also follows that clinicians must be ready to accept and live with uncertainty and to acknowledge that management decisions are often made in the face of relative ignorance of their true impact. [My emphasis]

The new paradigm puts a much lower value on authority.20 The underlying belief is that physicians can gain the skills to make independent assessments of evidence and thus evaluate the credibility of opinions being offered by experts. The decreased emphasis on authority does not imply a rejection of what one can learn from colleagues and teachers, whose years of experience have provided them with insight into methods of history taking, physical examination, and diagnostic strategies. This knowledge can never be gained from formal scientific investigation. A final assumption of the new paradigm is that physicians whose practice is based on an understanding of the underlying evidence will provide superior patient care. [My emphasis]

In addition to the traditional practice of medicine Guyatt describes a new set of behaviors, which he calls critical appraisal, as part of the practice of EBM:

The role modeling, practice, and teaching of evidence-based medicine requires skills that are not traditionally part of medical training. These include precisely defining a patient problem, and what information is required to resolve the problem; conducting an efficient search of the literature; selecting the best of the relevant studies and applying rules of evidence to determine their validity3; being able to present to colleagues in a succinct fashion the content of the article and its strengths and weaknesses; and extracting the clinical message and applying it to the patient problem. We will refer to this process as the critical appraisal exercise.

The original article also emphasizes the care of the patient as an individual person with emotional needs requiring a compassionate physician.

Another traditional skill required of sensitivity to patients' emotional needs. Understanding patients' suffering21 and how that suffering can be ameliorated by the caring and compassionate physician are fundamental requirements for medical practice. These skills can be acquired through careful observation of patients and of physician role models. Here too, though, the need for systematic study and the limitations of the present evidence must be considered. The new paradigm would call for using the techniques of behavioral science to determine what patients are really looking for from their physicians22 and how physician and patient behavior affects the outcome of care.23 [My emphasis]

On the value of experience and intuition Guyatt states:

...the teacher can point to a number of large randomized trials, rigorously reviewed and included in a meta-analysis, which allows one to say how many patients one must treat to prevent a death. In other cases, the best evidence may come from accepted practice or one's clinical experience and instincts. The clinical teacher should make it clear to learners on what basis decisions are being made. [My emphasis]


...it is important to expose learners to exceptional clinicians who have a gift for intuitive diagnosis, a talent for precise observation, and excellent judgment in making difficult management decisions. Untested signs and symptoms should not be rejected out of hand. They may prove extremely useful and ultimately be proved valid through rigorous testing. The more the experienced clinicians can dissect the process they use in diagnosis,31 and clearly present it to learners, the greater the benefit. Similarly, the gain for students will be greatest when clues to optimal diagnosis and treatment are culled from the barrage of clinical information in a systematic and reproducible fashion. [My emphasis]

Another important requirement of EBM daily practice is conducting computerized search of the literature. Guyatt explains the computerized literature search and appraisal should come from the learners when encountering a problem for which the answer is uncertain. This aspect in particular resembles one of the processes of Problem-Based Learning; generating questions. Our electronic access to information is more readily available these days thanks to the Internet and World Wide Web, this makes the practice of EBM as originally conceived more relevant.

It is crucial that critical appraisal issues arise from patient problems that the learner is currently confronting, demonstrating that critical appraisal is a pragmatic and central aspect, not an academic or tangential element of optimal patient care. The problem selected for critical appraisal must be one that the learners recognize as important, feel uncertain, and do not fully trust expert opinion; in other words, they must feel it is worth the effort to find out what the literature says on a topic. The likeliest candidate topics are common problems where learners have been exposed to divergent opinions (and thus there is disagreement and/or uncertainty among the learners). The clinical teacher should keep these requirements in mind when considering questions to encourage the learners to address. [My emphasis]

Just like scientists physicians try to understand how the world works. The difference is that scientists throughout history realized their methods were not successful when used in an unsystematic way. Scientists became aware of their limitations and invented a method that although not perfect is the best when compared to others. Only this way can scientist guarantee an objective method of knowledge progress. Other methods that claim scientific progress or trying to give answers about how the world works without using the scientific method are not being authentic. This is what Richard Feynman called cargo cult science.

According to Kuhn revolution occurs when scientists encounter anomalies that can no longer be explained away under the current paradigm. When the new paradigm is accepted the old way of seeing the world is no longer recognized by the scientists. Kuhn's explanation of scientific revolution has been criticized by many philosophers of science such as Karl Popper and Imre Lakatos. Popper and Lakatos, contrary to Kuhn, believed that science progresses incrementally and that although science practice is considered a social activity, its products are objectively independent of human cognition and other social aspects. I think what Guyatt is describing as a new practice of medicine resembles more of a Popper/Lakatos view of scientific progress where the emphasis is not discarding the old tradition but rather adding a systematic method of objectively examining the practice of medicine as best as possible.

There's more to be said about the history of evidence-based medicine and how it's being misunderstood, misused, and misapplied. Guyatt has also recognized how the current explanation of EBM practice does not yet explain certain aspects of medical practice. This signifies a very important aspects of scientific practice which Feynman called scientific integrity and I believe, among other things, it's something that should be better emphasized in education.

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1. You should attempt to re-express your target’s position so clearly, vividly, and fairly that your target says, “Thanks, I wish I’d thought of putting it that way.
2. You should list any points of agreement (especially if they are not matters of general or widespread agreement).
3. You should mention anything you have learned from your target.
4. Only then are you permitted to say so much as a word of rebuttal or criticism.
Daniel Dennett, Intuition pumps and other tools for thinking.

Valid criticism is doing you a favor. - Carl Sagan