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The Philosophy of Evidence-based Medicine



The Philosophy of Evidence-based Medicine

Jeremy H. Howick

ISBN: 978-1-444-34266-6 February 2011 BMJ Books 248 Pages

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Evidence-based medicine (EBM) has become a required element of clinical practice, but it is critical for the healthcare community to understand the ongoing controversy surrounding EBM. Seeking to address questions raised by critics, The Philosophy of Evidence-based Medicine challenges the over dependency of EBM on randomized controlled trials. This book also explores EBM methodology and its relationship with other approaches used in medicine.



Part I: Introduction.

1 The philosophy of evidence-based medicine.

1.1 What on earth was medicine based on before evidence-based medicine?

1.2 Scope of the book.

1.3 How the claims of EBM will be examined.

1.4 Structure of what is to come.

2 What is EBM?

2.1 EBM as a self-proclaimed Kuhnian paradigm.

2.2 The motivation for the birth of EBM: a sketch.

2.3 Original definition of EBM.

2.4 Reaction to criticism of the EBM system of evidence: more subtle, more or less the same.

3 What is good evidence for a clinical decision?

3.1 Introduction.

3.2 Evidence for clinical effectiveness.

3.3 Strong evidence tells us what?

Part II: Do randomization, double masking, and placebo controls rule out more confounding factors than their alternatives?

4 Ruling out plausible rival hypotheses and confounding factors: a method.

5 Resolving the paradox of effectiveness: when do observational studies offer the same degree of evidential support as randomized trials?

5.1 The paradox of effectiveness.

5.2 Observational studies: defi nition and problems.

5.3 Randomized trials to the rescue.

5.4 Defending the EBM view that randomized trials provide better evidence than observational studies.

5.5 Overcoming the paradox of effectiveness.

5.6 Conclusion: a more subtle way to distinguish between high- and low-quality comparative clinical studies.

Appendix 1: types of restricted randomization.

Appendix 2: Worrall’s arguments that randomization is required for classical hypothesis testing and establishing probabilistic causes.

6 Questioning double blinding as a universal methodological virtue of clinical trials: resolving the Philip's paradox.

6.1 The problems with double masking as a requirement for clinical trial validity.

6.2 The many faces of double masking: clarifying the terminology.

6.3 Confounders that arise from participant and caregiver knowledge.

6.4 The importance of successful double masking.

6.5 One (and a half) solutions to the Philip's paradox.

6.6 The full solution to the Philip's paradox: challenging the view that double masking rules out confounding factors when treatments are evidently dramatic.

6.7 Double masking is valuable unless the treatment effects are evidently dramatic, hence the Philip’s paradox does not arise.

7 Placebo controls: problematic and misleading baseline measures of effectiveness.

7.1 The need to control the placebo.

7.2 Legitimate placebo controls.

7.3 How placebo controls often violate the fi rst condition for legitimacy.

7.4 How placebo controls often violate the second condition for legitimacy.

7.5 Special problem for constructing placebos for complex treatments: case studies of exercise and acupuncture.

7.6 Summary and solution to the problem with illegitimate placebo controls.

8 Questioning the methodological superiority of "placebo" over "active" controlled trials.

8.1 Epistemological foundations of the ethical debate over the use of placebo-controlled trials.

8.2 Problems with the assay sensitivity arguments against ACTs.

8.3 Problems with the fi rst assay sensitivity argument against ACTs.

8.4 The second assay sensitivity argument.

8.5 Challenging the view that PCTs provide a measure of absolute effect size.

8.6 Questioning the claim that PCTs require smaller sample sizes.

8.7 Conclusion: a reassessment of the relative methodological quality of PCTs.

Appendix: more detailed explanation of why the second assay sensitivity argument fails.

Part III: Examining the paradox that traditional roles for mechanistic reasoning and expert judgment have been up-ended by EBM.

9 Transition to Part III.

9.1 Summary of Part II.

9.2 Introduction to Part III.

10 A qualifi ed defence of the EBM stance on mechanistic reasoning.

10.1 A tension between proponents of mechanistic reasoning and EBM views.

10.2 Clarifying the terminology: comparative clinical studies, mechanisms, and mechanistic reasoning.

10.3 Why the strong view that mechanistic reasoning is necessary to establish causal claims is mistaken.

10.4 Two epistemological problems with mechanistic reasoning.

10.5 Why EBM proponents should allow a more prominent role for high-quality (valid and based on "complete" mechanisms) mechanistic reasoning in their evidence hierarchies.

10.6 Mechanisms and other roles in clinical medicine.

10.7 Recommending a (slightly) more important role for mechanistic reasoning in the EBM system.

Appendix: cases where mechanistic reasoning led to the adoption of therapies that were either useless or harmful according to well-conducted clinical research.

11 Knowledge that versus knowledge how: situating the EBM position on expert clinical judgment.

11.1 Controversies surrounding the EBM stance on expert clinical judgement.

11.2 General clinical judgment belongs at the bottom of (or off) the hierarchy of evidence.

11.3 Individual clinical judgment also belongs at the bottom of the hierarchy.

11.4 The equally important non-evidential roles of expertise.

11.5 Conclusion.

Part IV: Conclusions.

12 Moving EBM forward.

12.1 Summary of fi ndings: the EBM philosophy is acceptable, but. . ..

12.2 Two new frontiers for EBM.



“Well-written, concise, engaging.  The Evidence-based medicine (from now on 'EBM') movement continues to go from strength to strength, with their hierarchy of medical evidence widely agreed upon and very influential in the theoretical and practical.” (The Guardian, 24 January 2014)

Review appeared in The Guardian - 24 January 2014

“In conclusion, The Philosophy of Evidence-Based Medicine is a must-have as a source of knowledge of and reference to the EBM movement. Howick presents the argument for EBM persuasively whilst giving sufficient coverage to alternative positions. I thoroughly recommend this text as both a 'way in' to the subject and a source of deeper understanding in the latest stage of medicine's fascinating journey, full of twists and turns in the search for the truth.”  (Economics & Philosophy, 1 January 2014)

“The book is well structured and makes an accessible and pleasant read. It deserves to be digested not only by philosophers with a methodological bent but by practitioners of EBM. After two decades of criticisms of various aspects of the increasingly popular EBM way of reasoning, it is about time EBM defenders tried to strike back, clarifying and justifying their positions. Howick’s book is a valuable effort that will hopefully enrich the continuing debate.”  (Theoria, 1 April 2013)

"Jeremy Howick has written the most comprehensive and fair philosophical treatment of EBM to date. Howick understands that EBM is not, first and foremost, a philosophical position, and that its various components (e.g., evidence hierarchies) are not primarily philosophical theses. Rather, they are attempts to improve the efficacy of medicine.... The book approaches its topic with the tools of mainstream analytical philosophy of science." (Philosophy of Science, 2013)

"The Philosophy of Evidence Based Medicine helps answer the question of how to think about medicine so that judgement can be made. The book addresses key questions about medical decision-making, such as: what role should mechanistic reasoning have in determining appropriate medical care? And, what weight, if any, should be given to expert opinions? This isn’t a book about how doctors think. It is about how doctors ought to think.... The Philosophy of Evidence Based Medicine is an extremely important and practical book about evidence-based medicine, and I consider it to be one of the most important contemporary books on the subject. I recommend it very highly." (The Medical Media Review, 2012)

"In The Philosophy of Evidence-Based Medicine, Jeremy Howick, PhD offers by far the most fully formed defence to date of the epistemology of EBM.... Well-written and as approachable as any work in the philosophy of science might hope to be.... Howick is to be commended for his careful analysis of epistemic ramifications of many of the methodologies of clinical epidemiology." (Journal of Evaluation in Clinical Practice, 2011)

"Howick's book provides a good overview of EBM's defense of the hierarchy of evidence and an excellent reference list for readers who want to know more about EBM and its critics." (Theory of Medical Bioethics, 2011)

"Since the 1990s, the practice of medicine has become dominated by a new methodological reasoning process - that of evidence-based medicine. This book unpacks the assumptions inherent in this methodology, shedding light on its contributions and limitations to patient care. It addresses misconceptions about and criticisms of EBM in a cogent manner and provides valuable insight into how the current world of medicine is being shaped. (Doody's, 2011)