The Philosophy of Evidence-based Medicine E-Book

Jeremy H. Howick

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 411

Veröffentlichungsjahr: 2011

Beschreibung

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.

Leseprobe

Contents

Acknowledgments

Foreword

Preface

Part I : Introduction

Chapter 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

Chapter 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

Chapter 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?

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

Chapter 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: definition 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

Chapter 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

Chapter 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 first 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

Chapter 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 first 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

Chapter 9 : Transition to Part III

9.1 Summary of Part II

9.2 Introduction to Part III

Chapter 10 : A qualified 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

Chapter 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

Chapter 12 : Moving EBM forward

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

12.2 Two new frontiers for EBM

References

Index

To question the foundations of a discipline or a practice is not necessarily to deny its value, but rather to stimulate a judicious and balanced appraisal of its merits.

—R. Ashcroft & R. ter Meulen [1]

It would be difficult to put the case for the clinical trial of new (or old) remedies more cogently or more clearly. The absence of such a trial in the past may well have led, to give one example, to the many years of inconclusive work on gold therapy in tuberculosis, while. . .the grave dangers of much earlier and drastic methods of therapeutics, such as blood-letting, purging, and starvation, would quickly have been exposed by comparative observations, impartially made.

—A.B. Hill & I.D. Hill [2]

The central problem of epistemology has always been and still is the problem of the growth of knowledge. And the growth of knowledge can be studied best by studying the growth of scientific knowledge.

—Karl Popper [3]

This edition first published 2011, © 2011 by Jeremy Howick

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Library of Congress Cataloging-in-Publication Data

Howick, Jeremy.

The philosophy of evidence-based medicine / Jeremy Howick, with a foreword by Paul Glasziou.

p. ; cm.

Includes bibliographical references and index.

ISBN 978-1-4051-9667-3 (pbk. : alk. paper)

1. Evidence-based medicine. 2. Medicine—Philosophy. I. Title.

[DNLM: 1. Evidence-Based Medicine. 2. Philosophy, Medical. WB 102.5]

R723.7.H693 2011

610—dc22

2010047393

A catalogue record for this book is available from the British Library.

This book is published in the following electronic formats: ePDF 9781444342659; Wiley Online Library 9781444342673; ePub 9781444342666

1 2011

Acknowledgments

Many of the ideas in this book about evaluating the differences between randomized trials and observational studies are John Worrall’s. I am also indebted to John for extensive feedback on several chapters in the book. I am equally indebted to Nancy Cartwright and Paul Glasziou. Nancy encouraged me to write the book, and without her feedback on my chapter on mechanistic reasoning it would have been a mess. Paul, together with Jeffrey Aronson, helped me conceptualize how to combine various types of evidence and were also encyclopaedic sources of fascinating medical examples. My collaboration with Paul and Jeffrey resulted in two publications.

Most of the book was written whilst I was a Medical Research Council (MRC) funded postdoctoral research fellow (G0800055) hosted by the Centre for Evidence-Based Medicine (CEBM) at Oxford’s Department of Public Health and Primary Care (DPHPC). Many people at the CEBM and DPHPC gave me invaluable advice, including Paul Montgomery, Rafael Perera, Jason Oke, Richard Stevens, Merlin Wilcox, David Mant, Amanda Burls, Alison Ward, Carl Heneghan, Su-May Liew, and Olive Goddard. Thanks to Kay, Claire, Suzie, and Andrew for encouraging frequent tea and biscuit breaks. Sir Iain Chalmers of the James Lind Library was enormously generous with his time and enriched my work in many ways, especially by encouraging me to be succinct. On one occasion, he claimed I took 30 pages to express a message he could express in 3; I succeeded in reducing it to 15.

Concurrent with my postdoctoral fellowship at Oxford I have been teaching philosophy to medical students at University College, London (UCL). My students provided me with a platform to teach my ideas (Emily Sweetman pointed out several typos in earlier drafts), and many of my colleagues at UCL gave me useful feedback. These include Steve Miller, Josipa Petrunic, Brian Balmer, Jon Agar, Norma Morris, and especially Donald Gillies.

Many other people have listened or read the ideas in these chapters at various conferences, meetings, or email exchanges. Space doesn’t permit me to mention all of them, but Gordon Guyatt, Brian Haynes, Dave Sackett, Murray and Eleanor Enkin, Alejandro Jadad, Ted Kaptchuk, Elizabeth Silver, Eileen Munro, Jon Williamson, Federica Russo, and Beatrice Golomb (many of the ideas in the conclusion are borrowed from Dr Golomb) were all helpful.

I would not have been able to write the book without (some) personal distractions, usually in the form of rowing. Thanks to Jonny Searle for making sure I woke up at 5.30 on Saturday mornings in the dark of the winter, to Paul Kelly for encouraging me to join the Wolf Pack, Colin Smith for being a recent training partner, and especially to the Great Eight (Phil, Fred, Nick, Ted, John, Sohier, Dave, Hirsh and most of all Scott Armstrong) for continuing to remind me that the world is the oyster of the bold.

Various friends, including Foad Dizadji-Bahmani, Jesse Elzinga, and Josh West, put up with me for various periods of time while I moved flats. Other friends, including Sebastien, Mark, Qarim, and Renaud, were always there when I needed them. Dick Fishlock has been a continued source of entertainment and inspiration, and Dusan gave me a break. Lastly, my mother (who I’m becoming increasingly convinced is an Angel), father (who generously supported my expensive education), sisters, Brett, John, Jack and Raven provided unconditional love that helped me keep going.

Stephen Hlophé, Mingy, and Dr Bali have helped keep me almost sane. Thank you to everyone I forgot to mention.

Foreword

In 1991 an international group formed to encourage clinicians to consider results of recent research when treating patients. They commenced writing a series of User’s Guides to reading research for JAMA, the Journal of the American Medical Association, and needed a new term to signal the intention of the series. After several suggestions, the group’s leader, Gordon Guyatt, proposed the term Evidence-Based Medicine. The new term was to ignite a movement that spread rapidly around the world. The methods of evidence-based medicine (EBM) have evolved since then, but the focus of the inventors – mostly clinicians – was the practical concern of bedside decision making. Understandably they paid less attention to the psychology, sociology or philosophy that might underpin EBM. However, now that EBM is well established in the medical world, deeper exploration by different disciplines seems warranted. This book is an examination and extension of the philosophy of EBM: a modern conversation between Aristotle and Hippocrates.

While the term Evidence-Based Medicine has a short history dating back to the 1990s, the ideas behind it have been evolving for centuries. A large part of the vocabulary of EBM – bias, confounding, randomization, placebo, confidence interval, etc. – has been invented and developed by statisticians and epidemiologists. But philosophers have been grappling with many of the same issues that lie behind the ideas, including the nature, and proof for, causal relationships, justification for induction, and errors in human observation, models, and reasoning. Many of these terms appear and are explained inside. Other ideas less familiar in the routine EBM books also enrich this text; for example, Phillip’s paradox, nocebo effects, and probabilistic causality.

The book is a rich treasure of examples. Some are akin to zen koans: thinking about them can be a struggle but considerably deepen understanding of EBM. Consider the randomized comparison of nicotine versus placebo but where both groups were also randomised to be told they received nicotine, received placebo, or not told anything (see Figure 8.4) – a 2×3 factorial design. What do the various possible comparisons tell you? Which is better: to have the nicotine patch but be told it is placebo, or have the placebo patch but be told you received nicotine? Considering these comparisons may change the way you think about the placebo effect and the place of placebos in trials.

EBMers have been focused on teaching, and getting the evidence in practice. However, less attention has been given to the philosophical roots of EBM. In particular, we have ignored or belittled the role of mechanism. The battle between mechanists and empiricists is long standing in both philosophy and medicine, but what have the two opposing ideas to offer each other, to researchers, and to the users of research? Chapter 10 is an excellent synthesis of both camps. This chapter is a crystallization of many long afternoons of stimulating discussion between the author, Jeffrey Aronson and myself. Besides the many insights developed in those conversations and set down here, I also learned the value of having the input and insight of other disciplines on the work of EBM. And had fun in the process. The challenge of working across disciplines though is great: basic assumptions are different, purposes are different, and even the vocabulary can be different. “Proof” means different things to philosophers, doctors, detectives and distillers. But with a generous dose of good-will, we found the interdisciplinary exploration fruitful for both philosophy and medicine. And worth continuing.

This work represents an important dialogue between EBM and philosophers of science. There has been too little. I searched MEDLINE for titles which include EBM and philosophy and found only six, but all from the last 6 years. Let me end with a quote from the earliest of these articles: Ashcroft and Ter Meulen introduce a special issue of the Journal of Medical Ethics that reported on a symposium on EBM by saying: “To question the foundations of a discipline or a practice is not necessarily to deny its value, but rather to stimulate a judicious and balanced appraisal of its merits; we offer the present selection of papers in that spirit.” So I hope you enjoy and learn from reading this, and seek out your local philosopher for a cup of tea or a pint of ale, and some stimulating discussion.

Professor Paul Glasziou PhD FRACGP MRCGP

Director, Department of Evidence-Based Medicine

University of Oxford, Oxford, UK

Preface

Most EBM “hierarchies” of evidence rank comparative clinical studies (including systematic reviews of randomized trials) above mechanistic reasoning (“pathophysiologic rationale”) and expert judgment. Within comparative clinical studies, randomized trials are considered to offer stronger evidence than observational studies. Early EBM proponents showed that many widely used therapies that had been adopted based on “lower” forms of evidence proved to be useless or harmful when subjected to evaluation by randomized trials. In spite of the compelling rationale, the EBM philosophy of evidence leads to several paradoxes. Perhaps the most striking is that many of the treatments in whose effectiveness we have the most confidence – that we consider to be most strongly supported by evidence – have never been supported by randomized trials of any description. These treatments include automatic external defibrillation to start a stopped heart, tracheostomy to open a blocked air passage, and the Heimlich maneuver to dislodge airway obstructions. While critics have attacked various aspects of the EBM methodology, the system as a whole has, with few exceptions, escaped scrutiny. After outlining the paradoxes (Chapter 1), I investigate what EBM is (Chapter 2), and how a claim that a treatment “works” should be unpacked (Chapter 3). Next, I defend a method for evaluating the relative strength of comparative clinical studies (Chapter 4), and I argue that the EBM position on randomized trials is, with a slight modification, sustainable (Chapter 5). The modification is to replace categorical hierarchies that place randomized trials on top with the requirement that comparative clinical studies should reveal an effect size that outweighs the combined effect of plausible confounders. In the next three chapters I evaluate the claims that double blinding (Chapter 6) and placebo controls (Chapters 7 and 8) enhance the quality of comparative clinical studies. I then examine the EBM position on mechanistic reasoning and expert judgment (Chapters 9–11). I argue that mechanistic reasoning, while beleaguered with often unrecognized problems, should be admitted as evidence, perhaps alongside evidence from comparative clinical studies. Meanwhile, I defend the EBM view that expert judgment is not reliable as evidence, but that expertise plays several other important roles that deserve more serious discussion in the EBM literature. My conclusion (Chapter 12) is that strict hierarchies should be replaced by the requirement that all evidence of sufficiently high quality should be admitted as evidential support, and that the various non-evidential roles of expertise deserve more discussion in the EBM literature.

PART I

Introduction

CHAPTER 1

The philosophy of evidence-based medicine

This is a thorough analysis of the justification for using evidence-based medicine (EBM) methodology. Why should we believe that EBM methods provide more reliable knowledge than other methods? While many have criticized various aspects of EBM, the system as a whole has, with a few notable exceptions [4,5], escaped careful scrutiny. One can, of course, raise critical questions about the foundations of EBM without denying its value [1]. And, in fact, my overall conclusions are mostly sympathetic with the EBM position and a central aim of this book is to clarify misunderstandings of what EBM actually involves. Much work in the philosophy of science is relevant to this analysis, including the logic of scientific discovery, the problem of underdetermination, the nature of causal inference and above all the logic of evidence (confirmation theory). Philosophers who are interested in how these central issues in the philosophy of science apply to contemporary medical science should find new and relevant material here. At the same time, medical professionals who would like to examine the underlying reasons why they should (or should not!) use EBM methods to determine whether the treatments they prescribe “work” will find this analysis useful.

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