Carl Heneghan and Douglas Badenoch
Centre for Evidence-based Medicine, Nuffield Department of Clinical Medicine, John Radcliffe Hospital, Headington, Oxford
© BMJ Books 2002 BMJ Books is an imprint of the BMJ Publishing Group All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording and/or otherwise, without the prior written permission of the publishers. First published in 2002 by BMJ Books, BMA House, Tavistock Square, London WC1H 9JR www.bmjbooks.com British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library ISBN 0 7279 1601 7 Typeset by Newgen Imaging Systems Pvt. Ltd. Printed and bound in Spain by GraphyCems, Navarra
Introduction Asking answerable questions Finding the evidence Appraising therapy articles Appraising diagnosis articles Appraising systematic reviews Appraising articles on harm/aetiology Appraising prognosis studies Applying the evidence Evidence-based medicine: glossary of terms Selected evidence-based healthcare resources on the web Levels of evidence and grades of recommendations Study designs Critically appraised topics (CATs) Index 1 2 5 11 18 25 29 33 37 43 49 50 55 57 62
This handbook was compiled by Carl Heneghan and Douglas Badenoch. The materials have largely been adapted from previous work by those who know better than us, especially other members of the Centre for Evidence-based Medicine (Chris Ball, Martin Dawes, Jonathan Mant, Bob Phillips, David Sackett, Kate Seers, Sharon Straus) and CASPfew (Steve Ashwell, Anne Brice, Andre Tomlin).
This “toolkit” is designed as a summary and reminder of the key elements of practising evidence-based medicine (EBM). It has largely been adapted from resources developed at the Centre for Evidence-based Medicine. For more detailed coverage, you should refer to the other EBM texts and web pages cited throughout. The first page of each chapter presents a “minimalist” checklist of the key points. Further sections within each chapter address these points in more detail and give additional background information. Ideally, you should just need to refer to the first page to get the basics, and delve into the further sections as required. Occasionally, you will see the dustbin icon on the right. This means that the question being discussed is a “filter” question for critical appraisal: if the answer is not satisfactory, you should consider ditching the paper and looking elsewhere. If you don’t ditch the paper, you should be aware that the effect it describes may not appear in your patient in the same way.
Definition of Evidence-based Medicine
Evidence-based Medicine is the “conscientious, explicit and judicious use of current best evidence in making decisions about individual patients”. This means “integrating individual clinical expertise with the best available external clinical evidence from systematic research”.1 We can summarise the EBM approach as a five-step model: 1. 2. 3. 4. Asking answerable clinical questions. Searching for the evidence. Critically appraising the evidence for its validity and relevance. Making a decision, by integrating the evidence with your clinical expertise and the patient’s values. 5. Evaluating your performance.
1. Sackett DL et al. Evidence based medicine: what it is and what it isn’t. BMJ 1996;312:71–2.
Asking answerable questions
The four main elements of a well-formed clinical question are: 1. 2. 3. 4. Patient or Problem Intervention Comparison intervention (if appropriate) Outcome(s)
Patient or Problem
Tips Starting with your patient ask “How would I describe a group of patients similar to mine?” Ask “Which main intervention am I considering?”
Specific example “In women over 40 with heart failure from dilated...