How to Read a Paper

The Basics of Evidence-based Medicine and Healthcare

Trisha Greenhalgh

• Publisher: Wiley-Blackwell
• Year: 2019
• ISBN:
  9781119484721
• Edition: 6
• Topic: Medicina
• Subtopic: Teoria, pratica e riferimenti medici

Required reading in many medical and healthcare institutions, How to Read a Paper is a clear and wide-ranging introduction to evidence-based medicine and healthcare, helping readers to understand its central principles, critically evaluate published data, and implement the results in practical settings. Author Trisha Greenhalgh guides readers through each fundamental step of inquiry, from searching the literature to assessing methodological quality and appraising statistics.

How to Read a Paper addresses the common criticisms of evidence-based healthcare, dispelling many of its myths and misconceptions, while providing a pragmatic framework for testing the validity of healthcare literature. Now in its sixth edition, this informative text includes new and expanded discussions of study bias, political interference in published reports, medical statistics, big data and more.

• Offers user-friendly guidance on evidence-based healthcare that is applicable to both experienced and novice readers
• Authored by an internationally recognised practitioner and researcher in evidence-based healthcare and primary care
• Includes updated references, additional figures, improved checklists and more

How to Read a Paper is an ideal resource for healthcare students, practitioners and anyone seeking an accessible introduction to evidence-based healthcare.

Chapter 1
Why read papers at all?

Does ‘evidence‐based medicine’ simply mean ‘reading papers in medical journals’?

Evidence‐based medicine (EBM), which is part of the broader field of evidence‐based healthcare (EBHC), is much more than just reading papers. According to what is still (more than 20 years after it was written) the most widely quoted definition, it is ‘the conscientious, explicit and judicious use of current best evidence in making decisions about the care of individual patients’ [1]. I find this definition very useful but it misses out what for me is a very important aspect of the subject – and that is the use of mathematics. Even if you know almost nothing about EBHC, you probably know it talks a lot about numbers and ratios! Anna Donald and I decided to be upfront about this in our own teaching, and proposed this alternative definition:

Evidence‐based medicine is the use of mathematical estimates of the risk of benefit and harm, derived from high‐quality research on population samples, to inform clinical decision‐making in the diagnosis, investigation or management of individual patients.

The defining feature of EBHC, then, is the use of figures derived from research on populations to inform decisions about individuals. This, of course, begs the question ‘What is research?’ – for which a reasonably accurate answer might be ‘Focused, systematic enquiry aimed at generating new knowledge.’ In later chapters, I explain how this definition can help you distinguish genuine research (which should inform your practice) from the poor‐quality endeavours of well‐meaning amateurs (which you should politely ignore).

If you follow an evidence‐based approach to clinical decision‐making, therefore, all sorts of issues relating to your patients (or, if you work in public health medicine, issues relating to groups of people) will prompt you to ask questions about scientific evidence, seek answers to those questions in a systematic way and alter your practice accordingly.

You might ask questions, for example, about a patient’s symptoms (‘In a 34‐year‐old man with left‐sided chest pain, what is the probability that there is a serious heart problem, and, if there is, will it show up on a resting ECG?’), about physical or diagnostic signs (‘In an otherwise uncomplicated labour, does the presence of meconium [indicating fetal bowel movement] in the amniotic fluid indicate significant deterioration in the physiological state of the fetus?’), about the prognosis of an illness (‘If a previously well 2‐year‐old has a short fit associated with a high temperature, what is the chance that she will subsequently develop epilepsy?’), about therapy (‘In patients with an acute coronary syndrome [heart attack], are the risks associated with thrombolytic drugs [clot busters] outweighed by the benefits, whatever the patient’s age, sex and ethnic origin?’), about cost‐effectiveness (‘Is the cost of this new anti‐cancer drug justified, compared with other ways of spending limited healthcare resources?’), about patients’ preferences (‘In an 87‐year‐old woman with intermittent atrial fibrillation and a recent transient ischaemic attack, do the potential harms and inconvenience of warfarin therapy outweigh the risks of not taking it?’) and about a host of other aspects of health and health services.

David Sackett, in the opening editorial of the very first issue of the journal Evidence‐Based Medicine, summarised the essential steps in the emerging science of EBM [2]:

1. To convert our information needs into answerable questions (i.e. to formulate the problem);
2. To track down, with maximum efficiency, the best evidence with which to answer these questions – which may come from the clinical examination, the diagnostic laboratory, the published literature or other sources;
3. To appraise the evidence critically (i.e. weigh it up) to assess its validity (closeness to the truth) and usefulness (clinical applicability);
4. To implement the results of this appraisal in our clinical practice;
5. To evaluate our performance.

Hence, EBHC requires you not only to read papers, but to read the right papers at the right time and then to alter your behaviour (and, what is often more difficult, influence the behaviour of other people) in the light of what you have found. I am concerned that how‐to‐do‐it courses in EBHC too often concentrate on the third of these five steps (critical appraisal) to the exclusion of all the others. Yet if you have asked the wrong question or sought answers from the wrong sources, you might as well not read any papers at all. Equally, all your training in search techniques and critical appraisal will go to waste if you do not put at least as much effort into implementing valid evidence and measuring progress towards your goals as you do into reading the paper. A few years ago, I added three more stages to Sackett’s five‐stage model to incorporate the patient’s perspective: the resulting eight stages, which I have called a context‐sensitive checklist for evidence‐based practice, are shown in Appendix 1.

If I were to be pedantic about the title of this book, these broader aspects of EBHC should not even get a mention here. But I hope you would have demanded your money back if I had omitted the final section of this chapter (‘Before you start: formulate the problem’), Chapter 2 (Searching the literature) and Chapter 16 (Applying evidence with patients). Chapters 3–15 describe step three of the EBHC process: critical appraisal – that is, what you should do when you actually have the paper in front of you. Chapter 16 deals with common criticisms of EBHC. I have written a separate book on the challenges of implementation, How to Implement Evidence‐Based Healthcare [3].

Incidentally, if you are computer literate and want to explore the subject of EBHC on the Internet, you could try the websites listed in Box 1.1. If you’re not, don’t worry at this stage, but do put learning/use web‐based resources to on your to‐do list. Don’t worry either when you discover that there are over 1000 websites dedicated to EBM and EBHC – they all offer very similar material and you certainly don’t need to visit them all.

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Box 1.1 Web‐based resources for evidence‐based medicine

Oxford Centre for Evidence‐Based Medicine: A well‐kept website from Oxford, UK, containing a wealth of resources and links for EBM. www.cebm.net

National Institute for Health and Care Excellence: This UK‐based website, which is also popular outside the UK, links to evidence‐based guidelines and topic reviews. www.nice.org.uk

National Health Service (NHS) Centre for Reviews and Dissemination: The site for downloading the high‐quality evidence‐based reviews is part of the UK National Institute for Health Research – a good starting point for looking for evidence on complex policy questions such as ‘what should we do about obesity?’ https://www.york.ac.uk/inst/crd/

BMJ Best Practice: An online handbook of best evidence for clinical decisions such as ‘what’s the best current treatment for atrial fibrillation?’ Produced by BMJ Publishing Group. https://bestpractice.bmj.com/info/evidence‐information

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Why do people sometimes groan when you mention evidence‐based healthcare?

Critics of EBHC might define it as ‘the tendency of a group of young, confident and highly numerate medical academics to belittle the performance of experienced clinicians using a combination of epidemiological jargon and statistical sleight‐of‐hand’ or ‘the argument, usually presented with near‐evangelistic zeal, that no health‐related action should ever be taken by a doctor, a nurse, a purchaser of health services or a policymaker, unless and until the results of several large and expensive research trials have appeared in print and approved by a committee of experts’.

The resentment amongst some health professionals to...