How to Read a Paper

TRISHA GREENHALGH, OBE, FMedSci is Professor of Primary Care Health Sciences, Nuffield Department of Primary Care Health Sciences, Medical Sciences Division, University of Oxford, UK.

Foreword to the first edition by Professor Sir David Weatherall xii

Preface to the sixth edition xiv

Preface to the first edition xvi

Acknowledgements xviii

Chapter 1 Why read papers at all? 1

Does ‘evidence‐based medicine’ simply mean ‘reading papers in medical journals’? 1

Why do people sometimes groan when you mention evidence‐based healthcare? 4

Before you start: formulate the problem 11

Exercises based on this chapter 13

References 14

Chapter 2 Searching the literature 16

What are you looking for? 17

Levels upon levels of evidence 18

Synthesised sources: systems, summaries and syntheses 19

Pre‐appraised sources: synopses of systematic reviews and primary studies 22

Specialised resources 23

Primary studies – tackling the jungle 23

One‐stop shopping: federated search engines 25

Asking for help and asking around 26

Online tutorials for effective searching 26

Exercises based on this chapter 27

References 27

Chapter 3 Getting your bearings: what is this paper about? 29

The science of ‘trashing’ papers 29

Three preliminary questions to get your bearings 31

Randomised controlled trials 35

Cohort studies 38

Case–control studies 40

Cross‐sectional surveys 41

Case reports 41

The traditional hierarchy of evidence 42

Exercises based on this chapter 43

References 43

Chapter 4 Assessing methodological quality 45

Was the study original? 45

Whom is the study about? 46

Was the design of the study sensible? 47

Was bias avoided or minimised? 49

Was assessment ‘blind’? 53

Were preliminary statistical questions addressed? 54

A note on ethical considerations 57

Summing up 58

Exercises based on this chapter 59

References 60

Chapter 5 Statistics for the non‐statistician 62

How can non‐statisticians evaluate statistical tests? 62

Have the authors set the scene correctly? 64

Paired data, tails and outliers 69

Correlation, regression and causation 71

Probability and confidence 73

The bottom line 75

Summary 77

Exercises based on this chapter 77

References 78

Chapter 6 Papers that report trials of drug treatments and other simple interventions 79

‘Evidence’ and marketing 79

Making decisions about therapy 82

Surrogate endpoints 82

What information to expect in a paper describing a randomised controlled trial: the CONSORT statement 86

Getting worthwhile evidence from pharmaceutical representatives 86

Exercises based on this chapter 89

References 89

Chapter 7 Papers that report trials of complex interventions 92

Complex interventions 92

Ten questions to ask about a paper describing a complex intervention 94

Exercises based on this chapter 99

References 100

Chapter 8 Papers that report diagnostic or screening tests 101

Ten men in the dock 101

Validating diagnostic tests against a gold standard 102

Ten questions to ask about a paper that claims to validate a diagnostic or screening test 107

Likelihood ratios 111

Clinical prediction rules 113

Exercises based on this chapter 114

References 115

Chapter 9 Papers that summarise other papers (systematic reviews and meta‐analyses) 117

When is a review systematic? 117

Evaluating systematic reviews 120

Meta‐analysis for the non‐statistician 125

Explaining heterogeneity 130

New approaches to systematic review 132

Exercises based on this chapter 133

References 133

Chapter 10 Papers that tell you what to do (guidelines) 137

The great guidelines debate 137

Ten questions to ask about a clinical guideline 141

Exercises based on this chapter 147

References 148

Chapter 11 Papers that tell you what things cost (economic analyses) 150

What is economic analysis? 150

Measuring the costs and benefits of health interventions 152

A note on ‘Choosing Wisely’ 157

Ten questions to ask about an economic analysis 157

Conclusions 162

Exercises based on this chapter 162

References 162

Chapter 12 Papers that go beyond numbers (qualitative research) 165

What is qualitative research? 165

Ten questions to ask about a qualitative research paper 169

Conclusions 176

Exercises based on this chapter 176

References 177

Chapter 13 Papers that report questionnaire research 179

The rise and rise of questionnaire research 179

Ten questions to ask about a paper describing a questionnaire study 180

Conclusions 188

Exercises based on this chapter 189

References 189

Chapter 14 Papers that report quality improvement case studies 191

What are quality improvement studies, and how should we research them? 191

Ten questions to ask about a paper describing a quality improvement initiative 193

Conclusions 200

Exercises based on this chapter 200

References 201

Chapter 15 Papers that describe genetic association studies 203

The three eras of human genetic studies (so far) 203

What is a genome‐wide association study (GWAS)? 204

Clinical applications of GWAS 207

Direct‐to‐consumer genetic testing 209

Mendelian randomisation studies 210

Epigenetics – a space to watch 211

Ten questions to ask about a genetic association study 212

Conclusions 216

Exercises based on this chapter 216

References 216

Chapter 16 Applying evidence with patients 219

The patient perspective 219

Patient‐reported outcome measures (PROMs) 221

Shared decision‐making 222

Option grids 223

N of 1 trials and other individualised approaches 227

Exercises based on this chapter 228

References 229

Chapter 17 Criticisms of evidence‐based healthcare 232

What’s wrong with EBHC when it’s done badly? 232

What’s wrong with EBHC when it’s done well? 235

Why is ‘evidence‐based policymaking’ so hard to achieve? 238

Exercises based on this chapter 239

References 240

Appendix 1 Checklists for finding, appraising and implementing evidence 242

Appendix 2 Assessing the effects of an intervention 252

Index 253