The Pocket Guide to Critical Appraisal

This second edition of the popular guide to critical appraisal is a fully updated revision of the previous edition. Written in the same easily accessible style, The Pocket Guide to Critical Appraisal now provides annotated checklists of the most common research designs. Consistent with recent developments in evidence-based medicine, these checklists distinguish between the risk of bias in the conduct of published studies and the value of the findings for healthcare delivery.

Five new chapters have been added and the original chapters have been rewritten, making the new edition a complete and concise guide for the evaluation of research quality. In addition to the checklists, the book also:

• describes how to quickly identify the information needed for the critical appraisal
• provides simple explanations of statistical significance and the interpretation of confidence intervals
• reviews the major sources of bias and their impact on research findings
• explains how to summarise the risk of bias
• outlines the concept of certainty of evidence and how to calculate it
• identifies the challenges in assessing the value of research findings

The Pocket Guide to Critical Appraisal is an essential guide for all health professions and students who read research papers and use their findings.

Iain K. Crombie is Emeritus Professor of Public Health at Dundee University, UK. He has published more than 160 research papers as well as books on critical appraisal, research methods, grant applications, and clinical audits. He has extensive experience teaching both undergraduate and postgraduate courses in epidemiology, medical statistics, and research methods.

Acknowledgements ix

Preface to the First Edition xi

Preface to the Second Edition xiii

Chapter 1 Introduction to Critical Appraisal 1

The aims of critical appraisal 1

Three stages of critical appraisal 2

Chapter 2 Do Not Read the Paper 4

The initial interrogation 5

The in-depth interrogation 6

Chapter 3 Identifying the Research Design 7

Surveys 7

Cohort studies 9

Case–control studies 10

RCTs 11

Cohort studies that evaluate the effectiveness of interventions 12

Systematic reviews 14

Chapter 4 Interpreting the Results 16

The effect size 17

Taking the play of chance into account 19

Factors that distort the effect size 22

Questionable research practices 24

Conclusion 25

Chapter 5 The In-Depth Interrogation 26

Bias 26

Critical questions for bias 27

Important questions for bias 27

Indicative questions for bias 33

Questions about value 36

Conclusion 39

Chapter 6 Appraising Surveys 40

The critical bias questions for bias 40

The complete list for appraising surveys* 43

Chapter 7 Appraising Cohort Studies 45

The critical questions for bias 45

The important questions for bias 49

The indicative questions for risk of bias 50

The complete list for the appraisal of cohort studies* 51

Chapter 8 Appraising Case–Control Studies 53

The critical questions for bias 53

The important questions for bias 55

The complete list for the appraisal of case–control studies* 58

Chapter 9 Appraising Randomised Controlled Trials 60

The critical questions for bias 60

The important questions for bias 64

The questions of value 67

The complete list for the appraisal of clinical trials* 68

Chapter 10 Cohort Studies That Evaluate the Effectiveness of Interventions 70

Overview of advantages of cohort treatment studies and challenges for critical appraisal 71

The critical questions for bias 72

The important questions for bias 76

The questions of value 78

Conclusion 78

The complete list for the appraisal of cohort studies that evaluate interventions 79

Chapter 11 Appraising Systematic Reviews 81

The critical questions for risk of bias 81

The important questions for risk of bias 86

The questions of value 88

The complete list for the appraisal of systematic reviews* 89

Chapter 12 Summarising Risk of Bias 91

Identify the risk of bias of the research designs 91

Review the biases in study design, conduct, and interpretation 92

Derive an overall rating 93

Summary 95

Chapter 13 Certainty of Evidence 96

The nature of certainty of evidence 96

Downgrading the certainty of evidence 97

Factors that increase certainty 100

Overall assessment of certainty 102

Conclusion 103

Chapter 14 Assessing Value 104

Measuring potential benefit 105

Harm and the balance between benefit and harm 106

Costs and cost effectiveness 107

Feasibility of implementation of a treatment 109

Health equity 109

Summary 111

Appendix: Further Reading 113

Index 131 

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