Diagnostic Tests Toolkit

Ann Van den Bruel, Department of Primary Care Health Sciences, University of Oxford, UK

Series Editors:
Carl Heneghan, Centre for Evidence Based Medicine, Oxford, UK

Rafael Perera, Department of Primary Care, University of Oxford, UK

Douglas Badenoch, Minervation Ltd, Edinburgh, UK

Introduction, ix

Chapter 1 Diagnosis in evidence-based medicine, 1

Diagnosis and screening, 1

Screening, 3

Symptoms, 3

Signs and elicited symptoms, 4

Bedside or point-of-care testing, 4

Laboratory tests, 4

Basic structure of studies of diagnostic tests, 4

Further reading, 5

Chapter 2 Evaluating new diagnostic tests, 6

Technical accuracy (‘Can it work?’), 7

Place in the clinical pathway (‘Where does the test fi t in the existing clinical pathway?’), 9

Ability of the test to diagnose or exclude the target condition (‘Does it work in patients?’), 10

The effect of the test on patient outcomes (‘Are patients better off?’), 12

Cost-effectiveness (‘Is it worth the cost?’), 14

Further reading, 15

Chapter 3 Asking an answerable clinical question, 16

Defining a clinical question for diagnostic tests – PIRT, 16

Further reading, 17

Chapter 4 Finding the evidence: how to get the most from your searching, 18

Combine textwords and thesaurus, 20

Search filters for diagnostic accuracy studies, 20

Further reading, 21

Chapter 5 Selecting relevant studies, 22

Selecting relevant studies, 22

Assessing validity, 23

What is the difference between bias and variability in diagnostic studies?, 23

The ‘ideal’ diagnostic study, 24

Flow charts of patients, 24

Chapter 6 Sources of bias in diagnostic studies, 26

Spectrum bias (also known as selection bias), 26

Verification bias (also called referral or work-up bias), 28

Incorporation bias, 29

Observer (or test review bias) bias, 30

Differential reference bias (double gold standard), 31

What are the effects of the different design-related biases?, 32

Further reading, 33

Chapter 7 Measures of discrimination of diagnostic tests, 34

Two by two tables, 34

Outcome measures, 36

Which measure should you use and why?, 38

The effect of prevalence on predictive values, 40

Effect of time on diagnostic accuracy, 41

Effect of severity of the target condition on diagnostic accuracy, 42

The referral fi lter, 42

Rules of thumb for interpreting likelihood ratios, 44

Further reading, 52

Chapter 8 Using diagnostic information in clinical practice, 53

Validity of data, 54

Problem-solving strategies that clinicians use in diagnosis, 55

Action thresholds versus testing thresholds (‘Will the test change my management?’), 57

Methods for combining test results, 58

Multivariable analyses, 60

How are clinical prediction rules developed?, 62

How to select a prediction rule for clinical practice, 64

Further reading, 65

Chapter 9 Screening tests, 66

What are screening tests?, 66

Different types of screening, 66

Ideal study design for screening tests, 68

Over-diagnosis, 74

Further reading, 74

Chapter 10 Systematic reviews of diagnostic test  accuracy studies, 75

The research question, 75

The literature search, 76

Assess the quality of individual studies included in the review, 79

Summarizing the results of diagnostic studies, 80

Combining data and interpreting meta-analyses of diagnostic studies, 85

Acknowledgements, 88

Further reading, 88

Appendix 1 Evidence-based medicine – a glossary of terms, 90

Appendix 2 Further reading, 96

Books, 96

Useful websites, 96

Useful journal articles, 96

Index, 98

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