Table of Contents. Preface to the third edition xiii. Preface to the second edition xv. Preface to the fi rst edition xvii. List of abbreviations xix

Transcription

1 Table of Contents Preface to the third edition xiii Preface to the second edition xv Preface to the fi rst edition xvii List of abbreviations xix PART 1 Developing and Validating Instruments for Assessing Quality of Life and Patient- Reported Outcomes 1 Introduction Patient ]reported outcomes What is a patient ]reported outcome? What is quality of life? Historical development Why measure quality of life? Which clinical trials should assess QoL? How to measure quality of life Instruments Computer ]adaptive instruments Conclusions 32 2 Principles of measurement scales Introduction 35

2 2.2 Scales and items Constructs and latent variables Single global questions versus multi ]item scales Single ]item versus multi ]item scales Effect indicators and causal indicators Psychometrics, factor analysis and item response theory Psychometric versus clinimetric scales Suffi cient causes, necessary causes and scoring items Discriminative, evaluative and predictive instruments Measuring quality of life: refl ective, causal and composite indicators? Further reading Conclusions 56 3 Developing a questionnaire Introduction General issues Defining the target population Phases of development Phase 1: Generation of issues Qualitative methods Sample sizes 66

3 3.8 Phase 2: Developing items Multi ]item scales Wording of questions Face and content validity of the proposed questionnaire Phase 3: Pre ]testing the questionnaire Cognitive interviewing Translation Phase 4: Field ]testing Conclusions Further reading 87 4 Scores and measurements: validity, reliability, sensitivity Introduction Content validity Criterion validity Construct validity Repeated assessments and change over time Reliability Sensitivity and responsiveness Conclusions Further reading 124

4 5 Multi ]item scales Introduction Significance tests Correlations Construct validity Cronbach s α and internal consistency Validation or alteration? Implications for formative or causal items Conclusions Factor analysis and structural equation modelling Introduction Correlation patterns Path diagrams Factor analysis Factor analysis of the HADS questionnaire Uses of factor analysis Applying factor analysis: Choices and decisions Assumptions for factor analysis Factor analysis in QoL research Limitations of correlation-based analysis 172

5 6.11 Formative or causal models Confirmatory factor analysis and structural equation modelling Chi-square goodness-of-fit test Approximate goodness-of-fit indices Comparative fit of models Difficulty-factors Bifactor analysis Do formative or causal relationships matter? Conclusions Further reading, and software Item response theory and differential item functioning Introduction Item characteristic curves Logistic models Polytomous item response theory models Applying logistic IRT models Assumptions of IRT models Fitting item response theory models: Tips Test design and validation IRT versus traditional and Guttman scales 209

6 7.10 Differential item functioning Sample size for DIF analyses Quantifying differential item functioning Exploring differential item functioning: Tips Conclusions Further reading, and software Item banks, item linking and computer-adaptive tests Introduction Item bank Item evaluation, reduction and calibration Item linking and test equating Test information Computer-adaptive testing Stopping rules and simulations Computer-adaptive testing software CATs for PROs Computer-assisted tests Short-form tests Conclusions Further reading 240

7 PART 2 Assessing, Analysing and Reporting Patient-Reported Outcomes and the Quality of Life of Patients 9 Choosing and scoring questionnaires Introduction Finding instruments Generic versus specific Content and presentation Choice of instrument Scoring multi-item scales Conclusions Further reading Clinical trials Introduction Basic design issues Compliance Administering a quality ]of ]life assessment Recommendations for writing protocols Standard operating procedures Summary and checklist Further reading Sample sizes 283

8 11.1 Introduction Signifi cance tests, p ]values and power Estimating sample size Comparing two groups Comparison with a reference population Non ]inferiority studies Choice of sample size method Non ]Normal distributions Multiple testing Specifying the target difference Sample size estimation is pre ]study Attrition Circumspection Conclusion Further reading Cross ]sectional analysis Types of data Comparing two groups Adjusting for covariates Changes from baseline 330

9 12.5 Analysis of variance Analysis of variance models Graphical summaries Endpoints Conclusions Exploring longitudinal data Area under the curve Graphical presentations Tabular presentations Reporting Conclusions Modelling longitudinal data Preliminaries Auto-correlation Repeated measures Other situations Modelling versus area under the curve Conclusions Missing data Introduction 393

10 15.2 Why do missing data matter? Types of missing data Missing items Methods for missing items within a form Missing forms Methods for missing forms Simple methods for missing forms Methods of imputation that incorporate variability Multiple imputation Pattern mixture models Comments Degrees of freedom Sensitivity analysis Conclusions Further reading Practical and reporting issues Introduction The reporting of design issues Data analysis Elements of good graphics 436

11 16.5 Some errors Guidelines for reporting Further reading Death, and quality-adjusted survival Introduction Attrition due to death Preferences and utilities Multi-attribute utility (MAU) measures Utility-based instruments Quality-adjusted life years (QALYs) Utilities for traditional instruments Q-TWiST Sensitivity analysis Prognosis and variation with time Alternatives to QALY Conclusions Further reading Clinical interpretation Introduction Statistical signifi cance 476

12 18.3 Absolute levels and changes over time Threshold values: percentages Population norms Minimal important difference Anchoring against other measurements Minimum detectable change Expert judgement for evidence-based guidelines Impact of the state of quality of life Changes in relation to life events Effect size statistics Patient variability Number needed to treat Conclusions Further reading Biased reporting and response shift Bias Recall bias Selective reporting bias Other biases affecting PROs Response shift 516

13 19.6 Assessing response shift Impact of response shift Clinical trials Non ]randomised studies Conclusions Meta ]analysis Introduction Defining objectives Defining outcomes Literature searching Assessing quality Summarising results Measures of treatment effect Combining studies Forest plot Heterogeneity Publication bias and funnel plots Conclusions Further reading 546 Appendix 1: Examples of instruments 547

14 Generic instruments E1 Sickness Impact Profi le (SIP) 549 E2 Nottingham Health Profi le (NHP) 551 E3 SF36v2TM Health Survey Standard Version 552 E4 EuroQoL EQ-5D-5L 555 E5 Patient Generated Index of quality of life (PGI) 557 Disease-specific instruments 559 E6 European Organisation for Research and Treatment of Cancer QLQ-C30 (EORTC QLQ-C30) 559 E7 Elderly cancer patients module (EORTC QLQ-ELD14) 561 E8 Functional Assessment of Cancer Therapy General (FACT-G) 562 E9 Rotterdam Symptom Checklist (RSCL) 564 E10 Quality of Life in Epilepsy Inventory (QOLIE-89) 566 E11 Paediatric Asthma Quality of Life Questionnaire (PAQLQ) 570 Domain-specifi c instruments 573 E12 Hospital Anxiety and Depression Scale (HADS) 573 E13 Short-Form McGill Pain Questionnaire (SF-MPQ) 574 E14 Multidimensional Fatigue Inventory (MFI-20) 575 ADL and disability 577 E 15 (Modifi ed) Barthel Index of Disability (MBI) 577 Appendix 2: Statistical tables 579

15 Table T1: Normal distribution 579 Table T2: Probability points of the Normal distribution 581 Table T3: Student s t ]distribution 582 Table T4: The χ2 distribution 583 Table T5: The F ]distribution 584 References 585 Index 613