Quality of Life. The assessment, analysis and reporting of patient-reported outcomes. Third Edition

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1 Quality of Life The assessment, analysis and reporting of patient-reported outcomes Third Edition PETER M. FAYERS Institute of Applied Health Sciences, University ofaberdeen School of Medicine and Dentistry, Scotland, UK and Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology (NTNU), Trondheim, Norway and DAVID MACHIN Medical Statistics Group, School of Health and Related Research, University of Sheffield, Sheffield, UK and Department of Cancer Studies and Molecular Medicine, University of Leicester, Leicester, UK WlLEY Blackwell

2 Contents Preface to the third edition Preface to the second edition Preface to the first edition List of abbreviations xiii xv xvii 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 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 dinimetric scales Sufficient causes, necessary causes and scoring items Discriminative, evaluative and predictive instruments Measuring quality of life: reflective, causal and composite indicators? Further reading Conclusions 56

3 vi 3 Developing a questionnaire Introduction General issues Defining the target population Phases of development Phase 1: Generation of issues Qualitative methods Sample sizes 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 Multi-item scales Introduction Significance tests Correlations Construct validity Cronbach's a and internal consistency Validation or alte ratio n? Implications for formative or causal items Conclusions Factor analysis and structural equation modelling Introduction Correlation patterns Path diagrams Factor analysis 154

4 vi: 6.5 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 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 Eitting item response theory models: Tips Test design and Validation IRT versus traditional and Guttman scales Differential item functioning Sample size for DIE 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 238

5 viii 8.11 Short-form tests Conclusions Further reading 240 PART 2 Assessing, Analystng 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 Introduction Significance 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 307

6 ix 12 Cross-sectional analysis Types of data Comparing two groups Adjusting for covariates Changes from baseline 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 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 427

7 X 16 Practica! and reporting issues Introduction The reporting of design issues Data analysis Elements of good graphics 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 MST Sensitivity analysis Prognosis and Variation with time Alternatives to QALY Conclusions Further reading Clinical interpretation Introduction Statistical significance 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 5Ü 19.2 Recall bias 512

8 xi 19.3 Selective reporting bias Other biases affecting PROs Response shift 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 instrumenta 547 Generic instruments El Sickness Im pact Profile (SIP) 549 E2 Nottingham Health Profile (NHP) 551 E3 SF36v2 Health Survey Standard Version 552 E4 EuroQoL EQ-5D-5L 555 E5 Patient Generated Index of quality of life (PGI) 557 Disease-sperific instruments 559 E6 European Organisation for Research and Treatment of Cancer QLQ-C30 (E0RTC 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 Ell Paediatric Asthma Quality of Life Questionnaire (PAQLQ) 570 Domain-specific 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

9 xii ADL and disability 577 E 15 (Modified) BartheL Index of Disability (MBI) 577 Appendix 2: Statistical tables 579 Table Tl: Normal distribution 579 Table T2: Probability points of the Normal distribution 581 Table T3: Student's f-distribution 582 Table T4: The distribution 583 Table T5: The F-distribution 584 References 585 Index 613

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

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 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