Quality of Life: Assessment, Analysis, and Interpretation

by Peter Fayers (Medical Research Council Clinical Trials Unit, London, UK<); David Machin (School of Health and Related Research, University of Sheffield, UK)

• ISBN13: 9780471968610
• ISBN10: 0471968617
• Format: Hardcover
• Copyright: 2000-06-01
• Publisher: WILEY

Summary

'Winner of first prize in the Basis of Medicine Category of the BMA Medical Book Competition 2001'The One Essential Comprehensive Volume on Quality of Life Research. Quality of life studies are now an essential part of the evaluation of any treatment. Written by two authors who are well respected within this field, this book is the first volume to lay down guidelines on assessing, analysing and interpreting quality of life data.Quality of Life: Assessment, Analysis and Interpretation Covers development of questionnaires through to analysis of studies Includes practical examples Fills a need in a rapidly growing area of interest Has a clear structure and consistent approach to the material covered This book is aimed at everyone involved in quality of life and is applicable to medical and non-medical, statistical and non-statistical readers. It is of particular relevance for clinical and biomedical researchers within both the pharmaceutical industry and practitioners in the fields of cancer and other chronic diseases.

Table of Contents

Preface	xi
Acknowledgements	xi
Part A Introduction	1	(42)
Introduction	3	(25)
What is quality of life?	3	(2)
Historical development	5	(2)
Why measure quality of life?	7	(7)
Which clinical trials should assess QoL?	14	(1)
How to measure quality of life	15	(1)
Instruments	16	(11)
Conclusions	27	(1)
Principles of Measurement Scales	28	(15)
Introduction	28	(1)
Scales and items	28	(1)
Constructs and latent variables	29	(1)
Indicator variables and causal variables	30	(2)
Single global questions versus multi-item questionnaires	32	(2)
Single-item versus multi-item scales	34	(2)
Psychometrics and item response theory	36	(2)
Psychometric versus clinimetric scales	38	(1)
Sufficient causes and necessary causes	39	(1)
Discriminative, evaluative and predictive instruments	40	(1)
Measuring QoL: indicator or causal items	41	(1)
Conclusions	42	(1)
Part B Developing and Testing Questionnaires	43	(112)
Scores and Measurements: Validity, Reliability, Sensitivity	45	(27)
Introduction	45	(1)
Content validity	46	(2)
Criterion validity	48	(2)
Construct validity	50	(7)
Reliability	57	(9)
Sensitivity and responsiveness	66	(5)
Conclusions	71	(1)
Multi-item Scales	72	(19)
Introduction	72	(1)
Significance tests	73	(1)
Correlations	74	(4)
Construct validity	78	(7)
Cronbach's α and internal consistency	85	(2)
Implications for causal items	87	(2)
Conclusions	89	(2)
Factor Analysis	91	(26)
Introduction	91	(1)
Correlation patterns	91	(2)
Path diagrams	93	(1)
Factor analysis	94	(1)
Factor analysis of the HADS questionnaire	95	(4)
Uses of factor analysis	99	(2)
Applying factor analysis: choices and decisions	101	(5)
Assumptions for factor analysis	106	(4)
Factor analysis in QoL research	110	(2)
Causal models	112	(3)
Conclusions	115	(1)
Further reading	116	(1)
Item Response Theory and Differential Item Functioning	117	(18)
Introduction	117	(1)
Item characteristic curves	118	(2)
Logistic models	120	(6)
Fitting IRT models: tips	126	(1)
Test design	126	(1)
IRT versus traditional and Guttman scales	127	(1)
Other latent trait models	128	(1)
Differential item functioning	128	(4)
Adaptive testing	132	(2)
Conclusions	134	(1)
Questionnaire Development and Scoring	135	(20)
Introduction	135	(1)
General issues	135	(1)
Defining the target population	136	(1)
Item generation	136	(2)
Forming scales	138	(3)
Scoring multi-item scales	141	(2)
Wording of questions	143	(1)
Pre-testing the questionnaire	144	(2)
Strategies for validation	146	(1)
Translation	147	(1)
Field-testing	148	(4)
Conclusions	152	(3)
Part C Analysis of QoL Data	155	(112)
Cross-sectional Analysis	157	(26)
Types of data	157	(2)
Comparing two groups	159	(9)
Adjusting for covariates	168	(4)
Analysis of variance	172	(4)
ANOVA models	176	(2)
Graphical summaries	178	(4)
Endpoints	182	(1)
Conclusions	182	(1)
Exploring Longitudinal Data	183	(20)
Area under the curve	183	(2)
Graphical presentations	185	(11)
Tabular presentations	196	(2)
Reporting	198	(3)
Conclusions	201	(2)
Modelling Longitudinal Data	203	(21)
Preliminaries	203	(1)
Auto-correlation	204	(4)
Repeated measures	208	(13)
Other situations	221	(2)
Conclusions	223	(1)
Missing Data	224	(24)
Introduction	224	(2)
Types of missing data	226	(2)
Why do missing data matter?	228	(2)
Missing items	230	(2)
Methods for missing items within a form	232	(3)
Missing forms	235	(1)
Methods for missing forms	236	(9)
Comments	245	(1)
Conclusions	246	(2)
Quality-adjusted Survival	248	(19)
Introduction	248	(1)
Preferences and utilities	249	(2)
Multi-attribute utility measures	251	(1)
Utility-based instruments	252	(1)
Quality-adjusted life years (QALYs)	253	(2)
Q-TWiST	255	(4)
Sensitivity analysis	259	(2)
Prognosis and variation with time	261	(3)
Healthy-years equivalent (HYE)	264	(1)
Conclusions	264	(3)
Part D Practical Aspects and Clinical Interpretation	267	(80)
Clinical Trials	269	(20)
Introduction	269	(1)
Choice of instrument	270	(1)
Compliance	271	(4)
Administration of QoL assessment	275	(2)
Recommendations for writing protocols	277	(10)
Standard operating procedures	287	(1)
Summary and checklist	287	(2)
Sample Sizes	289	(18)
Introduction	289	(1)
Significance tests, p-values and power	289	(1)
Estimating sample size	290	(3)
Comparing two groups	293	(8)
Comparison with a reference population	301	(1)
Equivalence studies	302	(1)
Choice of sample size method	303	(2)
Multiple endpoints	305	(1)
Conclusions	306	(1)
Practical and Reporting Issues	307	(15)
Introduction	307	(1)
Design issues	307	(2)
Data analysis	309	(4)
Elements of good graphics	313	(2)
Some errors	315	(3)
Guidelines for reporting	318	(4)
Clinical Interpretation	322	(25)
Introduction	322	(1)
Statistical significance	323	(1)
Absolute levels and changes over time	324	(1)
Threshold values, percentages	325	(1)
Population norms	325	(9)
Minimal clinically important difference	334	(2)
Impact of state of quality of life	336	(1)
Changes in relation to life events	337	(1)
Effect size	338	(3)
Effect sizes and meta-analysis	341	(1)
Patient variability	341	(2)
Number needed to treat	343	(2)
Conclusions	345	(2)
Appendix Examples of Instruments	347	(2)
Generic Instruments	349	(9)
E1 Sickness Impact Profile (SIP)	349	(2)
E2 Nottingham Health Profile (NHP)	351	(1)
E3 Medical Outcomes Study 36-Item Short Form-36 (SF-36)	352	(3)
E4 EuroQoL (EQ-5D)	355	(2)
E5 Patient Generated Index (PGI)	357	(1)
Disease-specific Instruments	358	(14)
E6 European Organization for Research and Treatment of Cancer (EORTC QLQ-C30)	358	(2)
E7 EORTC Head and Neck Module (EORTC H&N35)	360	(2)
E8 Functional Assessment of Cancer---General version (FACT-G)	362	(2)
E9 Rotterdam Symptom Checklist (RSCL)	364	(2)
E10 Quality of Life in Epilepsy (QOLIE-89)	366	(4)
E11 Paediatric Asthma Quality of Life Questionnaire (PAQLQ)	370	(2)
Domain-specific Instruments	372	(4)
E12 Hospital Anxiety and Depression Scale (HADS)	372	(1)
E13 Short Form McGill Pain Questionnaire (SF-MPQ)	373	(1)
E14 Multidimensional Fatigue Inventory (MFI-20)	374	(2)
ADL and Disability	376	(1)
E15 Barthel Index of Disability (modified) (BI)	376	(1)
Statistical Tables	377	(8)
T1 Normal distribution	378	(2)
T2 Probability points of the Normal distribution	380	(1)
T3 The t-distribution	381	(1)
T4 The χ2 distribution	382	(1)
T5 The F-distribution	383	(2)
References	385	(10)
Index	395