Quality of life outcomes in clinical trials and health care evaluation: a practical guide to analysis and interpretation
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| Main Author: | |
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| Format: | Book |
| Language: | English |
| Published: |
Chichester
Wiley
2009
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| Series: | Statistics in practice
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| Online Access: | Inhaltsverzeichnis |
| Physical Description: | XII, 365 S. Ill., graph. Darst. |
| ISBN: | 047075382X 9780470753828 |
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Record in the Search Index
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| adam_text | Titel: Quality of life outcomes in clinical trials and health care evaluation
Autor: Walters, Stephen John
Jahr: 2009
Contents
Preface xi
1 Introduction 1
Summary 1
1.1 What is quality of life? 1
1.2 Terminology 2
1.3 History 2
1.4 Types of quality of life measures 4
1.5 Why measure quality of life? 10
1.6 Further reading 11
2 Measuring quality of life 13
Summary 13
2.1 Introduction 13
2.2 Principles of measurement scales 13
2.2.1 Scales and items 13
2.2.2 Constructs and latent variables 14
2.3 Indicator and causal variables 15
2.3.1 Indicator variables 15
2.3.2 Causal variables 15
2.3.3 Why do we need to worry about the distinction between
indicator and causal items? 16
2.3.4 Single-item versus multi-item scales 16
2.4 The traditional psychometric model 16
2.4.1 Psychometrics and QoL scales 17
2.5 Item response theory 17
2.5.1 Traditional scales versus IRT 18
2.6 Clinimetric scales 18
2.7 Measuring quality of life: Indicator or causal items 19
2.8 Developing and testing questionnaires 19
2.8.1 Specify the research question and define the target population 19
2.8.2 Identify concepts 20
CONTENTS
2.8.3 Create instrument 21
2.8.4 Assess measurement properties 26
2.8.5 Modify instrument 30
2.9 Further reading 30
Choosing a quality of life measure for your study 31
Summary 31
3.1 Introduction 31
3.2 How to choose between instruments 31
3.3 Appropriateness 33
3.4 Acceptability 33
3.5 Feasibility 34
3.6 Validity 35
3.6.1 Tests for criterion validity 35
3.6.2 Tests for face and content validity 36
3.6.3 Tests for construct validity 36
3.7 Reliability 38
3.7.1 Repeatability reliability 40
3.7.2 Graphical methods for assessing reliability between two
repeated measurements 40
3.7.3 Internal reliability or internal consistency reliability 42
3.8 Responsiveness 44
3.8.1 Floor and ceiling effects 44
3.9 Precision 49
3.10 Interpretability 51
3.11 Finding quality of life instruments 53
Design and sample size issues: How many subjects do I need
for my study? 55
Summary 55
4.1 Introduction 55
4.2 Significance tests, F-values and power 56
4.3 Sample sizes for comparison of two independent groups 58
4.3.1 Normally distributed continuous data - comparing two means 58
4.3.2 Transformations 61
4.3.3 Comparing two groups with continuous data using non-parametric
methods 61
4.3.4 Dichotomous categorical data - comparing two proportions 63
4.3.5 Ordered categorical (ordinal) data 66
4.4 Choice of sample size method with quality of life outcomes 69
4.5 Paired data 70
4.5.1 Paired continuous data - comparison of means 70
4.5.2 Paired binary data - comparison of proportions 72
4.6 Equivalence/non-inferiority studies 73
4.6.1 Continuous data - comparing the equivalence of two means 74
4.6.2 Binary data - comparing the equivalence of two proportions 75
4.7 Unknown standard deviation and effect size 75
CONTENTS vii
4.7.1 Tips on obtaining the standard deviation 76
4.8 Cluster randomized controlled trials 76
4.9 Non-response 77
4.10 Unequal groups 77
4.11 Multiple outcomes/endpoints 79
4.12 Three or more groups 80
4.13 What if we are doing a survey, not a clinical trial? 80
4.13.1 Sample sizes for surveys 80
4.13.2 Confidence intervals for estimating the mean QoL of a population 81
4.13.3 Confidence intervals for a proportion 82
4.14 Sample sizes for reliability and method comparison studies 85
4.15 Post-hoc sample size calculations 86
4.16 Conclusion: Usefulness of sample size calculations 86
4.17 Further reading 86
Reliability and method comparison studies for quality of life
measurements 91
Summary 91
5.1 Introduction 91
5.2 Intra-class correlation coefficient 92
5.2.1 Inappropriate method 94
5.3 Agreement between individual items on a quality of life questionnaire 95
5.3.1 Binary data: Proportion of agreement 95
5.3.2 Binary data: Kappa 95
5.3.3 Ordered categorical data: Weighted kappa 96
5.4 Internal consistency and Cronbach s alpha 98
5.5 Graphical methods for assessing reliability or agreement between two
quality of life measures or assessments 99
5.6 Further reading 102
5.7 Technical details 102
5.7.1 Calculation of ICC 102
5.7.2 Calculation of kappa 103
5.7.3 Calculation of weighted kappa 104
5.7.4 Calculation of Cronbach s alpha 104
Summarizing, tabulating and graphically displaying quality of life
outcomes 109
Summary 109
6.1 Introduction l09
6.2 Graphs 1°
6.2.1 Dot plots II2
6.2.2 Histograms 112
6.2.3 Box-and-whisker plot 114
6.2.4 Scatter plots 116
6.3 Describing and summarizing quality of life data 116
6.3.1 Measures of location U7
6.3.2 Measures of spread 19
CONTENTS
6.4 Presenting quality of life data and results in tables and graphs 122
6.4.1 Tables for summarizing QoL outcomes 122
6.4.2 Tables for multiple outcome measures 124
6.4.3 Tables and graphs for comparing two groups 126
6.4.4 Profile graphs 129
Cross-sectional analysis of quality of life outcomes 133
Summary 133
7.1 Introduction 133
7.2 Hypothesis testing (using P-values) 134
7.3 Estimation (using confidence intervals) 137
7.4 Choosing the statistical method 138
7.5 Comparison of two independent groups 138
7.5.1 Independent samples f-test for continuous outcome data 140
7.5.2 Mann-Whitney U-test 144
7.6 Comparing more than two groups 146
7.6.1 One-way analysis of variance 147
7.6.2 The Kruskal-Wallis test 150
7.7 Two groups of paired observations 150
7.7.1 Paired f-test 153
7.7.2 Wilcoxon test 157
7.8 The relationship between two continuous variables 157
7.9 Correlation 160
7.10 Regression 165
7.11 Multiple regression 168
7.12 Regression or correlation? 171
7.13 Parametric versus non-parametric methods 171
7.14 Technical details: Checking the assumptions for a linear regression
analysis 173
Randomized controlled trials 181
Summary 181
8.1 Introduction 181
8.2 Randomized controlled trials 182
8.3 Protocols 182
8.4 Pragmatic and explanatory trials 182
8.5 Intention-to-treat and per-protocol analyses 183
8.6 Patient flow diagram 186
8.7 Comparison of entry characteristics 186
8.8 Incomplete data 189
8.9 Main analysis 191
8.10 Interpretation of changes/differences in quality of life scores 196
8.11 Superiority and equivalence trials 197
8.12 Adjusting for other variables 199
8.13 Three methods of analysis for pre-test/post-test control group designs 202
8.14 Cross-over trials 203
8.15 Factorial trials 206
CONTENTS ix
8.16 Cluster randomized controlled trials 209
8.17 Further reading 210
9 Exploring and modelling longitudinal quality of life data 217
Summary 217
9.1 Introduction 217
9.2 Summarizing, tabulating and graphically displaying repeated QoL
assessments 218
9.3 Time-by-time analysis 222
9.4 Response feature analysis - the use of summary measures 223
9.4.1 Area under the curve 223
9.4.2 Acupuncture study - analysis of covariance 227
9.5 Modelling of longitudinal data 229
9.5.1 Autocorrelation 231
9.5.2 Repeated measures analysis of variance 232
9.5.3 Marginal general linear models - generalized estimating
equations 232
9.5.4 Random effects models 237
9.5.5 Random effects versus marginal modelling 239
9.5.6 Use of marginal and random effects models to analyse data
from a cluster RCT 241
9.6 Conclusions 243
10 Advanced methods for analysing quality of life outcomes 249
Summary 249
10.1 Introduction 249
10.2 Bootstrap methods 251
10.3 Bootstrap methods for confidence interval estimation 251
10.4 Ordinal regression 255
10.5 Comparing two independent groups: Ordinal quality of life measures
(with less than 7 categories) 257
10.6 Proportional odds or cumulative logit model 258
10.7 Continuation ratio model 259
10.8 Stereotype logistic model 260
10.9 Conclusions and further reading 264
11 Economic evaluations 265
Summary 265
11.1 Introduction 265
11.2 Economic evaluations 266
11.3 Utilities and QALYs 266
11.4 Economic evaluations alongside a controlled trial 267
11.5 Cost-effectiveness analysis 267
11.6 Cost-effectiveness ratios 268
11.7 Cost-utility analysis and cost-utility ratios 269
11.8 Incremental cost per QALY 270
x CONTENTS
11.9 The problem of negative (and positive) incremental
cost-effectiveness ratios 272
11.10 Cost-effectiveness acceptability curves 273
11.11 Further reading 275
12 Meta-analysis 277
Summary 277
12.1 Introduction 277
12.2 Planning a meta-analysis 278
12.2.1 Is a meta-analysis appropriate? 279
12.2.2 Combining the results of different studies 279
12.2.3 Choosing the appropriate statistical method 280
12.3 Statistical methods in meta-analysis 282
12.3.1 The choice of effect measure: What outcome measures
am I combining? 282
12.3.2 Model choice: fixed or random? 283
12.3.3 Homogeneity 285
12.3.4 Fixed effects model 285
12.3.5 Forest plots 287
12.3.6 Random effects 289
12.3.7 Funnel plots 289
12.4 Presentation of results 293
12.5 Conclusion 294
12.6 Further reading 295
13 Practical issues 297
Summary 297
13.1 Missing data 297
13.1.1 Why do missing data matter? 297
13.1.2 Methods for missing items within a form 298
13.1.3 Methods for missing forms 300
13.1.4 The regulator s view on statistical considerations for
patient-level missing data 308
13.1.5 Conclusions and further reading on missing QoL data 309
13.2 Multiplicity, multi-dimensionality and multiple quality of life outcomes 310
13.2.1 Which multiple comparison procedure to use? 312
13.3 Guidelines for reporting quality of life studies 314
Solutions to exercises 319
Appendix A: Examples of questionnaires 335
Appendix B: Statistical tables 345
References 351
Index 361
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| isbn | 047075382X 9780470753828 |
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| spelling | Walters, Stephen John Verfasser aut Quality of life outcomes in clinical trials and health care evaluation a practical guide to analysis and interpretation Stephen J. Walters Chichester Wiley 2009 XII, 365 S. Ill., graph. Darst. txt rdacontent n rdamedia nc rdacarrier Statistics in practice HBZ Datenaustausch application/pdf http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&local_base=BVB01&doc_number=020174018&sequence=000002&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA Inhaltsverzeichnis |
| spellingShingle | Walters, Stephen John Quality of life outcomes in clinical trials and health care evaluation a practical guide to analysis and interpretation |
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| title_auth | Quality of life outcomes in clinical trials and health care evaluation a practical guide to analysis and interpretation |
| title_exact_search | Quality of life outcomes in clinical trials and health care evaluation a practical guide to analysis and interpretation |
| title_full | Quality of life outcomes in clinical trials and health care evaluation a practical guide to analysis and interpretation Stephen J. Walters |
| title_fullStr | Quality of life outcomes in clinical trials and health care evaluation a practical guide to analysis and interpretation Stephen J. Walters |
| title_full_unstemmed | Quality of life outcomes in clinical trials and health care evaluation a practical guide to analysis and interpretation Stephen J. Walters |
| title_short | Quality of life outcomes in clinical trials and health care evaluation |
| title_sort | quality of life outcomes in clinical trials and health care evaluation a practical guide to analysis and interpretation |
| title_sub | a practical guide to analysis and interpretation |
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