Quality of Life Outcomes in Clinical Trials and Health-Care Evaluation A Practical Guide to Analysis and Interpretation

by Walters, Stephen J.

• ISBN13: 9780470753828
• ISBN10: 047075382X
• Edition: 1st
• Format: Hardcover
• Copyright: 2009-10-26
• Publisher: Wiley

Summary

An essential, up-to-date guide to the design of studies and selection of the correct QoL instruments for observational studies and clinical trials.With the recent attention paid to QoL in clinical trials and observation studies, many new QoL methods have been created. The majority of available QoL books tend to focus on detailed coverage of the design of these new QoL studies. This book differs in that it aims to assist the busy statistician/clinician in selecting the right QoL study methodology, and thus save them time in trial design. Readers are offered a practical guide to the use of already available QoL instruments as opposed to guidance on the designing of specific methods. The book then sets out to assist the reader in the accurate analysis and interpretation of QoL outcomes.It will examine the problems caused by QoL outcomes (which tend to generate data with discrete, skewed and bounded distributions) before presenting conventional methods to tackle such problems (e.g. linear regression). More advanced approaches are then discussed including ordinal regression and computer intensive methods (e.g. bootstrapping).Throughout the text the use of real life case studies and worked examples taken from the Author's own work will illustrate the methods discussed, and exercises and solutions will help further the reader's experience. The book will also detail the use and implementation of the necessary software for statistical analysis, including SPSS, STATA and R. A supplementary website will also provide downloadable data files.

Author Biography

Stephen J. Walters – School of Health and Related Research, University of Sheffield. Dr Walters has had experience both in research and teaching, and is currently the Senior Lecturer in Medical Statistics at Sheffield University. He has conducted numerous grant-funded research projects, and has nearly 150 publications to his name. These include 85 articles in a range of refereed journals, 2 co-authored books, and contributed chapters in three other books.

Table of Contents

Preface

Introduction

Summary

What is quality of life?

Terminology

History

Types of quality of life measures

Why measure quality of life?

Further reading

Measuring quality of life

Summary

Introduction

Principles of measurement scales

Indicator and causal variables

The traditional psychometric model

Item response theory

Clinimetricscal

Measuring quality of life: indicator or causal items

Developing and testing questionnaires

Further reading

Choosing a quality of life measure for your study

Summary

Introduction

How to choose between instruments

Appropriateness

Acceptability

Feasibility

Validity

Reliability

Responsiveness

Precision

Interpretability

Finding quality of life instruments

Design and sample size issues: How many subjects do I need for my study?

Summary

Introduction

Significance tests, P-values and power

Sample sizes for comparison of two independent groups

Choice of sample size method with quality of life outcomes

Paired data

Equivalence/non-inferiority studies

Unknown standard deviation and effect size

Cluster randomized controlled trials

Non-response

Unequal groups

Multiple outcomes/endpoints

Three or more groups

What if we are doing a survey, not a clinical trial?

Sample sizes for reliability and method comparison studies

Post-hoc sample size calculations

Conclusion: Usefulness of sample size calculations

Further reading

Reliability and method comparison studies for quality of life measurements

Summary

Introduction

Intra-class correlation coefficient

Agreement between individual items on a quality of life questionnaire

Internal consistency and Cronbach's alpha

Graphical methods for assessing reliability or agreement between two quality of life measures or assessments

Further reading

Technical details

Summarizing, tabulating and graphically displaying quality of life outcomes

Summary

Introduction

Graphs

Describing and summarizing quality of life data

Presenting quality of life data and results in tables and graphs

Cross-sectional analysis of quality of life outcomes

Summary

Introduction

Hypothesis testing (using P-values)

Estimation (using confidence intervals)

Choosing the statistical method

Comparison of two independent groups

Comparing more than two groups

Two groups of paired observations

The relationship between two continuous variables

Correlation

Regression

Multiple regression

Regression or correlation?

Parametric versus non-parametric methods

Technical details: Checking the assumptions for a linear regression analysis

Randomized controlled trials

Summary

Introduction

Randomized controlled trials

Protocols

Pragmatic and explanatory trials

Intention-to-treat and per-protocol analyses

Patient flow diagram

Comparison of entry characteristics

Incomplete data

Main analysis

Interpretation of changes/differences in quality of life scores

Superiority and equivalence trials

Adjusting for other variables

Three methods of analysis for pre-test/post-test control group designs

Cross-over trials

Factorial trials

Cluster randomized controlled trials

Further reading

Exploring and modelling longitudinal quality of life data

Summary

Introduction

Summarizing, tabulating and graphically displaying repeated QoL assessments

Time-by-time analysis

Response feature analysis - the use of summary measures

Modelling of longitudinal data

Conclusions

Advanced methods for analysing quality of life outcomes

Summary

Introduction

Bootstrap methods

Bootstrap methods for confidence interval estimation

Ordinal regression

Comparing two independent groups: Ordinal quality of life measures (with less than 7 categories)

Proportional odds or cumulative logit model

Continuation ratio model

Stereotype logistic model

Conclusions and further reading

Economic evaluations

Summary

Introduction

Economic evaluations

Utilities and QALYs

Economic evaluations alongside a controlled trial

Cost-effectiveness analysis

Cost-effectiveness ratios

Cost-utility analysis and cost-utility ratios

Incremental cost per QALY

The problem of negative (and positive) incremental cost-effectiveness ratios

Cost-effectiveness acceptability curves

Further reading

Meta-analysis

Summary

Introduction

Planning a meta-analysis

Statistical methods in meta-analysis

Presentation of results

Conclusion

Further reading

Practical issues

Summary

Missing data

Multiplicity, multi-dimensionality and multiple quality of life outcomes

Guidelines for reporting quality of life studies

Solutions to exercises

Examples of questionnaires

Statistical tables

References

Index

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