Bayesian Design of Discrete Choice Experiments for Valuing Health State Utilities by Fatimah Ali ...

276 Pages·2015·2.66 MB·English

Bayesian Design of Discrete Choice Experiments for Valuing
Health State Utilities
by
Fatimah Ali Aloef
Thesis submitted to the University of Sheffield
for the degree of Doctoral of Philosophy
School of Mathematics and Statistics
January 2015

To my parents and my little family.

Acknowledgments
First I mostly thank my PhD supervisors Prof. Jeremy Oakley and Dr. Eleanor
Stillman for all their help and support. I really appreciate their valuable advices
during my PhD that contributed to make this thesis possible. It is of my honor to be
one of their students and benefit from their experiences.
I wish to express my sincere thanks to Dr. Kevin Walters and Prof. Peter Goos for
reading my thesis and providing me with significant and constructive suggestions in the
oral examination. This thesis could not have been completed without their generous
and professional assistances.
IamalsogratefultoProf. JohnBrazierattheScHARRoftheuniversityofSheffield
for providing us with the data sets for asthma case study and making available for us
to use their data. I would like also to thank the staff on the Mathematics department
for being friendly and helpful all the time.
I would like also thank all my friends (too many to present here but you know who
you are) for being supportive, and providing me the friendship I needed during my
studies and understanding my fluctuated mood during the PhD. I am really thankful
to my friends Sujunya Boonpradit and Madina Hassan for supporting and encouraging
me all the time.
I specially thank my dad, mum, and my brothers and sisters for their support and
prayers and for their entire love. Special thanks for my little family, my husband who
support me all the time and has faith in me and my intellect even when I felt down.
Also my kids Ali and the little angel Sarah where there is no words can describe how
much I do love them.

Abstract
Thisthesisaimstodevelopanefficientmethodologytoconstructefficientdiscretechoice
experiments (DCEs) for health state utility estimation within the QALY framework.
The use of the QALY measure in health economic evaluation together with meth-
ods related to measuring the QALY weight/health state utilities are reviewed in order
to establish the fundamental knowledge needed for valuing health. DCEs are used to
value health state utilities, which is simpler than other direct valuation methods. Nev-
ertheless, DCEs are still undergoing research to improve their uses in valuing utilities,
in particular in designing experiments which are used to construct the DCEs
The main issues with the current choice designs together with design considerations
for valuing utilities are identified in this thesis. Advanced work for constructing choice
designs, particularlyBayesianoptimaldesign, isreviewedtoconstructmoreefficientde-
signs for valuing utilities. Since constructing Bayesian optimal designs requires a prior
distribution for the unknown choice model parameters, Bayesian analysis is performed
for a real data to obtain appropriate prior distributions.
Constructing Bayesian optimal choice designs for valuing utilities within QALY
framework using the existing choice design software is investigated. We find there
are limitations because of the design considerations for valuing health state utilities
particularly in terms of anchoring utility values into the QALY scale (0-1 scale). We
then develop a new algorithm based on modifying the latest advanced choice design
algorithms such that they account for the design considerations which overcomes the
limitations with the existing design software. Methods for simplifying the choice design
questions are also provided.
We demonstrate the use of our design algorithm by constructing Bayesian choice
designs for asthma quality of life classification system (AQL-5D), and then investigate
the effect of the choice of the prior distribution on the choice of Bayesian designs.

Contents
1 Introduction 1
1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Economic Evaluation in Health Care . . . . . . . . . . . . . . . . . . . 2
1.3 Discrete Choice Experiments and Valuing Health . . . . . . . . . . . . 6
1.4 Motivation for Better Choice Design . . . . . . . . . . . . . . . . . . . 9
1.5 Aim of the Thesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.6 Thesis Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2 Valuing Health and Discrete Choice Experiments 14
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.2 QALYs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.2.1 Illustrative Example . . . . . . . . . . . . . . . . . . . . . . . . 16
2.3 Classification Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
ii
2.3.1 Generic Classification System . . . . . . . . . . . . . . . . . . . 18
2.3.2 Condition Specific Classification System . . . . . . . . . . . . . 20
2.3.3 Modelling Health State Classification System Valuation . . . . . 22
2.4 Measuring Preference . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2.4.1 Direct Valuation Techniques . . . . . . . . . . . . . . . . . . . . 24
2.4.1.1 Time Trade-Off . . . . . . . . . . . . . . . . . . . . . . 25
2.4.1.2 Standard Gamble . . . . . . . . . . . . . . . . . . . . . 27
2.4.1.3 Visual Analogue Scale . . . . . . . . . . . . . . . . . . 29
2.4.2 Direct Valuation Method Issues . . . . . . . . . . . . . . . . . . 30
2.4.3 Indirect Valuation Techniques . . . . . . . . . . . . . . . . . . . 31
2.4.3.1 Ranking . . . . . . . . . . . . . . . . . . . . . . . . . . 31
2.4.3.2 Discrete Choice Experiments . . . . . . . . . . . . . . 32
2.4.4 Advantages and Disadvantages of DCE Techniques . . . . . . . 34
2.5 Discrete Choice Models . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
2.5.1 Modelling Discrete Choice Data . . . . . . . . . . . . . . . . . . 37
2.5.2 Model Identification . . . . . . . . . . . . . . . . . . . . . . . . 40
2.5.3 Multinomial Logit Model . . . . . . . . . . . . . . . . . . . . . . 43
2.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
3 Literature Review: DCEs and their Design in Health Economics 49
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
iii