VALUATION OF QUALITY OF LIFE IN RHEUMATOID ARTHRITIS Laurien Buitinga

139 Pages·2012·1.7 MB·English

VALUATION OF QUALITY OF LIFE IN
RHEUMATOID ARTHRITIS

Laurien Buitinga
Thesis, University of Twente, 2012
© Laurien Buitinga
ISBN: 978-90-365-3467-3

Printed by Gildeprint Drukkerijen, Enschede, The Netherlands

The studies in this thesis were performed at the department of Psychology, Health and Technology
(PHT) of the University of Twente (Enschede) and the Arthritis Center Twente at Medisch Spectrum
Twente (Enschede). The rheumatology research program of PHT is financially supported by the Dutch
Arthritis Foundation (het Reumafonds). This project is financially supported by the foundation
‘Stichting Onderzoek en Zorgontwikkeling Reumacentrum Twente’.
Publication of this thesis was financially supported by the Dutch Arthritis Foundation (het
Reumafonds).
VALUATION OF QUALITY OF LIFE IN
RHEUMATOID ARTHRITIS

PROEFSCHRIFT

ter verkrijging van
de graad van doctor aan de Universiteit Twente,
op gezag van de rector magnificus,
prof. dr. H. Brinksma,
volgens besluit van het College voor Promoties
in het openbaar te verdedigen
op donderdag 20 december 2012 om 16.45 uur

door

Laurien Buitinga
geboren op 9 maart 1985
te Hengelo (OV)
Dit proefschrift is goedgekeurd door de promotor prof. dr. M.A.F.J. van de Laar en de assistent-
promotoren dr. E. Taal en dr. L.M.A. Braakman-Jansen.
Samenstelling promotiecommissie

Promotor: prof. dr. M.A.F.J. van de Laar

Assistent-promotoren: dr. E. Taal

dr. L.M.A. Braakman-Jansen

Leden: dr. G.J. Westerhof
(Universiteit Twente)

prof. dr. K.M.G. Schreurs
(Universiteit Twente)

prof. dr. M.J. IJzerman
(Universiteit Twente)

dr. A.E.R.H.C. Boonen
(Maastricht Universitair Medisch Centrum)

dr. P.F.M. Krabbe
(Universitair Medisch Centrum Groningen)

prof. dr. J.L. Severens
(Erasmus Universiteit Rotterdam)

Contents

Chapter 1 Objective & outline 10

Chapter 2 Theoretical background 16

Chapter 3 Comparative responsiveness of the EuroQol-5D and Short Form 6D 38
to improvement in patients with rheumatoid arthritis treated with
Tumor Necrosis Factor Blockers: results of the Dutch Rheumatoid
Arthritis Monitoring Registry

Chapter 4 A computer Time Trade-Off: a feasible and reliable alternative for 54
the interview Time Trade-Off in rheumatoid arthritis

Chapter 5 Construct validity of the interview Time Trade-Off and computer 68
Time Trade-Off in patients with rheumatoid arthritis: a cross-
sectional observational pilot study

Chapter 6 Future expectations and worst-case future scenarios of patients with 84
rheumatoid arthritis: a focus group study

Chapter 7 Worst-case future scenarios of patients with rheumatoid arthritis: a 98
cross-sectional study

Chapter 8 Chapter summary & discussion 112

Samenvatting (Dutch summary) 124

Dankwoord (Acknowledgements) 130

Curriculum Vitae 134

List of publications 138

Chapter

Objective & outline
10 Objective & outline

Patient-reported outcomes (PROs) including health-related quality of life (HRQoL) instruments have
gained attention in the medical world and in health economics. An increased awareness of the
importance of using PROs alongside clinical measures has led to their expanded use in clinical trials.
With the rising societal expenditures in health-care and the relatively limited resources, it is inevitable
that choices must be made with respect to reimbursement of health technologies. Within the field of
rheumatology, the economic burden of rheumatoid arthritis (RA) on society is high in terms of health-
care costs and costs due to loss in work productivity (1,2). The expanding indications for the use of
effective but very expensive biological therapies and the development of novel biological therapies
warrant economic evaluations in which the expected costs of these therapies are compared with the
expected benefits. One important form of economic analysis, namely cost-utility analysis (CUA),
incorporates HRQoL instruments into the assessment of benefits. Although these HRQoL instruments
are frequently carried out within an economic analysis, the performance of some of them in studies with
RA patients has not been examined extensively. In addition, different variants of some of these
instruments are used, which makes comparison of results between studies difficult. Furthermore,
research has shown that the measurement of HRQoL can be biased (3-7). Therefore, additional research
is required into the psychometric performance of these instruments and whether they can be improved
for patients with RA. The objective of this thesis was to examine the psychometric properties of some
HRQoL instruments used in economic analysis, and to examine alternative anchors for one HRQoL
instrument in RA patients, which could improve the measurement of HRQoL representing the patient
perspective.
The responsiveness of HRQoL questionnaires in rheumatoid arthritis
For CUAs of health technologies, utilities are commonly measured with the EuroQol-5D (EQ-5D) or
Short Form-6D (SF-6D). A review of Harrison et al. (8) has shown that there is no conclusive evidence
to favour any one measure (EQ-5D, SF-6D, Health Utility Index (HUI-2 or HUI-3)) with respect to
responsiveness to improvement, i.e. their ability to detect clinical improvements. The authors conclude
that more head-to-head comparisons are needed in longitudinal studies across the spectrum of RA
disease severity. Therefore, they performed another study comparing the EQ-5D and SF-6D (9) and
demonstrated in accordance with most previous studies into RA that the SF-6D was most responsive to
improvement. One study of RA showed, however, that the EQ-5D was more responsive than the SF-6D
(10). Nevertheless, these studies examined different aspects of responsiveness, i.e. internal or external
responsiveness. To contribute to the evidence of both internal and external responsiveness in RA
patients with active disease, in chapter 3 the responsiveness of the EQ-5D and SF-6D to improvement
was compared in patients with active RA treated with TNF-blockers, using both aspects of
responsiveness.
Computer versus interview administration of an HRQoL instrument in RA
The Time Trade-Off (TTO) and Standard Gamble (SG) are frequently used instruments for measuring
HRQoL by obtaining preferences for health states (‘utilities’) directly in patients. The SG has good
theoretical underpinnings (11), but is a complex instrument that requires respondents to incorporate
risk assessment into their responses. The TTO has been developed to be an easy alternative for the SG
with similar empirical properties as the SG, and overcomes the problems of explaining probabilities to
respondents (12-14). The TTO asks respondents to indicate how many years of life they are willing to
trade in order to become perfectly healthy, i.e. to avoid being in their current health state. It is assumed