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Cadth 2015 a4 2015 cadth values
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Transcript of Cadth 2015 a4 2015 cadth values
Using a discrete choice experiment with duration
to estimate values for health states on the QALY
scaleNick Bansback
Assistant ProfessorSchool of Population and Public Health, University of
British ColumbiaCIHR New Investigator
The Problem (1)
• Generic preference based measures (e.g EQ-5D, HUI, SF-6D) may sometimes not be sensitive enough to capture important changes in health
Espallargues M et al. The impact of age-related macular degeneration on health status utility values. Invest Ophthalmol Vis Sci. 2005 Nov;46(11):4016-23McTaggart-Cowan et al. The validity of generic and condition-specific preference-based instruments: the ability to discriminate asthma control status. Qual Life Res. 2008 Apr;17(3):453-62.
The Problem (1)
• Generic preference based measures (e.g EQ-5D, HUI, SF-6D) may sometimes not be sensitive enough to capture important changes in health
• As a result, there has been a huge increase in conjoint/ Discrete Choice Experiment studies looking at the value of more specific aspects of health
The Problem (2)
• DCE/conjoint studies have not produced values on the QALY scale. Hence none of these studies are amenable to incorporating into economic evaluation/informing policy
The Problem (2)
• DCE/conjoint studies have not produced values on the QALY scale. Hence none of these studies are amenable to incorporating into economic evaluation/informing policy
• Conventional elicitation approaches (Time Trade Off/Standard Gamble) are difficult to understand, and so tend to need a face to face interview – expensive and timely.
New Method: A discrete choice experiment with a duration attribute (referred to as DCEtto)
Health State A Health State B
Some problems in walking about
No problems in walking about
No problems with self-care Some problems with self-care
Some problems with performing my usual activities
Some problems with performing my usual activities
Moderate pain or discomfort No pain or discomfort
Not anxious or depressed Extremely anxious or depressed
Live for 10 years Live for 7 years
Choose A or B
Health State A Health State B
Some problems in walking about
No problems in walking about
No problems with self-care No problems with self-care
Some problems with performing my usual activities
No problems with performing my usual activities
Moderate pain or discomfort No pain or discomfort
Not anxious or depressed Not anxious or depressed
Live for 10 years Live for t years
Vary t until indifferent between A and B
DCE Requires if health state A is preferred to B and not the degree by which A is preferred to B
TTO DCEtto
Estimation
• Value for health state j in Time trade off:
• Estimate model on DCE data where x represents vector or coefficients for each attribute level and t is the duration
• Use estimated coefficients…• To solve
Advantages to the DCEtto• Simpler (fewer drop-outs)• Enables incorporation of all respondents, increasing
power and representativenessCognition
• Included with no change in task or arbitrary transformation
States worse than dead
• DCEs rooted in economic theory (RUT)Theory
• Quick to complete• Can be implemented on the web (cheaper)Practical
Bansback, et al. "Using a discrete choice experiment to estimate health state utility values." Journal of health economics 31.1 (2012): 306-318.Bansback, et al. "Testing a discrete choice experiment including duration to value health states for large descriptive systems: Addressing design and sampling issues." Social Science & Medicine 114 (2014): 38-48.
Case study
• New treatments for rheumatoid arthritis:• Offer more convenient modes of
administration
• But have less established evidence on long-term safety
vs
Coeff t WTPInfusion RefInjection 0.44* 10.39 2.11Tablet 1.16* 25.66 5.57Twice daily RefOnce weekly 0.21* 4.87 0.99Every 8 weeks 0.41* 9.85 1.9740 people out of 100 benefit Ref55 people out of 100 0.48* 12.47 2.3170 people out of 100 1.20* 28.27 5.7515 people out of 100 withdraw Ref10 people out of 100 withdraw 0.22* 5.49 1.055 people out of 100 withdraw 0.27* 6.68 1.3030 people out of 100 side-effect Ref18 people out of 100 side-effect 0.30* 7.88 1.425 people out of 100 side-effect 0.62* 14.84 2.95Limited confidence RefModerate confidence 0.23* 5.88 1.12Strong confidence 0.58* 14.37 2.76Life years (linear) 0.21* 9.11
Number of responses 14980Number of respondents 749p2 0.214
Results (n=749)• Market research
panel – inexpensive• 3 weeks for data
collection • Only 5 people
dropped out• 80 people failed
consistency check, but their inclusion/exclusion does not change results
Harrison M, Marra C, Shojania K, Bansback N. Societal preferences for rheumatoid arthritis treatments. Evidence from a Discrete Choice Experiment. Rheumatology. In Press
Results (on QALY scale)
Mode Frequency Benefit Serious SE Minor SE Imprecision
-.1
5-.
1-.
05
0.0
5.1
MR
S (
Util
ity)
Inje
ctio
n v
s In
fusi
on
Ora
l vs
Infu
sion
We
ekly
vs
Tw
ice
Dai
ly
8-W
eekl
y vs
Tw
ice
Da
ily
55/
100
vs
40/1
00
70/
100
vs
40/1
00
10/
100
vs
15/1
00
5/1
00
vs 1
5/1
00
18/
100
vs
30/1
00
5/1
00
vs 3
0/1
00
Mod
era
te v
s H
igh
Low
vs
Hig
h
Limitations
• Larger variance around results• requires more responses than TTO studies
• In other DCEtto studies, questions remain about large range of values
• Worst EQ-5D state ~-0.6
• Questions on how to incorporate into economic evaluation
• Clearer for developing values for condition specific non preference based QoL instruments (such as AQLQ)
• Possible double counting when combining with existing generic instruments