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Using a discrete choice experiment with duration to estimate values for health states on the QALY scale Nick Bansback Assistant Professor School of Population and Public Health, University of British Columbia CIHR New Investigator

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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

Example DCE choice set

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

Questions

• Is the DCEtto really easier than the TTO?• Should we be using this approach to

combine more specific aspects of treatments with generic derived QALYs?

• How can we validate the approach further?