This presentation reviews current methods for capturing how the general public values health states as background for discussion on applying these to chronic disorders of consciousness.

1. How Might We Use Stated Preference
Methods to Value Health States Associated
with Chronic Disorders of Consciousness?
Koonal Shah
Conference on Withholding and Withdrawing Treatment from
Patients in a Vegetative or Minimally Conscious State
9 May 2014 • York, University of York

2. Background: the QALY
• Health technology appraisals conducted by NICE and
other similar bodies are guided by cost-effectiveness,
usually using the quality-adjusted life year (QALY) to
measure health outcomes
• The QALY is a measure of health that combines quality of
life and length of life
• Quality of life is used as a “weighting”
• 1 represents “full health”
• 0 represents “dead”
• <0 represents a state that is “worse than being dead”
• 1 QALY = a year of perfect health

3. Valuing health status
• The “quality adjustment” in QALYs requires two
pieces of information:
1. A description of patients’ self-reported
health states
2. The valuation (on a 0-1 scale) of those
health states

4. The EuroQol
Group’s health-
related quality of
life instrument –
the EQ-5D-5L –
does not include
any health states
associated with
disorders of
consciousness

5. How do we obtain values?
• The NICE-recommended approach is ask members of the
general public:
• to consider a range of different health states, and
imagine what it would be like to live in them
• and to tell us how good or bad they are, in their view
• Everyone has different views about what aspects of
health and quality of life are most important
• For decision making, we need a set of “values” that
represents the average view of the general public

6. For every health
state, there is a
‘value’ on a 0-1
scale
Obtaining health state values

7. Methods for generating health
state values
• Stated preference methods such as time trade-off and
standard gamble are widely used to generate values of
health states defined by quality of life instruments
• But we are not aware of any examples of their use to
value minimally conscious or persistent vegetative states
• This lack of evidence about general public views hampers
efforts to evaluate the cost-effectiveness of interventions
related to disorders of consciousness, such as:
• alternative ways of delivering rehabilitation and nursing services
• intensive care for brain injury
• preventative measures such as road safety interventions

8. Visual analogue scale
• We would like to know how
good or bad you consider the
health state in the green box
to be.
• This scale is numbered from
0 to 100.
• 100 means the best health
you can imagine.
• 0 means the worst health
you can imagine.
• Mark an X on the scale to
indicate how you rate the
health state in the green box.

9. Time trade off
• A commonly used method is the time trade-off (TTO)
• Consider t years in full health (Life A)
• Consider x years in an impaired health state (Life B)
• Question: which is better, Life A or Life B?
• Keep changing t, until the respondent cannot choose between
Life A and Life B (“point of indifference”)
• The worse the health state, the more time in full health that
the respondent will be willing to sacrifice

10. TTO: opening step

11. TTO: opening step (MCS)

12. TTO: respondent prefers A

13. TTO: respondent prefers B

14. TTO: respondent expresses
strong distaste for health state

15. Standard gamble

16. Standard gamble (respondent
prefers Alternative 2)

17. To enquire about additional information and analyses, please contact Koonal Shah at
kshah@ohe.org
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