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Contingent valuation and public health: eliciting values from patients and the public

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school health service to focus on all children or those with special needs. ... Data on preferences allow us to analyse whether richer people tend to prefer one ... – PowerPoint PPT presentation

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Title: Contingent valuation and public health: eliciting values from patients and the public


1
Contingent valuation and public health eliciting
values frompatients and the public
  • PAPER PRESENTED
  • TO IDEP- GREQAM WORKSHOP
  • By Cam Donaldson
  • 23RD-24TH JUNE 2003

2
  • Political economy has to take as the measure of
    utility of an object the maximum sacrifice which
    each consumer would be willing to make in order
    to acquire the object....the only real utility is
    that which people are willing to pay for.
  • Jules Dupuit (1844)

3
What I am not doing today
  • Discrete choice/conjoint analysis
  • Willingness to accept
  • Conventional validity studies
  • e.g. payment vehicles
  • Mostly about enhancing the validity of WTP
    studies with respect to relevance to
    decision-makers.

4
Outline
  • Why WTP in health?
  • Using the values in decision making
  • Uptake of WTP studies
  • Patients and the public
  • Distributional issues
  • Progress in eliciting values from patients
  • Progress in eliciting values from the community?

5
What are we valuing?

Productivity
Resource inputs
UTILITY
Healthy time
How resources are used, e.g. process, location
6
WTP why we need it
  • strength of preference
  • can compare different goods
  • pulls together several factors
  • beyond health
  • more in line with theory? Less restrictive on
  • Mode of sacrifice
  • Evaluation space
  • Separability

7
Uptake of WTP
  • Do hypothetical questions give hypothetical
    answers?
  • Comparisons to revealed preference
  • Scope
  • Still developing (CV/SG)
  • Unethical to use in decision making?
  • Perceptions and guidelines
  • General problem with economics?

8
Whose values?
  • Whose values?
  • Patients Public
  • Private (1) (2)
  • Nature of
  • good Collectively (3) (4)
  • financed

9
USING WTP DATAfour main scenarios
  • (1) Patients private good
  • If WTP gt cost, implement
  • (2) Public private good
  • If WTP gt cost, implement
  • (3) Patients collective good
  • Three possibilities
  • (4) Public collective good
  • Need WTP and cost data for alternative uses of
    resources

10
WTP AND DISTRIBUTION OF INCOMECURRENT THINKING
  • ..the validity of this approach rests upon some
    important Paretian assumptions one being that
    individuals are the best judges of their own
    welfare, another being that the current
    distribution of income is appropriate.
  • OBrien B and Drummond MF (1994) Statistical
    versus quantitative significance in the
    socioeconomic evaluation of medicines.
    PharmacoEconomics, 5 389-398.
  • Cost-benefit analysiss primary valuation method
    is willingness to pay(authors emphasis) (WTP),
    an approach whose difficulty lies in its
    intrinsic favouring of the programs and diseases
    of the affluent over those of the poor
  • Gold M et al. (1996) Effectiveness in Health and
    Medicine. New York, Oxford Univ Press, pXXII

11
Distribution what to do?
  • Universal problem QALYs have it too
  • Leave values unweighted? (Pauly)
  • Decision-making view (Currie et al., Little etc)
  • Sensitivity tests (Boardman et al., Donaldson)
  • Direction of preference
  • Strength of preference within income groups
  • Sensitivity of end results to different weights

12
WTP for own care
  • ask patients to value their own treatment
  • example pre-natal CF testing
  • both parents have to test positive
  • disclosure versus non-disclosure
  • 127 out of 176 in trial responded to WTP
    questionnaire

13
RESULTS FROM CF SCREENING STUDY
  • (1) About 21!
  • (2) No difference between groups.
  • This result has been shown in other studies.

14
CF follow up WTP for each
  • make respondents aware of alternatives
  • reference point theory
  • example CF follow up
  • non-trial sample of 450 pregnant women asked
    about WTP for each method

15
RESULTS FROM CF FOLLOW UP
  • (1) Lower response rate.
  • (2) 61 preferred disclosure 27 preferred
    non- disclosure.
  • (3) Problems with validity.

16
MATCHING OF PREFERENCES AND WTP
  • Is WTPD gt or lt WTPND?
  • Pref Less Equal Greater Total
  • Disc 61 (17) 99 (28) 62 (17) 222 (62)
  • Non-disc 78 (22) 16 (4) 94 (26)
  • None 21 (6) 22 (6) 1 44 (12)
  • N.B. 90 people did not respond to this question.

17
MARGINAL APPROACH
  • Give the respondent details of each alternative
    (i.e. existing and alternative care) and ask
    them
  • - which they prefer
  • - what is the maximum amount they would be
    willing to pay to have their preferred rather
    than their less-preferred option.
  • This has been done in studies of
  • - management of miscarriage
  • - intra-partum care (postal open-ended)
  • - parents views of services for children
    (interview bidding).

18
STUDY OF CHILD HEALTH SERVICES
  • (1) 82 parents interviewed (out of 300 asked to
    participate)
  • (2) Each parent was asked one WTP question
    about each of three pairwise choices
  • inpatient stay versus day case for tonsillectomy
  • hospital-based versus local clinics for
    bedwetting
  • school health service to focus on all children or
    those with special needs.

19
RESULTS FROM STUDY OF CHILD HEALTH SERVICES
20
WTP AND DISTRIBUTION
  • Data on preferences allow us to analyse whether
    richer people tend to prefer one option and,
    therefore, whether mean (or median) WTP for that
    option is a result of greater purchasing power
    (i.e. ability to pay) as well as willingness to
    pay.
  • Therefore, analyse preferences by
  • - income
  • - social class

21
Distribution of preferences and mean WTP for
surgery by income group
  • Income (s per week)
  • lt100 100-150 150-230
    230-350 gt350
  • Inpatient 4 2 8 5 5
  • 25 75 44 56
    25
  • Day case 5 2 8
    4 6
  • 32 50 86 77
    43

22
USING THE RESULTS
  • (1)Assuming options are mutually exclusive, other
    things (including cost) being equal, the option
    to be implemented would be that preferred by
    whichever group could compensate the other and
    still remain better off.
  • (2)Where other things (e.g. cost) are not equal,
    if the option with greater WTP (and hence
    utility) also has a greater cost, the decision
    maker then has to decide whether this extra cost
    is worth incurring.

23
BROADER PRIORITY SETTING
  • 150 in Northern Norway were asked their maximum
    WTP for three public sector health care
    programmes
  • - a helicopter ambulance
  • - 80 more elective heart operations per annum
  • - 250 more hip replacements per annum.
  • WTP RESULTS (NOK n143)
  • Helicopter Hearts Hips
  • 316 306 232

24
Why WTP is important
  • The highest valued QALYs are for the helicopter,
    which might reflect a preference for the rule of
    rescue.
  • Life saving is more highly valued than the same
    QALY gain from life extension and life
    improvement
  • If the results are valid!

25
Problems with this method
  • Rank orderings do not match WTP orderings
  • Size of the good problems.
  • Hence, EuroWill, to examine
  • Can different countries do it?
  • Various methodological issues (size of good,
    closed-ended vs payment scale, informational
    effects, marginal approach, econometric issues)

26
Mean WTP (PPPGDP, 1999) using standard approach
27
WHERE NOW FOR WTP?Conduct of studies
  • Do not use WTP for own care
  • Open-ended questions are problematic
  • Use some form of payment vehicle
  • Postal questionnaires require careful design
  • Tests for effects of income/class are feasible
  • Marginal approach has potential for choices
    between close substitutes

28
WHERE NOW FOR WTP?Recommendations for research
  • Compare payment vehicles
  • More testing of the marginal approach
  • Extend to broader priority setting contexts
  • EUROWILL
  • External validity/strategic bias

29
Positive outlook
  • THE ECONOMIST OF OLD
  • Knows the price of everything and the value of
    nothing.
  • THE MODERN ECONOMIST
  • Knows the price, and is some way towards knowing
    the value, of health care at the margin.

30
Or....
  • ...MAUREEN LIPMANS MOTTO
  • Lifes like a questionnaire. You didnt ask to
    be sent it, cant think what the answers are, but
    might as well fill it in and hope it gets a
    laugh.
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