The valuation of diseasespecific questionnaires for QALY analysis

1
The valuation of disease-specific questionnaires
for QALY analysis

• To rescue data in absence of an utility measure
• Growth hormone deficiency in adults
• To increase sensitivity
• Benign Prostatic Hyperplasia (BPH)

2
Mapping

• Trying to map disease characteristics on EQ-5D
  etc.
• Nord E. Cost-utility analysis of Melphalan plus
  Prednisone with or without Interferon Alfa-2b in
  newly diagnosed multiple myeloma.
  Pharmacoeconomics 19971289-103.
• Can be done behind the desk
• Very quick
• Very dirty
• A low face validity

3
Mapping DALY style
4
QoL-AGHDA

• Quality of Life Adult Growth Hormone Deficiency
  Assessment
• 25 yes/no items
• Internet panel
• N 1075
• Both AGDHA and EQ-5D

5
From AGDHA to utilities (QALY)
EQ-5D 5 dimensions
AGHDA 25 dimensions
Utility Algorithm
Sum Score
Regression
Regression
Utilities
Total score
6
Regression Dutch AGHDA sum score on EQ-5D
7
The AGHDA has generic features

• AGHDA
• I have to struggle to finish jobs
• I feel a strong need to sleep during the day
• I often feel lonely even when I am with other
  people
• EQ-5D
• I have some problems with performing my usual
  activities
• I am moderate anxious or depressed
• Correlation makes sense

8
Does the EQ-5D make sense in BPH?

• MOBILITY
• I have no problems in walking about
• I have some.
• I am confined to bed
• SELF-CARE
• I have no problems with self-care
• I have some problems..
• I am unable
• USUAL ACTIVITIES
• I have no problems with performing my usual
  activities
• I have some problems
• I am unable.
• PAIN/DISCOMFORT
• I have no pain or discomfort
• I have moderate ..
• I have extreme..
• ANXIETY/DEPRESSION
• I am not anxious or depressed
• I am moderately..

Not sensitive for BPH
9
But what if the measure has little generic
features?

• International Symptom Prostate Score (IPSS)
• BPH
• Enlargement of the prostate
• Causes voiding problems in elderly men
• Difficulties to pee
• 7 questions How often have you
• had to push or strain to begin urination?
• had a sensation of not emptying your bladder
  completely?
• had to urinate again less than two hours after
  you finished urinating?
• found you stopped and started again several times
  when you urinated?
• you find it difficult to postpone urination?
• had a weak urinary stream?
• How many times did you most typically get up to
  urinate from the time you went to bed at night
  until the time you got up in the morning?

10
4 different methods

• Review
• Mortimer, MDM, 2008 Jan-Feb28(1)66-89.
• Regression (32)
• Direct valuation (8)
• Effect size translation (5)
• Response mapping (1)

10
11
Can we convert the IPSS outcomes into utilities?

• Attribute TTO values to the IPSS health states
• Problem IPSS has 279.936 health states
• 7 items, 6 answer levels 6x6x6x6x6x6x6
  279.936 health states
• Too many to value with TTO
• Reduce number of health states
• Reduce items
• Factor analysis
• Reduce answer levels
• Combine answer levels

12
Reduce number of health states

• Factor analysis on patients IPSS responses
• N 1414
• Two main factors
• Obstructive (alpha 0.8018)
• Irritative (alpha 0.7165)
• Confirmed in literature
• Factors divided in 3 levels
• Number of health states reduced to 33 9
• Can be valued directly
• TTO
• General public, representative for gender/age
  (N170)

13
Exercise

• Value the 9 health states of the reduced IPSS
• Tests feasibility can it be done?
• Compare values with earlier research
• Test reliability can we repeat the observation?
• Scientific prove (observation is independent of
  examination)
• Do different groups of people have different
  values

14
QALY weights for BPH
15
Comparing ISPOR 2003 with population
16
How to come to these values?
17
Treatment effect
18
Effect sizes translation
19
Disease specific utilities are not equal to
generic utilities

• Only the disutility of the specific disease is
  valued
• Generic and specific utilities are not on the
  same scale
• Generic top anchor absence of any impairment
• Specific top anchor absence of specific
  impairment
• Co morbidity might still be present

20
How to interpret disease specific utilities

• Value of life years traded off in TTO differ
• Healthy subject 1 life year is 1.0 QALY
• Sick subject 1 life year is 0.5 QALY
• Life years of healthy persons are more worth than
  those of sick
• Overall health states influence disutility
• 20 trade off at 1.00 disutility 0.20
• 20 trade off at 0.80 disutility 0.16
• 20 trade off at 0.60 disutility 0.12
• Raw disease specific trade-off overestimated gains

21
Specific utilities should be corrected for
average morbidity

• Solution multiplicative model
• Multiply disease specific value with average
  value
• Values have to be multiplied by average value for
  age group.
• For instance in IPSS
• male age 55-64 overall QoL utility 0.81
• Most severe BPH 0.87
• Male age 55-64 with most severe BPH 0.81 x 0.87
  .7047
• Maximum gain reduces from
• Raw score 1.00 - 0.87 0.13
• Adjust score 0.81 - 0.70 0.11
• 15 reduction

22
Rue of thumb

• Overestimated CE-ration by 15
• Using specific utilities
• Proposed by Fryback Lawrence, MDM 1997
• Bias most prominent in VAS, SG en WTP
• Less in TTO
• King, Styn, Tsevat, Roberts, MDM 2003

23
Discussion

• When diseases specific utilities?
• To rescue data,
• When generic is not sensitive
• But generic instruments are more sensitive than
  expected
• A minor issue remains a minor issue
• Generic utility needed for correcting dis. spec.
  weights
• Rule of thumb Include both types
• Generic for purpose of utilities
• Disease specific for backup and/or validation of
  generic utilities

24
Conclusion

• We can validate dis spec questionnaire for the
  use in economic appraisal
• E.g., AGDHA/ IPSS have QALY-weights
• New and already published research can be
  converted into QALYs
• Advantage use specific QALYs measures
• High sensitive disease specific measures for
  QALY-analysis
• Rescuing data
• Disadvantages
• Not directly compatible with generic utilities
• 15 correction needed in disease specific