1
Q
HRQOL + PPM/Utilities
A
- Single number between 0-1 that reflect the economic concept of utility (value to society) of a health state
- “Y” axis = PPM
- Combines different domains of HRQOL
- Societal perspectives for health
- Can be measured for each person in a society regardless of severity of disease
2
Q
QALYs
A
- Combines both quantity and quality of life into one measure
- HRQOL of a health state = patient preference measure on a scale of 0 (dead) to 1
- Time spent at the health state, in years
- Tabulate changes in health related QoL over time
3
Q
QALY Numerical Issues
A
- Interval level measure: difference from 0-1 the same as 0.9-1
- QALY scales are considered uniform between illnesses (0.1 gain in diabetes is same as 0.1 gain in CHF)
4
Q
Why Measure QALY?
A
- Purpose of health care is to gain the most “total health” for society given the available resources
- By comparing HRQOL gains of different disease treatments, society can make good decisions for resource allocation
- Seek to maximize total amount of health state utilities by selecting treatments with the most gain and the least cost
- Underlying ethical goal: distributive justive
5
Q
PPM Key Concepts
A
Public vs patient views of relative value (utility) of health states
- Values are developed from public perspective, then applied at the patient perspective
- Persons experiencing the disease usually value the health state higher than society (higher PPM)
Across society and health states, “relative” comparisons are theoretically valid within a society
- Rural New Mexico residents and NYC residents may not place an equal value on a particular health state, but across ALL of society the relative PPM of health state is measurable and comparable to other health states
- Differences exist between countries, each has different scaling
6
Q
Methods Measuring PPMs
A
- Direct measurement: specific questions designed to determine PPMs
- Indirect measurements: Validated HRQOL survey, survey responses obtained alongside direct PPM measures and made to mathematically convert responses to values obtained from direct measurements
7
Q
Direct Measures of PPMs
A
Common Aspects
- Specific description of health state is provided
- Subjects may or may not have experienced the disease
- Uniform conditions/descriptions to all subjects
Techniques
- Rating scales
- Time trade off
- Standard gamble
8
Q
Rating Scales
A
- VAS: Visual analog scale, most common
- Anchors: ends of scale, 0 = worst possible state/death, 100 = “optimal” or “full” health
- Similar to other health rating scales
- Needs adjustments, based on responses from other direct PPM instruments to be considered a valid PPM
9
Q
Visual Analog Scale
A
- Utility value converted to value between 0-1
- Positives: easy to explain, comparative to other rating scales, very quick to administer
- Criticisms: ordinal v.s. interval along scale, reliability may be suspect, impact of relatively trivial illness may be overstated, results often lower than other techniques
10
Q
TTO
A
- Time Trade-Off
- Respondent makes choice about trading off years of life for better health for a shortened life span
- How many months out of a year of life would you give up to live the remaining time in optimal health
11
Q
TTO Positives/Criticisms
A
Positives
- Easy to explain
- Relatively quick to administer
Criticisms
- Values are not true utilities, because risk isn’t considered
- Respondents may get confused understanding the concept of trading time
- Unrealistic: in most situations, you don’t have to choose to live fewer years
12
Q
Standard Gamble Techniques
A
- Theory: utilities are preferences measured under uncertainty and involve risk
- Standard gamble techniues incorporate risk and uncertainty into the assessment
- Would you accept a treatment to restore you to optimal health if you had designated health state if there was a __% risk of death
- Percentage difference between two alternatives is the PPM measure
13
Q
Standard Gamble Technique Positives/Criticisms
A
Positives
- Conceptually sound with utility theory
- Incorporates level of risk adversity of population
Criticisms
- Risk of death decisions are uncommon for most medical conditions
- Subjects may have cognitive difficulties understanding the trade-off between quality/quantity of life
14
Q
Indirect PPM Measures
A
- Validated, reliable survey instruments
- Responses collected as well as direct PPM in a population
- Formulas developed to convert responses on survey questions to PPMs
- Advantages: Time, interviewer training, interview techniques, results within different domains of health
- Disadvantages: assumes the population values are correct, relevant and appropriate
15
Q
Indirect PPM Considerations
A
- Theoretical constructs (Direct measurement methods)
- Ease of administration
- Validity/reliability
- Relevance to condition (responsiveness)
- COST
16
Q
EQ-5D
A
- Indirect PPM/QALY Instrument
- 5 questions plus a VAS and demographics
- Domains: mobility, self care, usual activities, pain/discomfort, anxiety/depression
- 245 health states
- Ease of administration
- European gold standard (?)
17
Q
HUI
A
- Health Utilities Index
- Indirect PPM/QALY Instrument
- 15 questions
- Mark II: 7 dimensions, 24,000 health states
- Mark III: 8 dimensions, 972,000 health states
- Domains: vision, hearing, speech, ambulation, dexterity, emotion, cognition, pain
- Ease of administration
- Canadian gold standard (?)
- Scoring functions convert to PPMS
18
Q
QWB
A
- Quality of well being scale
- Weighted desirability of different health states
- Domains: symptoms/problems plus mobility, physical activity, social activity
- Interviewer administered/20 minutes
- Self-administered forms available
- Weighted health state measures
- Used in Oregon Medicaid experiment
19
Q
SF-6D
A
- Uses SF-36 and SF-12 in economic evaluations together
- 6 dimensions: physical, mental health, bodily pain, social functioning, role-limitations, vitality
- Describes 18,000 possible health states
- Preference weights were determined using SG
20
Q
PPM/QALY Controversies
A
- Healthy populations vs patients with the disease
- Senstivity of PPMs to disease changes/treatments
- Simplicity vs theoretical soundness
- Health states that do not fit between the two ends of the scales
21
Q
QALY Controversies
A
- Measurement issues between instruments, populations, patients
- Use of PPMs in patients, bias against treating the disease: individuals adjust to limitations and viewpoints can change over time
- Large variability indicates inadequacies of PPM measures
22
Q
Conclusion
A
- PPM or Health Utility: the assessment of relative value of variety of health states
- QALYs incorporate quality and quantity of life
- PPMs/QALYs are measured directly and indirectly, through questionnaires
- Theoretical and cognitive difficulties exist with measuring PPMs and therefore QALYs
836
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