VALUATION OF HEALTH STATES Flashcards
Definition of Health Economics?
Application of economic models and empirical techniques to the analysis of-decision making by healthcare agents with respect to health care
Why do we value health states?
Need to know how much the health state or change in state is valued … what it is worth to the individual i.e. a measure of preference
Compare health states with each other
Main criteria for judging how good a health-related quality of life (HRQOL) indicators is?
- RELIABILITY - produces consistent measurements
- VALIDITY - measures what is supposed to be measured
- RESPONSIVENESS - how sensitive the result from the HRQOL indicator are to changes in health
- FEASIBILITY - is it possible to use the indicators
Special requirements for the HRQOL indicators?
- should provide an unambiguous measure of benefit … say whether treatment is better or worse
- single number that summaries health change
- should be capable to comparing different possible uses of scarce resource
- efficient and equitable use of resources
- should be capable of being interpreted in terms of values
- benefits = value of outputs
- costs = value of inputs
What do non-monetary valuations of health capture?
Consider measures of health that encapsulate both morbidity and mortality … account for the fact that health is multidimensional
Aim of non-monetary valuations of health?
End goal is the construction of a meaningful measure of health: Quality Adjusted Life Years (QALYs) … two dimensions:
- life-expectancy (as a measure of the extra life-years that may be procured)
- quality adjustment/quality of life (as weights indicating the healthiness of the expected life-years)
we want a method of valuation of health states which “can simultaneously capture gains from reduced morbidity (quality of life gains) and reduced mortality (quantity of life gains)” (Drummond et al. 2015)
Types of measure?
ORDINAL: ranking health states
CARDINAL - INTERVAL SCALE: each unit increment on the scale is equal
CARDINAL - RATIO: each unit increment on the scale is equal and zero is meaningful … we want this one
Stages of obtaining health state valuation?
- Describe and measure health state … usually based on interviews/questionnaires in which respondents are presented with ‘scenarios’ that describe a health state
- Valuation of the health state … need to elicit preference values
- methods for attaching non-monetary valuation to health states
Definition of Visual Analogue Scale?
A scale that provides anchor points against which respondents rank the desirability of health states in their opinion (based on their value preferences)
What is the Visual Analogue Scale?
Scale has to cover the entire spectrum of feasible states
- best imaginable health state … worst imaginable health state
How does the Visual Analogue Scale work?
- respondents are given a set of health states (or based on their existing health state)
- Asked to value the health states and place them on the scale
Advantages of the Visual Analogue Scale?
Easy to use and understand … useful to introduce respondents to health states
Good response rate - quick to complete
Useful as a robustness check for other methods of valuation
Can be used in a time series
Disadvantages of the Visual Analogue Scale?
No notion of opportunity cost … do not have to trade-off quantity or quality of life
Spreading effect … respondents try to use the whole scale
Context bias … respondents may not be indicating strength of preference, but simply just ranking their preference of health state 1 over 2 i.e. ordinal ranking
No clarity that a change from 0 to 25 is valued the same as 25 to 50 … no anchor to show death
Torrance et al. (2001) argue that can only value max. of 6 health states otherwise process loses usefulness
Definition of Time Trade Off?
Embodies the notion of sacrifice between quality of life and quality of life
How does Time Trade Off work?
Method tries to estb. where indv. is indifferent between 2 options by varying the amount of time spent in full health
A. Respondent chooses between 2 options for a given health state
1. full-length of life in the health state to be valued (LOLb)
2. shorted period of life in full health (LOLa)
B. Vary the time spent in full health until indv. is indifferent between the 2 options
C. Final utility score is reached at point of indifference … QOLb = LOLa/LOLb
Assumption made in Time Trade Off?
People will choose the option that produces the highest QALY value
Advantages of Time Trade Off?
Based on choice – embodies at least a stated account of opportunity costs
Addresses quality vs. quantity trade off … people thinking about trade-off between quality of life and quantity of life
Fairly easy to understand
Disadvantages of Time Trade Off?
Assumes thats nothing changes once indvs. have made their choice … individuals trade off a constant proportion of their remaining life years
- But value might change as duration in state changes e.g. some severe states become intolerable
- Time preference may contaminate values … mix up preferences over time - e.g. health state might be fine at one age but not another
No account taken of risk … risk neutrality assumed
Unrealistic alternatives … e.g. telling a 60yr old that they could live for 60 years is unfeasible - have to ensure that ‘full length of life’ is realistic for the indv.
Definition of Standard Gamble?
Embodies the notion of sacrifice between health and risk
How does Standard Gamble work?
Method tries to estb. where people are indifferent between the two options by varying the probability of living in full health
A. Respondent chooses between 2 options for a given health state
1. health state with certainty (H1) … live in a specified health state worse than full health for the rest of your life
2. two different health states with uncertainty (H2 and H3) … probability p of living in full health for the rest of your life OR probability (1-p) of immediate death
B. Vary the probability of living in full health until indv. is indifferent between the 2 options
C. At the point of indifference … i = p = utility value of H1
Advantages of Standard Gamble?
Economic gold standard – von Neumann-Morgernstern utilities/probabilities
- Directly consider these to be utilities which can directly compare
Based on choice and sacrifice … like real life
Involves uncertainty and is therefore more realistic for medical decision making
Addresses the quantity/quality trade-off
Disadvantages of Standard Gamble?
Probability can be difficult for respondents to understand
Probabilities can be unrealistically high (risk aversion) …
SG results affected by attitude to risk
Method applies only to a chronic health state that is preferred to death
Definition of Generic multi-attribute utility scales?
Provides a profile of a person’s health state
Example of a Generic multi-attribute utility scales?
EQ-5D-3L
- one of the most widely reported multi-attribute index measure of health status in both clinical and economic studies
- NICE’s preferred measure of HRQOL in adults
EQ-5D-5L
How does EQ-5D-3L work?
- Health state classification system … Asks individuals to rate 5 dimensions (mobility, self-care, usual activities, pain/discomfort, anxiety/depression) on 3 levels (roughly speaking: no problems, moderate problems, extreme problems) which best describes their health state
- Tariff of utility values for all health states is defined by the classification of the coded health state … predicts values for the weights and can therefore be used to value all 243 possible state classification
- Weighted utility score gives QALYs … spending a year in the state would deemed to be X QALYs
Advantages of EQ-5D-3L?
Ask people questionnaire and can directly assign utility … most reliable and effective method
243 (3^5) possible classifications
Can show changes in health state over time as indvs. move through different classifications
Disadvantages of EQ-5D-3L?
Only 3 levels … EQ-5D-5L has more levels (can be more precise)
Might not pick everything people value with respect to health – descriptive questionnaire which tells patients what to value with regards to their health
Cross country comparisons are made difficult as some use TTO score and VAS score to get utility score … NICE uses TTO score
What do monetary valuations of health capture?
Two main types Cost-Benefit Analysis approach can be used to directly elicit the monetary value of health care benefits
Definition of Revealed Preference?
Valuation of health that can be inferred from real choices made in the everyday world … choices reveal people’s preferences
How can Revealed Preference capture health state valuation?
Can be used to value a specific health intervention, or to value a “statistical life” … what people are willing to pay to reduce their risk of death
How does Revealed Preference work?
- Find upper and lower bounds of prices a person is willing to pay for health intervention
- Vary prices between these two limits and person’s choices can be observed
- Identify person’s maximum willingness to pay … that shows have much they value the health care intervention
Definition of Stated Preference?
Hypothetical choices are considered via surveys or experiments (willingness to pay studies) … asks how much person is willing to pay hypothetically
How does Stated Preference work?
- Survey respondents are presented with a situation/scenario
- Ask respondents how much willing to pay for the intervention … what is the max you are willing to pay?
Advantages of Monetary valuation methods?
Measures the monetary value of any health benefits gained by the patients + the value to society of other consequences e.g. ability to take paid employment
Disadvantages of Monetary valuation methods?
Difficult to design the experiment
- Need to make sure hypothetical scenarios are valid and realistic to avoid respondent answering based on what the researcher wants to hear
- Must be representative of the population using the service
Poor observed correlation between hypothetical and real WTP
- Incentives/context may be different in important ways
- Environment in which make the decisions will be different
Ultimately implies a cost-benefit-type analysis that we may deem to be inappropriate in the sphere of health and healthcare
Evaluation of methods of monetary and non-monetary valuation of health states.
Need to be aware of the perspective/viewpoint for evaluation
- Purpose of economic evaluation will have fundamental impact on the viewpoint from which the evaluation is to be performed
- Viewpoint chosen can affect the judgement whether something is good or not good value for money
Valuations are dependent on people’s opinion of pain/illness
- Some may value pain higher or lower in comparison to others
