Utility AssessmentUtility AssessmentHINF 371 - Medical MethodologiesHINF 371 - Medical Methodologies

Session 4Session 4

Objective Objective

To review utility assessment To review utility assessment techniques and discuss their use techniques and discuss their use determining benefits for determining benefits for interventionsinterventions

ReadingReading

Roberts M S and Sonnenberg F A (2000) Chapter 3: Roberts M S and Sonnenberg F A (2000) Chapter 3: Utility Assessment under Expected Utility and Rank Utility Assessment under Expected Utility and Rank Dependent Utility Assumptions, in Chapman G B and Dependent Utility Assumptions, in Chapman G B and Sonnenberg F A (eds) Decision Making In Health Care: Sonnenberg F A (eds) Decision Making In Health Care: Theory, Psychology and Applications, Cambridge Theory, Psychology and Applications, Cambridge University Press, USAUniversity Press, USA

Goldstein MK and Tsevat J (2007) Chapter 24: Assessing Goldstein MK and Tsevat J (2007) Chapter 24: Assessing Desirability of Outcomes States, in Interactive Textbook Desirability of Outcomes States, in Interactive Textbook on Clinical Symptom Research, on Clinical Symptom Research, http://symptomresearch.nih.gov/chapter_24/index.htmhttp://symptomresearch.nih.gov/chapter_24/index.htm

Goldstein MK and Tsevat J (2000) Chapter 12: Applying Goldstein MK and Tsevat J (2000) Chapter 12: Applying Utility Assessment at the Bedside, in Chapman G B and Utility Assessment at the Bedside, in Chapman G B and Sonnenberg F A (eds) Decision Making In Health Care: Sonnenberg F A (eds) Decision Making In Health Care: Theory, Psychology and Applications, Cambridge Theory, Psychology and Applications, Cambridge University Press, USAUniversity Press, USA

Stiggelbout MA (2000) Chapter 11: Assessing Patient’s Stiggelbout MA (2000) Chapter 11: Assessing Patient’s Preferences, Preferences, in Chapman G B and Sonnenberg F A (eds) in Chapman G B and Sonnenberg F A (eds) Decision Making In Health Care: Theory, Psychology Decision Making In Health Care: Theory, Psychology and Applications, Cambridge University Press, USAand Applications, Cambridge University Press, USA

Evidence PreparationEvidence Preparation

Engine where data is translated into

information

Levels of Decision Levels of Decision MakingMaking

Micro level: Patient level decision Micro level: Patient level decision makingmaking

Meso level: Organization level Meso level: Organization level decision makingdecision making

Macro level: Society level Macro level: Society level decision makingdecision making

Meta level: Across sectorsMeta level: Across sectors

Utility Assessment Utility Assessment What is it?What is it?

In economics, utility is a measure of the relative In economics, utility is a measure of the relative happiness or satisfaction (gratification) gained by happiness or satisfaction (gratification) gained by consuming different bundles of goods and services.consuming different bundles of goods and services.

The doctrine of utilitarianism saw the maximization The doctrine of utilitarianism saw the maximization of utility as a moral criterion for the organization of of utility as a moral criterion for the organization of society. According to utilitarians, society should society. According to utilitarians, society should aim to maximize the total utility of individuals, aim to maximize the total utility of individuals, aiming for "the greatest happiness for the greatest aiming for "the greatest happiness for the greatest number".number".

Measuring the utility of health states based on Measuring the utility of health states based on preferences of patientspreferences of patients

Respondents assess the desirability of life in certain Respondents assess the desirability of life in certain statesstates May be respondents own current health stateMay be respondents own current health state May be hypothetical state other than their own May be hypothetical state other than their own

current health presented to respondents for current health presented to respondents for ratingrating

Two models of Direct Utility Two models of Direct Utility AssessmentAssessment

The standard gamble: what probability of painless and The standard gamble: what probability of painless and immediate death she would risk in order to be restored to immediate death she would risk in order to be restored to perfect health or better health than the state under perfect health or better health than the state under consideration.consideration. If a subject is willing to take up to a 20 % risk of death in exchange If a subject is willing to take up to a 20 % risk of death in exchange

for and 80 % change of perfect health rather than accept the for and 80 % change of perfect health rather than accept the intermediate state for certain, then the utility of the intermediate intermediate state for certain, then the utility of the intermediate state is 0.8state is 0.8

Time Trade-off: willingness to live shorter but healthier life - Time Trade-off: willingness to live shorter but healthier life - equals one minus the maximum proportion of time that the equals one minus the maximum proportion of time that the subject is willing to trade offsubject is willing to trade off

Willingness-to-pay: how much one would be willing to pay to Willingness-to-pay: how much one would be willing to pay to avoid an undesirable health state.avoid an undesirable health state.

Person Trade-off: how many outcomes of one kind respondents Person Trade-off: how many outcomes of one kind respondents consider equivalent in social value to x outcomes of another consider equivalent in social value to x outcomes of another kindkind

Rating scales: e.g. Sickness Impact Profile, Nottingham Health Rating scales: e.g. Sickness Impact Profile, Nottingham Health Profile, Older Americans Resources and Services (OARS), SF-36, Profile, Older Americans Resources and Services (OARS), SF-36, Quality of Well Being, Visual Analog ScaleQuality of Well Being, Visual Analog Scale

Two models of preference Two models of preference assessmentassessment

Health state classification systems Health state classification systems (indirect utility assessment): (indirect utility assessment): respondent’s health status is respondent’s health status is ascertained, and then utilities ascertained, and then utilities assessed or derived mathematically assessed or derived mathematically from a reference group are mapped from a reference group are mapped onto that health stateonto that health state Descriptive system – set of attributes and Descriptive system – set of attributes and

health state is described by indicating health state is described by indicating appropriate level of functioning appropriate level of functioning

Scoring formula - Scoring formula -

Good description of the outcome Good description of the outcome state must be neededstate must be needed

Patients may have difficulty Patients may have difficulty anticipating their future anticipating their future preferencespreferences

Application of Utility Application of Utility AssessmentAssessment

Integration to medical decision making with Integration to medical decision making with individual patientsindividual patients

To calculate QALYs: the QALYs associated with To calculate QALYs: the QALYs associated with an intervention are estimated as the sum of the an intervention are estimated as the sum of the future expected life years weighted by the future expected life years weighted by the quality of life (expected utility) in each time quality of life (expected utility) in each time interval. interval.

An intervention can increase the number of An intervention can increase the number of QALYs by changing the quality weighting QALYs by changing the quality weighting (utility) even if it has no effect or a negative (utility) even if it has no effect or a negative effect on survival; an intervention that improves effect on survival; an intervention that improves symptoms can increase the expected utility.symptoms can increase the expected utility.

To identify quality weighting; To identify quality weighting; Measure of the impact of the intervention on the Measure of the impact of the intervention on the

distribution of health statesdistribution of health states Assessing the preferences (utilities) for these Assessing the preferences (utilities) for these

alternative states of healthalternative states of health

QALYsQALYs

Except for discounting, the long Except for discounting, the long term effect of QALY is a linear term effect of QALY is a linear function of a one year effectfunction of a one year effect

The effect of treating multiple The effect of treating multiple individuals is a linear function of individuals is a linear function of treating one individualtreating one individual

DifficultiesDifficulties

TTO: people tend to value earlier TTO: people tend to value earlier years more than the later yearsyears more than the later years

SG same as TTOSG same as TTO Different estimates of the health state Different estimates of the health state

when you are in itwhen you are in it Differences in risk taking behaviourDifferences in risk taking behaviour Leaving out risk gives much greater Leaving out risk gives much greater

relative weight to preventing or relative weight to preventing or curing minor disabilities compared curing minor disabilities compared with major disabilities than do utilitieswith major disabilities than do utilities

Scaling problems (e.g. absence of Scaling problems (e.g. absence of disease versus perfect health)disease versus perfect health)