药物经济学中效用的基本概念课件

1、Measuring health utilities for economic evaluationWhat is utility?In economics, utility is a measure of relative satisfaction. It is a term referring to the total satisfaction received by a consumer from consuming a good or service.2Preference, value, utilityPreference is greater liking/desire towar

2、d something over othersValue measures preference under certaintyUtility measures preference under uncertaintyWhat is the “utility” in cost utility analysis?3Health utilityA single measure for multiple (composite?) health outcomes (i.e. effectiveness, and side effects)Anchored at 0 for dead and 1 for

3、 full healthComparability across different treatments or diseases4von Neumann-Morgenstern utility theory“A mathematical decision theory describing how a rational individual should make decisions when faced with uncertain outcomes.” von Neumann and Morgenstern 19445Axioms of vNM utility theoryExisten

4、ce and transitivity of preference A B or A B or A B If A B and B C , then A C If A B and B C , then A C Independence of preference If A B then pA +(1-p)C pB +(1-p)C Continuity of preference If A B and B C, then existing a probability p, B pA +(1-p)C6How to measure health utilities?With established e

5、licitation techniquesDirect measureDesigning your own questionnaire/protocolApplying directly elicitation techniquesIndirect measure Use of established questionnaireCalculating health utilities using scoring algorithms based on elicitation techniques Without established elicitation techniquesJudgmen

6、t7Direct measuresVisual analogue scale (VAS)Standard gamble (SG)Time trade-off (TTO)Discrete choice experiment (DCE)8Steps for direct measurement9Step OneDeveloping health state descriptionsStep TwoEliciting preferences Step ThreeCalculating health utilitiesVisual Analogue Scale (VAS)10VASA responde

7、nt ranks health states according to his/her preference and then places them on a line or scale Interval or spacing between placements corresponds to the difference in preference as perceived by that respondentMeasuring preference under certainty11Variants of VAS12Health state descriptionU(insomnia)

8、= m/10 = 0.40 Death m Full health13InsomniaVAS-chronic states14U(insomnia) = (m-d)/(p-d) = 0.38p Full healthd DeathInsomniap m VAS - temporary states15 Value of Tj on a scale from 0 (Ti) to 1 (healthy): V(Tj) = m/10m Value of Ti on a scale from 0 (death) to 1 (healthy): V(Ti) = p/10Value of Tj on a

9、scale from 0 (death) to 1 (healthy): V(Tj) = p/10+ (m/10)(10-p)/10) = 0.3+0.28 = 0.58 TjTi step 1:Healthy step 2:Ti HealthyDeath p mStandard Gamble (SG)16SGFirst presented by von Neumann and Morgenstern in 1944Classic method based directly on the vNM utility theoryExtensively used in decision analys

10、isMeasuring preference under uncertainty17Risk-based choices in SG questionsFinding p such that:U (Hi)= pU(HFull health) +(1-p)U(Hdeath) = p18What does a utility tellThe greater a persons willingness to accept the risk of death to avoid living in a health state, then the lower is the utility for tha

11、t health state to him/her.19Full healthInsomniapDeath1- pAssume p=0.8 would risk 20% chance of death to avoid living with insomniaCHOICEMEASUREMENTU (Full health)U (Insomnia)U (Death)=0=0.8=1Find pUTILITY SCALE1-ppSG- chronic states Insomnia1090% chance% chanceFull healthDeathCHOICE “A”CHOICE “B”100

12、% chanceC0.900.10U(insomnia)= p/100U(insomnia)= 0.990/10 10/90 50/5020SG-chronic states (contd)Insomnia9010% chance% chanceFull healthDeathCHOICE “A”CHOICE “B”100% chanceC0.100.902122Worse than death?Loneliness1000% chance% chanceFull healthDeathCHOICE “A”CHOICE “B”100% chanceC0.100.9023SG - worse t

13、han death statesDeath9010% chance% chanceFull healthLonelinessCHOICE “A”CHOICE “B”100% chanceC0.100.90 p*U(full health) + (1 - p)*U(loneliness)=0 24SG temporary statesHealth state i(better)7525% chance% chanceHealthyHealth state j(worse)CHOICE “A”CHOICE “B”100% chanceC0.250.75U(Hi)= 0.25+0.75U(Hj)U(

14、Hi)= p+ (1 - p)U(Hj)Time trade-off (TTO)26TTODeveloped specifically for use in health care by Torrance et al (1972).Designed to obtain comparable scores to the SGHow much time a respondent would like to give up to be in a healthier state compared to a less health stateMeasuring preference under cert

15、ainty27TTO - chronic statesU(insomnia)=0.5U(insomnia)=x/tFull healthDeathLIFE AxInsomniaDeathLIFE Bt28TTO worse than death statesU(full health)*x +U(loneliness)*(t-x)= 0U(loneliness)= - 0.25DeathLIFE B LonelinessFull healthLIFE Axt29TTO- temporary statesHealth state j(worse)HealthyHealth state i(bet

16、ter)HealthyLIFE ALIFE BV(Hi)=0.6+0.4V(Hj)xtDiscrete choice experiment (DCE)31DCEAn attribute-based approach to collected stated preferenceRooted in the economic theory of random utility maximizationOriginally developed in transport economics and marketing researchMeasuring preference under certainty

17、 or uncertainty32A simple DCE example33Would you prefer to live in State A or State B?State AInsomniaState BUse of DCECloser to real world decision makingLess cognitive demanding without need of indicating degree of preferenceLatent utility scale vs health utility scale34Full healthDeadState 1State

18、21.00.0TTO health utility DCElatentutilityComparison of VAS, SG, TTO, and DCE35VASTTOSGDCEDurationImplicitExplicitImplicitImplicit/ExplicitRiskNoNoYesYes/NoPreference responseStatedRevealedtime-based choicesRevealed risk-based choicesStatedScoringDirectDirectDirectIndirectOutcomeCertainCertainUncert

19、ainUn/certainDirect measuresTime and cost consumingComplexNot feasible for every studyDifferent direct measures generate different results 36Indirect measure37MeasurementValuationHealth stateQuestionnairePublic preferenceHealth UtilityIndirect measurePatient38Multi-attribute health status classifica

20、tion systems/utility-based instrument39Adapted from Brazier et al., Health Technology Assessment 1996The EQ-5D40414142Health utility/value for state 11223?Calculating the raw score = 1+1+2+2+3=9Standardizing the score = 100-100*(9-5)/(15-5)=60Converting to value= 60/100=0.6 43EQ-5D-3L UK scoring alg

21、orithm44Full health1.000Constant term (for any dysfunction state)-0.081Mobility level 2-0.069Mobility level 3-0.314Self-care level 2-0.104Self-care level 3-0.214Usual activities level 2-0.036Usual activities level 3-0.094Pain/discomfort level 2-0.123Pain/discomfort level 3-0.386Anxiety/depression le

22、vel 2-0.071Anxiety/depression level 3-0.236N3 (level 3 occurs for at least one dimension)-0.269An example health state 1122345Full health1.000Constant term (for any dysfunction state)-0.081Mobility level 2-0.069Mobility level 3-0.314Self-care level 2-0.104Self-care level 3-0.214Usual activities leve

23、l 2-0.036Usual activities level 3-0.094Pain/discomfort level 2-0.123Pain/discomfort level 3-0.386Anxiety/depression level 2-0.071Anxiety/depression level 3-0.236N3 (level 3 occurs for at least one dimension)-0.269U(11223) =0.255Indirect measuresAdvantagesQuick, easy and efficientScoring algorithm de

24、rived from general publicDisadvantagesDifferent systems cover different dimensions of healthScoring algorithms were derived from different populations (e.g. HUI3 from Canada vs EQ-5D from UK or US)Different systems give different results46Which instrument to use?Credibility?Relevant health dimension

25、s covered?Audience preference (e.g. the EQ-5D from NICE)?The population scoring algorithm was derived from?Licensing fee?47Direct measures vs indirect measures48Direct measuresIndirect measuresTime durationLongShortCostHighLowComplexityHighLowSource of preferenceGeneral population or patientsGeneral

26、 populationSensitivityHighLowEthical concernYesNoQuestionnaireNew and specificExistingUtility calculationDirect use of elicitation techniquesExisting scoring algorithmsCost utility analysis49Quality adjusted life year (QALY)A year of life weighed by its quality (e.g. utility). A year in full health is considered equal to 1.0 QALY. The value of a year in ill health would be discounted based on a persons preference. Measures both mortality and morbidityFirst introduced by Klarman in 1968Popularized by Weistein and Stason (N Eng J Med 1977)Equity assumption: the QALY for a person li