CUA cost utility analysis

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CostUtilityAnalysis*

Introduction

CUAvs.CEA

MeasuringUtility

Applications

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And in the end, it's not the years in your

life that count. It's the life in your years.

(Abraham Lincoln)

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SubsetofCEA

OutcomeisQualityAdjustedLifeYear(QALY)Allowscomparisonsofdifferentprograms(unlike

CEA)acrossdiseasesandconditions

StandardCEAcannotbeusedforcomparisonsacross

diseasegroups

StandardCEAcannotshowanoverallassessmentofa

treatment(e.g.impactofsideeffects)

CUAwasdevelopedasaresponsetothe

humancapital(HK)approach

CostUtilityAnalysis4

1. Somemedicalinterventionsmaybeassociatedwithsignificantincreasesinthenumberoflifeyearssavedbutreducedqualityoflife

2. Conversely,amedicalinterventionmayresultinfewlifeyearssavedbutenhancedqualityoflife

forexamplecoronarybypassoperationsinelderlymen

OnceUponaQALY

Klarman et al. (1968), who introduced theconcept of a QALY in that year, noticed that

the quality of life with a kidney transplant

was better than with dialysis. Theyestimated that the improvement was 25%

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1yearoffullfunctionisafullQALY

DisabilityreducestheQALYbysome

proportiona,and

(1 a)=brepresentstheproportionofquality

ofliferemaining

QALY

10 b

0 = death full quality of life

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EndStageRenalDisease(ESRD)

1. dialysisthreetimesaweeksaveslivesbutdoesnotgetonebacktob1=1,soitisusefultoknow

thelevelofb1inthiscase,andcompareitto

2. kidneytransplantationwhichdoesrestorea

patienttonearfullfunction,sob2 1 andb2>b1.

But,byhowmuch?

QALY Anexample7

Problems1. Itlackssensitivitytopopulationswithgenerallygood

health. Activitiesaresobasiconlythequitefrailhavesignificantnumbersoflimitations.

2. Anequalweightforeachactivitymaynotbeappropriate

3. Allscaleincrementsareweightedequally

4. Theassumption thatanaveragecanbecalculatedasthesumofindividualscoresdividedbythenumberofindividualsisproblematic

ConstructionofindicesbasedonLikerttypescales

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o TheeconomiststakeonQALYs

1. Quantifyingutilityisproblematicatbest

2. Aggregatingutilityacrossanentire

populationisevenworse Preferencesdifferacrossindividualsandtime(TTO)

QALYSomeconceptualproblems

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durationmaximum

1QALY

t

t

tt

r

qF

CalculationofQALY

Ifonedismissestheconcernsvoicedby

economists,

and

weights

have

been

agreed

upon,

measuresofqualityoflifemaybecomputedas

Ft = probability of survival at time t; qt is the weight

Ft : probability of survival at time t

qt = weight

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WhentouseCUAasopposedtoCEA

1. Qualityoflifeisanimportantoutcome

2. Healthrelatedqualityoflifeisanimportantoutcome

3. Bothmortalityandmorbidityareinvolved

4. Programshaveawiderangeofoutcomes

5. Newanalysisofprogramstobecomparedwiththosealreadyanalyzed

CUAvs.CEA11

1. Outcomesareequallyeffective

2. Thereisevidenceonlyofintermediate,asopposedtofinal,effectivenessoftreatment

3. If

effectiveness

data

indicates

an

obviously

dominantprogram

4. Whentheprocessofobtainingthedataisitselfdeemednotcosteffective

WhennottouseCUA12


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Twobasicmethodsofconstructingthisindex

(more

on

this

later)a. Individualswiththehealthconditionbeingassessedb. Professionalswithknowledgeoftheconditionbeing

assessed

Factorsconsideredincludesensation,mobility,emotion,cognition,selfcare,pain,fertility

Alternatively,Likert pointscalesmaybeusedtohelpinterviewees (seenextslide)

UtilityIndices13

A=improvementinquality

B=increaseinlifeyears

Discounting offuture

Potentialcrossingofinterventionandnoninterventionpaths

QALYdiagrams14

QALYdiagrams15


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NeteffectsQWB=QualityofWellBeing

ANEXAMPLEOFCALCULATING&USINGQALYEddy,D.M.(1991) OregonsMethods. DidCostEffectivenessAnalysis Fail,?Journal oftheAmericanMedicalAssociation, 116:

21352141

durationQWBQWB 01

With treatment Without treatment

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ANEXAMPLEOFCALCULATING&USINGQALY

continued

Each of the alternatives may consist of multiple different states. For example, thetreatment alternative may be associated with several possible outcomes, each having acertain probability, i.e. (see Table)

Treatment or not for appendicitis

Alternative and possible outcomes Probability Weight

Treatment

Death 0.01 0.00Symptoms of abdominal pain 0.01 0.747Survival with symptoms such as vomiting, fever, chills, etc 0.01 0.630No adverse effects 0.97 1.00

No treatment

Death 0.99 0.00No adverse effects 0.01 1.00

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Evaluationoftreatment


continued

N

i

ii WQWB 1,1 Pr

98377.000.197.0630.001.0747.001.000.001.0

N

i

ii WQWB 0,0 Pr

01.000.101.000.099.0

The difference is

0.98377 0.01 = 0.974

(continued on next slide)

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Multiplybyduration

Assumeanaverageremaininglifetimeof47years,thentheneteffectis

Thecostcomponent

TheMedicaidcostofappendicitisis$5744,so,the

cost/QALYratiois


continued

778.45974.047

125$778.45

5744

QALY

Cost compare to ratiosfrom other treatmentsto prioritize

Questions/Comments

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Note: not discounted!

MeasuringUtilities20

1. Identifyrelevanthealthstates

2. Describingthestages Duration(T)isofparticularimportance

Problem:UbarisafunctionofT.

3. Selectionofindividualstobeinterviewed(i.e.whose

preferences?)a. C UAperspective thosedirectlyaffectedorthegeneralpublic

b. C BAperspective allaffectedparties(societys)

4. Selectamethod(referstotypes&structureofquestionsasked)formeasurement (nextfewslides)

a. Categoryratingscale(RS)

b. Standardgamble(SG)

c . T imetradeoffmodel(TTO)

MeasuringUtilities:Stages21


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thethermometermethod

Themethodsformeasurement1.TheCategoryratingscale(RS)

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Assumetwostatesofutility

Allotherhealthstatesareassumedtooccurwithcertainty

Theindividualthenmakespairwisecomparisonsbetweeneachstate

andoneoftheextremes

Example(acasewithjusttheextremes)

Theprobabilityofenjoyingtheutilityofthehealthystate:

Expectedutility:

So,iftheprobabilityis0.80thentheexpectedutilityis0.80

Seediagramonnextslide

Themethodsformeasurement2.StandardGamble(SG)

0DeathU and 1HealthU

HU DUHUUE ).1(.

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Lettheexpectedremaininglifetimeforapersonwitharthritis

bet(knownbyassumption)

Howmanyyears(sayx)inthehealthystatewouldmakethe

individualindifferentbetweenthetwostates? Inother

words:

Themethodsformeasurement3.TimeTradeOffModel(TTO)

AUtHUx

Equals 1

t

xAU Expression reduces to

Continued if next slide

Since t is known (say a

person with arthritis lives

another 40 years), then, if

the individual cannot

decide between living 20

healthy years or 40

arthritic years, the utility of

a year with arthritis is

(20/40 = 0.5).

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Arthritisexamplediagram


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Preferencesfortemporaryhealthstates(reductions)canbemeasuredrelativetoeachotherwiththeTTOapproach. Thefigurebelowshowstwointermediatestates.

Alternative1isassociatedwithasmallerbutrelativelylongerreductioninhealth


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1. Whatisbeingaskedinaquestion?a. IntheRSmethod,peopleareaskedtoapplyanumericscaledirectlytoa

condition.

b. IntheSGmethod,peopleareaskedtogamblewiththeirhealth

c. IntheTTOmodel,timepreferenceswillbeaffectedbythenumberofyears.

2. Howisitasked? Howisthequestionframed Whatbenchmarksoranchorsareusedtoexpress

onespreferences?

Considerationsthataffectindicesderivedbythethree

methods

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Selectedresultsfromcomparativevaluationstudies

Author N Kind of subjects SG RS TTO State

Torrance(1976) 43 Students 0.75 0.61 0.76 Not indicated0.73 0.58 0.700.60 0.44 0.630.44 0.26 0.38

Bombardier et al. (1982) 52 Health care personnel 0.85 0.65 0.78 Walking stickPatient s 0.81 0.47 0.58 Walking frame

F am ily 0 .6 4 0 .2 9 0 .4 1 N eeds s up er vision w hen w alking0.55 0.18 0.28 Needs oneassistant for walking0.38 0.08 0.11 Needs two assista nts

Llewellyn-Thomaset al. (1984) 64 Patients 0.92 0.74 Tired, Sleepless0.84 0.68 Unable to work. Somepain0.75 0.53 Limited walking.

Unable to work. Tired0.66 0.47 In house. Unable to work. Vomiting0.30 0.30 In bed in hospital. Needs help with

self-care. Trouble remembering

Read et al. (1984) 60 Doctors 0.90 0.72 0.83 Moderate angina0.71 0.35 0.53 Severe angina

Breast cancer:Richardson et al. (1989) 46 Health care personnel 0.86 0.75 0.80 Removed breast unconcerned

0.44 0.48 0.41 Removed breast. Stiff arm. Tired.Anxious. Difficulties with sex. Cancerspread. Constant pain.

0.19 0.24 0.16 Tired. Expecting not tolive long.

Source: Nord 91992) Methods for QualityAdjustment ofLife Years, Social Science and Medicine, 34: 559-569

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AnApplication:UtilitieswithHIVInfection

Bayoumi, A.M. and Redelmeier, D.A. (1999) Economic Methods for Measuring the Quality of Life Associated with HIV Infection, Quality ofLife Research8: 471-480

Table: Ratings of standardized health states

Elicitation Method Symptomatic HIVa Minor ADIb Major ADIc

Standard GambleMean 0.80 0.65 0.42

Median 0.90 0.75 0.40

Range 0.005-1.00 0.00-1.00 0.00-1.00

Time Trade-offMean 0.81 0.65 0.44

Median 0.96 0.75 0.50

Range 0.004-1.00 0.00-1.00 0.00-1.00

Visual AnalogMean 0.70 0.46 0.25Median 0.70 0.49 0.21

Range 0.32-0.95 0.00-0.81 0.00-0.70a.

Symptomatic HIV with no AIDS Defining Illnesses (ADI)b. Examples: pneumonia and TB

c.

Examples: wasting syndrome

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Documents

CUA cost utility analysis