Introduction to Introduction to

QALYs and PreferenQALYs and Preferen

Measurement in CEMeasurement in CE

Patsi Sinnott, PT, PhD, MPH

HERC Economics Course

Oct. 31, 2012
Overview

 B i f f CEA Brief review of CEA  Outcomes in CEA  Concept of QALYs for a CEA  Estimating QALYs Estimating QALYs  Guidelines on selecting measures

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The ICER

CEA compares the outcomes and c

of two (or more) i ti interventions

(Cost study Cost usual care ) 

Outcomesstudy Outcome

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Policy Implications 

 Who is your audience?  How will the results be used?  What perspective should you use? What perspective should you use? 
CEA/CUA review CEA/CUA review

 CEA compares the outcomes and 

CEA compares the outcomes and 

two (or more) interventions; 

– The outcome is defined by the healt

achieved with the intervention achieved with the intervention. 

– The outcome (s) are quantified in a 

sca

le 

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Scenario 

 Intervention to reduce/eliminate post-o

infections in patients following hip frainfections in patients following hip fra

repair 
What costs to include?
What outcomes to use

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Scenario 

 Intervention to reduce/eliminate post-o

infections in patients following hip frainfections in patients following hip fra

repair 
Outcomes for CEA

 Perspective – Hospital system (pa

– 

Natural U 

U

n

its 
o e

Outcomes for CEA 

 Perspective – Societal? 

– Q ifi l h f ill /lif Quantifies length of illness/life– Qu ality of life– Comparable across programs 
The Quality Ad justed Life 

(QALY) 

 Describes duration of illness/years 

Describes duration of illness/years 

survival, adjusted for quality of lif

experienced during that survival experienced during that survival. 

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QALYs Overview 

 You have 1 year in perfect health 

QALY 

 I have 1 year in I have 1 year in 

“good ” health (.80 health (.80 

QALY) 

 1 year difference = .20 QALYs 
Estimation of QALYs Estimation of QALYs

 Re

quires: 

– Description of the health states expe

b ti / bj t by patien

t

s

/subjec

ts 

– Estimation of the duration of each h

state 

– Comparison to or assessment of ind

Comparison to or assessment of ind

or community preferences for each 

state 

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QALY Example 

New cancer treatment vs. standard of caW i e

i

g

hts range 

from 

0

-

1 

6 mo. 6 mo. 6 mo. 6 mo. T

New Txt. 

.90 

(.90 x .50) 

.30 

(.30 x .50) 

.50 

(.70 x .50) 

.25 

(.25 x .50) 

( 45+ (.45+

.53

UC .90 (.90 x .50) .50 (.50 x .50) .25 (.25 x .50) 

-

(.45

.41
Calculating Calculating cost/QALY cost/QALY 

 ICER – New txt vs. standard care 

(hypothetical all other costs are equa

($10,000  $0/( .268 .2065)  $162, 60
Deriving preferences or utiliti

Deriving preferences or utiliti

health states

 Basic methodology: 

– I di id l id l fl 

I

ndi

vidua

ls provide a persona

l refle

the relative value (preference weighdifferent health states experienced o

described.

 Patients P id rov ers 

 Community Sample 

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Deriving preferences or ut

Deriving preferences or ut

 Three meth

o

ds 

to 

der

ive pre

ference

– Off the shelf – Direct: – Indirect: 

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Off-the-shelf values

 Use preference weight determined 

another study for h t f i 

ealth state of in

– Not all health states have been char

 Useful in decision modeling 

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Direct methods

 Individuals asked to choose (decla

preferences) b

e

tween th 

e

ir current 

state and alternative health status scenarios 

 I di id l k th h i b 

I

ndi

vidua

ls ma

ke these c

h

o

ices 

ba

their own com

prehensive health st

the time of measurement) 

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How are you today? How are you today?

 You are able to see

, hear and s

peak no

 You require the help of another person 

cane to walk or get around cane to walk or get around. 

 You are occasionally angry, irritable, a

andd d 

depresse

d. 

 You are able to learn and remember no You are able to eat, bathe, dress and u

toilet normally. toilet normally. 

 You are free of pain and discomfort. 

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Direct: Standard Gamble 

Direct: Standard Gamble 

 Live rest of life in 

current health state; or 

 “take a pill (with risks) to be restored risks) to be restored to perfect health”  Scale represents risk Scale represents risk of death respondent is willin

g to bear in 

or

der to 

be restore

d 

to full health. 

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Considering the health st

Considering the health st

described

 What risk of death would you be w

t t k (b t ki ill t ) t b to 

t

a

ke (by 

t

aking a pill, e

tc.) 

to 

be 

restored to (y our ) p 

perfect health

 10%?  20%  0% 
Direct method: time trade

Value 

Current health 

Years of life 

0

t1 

t
Considering the health st

Considering the health st

described

 How many years of life in your cu

st t ld b illi t i 

t

a

te would you 

be willing 

to g

ive 

live out 

your life in 

perfect health

 5 years  10 years  Any years? Any years? 
Direct Methods (SG, TT

Direct Methods (SG, TT

 May be necessary if effects of 

intervent

ion are comp

lex: 

– Multiple domains Multiple domains – Effects not captured in indirect or d

specifi i c 

instruments 

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Direct Method (SG TT

Direct Method (SG, TT

 High variance in estimates from p

i t i in a 

t

r

i

a

l 

– Reflect risk aversion

, feelin

g about 

disability 

– High variance = large sample size High variance = large sample size 

 Not the “communit

y value” s

pecif

Gold et al 

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Indirect Methods

 Study subjects complete several su

d i ur

ing a s

t

u

dy. 

 Multiple domains of health Multiple domains of health  Composite describes the health sta

the respondent at that moment the respondent at that moment 

 Com

posite state is linked to result

previously studied community sam

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How are you today (#2

 Which statements best describe yo

t d ? t

o

day? 

 Mobility: 

– No problems, some problems, extreme p

 Pain  Anxiety/depression  Self-care  Usual activity 

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How many health state
Indirect Measures Indirect Measures

 Health Utility Index (HUI) Health Utility Index (HUI)  Euro

Qol 

( QE

Q-5D

) 

 Quality of Well-Being Scale (QW SF-6D 

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Indirect measures vary 

 Dimensions or attributes included The size and nationality of the sam

population used to establish the wpopulation used to establish the w

 Health states defined by the surve How the summary score is calcula

etc. 
Indirect measures 

 Standard surve

ys that are widelyu

 Review published studies on 

psychometric properties in the popof interest of interest 

 May lack “responsiveness ” 

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Health Utility Index (HU

Utility Index (HU

 41 questions (many items can be skipp

41 questions (many items can be skipp

– can derive both HUI Mark 2 and HUI Ma

h lth tilit health utility scores. 

 8 domains of health and 972,000 health 

– vi is on, hearing, speech, ambulation, dexte

emotion, cognition, and pain 

 Basis of domain weights: 

– Canadian community sample rated hypoth

health states 

– Utility theory 

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EuroQol EQ-5D

 5 questions in 5 domains of health 

– M bilit lf M

obility, self-care, usual ti i 

l acti

vit y, pa

i

n/d

or anxiety/depression 

– 245 health states. 

 Basis of domain weights: Basis of domain weights: 

– Past studies based on British community – New US weights recently published 

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The QWB The QWB

Quality of Well-Being Scal

 Two versions 

– Interviewer or self Interviewer or self -administered (QW

administered (QW

 QWB-SA is more feasible 

– 76 questions; 1215 health states def– Includes sy p m toms, mobility, p y y, ph si

activity, & social activity

 Basis of domain weights: Basis of domain weights: 

– Primary care patients in San Diego, 

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–

SF -6D *

 Converts SF-36 or SF-12 scores to 

utili it es 

– When based on SF-36, uses 10 items – When based on SF-12, uses 7 items 

 6 health domains 6 health domains 

– physical functioning, role limitations, soc

functioning pain mental health and vitafunctioning, pain, mental health, and vita

 Defines 18,000 health states  Basis of domain weights 

– British community sample British community sample 

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Disease-specific survey

specific survey

 When to use? When to use?  How to use? 

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Disease-specific survey

specific survey

 Key methods issues: Key methods issues: 

– Difficult to describe health state to 

community respondent

– Difficult to establish values when th

large number of possible health stat

 Expensive but potentially sensitiv

Expensive, but potentially sensitiv

variations in quality of life for this 

disease 

 Often used in addition to generic m

Often used in addition to generic m

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-

Which method to use? 

 Trade -off between sensitivity an

off between sensitivity an

burden 

 Start with a literature search re 

condition of interest condition of interest 

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Hierarchy of methods 

 Off-the-shelf utility values  Indirect Measures (HUI, EQ-5D

QWB SF,

-6D) 

 Disease Disease 

-specific survey during 

specific survey during 

and transform later to preferen

 Direct measures (SG, TTO) 

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Important Resources Important Resources 

 Tufts Center for Risk Assessment 

– http://research.tufts-nemc.org/cear4 

 Brazier J Brazier 

J, Deverill Deverill 

M, Green C H

Green 

C, H

R, Booth A. A Review of the use 

health status measures in economihealth status measures in economi

evaluation. Health Technol Assess 1999;3(9).

– http://www.hta.ac.uk/project/2481.a

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Important Resources 

 Table of published utility weights 

(preferences) for different health s(preferences) for different health s

– http://www.tufts-nemc.org/cearegis

 Preference Measurement in Economic 

Analysis. Guidebook. VA Health EconAnalysis. Guidebook. VA Health Econ

Resource Center. 

http://herc research va gov/publications/guidebookhttp://herc.research.va.gov/publications/guidebook
QUESTIONS and COMMEN

QUESTIONS and COMMEN

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