university of minnesota medical technology evaluation and market research department of healthcare...

University of Minnesota

Medical Technology Evaluation and Market

Research Department of Healthcare Management

Course: MILI/PUBH 6589Spring Semester, 2013Stephen T. Parente, Ph.D.

Carlson School of Management, Department of Finance

Class OverviewMeasuring Effectiveness

Health state 101

Specifying clinical outcomes

Measuring outcomes

Use of decision trees in effectiveness analysis

Terminology: “Health State”

““The health of an The health of an individual at any individual at any

particular point in time.” particular point in time.”

[Gold et al 1996]

When Considering an Assessment of Health: Two

areas of concern• Length of life

– mortality rates– life expectancy

• Quality of life– ability/disability– independence– other aspects of health & well-being

1. quality of life

2. combination of quality & length

We need measurement scales for

What do we mean by “measurement” of outcomes?

Measurement• Process of setting up a correspondence

between

–Some set of things (here health states)

–Numbers

• So that qualitative relations among the things (such as “better than”) are reflected by the quantitative numerical relationships

Some differences in scales matter; some don’t

A No pain at all 0 10 0B A little pain 1 20 0.5C Painful 2 30 2D Hurts like hell 3 40 20

Pain ratings from 6 people: A,B,B,B,C,D

Averages on 3 different scales:

1.33 23.33 3.92

Goal of health outcome measurement

• Assign scales so that when we do arithmetic, the averages work out the way we think they should.

• Use common vales to permit apples to apples comparison.

How about a single measure that combines morbidity & mortality?

• Simple idea:

Weight each year of life with a measure of degree of good/poor health.

Add up the weighted life years.

DeadDead

ExcellentExcellent

Ove

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ver

all

all

Healt

Healt

hhQu

ali

Qu

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additional years of lifeadditional years of lifenownow deathdeath

QALYs = area under this curve QALYs = area under this curve QALE = average number of QALYs QALE = average number of QALYs experiencedexperienced by a cohort by a cohort of the same starting age and quality of lifeof the same starting age and quality of life = best estimate of future health-adjusted life years for = best estimate of future health-adjusted life years for random member of the cohortrandom member of the cohort

““Life Path” = the Life Path” = the general health general health outcomeoutcome

Mathematical Assumption to make QALY tractable:

• “Q” weighting is separable from duration of the health state it represents and other health states in the life path

– simplifies data collection immensely!– Life expectancy obtained from

medical data– combined mathematically instead of

by judgment

Issues ...• What aspects of “health” are

normally covered in a health-related quality of life (HRQOL) measure?

• How is a health classification system operationalized?

• How are numbers (weights) assigned to health states?

Illustrate with several different measures

• QWB Quality of Well-being scale• HUI Health Utility Index• YHL measure in Years of Healthy

Life• EQ-5D EuroQol health status

measure• SF-36 Questionnaire-based health

profile

DeadDead

ExcellentExcellent

Overall Overall HRQOLHRQOL

additional years of lifeadditional years of lifenownow deathdeath

Continuum of health state weights

DeathDeath

ExcellentExcellent

Overall Overall HealthHealth

Descriptionsystem covering allhealth states

Numericalscale

Function corresponding states to scale values so arithmetic “works”

Health Status Measurement System

“The health of an individual at any

particular point in time.” • Things “health” might include ...

– Functional abilities? Which ones?– Pain?– Other?

“Dimensions” of Health

Typical Concepts & Domains

• Health Perceptions• Social Function

– Soc. relations– role function– intimacy– communication

• Impairment– sensory

function/loss– symptoms

• Psychological Funct.– Cognitive– emotional– mood/feelings

• Physical Function– mobility– physical activity– self-care

F ig u re 1 . A P oss ib le H ie ra rch ica l V iew o f H ea lth D im en s ion s

S e lf-p erce ived(se lf-ra ted )

H ea lth

M ob ility

D a ilyac tivit ies

P h ys ica lF u n c tion

w ithF am ily & F rien d s

M ajo r L ifeR o le

R ec rea tion

S oc ia l/R o leF u n c tion

M em ory

P rob lemS o lvin g

C og n it iveF u n c tion

A b ility toF u n c tion

P a in

E n erg y/V ita lity

H ap p in essM ood

D ep ress ion /A n xie ty

S e lf Im ag e

E m otion a l

V is ion

H earin g

S en sory

E xis ten tia l/E xp erien tia l

S ym p tom s &C ap ab ilit ies

O vera ll H ea lth

A Hierarchy of Health Dimensions

Health states are multidimensional

• Measure as vector

–one number for each dimension

• Create one summary number

• State 1

– intermittent moderate pain– no mobility limitations– able to do normal socio-occup.

functions• State 2

– continuous mild pain– mobility limitation– some occupational restrictions

Example

Profile (“vector”) representationProfile (“vector”) representation1. Decide what dimensions

2. Develop scales for each dimension

3. Develop process for locating patients on each dimension

PF SF PA = (70, 30, 50)B = (55, 60, 90)

Physical Function

Social Function

Pain

A

B

Single number (“scalar”) representation:

1. Same steps as for a profile

+2. Develop process for aggregating the attributes into one summary number.

OR

Just do direct aggregate scaling

100

65

45

0

State B

State A

Perfect health

dead

Example classification scheme: YHL

Self-rated health

Excel. VGood Good Fair Poor

none

limited. in “other” activities

limited in major activity

cannot do major activity

need help in IADLs

need help in ADLSs

Fu

ncti

on

al

ab

ilit

y

Example classification scheme: YHL

Self-rated health

Limits:Excel. VGood Good Fair Poor

none

ltd. in “other”activities

ltd. in majoractivitycannot do majoractivity

need help inIADLs

need help inADLSs

5 levels of self-rating x

6 levels of function

= 30 health states

An intermediate health stateBest Worst

Self-rated health

Limits:Excel. VGood Good Fair Poor

none

ltd. in “other”activities

ltd. in majoractivitycannot do majoractivity

need help inIADLs

need help inADLSs

An intermediate health stateBest Worst

Scaling the Health States:

1.0

Dead

0.0? ?

Self-rated health

Excel. VGood Good Fair Poor

none 1.0 0.92 0.84 0.63 0.47

limited. in“other” activities

0.87 0.79 0.72 0.52 0.38

limited in majoractivity

0.81 0.74 0.67 0.48 0.34

cannot do majoractivity

0.68 0.62 0.55 0.38 0.25

need help inIADLs

0.57 0.51 0.45 0.29 0.17

need help inADLSs

0.47 0.41 0.36 0.21 0.10

Weights for YHLF

un

ctio

nal

ab

ilit

y

Note: “dead” = 0.00

Definitions …..

• HALYs: health-adjusted life years using a health status measure for health weights

– QALYs: quality-adjusted life years

… a type of HALY computed using a HRQOL measure for health weights.

Disease Specific General Health

non-preference

physical measures

Many! e.g.

joint countstotal cholesterol

--

rating scales

Many!

SIP, Rand GHS, COOP, MOS short forms EVGFP

preference based

indexed ?

QWB, HUI, EQ-5D,YHL?

patient’s own prefs. ad hoc ad hoc

Disease-specific instruments

• Very specific to intended effects of treatments

• Can be sensitive to small changes in disease activity/status

• Clinicians can link to specific actions

But disease-specific measures may miss things

• Many treatments have unintended effects (arthritis & hearing)

• Many people (especially when older) have multiple health conditions (median number is 3) ...

Why an interest in measures of General Health?

(aka “generic measures”)

• Allows many comparisons:– across diseases– in people with multiple conditions– across studies

• Needed for cost-effectiveness studies

Medical Outcomes Study -- “short forms”

• Derived from Rand General Health Survey• Originally 250+ questions• Published short forms that are in use:

– SF-12– SF-20– SF-36

SF-36• 8 components, scaled worst=0 to

best=100Physical functioningRole function (from physical limitation)PainGeneral Health Perception Mental healthVitalitySocial functioningRole function (from emotional limitation)Mental health

New Scaling for SF-36 & SF-12

• PCS : physical component scale

• MCS: mental component scale

Two web sites for SF-36

• http://www.sf-36.org/demos/SF-36.html

• http://www.sf-36.org/images/maruishslide1.jpg

Decision Tree Overview: Movement Across Health States Over Time

What’s Next?

• Break

• Technology Evaluation Roundtable

• Projects