university of minnesota medical technology evaluation and market research department of healthcare...
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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
rO
ver
all
all
Healt
Healt
hhQu
ali
Qu
ali
tyty
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