Transcript No Slide Title

Quality of Life:
What Are We Measuring?
Geraldine Padilla, PhD
Professor and Associate Dean
UCSF School of Nursing
WHAT ARE WE MEASURING?
• What do you want to measure?
• Why do you want to measure QOL?
• How will QOL be measured?
• What is the meaning of a QOL score?
WHAT DO YOU WANT TO
MEASURE?
• Global measure
• Health-related measure
• Unidimensional measure
• Multidimensional measure
WHAT DO YOU WANT TO
MEASURE?
QOL Global definition: focus on
perceived gap
“the extent to which hopes and
ambitions are matched by
experience” (Calman, 1984)
WHAT DO YOU WANT TO
MEASURE?
QOL Global definition: focus on
personal judgment of positive &
negative attributes
“a personal statement of the
positivity or negativity of attributes
that characterize one’s life” (Grant,
Padilla, Ferrell, Rhiner, 1990 )
WHAT DO YOU WANT TO
MEASURE?
QOL Global definition: focus on
perceived position compared to
personal criteria, i.e. gap
" an individual's perception of their
position in life in the context of the
culture and value systems in which
they live and in relation to their
goals, expectations, standards &
concerns.“ (WHO, 1993)
WHAT DO YOU WANT TO
MEASURE?
QOL Global definition: focus on
perceived satisfaction and
importance
“an individual’s perceptions of wellbeing that stem from satisfaction or
dissatisfaction with dimensions of
life that are important to the
individual” (Ferrans, Powers, 1985)
WHAT DO YOU WANT TO
MEASURE?
QOL health-related definition: focus
is uni-dimensional on physical
function
(Karnofsky, 1949)
WHAT DO YOU WANT TO
MEASURE?
QOL health-related definition: focus
on self-report of two-dimensional
factors
“QOL… refers to a person or group's
perceived physical and mental health
over time. (http://www.cdc.gov/hrqol/)
WHAT DO YOU WANT TO
MEASURE?
QOL health-related definition: focus
on realistic self-report of multidimensional aspects
“a pragmatic, day to day, functional
representation of a patient’s
physical, psychological, and social
response to a disease and its
treatment” (Schipper, 1990)
WHAT DO YOU WANT TO
MEASURE?
QOL health-related definition: Focus
on satisfaction with function based
on perceived gap
“Patient’s appraisal of and
satisfaction with their current level
of functioning as compared to what
they perceive to be possible or
ideal” (Cella, Tulsky, 1990)
WHAT DO YOU WANT TO
MEASURE?
QOL health-related definition: focus on
level & satisfaction with function
& control over illness
“state of well-being...composite of …
ability to perform everyday activities
which reflect physical, psychological
and social well-being, and patient
satisfaction with levels of functioning
and the control of disease and/or
treatment related symptoms” (Gotay et al.,
1992)
WHAT DO YOU WANT TO
MEASURE?
QOL health-related definition: focus on
multidimensional factors in context of
survival time
"Health-related QOL is the value
assigned to duration of life as modified
by the impairments, functional states,
perceptions and social opportunities
influenced by disease, injury, treatment
or policy.” (Patrick, Erickson, 1993)
WHAT DO YOU WANT TO
MEASURE?
QOL health-related definition: focus
on self-report of multi-dimensional
factors
"... a unique perception, denoting
the way that individual patients feel
about their health status and/or
nonmedical aspects of their lives.“
(Gill and Feinstein, 1994)
WHAT DO YOU WANT TO MEASURE?
Summary of HRQOL definitions
• Function, well-being (phy, psych, soc, spirit)
• Personal judgment weighing good and bad
aspects of life in context of culture, values
• Value placed on duration of life modified by
disease, treatment, policy
• Ability to perform everyday activities
• Satisfaction with important dimensions of
well-being, e.g. function
• Gap between hope & experience, ideal &
possible, expectations & current position
• Control over disease
WHY DO YOU WANT TO MEASURE
QUALITY OF LIFE?
• Is QOL a measure of treatment efficacy?
• Is QOL a measure of the quality of
survivorship?
• What are the QOL consequences of
research interventions, treatment, care?
• Do patients and clinicians see the
patient’s QOL in the same way?
WHY DO YOU WANT TO MEASURE
QUALITY OF LIFE?
• Do patients consider length of life or QOL
more important?
• Is prolonging life at any QOL cost
reasonable, desirable?
• Is cure the most important outcome?
• Is relief of physical symptoms enough?
• Do symptom clusters determine QOL level?
WHY DO YOU WANT TO MEASURE
QUALITY OF LIFE?
• Do potential QOL outcomes influence
health policy?
• Because resources are finite, do QOL
considerations influence who gets
treated?
• Do potential QOL outcomes influence
physicians’ treatment recommendations,
and patients’ treatment choice?
HOW WILL QUALITY OF LIFE BE
MEASURED?
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•
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Quality of Life theory
Measurement theory
Reliability, validity
Domains, dimensions, subscales
Qualitative and/or quantitative methods
Questionnaires, standardized instruments,
websites
HOW DO YOU WANT TO MEASURE QOL?
QOL THEORY
Importance of QOL Theory:
• Impose conceptual clarity by
distinguishing between predictors
and attributes of HRQL
– QOL Predictor: symptom severity,
intensity, frequency
– QOL Attribute: perceived symptom
distress
HOW DO YOU WANT TO MEASURE QOL?
QOL THEORY: PREDICTORS, DOMAINS
Physical wellbeing &
Symptoms
Psychological
well-being
Pain
Social well-being
Spiritual wellbeing
Ferrell, Grant, Padilla et al., 1991
HOW DO YOU WANT TO MEASURE QOL?
QOL THEORY: PREDICTORS, DOMAINS
Duration of Life
Disease and Injury
Impairments
Environment
Prognosis
Physical-Psych-Social Func.
Health Perceptions
Opportunity for Health
Patrick, Erickson, 1993
HOW DO YOU WANT TO MEASURE QOL?
QOL THEORY: PREDICTORS, DOMAINS
Wilson, Cleary 1995
HOW DO YOU WANT TO MEASURE QOL?
QOL THEORY: PREDICTORS, DOMAINS
Response Shift & HRQOL (Sprangers & Schwartz, 1999)
Antecedents
Catalysts
Accommodation Process
QOL Outcomes
Appraisal
Accommod.
Discrepancy Mechanisms:
Response
Cope
Compare
Reorder goals
Reframe
expectations
Sprangers, Schwartz, 1999
Shift:
QOL
Reconceptualize
Recalibrate
Reprioritize
HOW DO YOU WANT TO MEASURE QOL?
QOL THEORY: PREDICTORS, DOMAINS
Ashing-Giwa, 2005
HOW DO YOU WANT TO MEASURE QOL?
MEASUREMENT THEORY/MODELS
Classical Test Theory
• Traditional psychometrics, validity (e.g. factor
analysis) and reliability (e.g. Cronbach’s alpha),
are critical characteristics of tests/scales.
• Measurement scales based on averages or
simple summations of scale items.
HOW DO YOU WANT TO MEASURE QOL?
MEASUREMENT THEORY/MODELS
• Item Response Theory:
• “… mathematical models that describe, in
probabilistic terms, relationships between
response to a survey question and one’s
level of the ‘latent variable’ measured (p. 55)
• Latent variable: Construct that can’t be
directly measured by a single observable
variable or item. Indirectly measured with
multiple items in a multi-item scale. (p. 56)
HOW DO YOU WANT TO MEASURE QOL?
MEASUREMENT THEORY/MODELS
Item Response Theory:
• Level of QOL accounts for one’s probable
response to each item in a QOL questionnaire.
• Value of IRT – Investigator can determine
– contribution of each item in measuring the
underlying construct
– redundancy of an item relative to other
items in the scale
– appropriateness of response categories
(Reeve, Fayer p. 63)
HOW DO YOU WANT TO MEASURE QOL?
OTHER MEASUREMENT ISSUES
• Reliability
• Validity
• Domain/dimension subscales
HOW DO YOU WANT TO MEASURE QOL?
METHODOLOGICAL CONSIDERATIONS
Different results with different methods:
• Qualitative methods - thematic analysis of
data from interviews
• Quantitative instruments - standardized or
home grown questionnaires
– Global, health-related
– domain specific
HOW DO YOU WANT TO MEASURE QOL?
METHODOLOGICAL CONSIDERATIONS
Translated or linguistically-culturally tailored
measures – equivalence across cultures or
languages
– Conceptual (equivalent domains, determined
qualitatively)
– Items (measure same domain, are relevant)
– Semantic (words, phrases have same meaning)
– Operational (same format, scoring, item scaling)
– Measurement (reliability, validity, means, SDs)
– Function (instrument does what it is supposed to
do equally well across cultures/languages
(Herdman, Fox-Rushby, & Badia, 1998)
HOW DO YOU WANT TO MEASURE QOL?
METHODOLOGICAL CONSIDERATIONS
Different results with different methods:
• Self-report and/or proxy report
• Short and/or long time period
• Single or multiple measures
• Short or long measures
• Home, clinic, hospital, community
• Time of measurement in relation to a
catalyst
HOW DO YOU WANT TO MEASURE QOL?
RESPONDENT CONSIDERATIONS
Different measures for different populations:
• Adult, adolescent, child
• Healthy, ill, survivor
• Type of illness, disease, symptom
• Health care provider, caregiver
• Men, women
HOW DO YOU WANT TO MEASURE
QUALITY OF LIFE?
Websites of Quality of Life Measures
• BiblioPro: QOL questionnaires in Spanish
http://bibliopro.imim.es/
• Center for QOL Research in Nursing Science
http://www.uib.no/isf/people/doc/qol/httoc.htm
• Brown University
http://www.chcr.brown.edu/pcoc/Quality.htm
• Center for Disease Control and Prevention
http://www.healthmeasurement.org/Measures.html
• Websites for disease/symptom-related QOL Meas.
MEANING OF QOL SCORES
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Missing data
Implicit theories of change & response shift
Confounding variables
Linear and nonlinear relationships
Clinical versus statistical significance
MEANING OF QOL SCORES?
ANALYSIS & INTERPRETATION
Physical Well-being – U-shaped quadratic
model
10.00
QPHYS
7.50
5.00
2.50
0
0
6.25
12.50
W EEKS
18.75
25.00
MEANING OF QOL SCORES?
ANALYSIS & INTERPRETATION
Physical Well-being – patterns of 82 Subjects
10.36
QPHYS
8.40
6.44
4.48
2.52
-1.25
5.63
12.50
W EEKS
19.38
26.25
MEANING OF QOL SCORES?
ANALYSIS & INTERPRETATION
Physical Well-being – U-shaped pattern
Lev-id
011
10.36
QPHYS
8.40
6.44
4.48
2.52
-1.25
5.63
12.50
W EEKS
19.38
26.25
MEANING OF QOL SCORES?
ANALYSIS & INTERPRETATION
Physical Well-being – Flat-high pattern
10.00
QSOC
7.50
5.00
2.50
0
0
6.25
12.50
W EEKS
18.75
25.00
MEANING OF QOL SCORES?
ANALYSIS & INTERPRETATION
Clinical versus Statistical Significance:
Q. What is the minimal clinically important
difference (MCID)?
A. It is “the smallest difference… which
patients perceive as beneficial and would
mandate, in the absence of troublesome side
effects and excessive cost, a change in the
patient’s management.” (Jaeschke, et al.,
1989)
MEANING OF QOL SCORES?
ANALYSIS & INTERPRETATION
Clinical versus Statistical Significance:
• For the SF-36: MCID typically in 3-5 point
range; difference of 1 - 2 points not important
(Samsa 1999, p. 149)
• Value of achieving a MCID depends on the
cost to produce the change
• MCID can be misleading when using average
change scores (e.g. 10 Ss +3 change, 10 Ss 0
change. M= 1.05)
MEANING OF QOL SCORES?
ANALYSIS & INTERPRETATION
Clinical versus Statistical Significance:
• What change in care management is
warranted based on a patient’s report of
minimum discernable difference or
clinician’s judgment of clinically significant
difference?
• MCID for HRQoL may differ with context
such as adjuvant therapy versus palliative
treatment.
MEANING OF QOL SCORES?
ANALYSIS & INTERPRETATION
Clinical versus Statistical Significance:
MCID estimation problems
• Magnitude of change varies depending on
distribution and external standard
• Amount of change may depend on the
direction of change
• Meaning of change depends on where you
start (baseline value)
WHAT ARE WE MEASURING?
• What do you want to measure?
• Why do you want to measure QOL?
• How will QOL be measured?
• What is the meaning of a QOL score?
Thank You!
Questions?