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ByElizabeth Glaser, MS, MA, ACRN, RN-BCHeller School for Social Policy and ManagementBrandeis University415 South Street, MS 035Waltham, Massachusetts. USA 02453eglaser@brandeis.edu Wednesday, April 17th, 2013: Health related quality of Life1Introduction to Cost Effectiveness and Cost Benefit Analysis Class 3 - 3 Feb 20101Part 1:Health-related quality of life 2Health related quality of life- HRQOLHRQOL- DefinitionMeasurement types and tools:health status measures preference-based measuresMeasurement issuesRecall-biasOrdering errors, objections, invariant responses

3Quality of life quality of life subjective perception of life satisfaction

Very broad can cover aspects of life beyond health

4HealthA state of complete physical, mental, and social well-being not merely the absence of disease . (WHO,1991)

5Health related quality of life Health related quality of life ( HRQOL)

An individuals subjective perception of the impact of health status, including disease and treatment, on physical, psychological, and social functioning.Leidy NK, Revicki DA, and Genest B. "Recommendations for evaluating the validity of quality of life claims for labeling and promotion." Value in Health 2.2 (1999): 113-127.

6HRQOL measurementTypically measured by one of two survey methods :

Health status

Preference-based or utility7Health status measures Measure perceived general health, impairment,or disease by subjective assessment of symptoms or impairments:

Within domains which address health concepts:

DomainHealth conceptpain physical healthgeneral well-beingmobilityability to care for selfsocial functioning, role functioning ability to participate in daily work, school and leisure activitiesmood: anxiety and depressionmental health

8Health status measures Period - Entire survey may cover a specific period or have individual questions which ask about perceptions within a specific time frame.

Viewpointdirect survey of a personIndirect proxy survey of a child or impaired person

9Health status measures Instruments to measure health status:early instrument Sickness Impact Profile Short Form : SF-36, SF-12, SF-8 WHOQOL-100, WHOQOL-BREF

10Health status measures Short Form :SF-8 http://www.sf-36.org/demos/SF-8.html

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14Preference-based or utility measures A generic utility questionnaire collects data on quality of life in a way that enables it to be applied to a pre-scaled matrix of health state preferences (values).(Bowling, 2001)

15Preference-based or utility measures valuation of a particular health state

the state is valued as one number scaled between 1.0 ( perfect health) and 0.0 (state equivalent to being dead)

health states worse than being dead can be scaled to less than zero.

16Preference-based or utility measures* Utility measurement The definition and description of a set of health states of interest

Valuation of health states of interest through measurement of preferences *NICE, April 2009. Document NPR09/1103

17Preference-based or utility measures* Applied by :Direct measurement of utilities can be for condition or disease-specific health states.

Indirect measurement of utilities performed by applying utility algorithms to generic or disease-specific preference-based questionnaires, or bymapping from a disease-specific health- HRQOL instrument onto the utility algorithm of a generic instrument such as the EQ-5D (EuroQol five dimension) or HUI2 (Health Utilities Index-2)*NICE, April 2009. Document NPR09/1103

18Visual analogue scale (VAS)*VAS measures a characteristic or attitude that ranges across a continuum of values that cannot easily be measured directly.

The patient marks on the line the point that they feel represents their perception of their current state.*2001 Blackwell Science Ltd, Journal of Clinical Nursing, 10, 697706

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Community-based valuation of disease states22Community-based valuation of highest and lowest disease states23

Adapted from Salomon JA, Vos T, Hogan DR, et al. Common values in assessing healthoutcomes from disease and injury: disability weights measurement study for the GlobalBurden of Disease Study 2010. Lancet 2012; 380: 212943.

EuroQol 5D24

25Which should you choose?Health status measuresOutcomes for medical decision making, clinical trials, and epidemiology

Preference-based or utility measuresOutcomes for medical decision making, policy, resources decisions and to calculate QALYs

26Which should you choose?In general , economic evaluations require the use of preference-based or utility measures over health status measures

27Calculating QALYs#Utilities are used to calculate QALYs

Utility of health state * life years = QALYs

Example: utility for metastatic breast cancer state = 0.85.If chemotherapy extends life in this state by 6months, QALYs saved = 0.85 * 0.5 years = 0.425.

# Wittenberg,201028

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32Simple quality-adjusted life-year calculations**Source: Drummond et al. 2005, Box 6.8, p. 182

33Introduction to Cost Effectiveness and Cost Benefit Analysis Class 5 - 13 Feb 201033Other uses for utilitiesDesk studies For retrospective studies or theoretical scenarios Where can you find data?Literature from previous studies which use utilities Global Burden of Disease or others.Using an established scaleInstruments are relative 34Qualityadjusted life-years from an intervention**From: Torrace (1996) Fig 1 and Gold (1996) Fig. 4.2 Source: Drummond et al. 2005, Fig. 6.6, p. 173

35Introduction to Cost Effectiveness and Cost Benefit Analysis Class 5 - 13 Feb 201035Use of utilities and health preference*In practice, preferences often used as proxies for utilitiesMeasurement differs between preferences and utilitiesUtilities often more difficult to measureInstruments vary (e.g., time trade off measures preferences, standard gamble measures utility)*Wittenberg36Survey instrumentsQuick review of survey instruments:

Surveys should be reliable, producing the same, or very similar results, on two or more administrations to the same respondents.

Internal reliability

37Survey instrumentsInternal reliability- How well does each item hold together to measure the bigger picture , the underlying construct? measured by Cronbach's alpha Acceptable range .70-.90.90 the instrument questions are too redundant

38Survey instrumentsValidity 4 aspects

Face validity are the questions clear and easily understood?

content validity-does the survey cover all aspects of the thing that you are measuring?

39Survey instrumentsValidity 4 aspectscriterion validity- does the test hold up over time and when compared to a known standard ?

construct validity- does the survey measure what you want it to measure?

40Measurement issues- recall bias Recall bias due to timeEvaluation of the optimal recall period for disease symptoms in home-based morbidity surveillance in rural and urban Kenya, Feikin et al, International Journal of Epidemiology 2010;39:450458.

collected illness data among 53,000 people during fortnightly home visits in rural and urban Kenya.

Dates of cough, fever and diarrhea in the past 2 weeks and health-seeking behaviour were recorded.

41Measurement issues- recall bias Incidence rates were modeled with Poisson regression for data over a one year period

Incidence rates dropped by proximity in time to the study visit.

i.e., there was higher incidence within 06 days period than 713 days before the home visit

This was true across all symptoms, sites and ages.

42Measurement issues- recall bias Recall decay was steeper for:Rural >urban sites , proxy >self-reported symptoms

Recall of documented clinic visits & prescriptions declined by 7, 15 and 23% per week in children aged