Applying Expectancy-value ModelApplying Expectancy-value Modelto understand Health Preferenceto understand Health Preference

An Exploratory StudyAn Exploratory Study

Xu-Hao ZhangXu-Hao Zhang

Department of PharmacyDepartment of Pharmacy

National University of SingaporeNational University of Singapore

Outline of Presentation Outline of Presentation

IntroductionIntroduction

Health Preference & the Expectancy-value modelHealth Preference & the Expectancy-value model

Methods Methods

Study Design & Statistical Analysis Study Design & Statistical Analysis

Results Results

Discussion Discussion

Conclusions Conclusions

Health PreferenceHealth Preference

Indicating people’s preference of a particular health Indicating people’s preference of a particular health statestate

Measured by Measured by RSRS (Rating Scale)(Rating Scale) / TTO / SG / TTO / SG Quantified as Quantified as utility scoresutility scores

Confined to bed Some problems washing or dressing self Unable to perform usual activities No pain or discomfort Extremely anxious or discomfort

100

0

8

WhyWhy do we needdo we need to understand health preference?to understand health preference?

Health PreferenceHealth Preference

Utility Utility ScoresScores

Preference-based HRQoL instruments

CUA for treatment comparisons

Reported: Health preference to be associated with

different demographic backgrounds

Diseasemanagement

HowHow can wecan we understand health preference ?understand health preference ?

хх

Health PreferenceHealth Preference

Health preferenceHealth preference Attitude Attitude

Expectancy Expectancy - - valuevalue model model

Subjective probability that Subjective probability that the attitude has the attributethe attitude has the attribute

Attitudinal Attributes Attitudinal Attributes

Evaluative value of Evaluative value of the attribute the attribute

External

External Variables

Variables

Objectives of the studyObjectives of the study

To generate factors of the health preference To generate factors of the health preference

for the “for the “Expectancy-value modelExpectancy-value model” (“” (“EVMEVM”)”)

To investigate the usefulness of To investigate the usefulness of EVM EVM in in

explaining health preference explaining health preference

Study Design Study Design

Focus group approach Focus group approach Attitudinal Attributes (AA) Attitudinal Attributes (AA)

QuestionnaireQuestionnaireDevelopment Development

Pilot studyPilot study One-to-one interview Eligible Chinese and Indian Singaporeans (aged above 20 and with over 6 yrs of education) across 5 age groups (20-29;30-39;40-49;50-59; 60+)

9

Questionnaire DevelopmentQuestionnaire Development1.1. Design:Design:

Measure of health preference of the health state by a 0-100 Visual Measure of health preference of the health state by a 0-100 Visual Analogue Scale Analogue Scale (VAS)(VAS)

Expectancy and value of each attribute, measured on a Expectancy and value of each attribute, measured on a 7-point Likert Scale 7-point Likert Scale

External variables: age, gender, ethnicity, education, housing, mariExternal variables: age, gender, ethnicity, education, housing, marital status, and concurrent chronic diseasestal status, and concurrent chronic diseases

2.2. Face validity: Face validity:

Reviewed by 10 postgraduate students Reviewed by 10 postgraduate students

3.3. Finalization: Finalization:

Amended accordingly, if necessary Amended accordingly, if necessary

Statistical AnalysisStatistical Analysis

Univariate analysis: Univariate analysis:

To identify external variable(s) to be included in EVM

Multiple linear regression models (MLR):

To investigate the explanative power of EVM by examining attitudinal attributesattitudinal attributes and significant external variables (if any) separately or in combination

Results Results

Demographic information: Demographic information: 25 Chinese and 21 Indian Singaporeans 25 Chinese and 21 Indian Singaporeans Age: 45.0 (SD: 15.55) yearsAge: 45.0 (SD: 15.55) years 55.6% female55.6% female

Four attitudinal attributes generated:Four attitudinal attributes generated: reduction in Health-related quality of life (RQoL) reduction in Health-related quality of life (RQoL) adding a burden to family (BTF) adding a burden to family (BTF) dependence on others ( DOO) dependence on others ( DOO) inability to work or study (ITW)inability to work or study (ITW)

Ethnicity Ethnicity to be the only external variable identified to to be the only external variable identified to cause significant difference in VAS scorecause significant difference in VAS score (p<0.05)(p<0.05)

ResultsResults

Chinese Indian Ethnicity

0

10

20

30

40

50

60

70

vas

34

36

4

20

13

16.9(11.8)6.9 (16.7)

ResultsResults

Power of EVM in explaining health preference:Power of EVM in explaining health preference:

The combined sample

(n=46)

Chinese

(n=25)

Indians

(n=21)

EVM

(sum of 4AA, ethnicity)

0.27 * 0.13 0.24*

Sum of 4 AA 0.16 * / /

Ethnicity 0.11 * / /

Table 1. Regression analysis on EVM, AAs and ethnicity

Figures shown as adjusted R square: *p<0.05

ResultsResults Power of each AA in explaining health preferencePower of each AA in explaining health preference

The combined sample

(n=46)

Chinese

(n=25)

Indians

(n=21)

RQol RQol 0.14 *0.14 * 0.16 *0.16 * 0.12 *0.12 *

BTFBTF 0.16 *0.16 * 0.14 *0.14 * 0.09 *0.09 *

DOODOO 0.10 *0.10 * 0.040.04 0.23 *0.23 *

ITW ITW 0.07 *0.07 * 0.09*0.09* 0.0030.003

Table 2. Regression analysis on each AA

Figures shown as adjusted R square; The scores of 4 AAs are not statistically different for two ethnic groups; *: p<0.05

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DiscussionDiscussion

Significance of the study Significance of the study the 1st ever to investigate factors influencing health preferencethe 1st ever to investigate factors influencing health preference

from the psychological angle from the psychological angle demonstrating usefulness of EVM in explaining health preferencedemonstrating usefulness of EVM in explaining health preference providing justification of its application to other populations to providing justification of its application to other populations to

enable comparisonsenable comparisons

Limitations Limitations Small sample sizeSmall sample size generalization of the result generalization of the result х

Studies with larger sample size are suggested to verify the results Studies with larger sample size are suggested to verify the results

The Expectancy-value model is helpful The Expectancy-value model is helpful in explaining the variances in health in explaining the variances in health preference. preference.

Future studies with larger sample sizes Future studies with larger sample sizes and among other populations are and among other populations are suggested for its further verifications.suggested for its further verifications.

ConclusionsConclusions

Thank You !Thank You !