Usefulness of EQ-5D for evaluation of health-related quality of life in young adults with first-episode psychosis
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To evaluate the psychometric properties of the EQ-5D and the usefulness of this instrument in psychiatric practice as a measure of health-related quality of life (HRQoL) in a sample of young adults with first-episode psychosis.
The validity of individual questionnaire items is studied using an Item Response/Latent Trait Theory modeling approach. Sensitivity of response patterns on EQ-5D items to particular diagnostic subtypes of psychosis is investigated using a finite mixture modeling approach through latent class analysis. Finally, a structural equation modeling framework is used to study differential item functioning via a multigroup approach.
Results suggest that the data closely correspond to the Rasch Rating Scale Model, and therefore that EQ-5D latent scores are equal interval measures. Despite comprising relatively few items, the instrument yields reliable measures of HRQoL for group comparisons and cost-effectiveness evaluation, but EQ-5D score is too imprecise for the assessment of HRQoL for clinical purposes at the individual level. A significant relationship was found between EQ-5D responses and type of psychosis due to inclusion of item anxiety/depression in EQ-5D. Two items (anxiety/depression, functioning in usual activities) showed an ethnicity bias.
Psychometric evidence confirmed the EQ-5D to be a valid, interval measure that is scalable according to Rasch principles.
KeywordsQuality of life Psychosis Psychometrics
A generic concept reflecting concern with the modification and enhancement of life attributes with focus on physical and mental health
Portrayed equal interval scale with maximum point scores of 100 (denoting “best imaginable health”) and a lowest score of zero (denoting “worst health imaginable”)
Measure of cost-effectiveness of interventions in healthcare settings
- DSM IV
Diagnostic and statistical manual of mental disorders, 4th edition
Operational criteria checklist for psychotic and affective illness
Positive and negative syndrome scale used for assessment of severity of psychopathology
Method for detection measurement bias of items with respect to groups
This study was funded by the Department of Health. TJC and PBJ are supported by the Wellcome Trust Grant number 088869/B/09/Z. PBJ acknowledges support from the NIHR for the CLAHRC for Cambridgeshire & Peterborough. We would like to thank the clinical teams taking part in the National Eden Study.
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