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Classical test theory versus Rasch analysis for quality of life questionnaire reduction

BACKGROUND: Although health-related quality of life (HRQOL) instruments may offer satisfactory results, their length often limits the extent to which they are actually applied in clinical practice. Efforts to develop short questionnaires have largely focused on reducing existing instruments. The app...

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Autores principales: Prieto, Luis, Alonso, Jordi, Lamarca, Rosa
Formato: Texto
Lenguaje:English
Publicado: BioMed Central 2003
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC194220/
https://www.ncbi.nlm.nih.gov/pubmed/12952544
http://dx.doi.org/10.1186/1477-7525-1-27
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author Prieto, Luis
Alonso, Jordi
Lamarca, Rosa
author_facet Prieto, Luis
Alonso, Jordi
Lamarca, Rosa
author_sort Prieto, Luis
collection PubMed
description BACKGROUND: Although health-related quality of life (HRQOL) instruments may offer satisfactory results, their length often limits the extent to which they are actually applied in clinical practice. Efforts to develop short questionnaires have largely focused on reducing existing instruments. The approaches most frequently employed for this purpose rely on statistical procedures that are considered exponents of Classical Test Theory (CTT). Despite the popularity of CTT, two major conceptual limitations have been pointed out: the lack of an explicit ordered continuum of items that represent a unidimensional construct, and the lack of additivity of rating scale data. In contrast to the CTT approach, the Rasch model provides an alternative scaling methodology that enables the examination of the hierarchical structure, unidimensionality and additivity of HRQOL measures. METHODS: In order to empirically compare CTT and Rasch Analysis (RA) results, this paper presents the parallel reduction of a 38-item questionnaire, the Nottingham Health Profile (NHP), through the analysis of the responses of a sample of 9,419 individuals. RESULTS: CTT resulted in 20 items (4 dimensions) whereas RA in 22 items (2 dimensions). Both instruments showed similar characteristics under CTT requirements: item-total correlation ranged 0.45–0.75 for NHP20 and 0.46–0.68 for NHP22, while reliability ranged 0.82–0.93 and 0.87–94 respectively. CONCLUSIONS: Despite the differences in content, NHP20 and NHP22 convergent scores also showed high degrees of association (0.78–0.95). Although the unidimensional view of health of the NHP20 and NHP22 composite scores was also confirmed by RA, NHP20 dimensions failed to meet the goodness-of fit criteria established by the Rasch model, precluding the interval-level of measurement of its scores.
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spelling pubmed-1942202003-09-16 Classical test theory versus Rasch analysis for quality of life questionnaire reduction Prieto, Luis Alonso, Jordi Lamarca, Rosa Health Qual Life Outcomes Research BACKGROUND: Although health-related quality of life (HRQOL) instruments may offer satisfactory results, their length often limits the extent to which they are actually applied in clinical practice. Efforts to develop short questionnaires have largely focused on reducing existing instruments. The approaches most frequently employed for this purpose rely on statistical procedures that are considered exponents of Classical Test Theory (CTT). Despite the popularity of CTT, two major conceptual limitations have been pointed out: the lack of an explicit ordered continuum of items that represent a unidimensional construct, and the lack of additivity of rating scale data. In contrast to the CTT approach, the Rasch model provides an alternative scaling methodology that enables the examination of the hierarchical structure, unidimensionality and additivity of HRQOL measures. METHODS: In order to empirically compare CTT and Rasch Analysis (RA) results, this paper presents the parallel reduction of a 38-item questionnaire, the Nottingham Health Profile (NHP), through the analysis of the responses of a sample of 9,419 individuals. RESULTS: CTT resulted in 20 items (4 dimensions) whereas RA in 22 items (2 dimensions). Both instruments showed similar characteristics under CTT requirements: item-total correlation ranged 0.45–0.75 for NHP20 and 0.46–0.68 for NHP22, while reliability ranged 0.82–0.93 and 0.87–94 respectively. CONCLUSIONS: Despite the differences in content, NHP20 and NHP22 convergent scores also showed high degrees of association (0.78–0.95). Although the unidimensional view of health of the NHP20 and NHP22 composite scores was also confirmed by RA, NHP20 dimensions failed to meet the goodness-of fit criteria established by the Rasch model, precluding the interval-level of measurement of its scores. BioMed Central 2003-07-28 /pmc/articles/PMC194220/ /pubmed/12952544 http://dx.doi.org/10.1186/1477-7525-1-27 Text en Copyright © 2003 Prieto et al; licensee BioMed Central Ltd. This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose, provided this notice is preserved along with the article's original URL.
spellingShingle Research
Prieto, Luis
Alonso, Jordi
Lamarca, Rosa
Classical test theory versus Rasch analysis for quality of life questionnaire reduction
title Classical test theory versus Rasch analysis for quality of life questionnaire reduction
title_full Classical test theory versus Rasch analysis for quality of life questionnaire reduction
title_fullStr Classical test theory versus Rasch analysis for quality of life questionnaire reduction
title_full_unstemmed Classical test theory versus Rasch analysis for quality of life questionnaire reduction
title_short Classical test theory versus Rasch analysis for quality of life questionnaire reduction
title_sort classical test theory versus rasch analysis for quality of life questionnaire reduction
topic Research
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC194220/
https://www.ncbi.nlm.nih.gov/pubmed/12952544
http://dx.doi.org/10.1186/1477-7525-1-27
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