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Confirmatory factor analysis of the thyroid-related quality of life questionnaire ThyPRO.

ABSTRACT: Thyroid diseases are prevalent and chronic. With treatment, quality of life is restored in most, but not all patients. Construct validity of the thyroid-related quality of life questionnaire, ThyPRO, has been established by multi-trait scaling, but not evaluated with more elaborate methods. The purpose of the present study was to evaluate dimensionality of the ThyPRO scales and to attempt to understand possible item misfit through structural equation modeling for categorical data.The current 85-item version of ThyPRO consists of 13 scales, covering domains of physical (4 scales) and mental (2 scales) symptoms, function and well-being (3 scales) and participation/social function (4 scales). The data were collected from a cross-sectional sample of 907 thyroid patients. One-factor confirmatory models were fitted to each scale, and evaluated by model fit statistics (comparative fit index >0.95, root mean square error of approximation <0.08), magnitude of factor loadings, model residual correlations and modification indices (MI). Indications of multi-dimensionality were tested in bi-factor models. Possible item misfit was evaluated in a combined, investigational model.Each ThyPRO scale was adequately represented by a unidimensional model after minor revisions. Eleven items were identified in the unidimensional models as potentially misfitting and were investigated further by multidimensional modeling.Elaborate psychometric modeling supported the construct validity of the ThyPRO. However, 11 potentially misfitting items and 18 items with local dependence to other items are candidates for removal in future item reduction processes.

SUBMITTER: Watt T

PROVIDER: S-EPMC4172819 | biostudies-literature | 2014 Sep

REPOSITORIES: biostudies-literature

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Confirmatory factor analysis of the thyroid-related quality of life questionnaire ThyPRO.

Watt Torquil T Groenvold Mogens M Deng Nina N Gandek Barbara B Feldt-Rasmussen Ulla U Rasmussen Åse Krogh ÅK Hegedüs Laszlo L Bonnema Steen Joop SJ Bjorner Jakob Bue JB

Health and quality of life outcomes 20140910

<h4>Background and aim</h4>Thyroid diseases are prevalent and chronic. With treatment, quality of life is restored in most, but not all patients. Construct validity of the thyroid-related quality of life questionnaire, ThyPRO, has been established by multi-trait scaling, but not evaluated with more elaborate methods. The purpose of the present study was to evaluate dimensionality of the ThyPRO scales and to attempt to understand possible item misfit through structural equation modeling for categ ...[more]

PMID: 25213857

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Project description:Study questionWhich of the competing models of the Endometriosis Health Profile 30 Questionnaire (EHP-30) factor structure is best supported by confirmatory factor analysis (CFA)?Summary answerFindings support a five-factor first-order model of the EHP-30, thereby lending support to the model originally suggested by the questionnaire developers.What is known alreadyEndometriosis has a negative impact on quality of life, and measures specifically developed to address this impact, such as the EHP-30, are vital in research and disease management. Previous studies have found different models of the EHP-30 factor structure, and generated uncertainty regarding how to use the questionnaire. CFA can be applied to compare competing factor models and determine the underlying structure of a questionnaire.Study design size durationThis cross-sectional multicenter study included 304 women with endometriosis recruited from three different public health service endometriosis clinics (referral centers for treatment of severe endometriosis) and the Danish Endometriosis Patients Association from 2014 to 2015.Participants/materials setting methodsDiagnosis of endometriosis was confirmed in medical records for 84.2% and by histology for 66.8% of participants. Questionnaires (the licensed Danish version of the EHP-30) were sent by post two times with a 6- to 12-week interval. CFA was used to examine construct validity and Bland-Altman plots to examine test-retest reliability and the convergent validity with the Short Form 36 version 2.Main results and the role of chanceResponse rate was high (87.6%). CFA supported the original first-order five-factor structure of the EHP-30, and thereby, the use of five separate scale-scores in clinical and research practice. Visual inspection of Bland-Altman plots suggested excellent test-retest reliability of the EHP-30 and supported the use of a disease specific quality of life instrument for women with endometriosis.Limitations reasons for cautionDiagnosis could not be confirmed through histology data in 33.2% of participants. However, subgroup analyses based on women with confirmed histology only, yielded similar results. Data related to menstrual cycle stage and the use of hormonal and pain medication during questionnaire completion were not collected. A larger study, including data from different countries on different continents, would be better designed to exclude potential population bias.Wider implications of the findingsEHP-30, with its original five-factor structure, appears to be a valid, stable, and specific quality of life measure for women with endometriosis. It seems easy to understand, quick to administer, and importantly, scoring might be unaffected by cyclical/menstrual pain symptoms related to endometriosis. The finding of a five-factor model from different studies across several countries supports the crosscultural validity of the EHP-30.Study funding/competing interestsThis work was supported by the Danish Endometriosis Association, which is a nongovernmental organization run by women with endometriosis and by a scholarship from the Health Research Fund of Central Denmark Region. The authors have no conflicts of interest.Trial registration numberThe Danish Data Protection Agency (J.nr: 2013-41-2264).

Dataset Information

Confirmatory factor analysis of the thyroid-related quality of life questionnaire ThyPRO.

Publications

Confirmatory factor analysis of the thyroid-related quality of life questionnaire ThyPRO.

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