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Structural Equation Modeling of the Relationship between Disease Activity and Health-related Quality of Life Variables in Crohn’s Disease
Linköping University, Department of Clinical and Experimental Medicine, Infectious Diseases. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Clinical and Experimental Medicine, Gastroenterology and Hepatology. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Clinical and Experimental Medicine, Gastroenterology and Hepatology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Centre, Department of Endocrinology and Gastroenterology UHL.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Objective. Disease activity (DA) and health-related quality of life (HRQL) are two major endpoints in outcome assessment of Crohn’s disease (CD).  A health concept model of the relationship between DA and HRQL encompassing five dimensions (biological variables, symptoms, function, worries, and general well-being) in inflammatory bowel disease (IBD) has been postulated previously, forming the basis of the IBD HRQL instrument, the Short Health Scale (SHS). This study evaluates the model, using structural equation modeling technique (SEM) on DA and HRQL data from a cohort of CD patients.

Methods. The relationships of the five dimensions represented by 14 health measures of 283 CD patients were analyzed by confirmatory factor analysis and SEM, using SPSS AMOS v18.0.

Results. All parameter estimates proved significant, and the goodness-of-fit indices were good (χ2=104.2, df=69, p=0.004, CFI=0.986, RMSEA=0.043). A revision of the structural pathway, in which well-being precedes worries, was suggested from empirical data.

Conclusion. The postulated health concept model proved to be a valid and plausible approximation of the relationship between disease activity and subjective health perception in CD. The results support the use of the SHS for subjective health assessment in CD.

Keyword [en]
Crohn’s disease; inflammatory bowel disease; health-related quality of life; disease activity; structural equation modeling
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-66242OAI: oai:DiVA.org:liu-66242DiVA: diva2:402693
Available from: 2011-03-09 Created: 2011-03-09 Last updated: 2011-03-09Bibliographically approved
In thesis
1. Crohn’s Disease in Sickness and in Health: Studies of Health Assessment Strategies and Impact on Health-Related Quality of Life
Open this publication in new window or tab >>Crohn’s Disease in Sickness and in Health: Studies of Health Assessment Strategies and Impact on Health-Related Quality of Life
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Background and aims. Crohn’s disease (CD) is a chronic inflammatory bowel disease (IBD) with potentially deleterious effects on well-being and daily-life functioning. A complete picture of health status in CD therefore comprises both disease activity (DA) and health-related quality of life (HRQL). Several measures of DA and HRQL in CD have been developed. Some have gained prominence as standard endpoints in clinical trials, but none has been validated in Swedish CD patients and their use in clinical practice has been limited. A conceptual health status model of five dimensions (Biological variables, Symptoms, Function, Worries, and Well-being) has been proposed for IBD health assessment, enabling the construction of the Short Health Scale (SHS), a four-item questionnaire intended to facilitate assessment and interpretation of HRQL in IBD.

The aims of this thesis were: (1) to evaluate the Swedish versions of the Inflammatory Bowel Disease Questionnaire (IBDQ) and the Rating Form of IBD Patient Concerns (RFIPC); (2) to evaluate the Short Health Scale; (3) to study the relationship between DA and HRQL variables by identifying determinants of DA outcome and by validating the SHS health status model; (4) to describe the spectrum of disease-related worries and repercussions on general HRQL in a context of social variables, sickness, and disability.

Methods. The thesis is based on clinical variables and HRQL data measured in a population-based cohort of 505 CD patients, consecutively included in conjunction with their regular outpatient visits at three hospitals (Jönköping, Örebro, Linköping). The HRQL questionnaires were evaluated regarding construct validity, reliability, and responsiveness. Multivariate analyses were used to investigate the relationship between Crohn’s Disease Activity Index (CDAI) and physician-assessed DA. The SHS health status model was validated with structural equation modelling (SEM). Disease-related worries and concerns, general HRQL, social variables, sickness, and work disability were compared with data from background population or patients with ulcerative colitis (UC).

Results. The IBDQ had good validity, reliability, and responsiveness, but the original dimensional structure was not supported. The RFIPC was valid, and reliable, but less sensitive to change in disease activity. The SHS had the highest completion rate and proved adequate psychometric properties. The CDAI correlated weakly with the physician’s appraisal of disease activity, being more influenced by subjective health perception than objective disease activity. SEM showed that the SHS model had a good fit to measured data, explaining >98% of the covariance of the variables. Worries and general HRQL impairment were greater in CD than in UC, especially for women. Disease complications and impaired life achievements elicited most worries. CD patients had lower educational level. Female patients were more often living single. The rates of long-term sickness and disability were doubled compared with background population, with worse outcome for women.

Conclusions. The IBDQ, the RFIPC, and the SHS all demonstrated adequate psychometric properties. The SHS was easier to administer and provided a more comprehensive picture of subjective health status. The weak correlation between CDAI and physician-assessed DA was explained by a strong influence of subjective variables on CDAI, stressing the importance of assessing DA and HRQL separately. The SHS health status model was further supported by SEM. CD has tangible effects on subjective health perception, worries and work capacity, especially for women.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2011. 87 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1228
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-66249 (URN)978-91-7393-227-1 (ISBN)
Public defence
2011-04-08, Berzeliussalen, Hälsouniversitetet, Campus US, Linköpings universitet, Linköping, 13:00 (Swedish)
Opponent
Supervisors
Available from: 2011-03-09 Created: 2011-03-09 Last updated: 2012-03-22Bibliographically approved

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