Crohn’s Disease in Sickness and in Health : Studies of Health Assessment Strategies and Impact on Health-Related Quality of Life

Sammanfattning: 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.