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- [Show abstract] [Hide abstract] ABSTRACT: A cross-sectional survey using patient questionnaires was conducted. OBJECTIVE To assess whether the Roland Disability Questionnaire satisfies the Rasch model including unidimensionality and item separation. The Roland Disability Questionnaire, the most widely used patient-assessed measure of health outcome for back pain, has undergone several evaluations for its measurement properties including reliability, validity, and responsiveness. However, there is no published work relating to the underlying dimensionality of the instrument and the extent to which individual items contribute to the construct of physical disability resulting from low back pain. Patients entering a randomized controlled trial of exercise, manipulation, and usual management for back pain completed a questionnaire that included the Roland Disability Questionnaire. The Winsteps program was used to assess whether the Roland Disability Questionnaire fits the Rasch model. Item fit was assessed using the Infit and Outfit statistics. The Roland Disability Questionnaire was completed by 1008 (90%) of the patients taking part in the trial. Most of the items in the Roland Disability Questionnaire contribute to a single underlying construct. However, four items had poor Outfit statistics, suggesting that they do not contribute sufficiently to the scale hierarchy. Several items positioned around the middle of the hierarchy are not sufficiently distinct in terms of difficulty. There were very few items positioned at the extremes of the hierarchy. The Roland Disability Questionnaire largely satisfies the Rasch model for unidimensionality. However, the instrument could be improved through the removal of poorly fitting items and the addition of items at the upper and lower points of the scale hierarchy. The distribution of Roland Disability Questionnaire scores should be carefully considered before statistical testing is undertaken. Rasch transformed scores can be used to deal with deficiencies in the scale hierarchy.
- [Show abstract] [Hide abstract] ABSTRACT: To identify available disease-specific measures of health-related quality of life (HRQL) for diabetes and to review evidence for the reliability, validity and responsiveness of instruments. Systematic searches were used to identify instruments. Instruments were assessed against predefined inclusion and exclusion criteria. Letters were sent to authors requesting details of further instrument evaluation. Information relating to instrument content, patients, reliability, validity and responsiveness to change was extracted from published papers. The search produced 252 references. Nine instruments met the inclusion criteria: Appraisal of Diabetes Scale (ADS), Audit of Diabetes-Dependent Quality of Life (ADDQoL), Diabetes Health Profile (DHP-1, DHP-18), Diabetes Impact Measurement Scales (DIMS), Diabetes Quality of Life Measure (DQOL), Diabetes-Specific Quality of Life Scale (DSQOLS), Questionnaire on Stress in Diabetic Patients-Revised (QSD-R), Diabetes-39 (D-39) and Well-being Enquiry for Diabetics (WED). The shortest instrument (ADS) has seven items and the longest (WED) has 50 items. The ADS and ADDQoL are single-index measures. The seven multidimensional instruments have dimensions covering psychological well-being and social functioning but vary in the remainder of their content. The DHP-1 and DSQOLS are specific to Type 1 diabetes patients. The DHP-18 is specific to Type 2 diabetes patients. The DIMS and DQOL have weaker evidence for reliability and internal construct validity. Patients contributed to the content of the ADDQoL, DHP-1/18, DQOL, DSQOLS, D-39, QSD-R and WED. The authors of the ADDQoL, DHP-1/18, DQOL, DSQOLS gave explicit consideration to content validity. The construct validity of instruments was assessed through comparisons with instruments measuring related constructs and clinical and sociodemographic variables. None of the instruments has been formally assessed for responsiveness to changes in health. Five of the diabetes-specific instruments have good evidence for reliability and internal and external construct validity: the ADDQoL, DHP-1/18, DSQOLS, D-39 and QSD-R. Instrument content should be assessed for relevance before application. The instruments should be evaluated concurrently for validity and responsiveness to important changes in health.
- [Show abstract] [Hide abstract] ABSTRACT: To determine whether depression or anxiety co-occurs with ulcerative colitis (UC) or Crohn's disease (CD) more often than expected by chance, and, if so, whether the mental disorders generally precede or follow the inflammatory bowel diseases (IBD). Nested case-control studies using a database of linked hospital record abstracts. Southern England. Both depression and anxiety preceded UC significantly more often than would be predicted from the control population's experience. The associations were strongest when the mental conditions were diagnosed shortly before UC, although the association between depression and UC was also significant when depression preceded UC by five or more years. Neither depression nor anxiety occurred before CD more often than expected by chance. However, depression and anxiety were significantly more common after CD; the associations were strongest in the year after the initial record of CD. UC was followed by anxiety, but not by depression, more often than expected by chance and, again, the association was strongest within one year of diagnosis with UC. The concentration of risk of depression or anxiety one year or less before diagnosis with UC suggests that the two psychiatric disorders might be a consequence of early symptoms of the as yet undiagnosed gastrointestinal condition. The data are also, however, compatible with the hypothesis that the psychiatric disorders could be aetiological factors in some patients with UC. Most of the excess anxiety or depression diagnosed subsequent to diagnosis of IBD occurs during the year after IBD is diagnosed and the probable explanation is that the mental disorders are sequelae of IBD.
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