Rasch analysis of the Multiple Sclerosis Impact Scale MSIS-29.

BACKGROUND: Multiple Sclerosis (MS) is a degenerative neurological disease that causes impairments, including spasticity, pain, fatigue, and bladder dysfunction, which negatively impact on quality of life. The Multiple Sclerosis Impact Scale (MSIS-29) is a disease-specific health-related quality of life (HRQoL) instrument, developed using the patient's perspective on disease impact. It consists of two subscales assessing the physical (MSIS-29-PHYS) and psychological (MSIS-29-PSYCH) impact of MS. Although previous studies have found support for the psychometric properties of the MSIS-29 using traditional methods of scale evaluation, the scale has not been subjected to a detailed Rasch analysis. Therefore, the objective of this study was to use Rasch analysis to assess the internal validity of the scale, and its response format, item fit, targeting, internal consistency and dimensionality. METHODS: Ninety-two persons with definite MS residing in the community were recruited from a tertiary hospital database. Patients completed the MSIS-29 as part of a larger study. Rasch analysis was undertaken to assess the psychometric properties of the MSIS-29. RESULTS: Rasch analysis showed overall support for the psychometric properties of the two MSIS-29 subscales, however it was necessary to reduce the response format of the MSIS-29-PHYS to a 3-point response scale. Both subscales were unidimensional, had good internal consistency, and were free from item bias for sex and age. Dimensionality testing indicated it was not appropriate to combine the two subscales to form a total MSIS score. CONCLUSION: In this first study to use Rasch analysis to fully assess the psychometric properties of the MSIS-29 support was found for the two subscales but not for the use of the total scale. Further use of Rasch analysis on the MSIS-29 in larger and broader samples is recommended to confirm these findings.

Who is identified when screening for depression is undertaken in general practice? Baseline findings from the Diagnosis, Management and Outcomes of Depression in Primary Care (diamond) longitudinal study.

OBJECTIVES: To report the baseline characteristics of the Diagnosis, Management and Outcomes of Depression in Primary Care (diamond) study cohort and discuss the implications for depression care in general practice. DESIGN: A prospective longitudinal study beginning in January 2005. PARTICIPANTS AND SETTING: Adult patients with depressive symptoms identified via screening with the Center for Epidemiologic Studies Depression Scale (CES-D > or = 16) in 30 randomly selected Victorian general practices. MAIN OUTCOME MEASURE: Depression status on the Patient Health Questionnaire (PHQ). RESULTS: 789 patients form the cohort (71% women). At baseline, 47% were married, 21% lived alone, 36% received a pension or benefit, 15% were unable to work, 23% reported hazardous drinking, 32% were smokers, 39% used antidepressants and 19% used sedatives. 27% satisfied criteria for current major depressive syndrome (MDS) on the PHQ, while 52% had "persistent" depressive symptoms, and 22% had "transient" depressive symptoms, lasting at most a few weeks. Of those satisfying criteria for MDS, 49% were also classified with an anxiety syndrome, 40% reported childhood sexual abuse, 57% reported childhood physical abuse, 42% had at some time been afraid of their partner, and 72% reported a chronic physical condition; 84% were receiving mental health care (either taking antidepressants or seeing a health practitioner specifically for mental health care) compared with 66% of those with persistent depressive symptoms and 57% with transient depressive symptoms. CONCLUSION: This method of screening for depressive symptoms in general practice identifies a group of patients with substantial multiple comorbidities -- psychiatric, physical and social problems coexist with depressive symptoms, raising challenges for the management of depression in general practice.