Multiple Sclerosis Impact Scale (MSIS-29): reliability and validity in hospital based samples.

BACKGROUND AND AIM The psychometric properties of rating scales are sample dependent and need evaluations in different samples. The Multiple Sclerosis Impact Scale (MSIS-29), a new patient based rating scale for multiple sclerosis (MS) was predominantly developed from a community based sample derived from the MS Society. A number of important patient characteristics of this sample remain unknown. The aim of the study was to evaluate five psychometric properties of the MSIS-29 in three hospital based samples: people admitted for rehabilitation, people admitted for intravenous corticosteroid treatment for MS relapses, and people with primary progressive MS. METHODS People with MS were recruited from the three clinical settings. They completed several health measures. MSIS-29 data were evaluated for data quality, scaling assumptions, acceptability, reliability and validity, and compared with those from a previously reported community based study. RESULTS A total of 233 people (rehabilitation p=53; corticosteroids p=76; primary progressive p=104) completed questionnaires. In all samples, missing data were low (or=0.91). Correlations between the MSIS-29 and other scales were consistent with a priori hypotheses. Findings were consistent with those from the community samples. CONCLUSIONS The psychometric properties of the MSIS-29 are consistent across three hospital based samples, and similar to those in the community samples. These findings further support its use as an outcome measure in different clinical settings.