Multiple Sclerosis Impact Scale (MSIS-29): relation to established measures of impairment and disability.

Abstract

To validate the newly developed Multiple Sclerosis Impact Scale (MSIS-29) in a large, well characterized, independent group of MS patients by investigating the relation between the MSIS-29 and the Guy's Neurological Disability Scale (GNDS), the Expanded Disability Status Scale (EDSS) and the MS Functional Composite (MSFC). Two hundred MS patients were recruited at our outpatient department. At the same visit GNDS, EDSS, MSFC and MSIS-29 were assessed. Data obtained from GNDS, EDSS and MSFC assessment were compared to both physical and psychological impact scores of the MSIS-29. In addition the contribution of GNDS subcategories, EDSS functional systems and MSFC components to the physical and psychological impact scores of the MSIS-29 was studied. Median scores were 37.5 for the physical and 22.2 for the psychological impact score of the MSIS-29, 13.0 for GNDS and 4.0 for EDSS. Mean MSFC was 0.07. The physical impact score showed good correlations with both GNDS (0.79) and EDSS (0.68) and a moderate correlation with the MSFC (-0.53). The psychological impact score showed weak correlations with EDSS (0.22) and MSFC (-0.30) and a moderately strong correlation with the GNDS (0.58). In 50 (25%) patients, scores on physical and psychological impact scales diverted, i.e., a relative high score on one scale combined with a relative low score on the other scale. This was related to the clinical disease course. Our study supports the use of the MSIS-29 as a measure for the assessment of physical impact of MS on normal daily life. In addition, our data provides a deeper understanding of the factors that determine both physical and psychological disease impact. Discrepancies between the latter two aspects deserve further attention.