Comparison of patient-reported outcome measures in multiple sclerosis

Background - Patient-reported outcome measurements (PROMS) have been proposed sensitive outcome parameters in multiple sclerosis (MS). In this study, we assessed a German version of the Multiple Sclerosis Impact Scale (MSIS-29) and a revised version of the Hamburg Quality of Life Questionnaire in Multiple Sclerosis (HAQUAMS) in comparison with rater- and physician-based tools. Methods - Consecutive MS patients (n = 117) of the MS outpatient unit were included. In addition to MSIS-29 and HAQUAMS, the following parameters were obtained: Expanded Disability Status Scale (EDSS) and modified Multiple Sclerosis Functional Composite (MSFC) [9-hole peg test (9HPT), 25-foot walk test and symbol digit modalities test]. We investigated validity, internal consistency and test-retest reliability as well as correlation between these measures. Results - Internal consistency (Cronbach's alpha <= 0.96) and test-retest coefficients (ICC <= 0.87) of both scales were high and satisfied psychometric standards. Convergent and discriminant validity was supported by direction, magnitude and pattern of correlation with other rater-based measures depending on the functional subdomain. Both MSIS-29 and HAQUAMS correlated with EDSS (rho = 0.55 vs 0.62), but stronger correlation was found between MSIS-29 and HAQUAMS total score (rho = 0.90). Both scales distinguished between patient groups of varied disease severity and cognitive impairment. Conclusion - Patient-reported outcome measurements as MSIS-29 and HAQUAMS seem to be valid instruments to detect different impairment levels in comparison with traditional rater-based instruments like EDSS or MSFC.