Measurement Characteristics and Clinical Utility of the 29-Item Multiple Sclerosis Impact Scale

The Multiple Sclerosis Impact Scale (MSIS-29) is a 29-item self-report measure comprised of 20 items associated with a physical scale and 9 items associated with a psychological scale.¹ Items question patients (or their proxies) about the impact of multiple sclerosis (MS) on day-to-day life in the last 2 weeks. All items have 5 response options from 1 (not at all) to 5 (extremely). Each of the 2 scales are scored by summing the responses across items, then converting to a 0 to 100 scale, where 100 indicates greater impact of disease on daily function (worse health). The items were selected via a standardized psychometric process: generating a large item pool from patient interviews and professional judgment, then winnowing down to the current items based on pilot and field testing.¹ Reliability and validity evidence have been obtained in multiple samples of people with MS from disability levels of 0 to 9.5 on the Expanded Disability Status Scale. The MSIS-29 is responsive to intervention, with a change score of about 8 on the physical scale or about 6 on the psychological scale having moderate to high sensitivity and specificity for patients, indicating whether they had improved or not. A 7-member MS Outcome Measure Task Force of the neurology section of the American Physical Therapy Association highly recommends this measure for use in this population across disability levels and practice settings (http://neuropt.org/go/healthcare-professionals/neurology-section-outcome-measures-recommendations/multiple-sclerosis).