Patient-reported outcomes importantly reflect the lived experiences of persons with multiple sclerosis (MS)
however, given the broad array of MS symptoms, comprehensive evaluation can be burdensome, especially with lengthy questionnaires. The MS Impact Scale queries twenty different physical difficulties (MSIS-20). In 1150 patients with MS, evaluation of internal consistency indicated redundancy in the MSIS-20 (Cronbach's alpha: 0.96), but optimal internal consistency (0.90) of a six-item short form (MSIS-SF
first six MSIS items). The MSIS-20 and MSIS-SF showed comparably strong associations with objective physical disability. The MSIS-SF provides a psychometrically robust, less burdensome, and time-efficient option for assessing patient-reported physical disturbance.