Validation of a Six-Item Multiple Sclerosis Impact Scale Short Form (MSIS-SF) for Efficient Assessment of Patient-Reported Physical Disturbance.

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.