Measuring Disability Progression with the Multiple Sclerosis Functional Composite

Abstract

The multiple sclerosis functional composite (MSFC) is a three-part quantitative objective measure of neurologic function, measuring leg (timed 25-foot walk [25FTW]), arm (nine-hole peg test [9HPT]), and cognitive (three-second paced auditory serial addition test [PASAT3]) function. The MSFC was developed to be a more sensitive measure of disability than the expanded disability status scale (EDSS) and has excellent reliability. Validity is supported by moderately strong correlations with EDSS, brain atrophy, and quality of life. Advantages of the MSFC include its continuous scale and inclusion of several disease dimensions. Limitations include practice effects, the lack of a visual function component, variations in reference populations, and limited understanding of clinically relevant MSFCz-score changes. MSFCz-score change has been used as a secondary end-point in MS trials, but EDSS progression remains the primary disability outcome. A new approach to MSFC data involves defining MSFC progression as worsening in an MSFC component by 15–20% over three months. With further study, this could be used as a primary disability outcome in future clinical trials.