Benchmarks of meaningful impairment on the MSFC and BICAMS

Abstract

Background: Cognitive and motor abilities in multiple sclerosis (MS) are typically quantified using reliable, consensus standard tests validated in the MS population. While these performance measures are associated with vocational disability in parametric analyses, translation of raw scores into anchors reflecting clinically relevant, functional impairment requires further research. Objective: To examine performance-based motor and cognitive outcomes among definitive anchors that designate varying degrees of functional impairment, thereby establishing benchmarks for score interpretation. Methods: We evaluated MS patients and healthy controls, all undergoing a brief test battery. Outcomes were derived from the MS Functional Composite (MSFC) and the Brief International Cognitive Assessment for MS (BICAMS). Functional impairment anchors were (1) disability benefits, (2) employed with negative work events, and (3) employed without problems. Results: All measures yielded statistically significant differences across all levels of work status, after accounting for the effects of age and education. Benchmark values distinguished the functional impairment groups. When evaluated in combination, the Timed 25-Foot Walk and the Symbol Digit Modalities Test were the most robust predictors of functional decline. Conclusion: We have established benchmark scores for popular motor and cognitive tests that are associated with specific degrees of impairment in work status.