Self-report versus performance measure in gauging level of function with multiple sclerosis

Background: Multiple sclerosis (MS) is a debilitating, progressive disease with no known cure. Symptoms vary widely for persons with MS and measuring levels of fine motor, gross motor and cognitive function is a large part of assessing disease progression in both clinical and research settings. While self-report measures of function have advantages in cost and ease of administration, questions remain about the accuracy of such measures and the relationship of self-reports of functioning to performance measures of function. Objective: The purpose of this study was to compare scores on a self-report measure of functional limitations with MS with a performance based measure at five different time points. Methods: Sixty participants in an ongoing longitudinal study completed two measures of function annually over a five-year period - the self-report Incapacity Status Scale and the MS Functional Composite (MSFC), a performance test. Pearson correlations were used to explore the association of self-report and performance scores. Results: There were moderate to strong correlations among the ISS total (r = -.53 to -.63, p < .01) and subscale scores of gross (r= .79 to .87; p < .01)) and fine (r= .47 to .69; p < .01) motor function and the corresponding MSFC performance measure. The pattern of change over time in most scores on self-report and performance measures was similar. Conclusion: Findings suggest that the self-report measure examined here, which has advantages in terms of feasibility of administration and patient burden, does relate to performance measurement, particularly in the area of gross motor function, but it may not adequately reflect cognitive function.