Concurrent validity of the MS functional composite using MRI as a biological disease marker

Introduction: The MS Functional Composite (MSFC), a recently developed outc ome measure for MS clinical trials measuring three dimensions (ambulation/l eg function, arm/hand function, and cognition), was applied to 134 patients with MS to study the concurrent validity, using MRI measurements as a biol ogical disease marker. The results were compared to correlations between th e traditionally applied Expanded Disability Status Scale (EDSS) and MRI mea surements in the same patients. Methods: The assessments of MSFC and EDSS w ere performed in combination with brain MRI. MRI consisted of T1- and T2-we ighted images, from which the hypointense and hyperintense lesion loads wer e quantified. Results: The MSFC score ranged from -2.54 to 0.99. The median EDSS was 3.0 (interquartile range [IQR] 1.5 to 6.0). The median T2-weighte d lesion load was 8.4 cm(3) (IQR 3.4 to 19.8) and the median T1-weighted le sion load was 1.1 cm3 (IQR 0.3 to 3.2). Correlations between the MSFC and b oth T1 (-0.24) and T2 (-0.25) lesion loads were demonstrated, but not betwe en the EDSS and both MRI parameters. Significant correlations between MSFC components and T1 and T2 lesion loads existed for cognitive function and ar m/hand function, but not for ambulation. If relapse-onset patients (relapsi ng-remitting and secondary progressive) were combined, the correlation betw een MSFC and MRI parameters became stronger for both T1 (-0.37) and T2 lesi on loads (-0.35). Conclusions: The authors present the concurrent validity of the MSFC with a biological disease marker by showing correlations with M RI. Specifically, they demonstrate significant correlations with cognition and arm/hand function assessments, domains that are not well represented in the EDSS.