Concurrent validity of the MS Functional Composite using MRI as a biological disease marker

The MS Functional Composite (MSFC), a recently developed outcome measure for MS clinical trials measuring three dimensions (ambulation/leg function, arm/hand function, and cognition), was applied to 134 patients with MS to study the concurrent validity, using MRI measurements as a biological disease marker. The results were compared to correlations between the traditionally applied Expanded Disability Status Scale (EDSS) and MRI measurements in the same patients.

The assessments of MSFC and EDSS were performed in combination with brain MRI. MRI consisted of T1- and T2-weighted images, from which the hypointense and hyperintense lesion loads were quantified.

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-weighted lesion load was 8.4 cm(3) (IQR 3.4 to 19.8) and the median T1-weighted lesion load was 1.1 cm(3) (IQR 0.3 to 3.2). Correlations between the MSFC and both T1 (-0.24) and T2 (-0.25) lesion loads were demonstrated, but not between the EDSS and both MRI parameters. Significant correlations between MSFC components and T1 and T2 lesion loads existed for cognitive function and arm/hand function, but not for ambulation. If relapse-onset patients (relapsing-remitting and secondary progressive) were combined, the correlation between MSFC and MRI parameters became stronger for both T1 (-0.37) and T2 lesion loads (-0.35).

The authors present the concurrent validity of the MSFC with a biological disease marker by showing correlations with MRI. Specifically, they demonstrate significant correlations with cognition and arm/hand function assessments, domains that are not well represented in the EDSS.