Do Depressive and Anxiety Symptoms Influence the Construct Validity of Multiple Sclerosis Walking Scale-12 Scores?

Purpose/Objective: Walking dysfunction, depression, and anxiety are prevalent, burdensome, and interrelated outcomes in persons with multiple sclerosis (MS). The 12-item Multiple Sclerosis Walking Scale (MSWS-12) is a common patient-reported outcome (PRO) of walking dysfunction in research and practice involving MS, but the construct validity of its scores might be influenced by symptoms of depression and anxiety. This study examined if symptoms of depression and anxiety influenced the construct validity of MSWS-12 scores. Research Method/Design: The sample included 189 participants with MS who completed the MSWS-12, Hospital Anxiety and Depression Scale (HADS-Depression subscale [HADS-D] and HADS-Anxiety subscale [HADS-A]), 6-minute walk (6MW), and timed 25-foot walk (T25FW). We conducted bivariate correlation analysis to examine the associations between MSWS-12 scores and both the 6MW and T25FW, while controlling for HADS-D and HADS-A scores. Results: MSWS-12 scores were significantly correlated with the 6MW (r = −.752), T25FW (r =.694), HADS-D (r =.405), and HADS-A (r =.235). The correlations between MSWS-12 and 6MW (pr = −.725) and T25FW (pr =.685) did not change when controlling for HADS-D and HADS-A scores. The correlations between MSWS-12 and 6MW (r = −.708 and r = −.726) and T25FW (r =.687 and r =.748) were strong in subsamples with elevated HADS-D and HADS-A scores. Conclusions/Implications: Our results strengthen the validity evidence for MSWS-12 scores as a PRO of walking dysfunction in MS, including among those with symptoms of depression and anxiety. Impact and Implications: The 12-item Multiple Sclerosis Walking Scale (MSWS-12) is a widely utilized valid patient-reported measurement of walking dysfunction in persons with multiple sclerosis (MS). Symptoms of depression and anxiety may impact the patient's objective and self-reported walking ability; however, they do not bias the construct validity of MSWS-12 scores. Our results strengthen the evidence for the construct validity of MSWS-12 scores and its application in clinical research and practice with persons with MS. [ABSTRACT FROM AUTHOR]