Objective: To examine the validity of the timed Up and Go (TUG) test as a measure of functional mobility in persons with multiple sclerosis (MS) by using a comprehensive framework based on construct validity (ie, convergent and divergent validity).

Design: Cross-sectional study. Setting: Hospital setting. Participants: Community-residing persons with MS (N=47). Interventions: Not applicable. Main outcome measures: Main outcome measures included the TUG test, timed 25-foot walk test, 6-minute walk test, Multiple Sclerosis Walking Scale-12, Late-Life Function and Disability Instrument, posturography evaluation, Activities-specific Balance Confidence scale, Symbol Digits Modalities Test, Expanded Disability Status Scale, and the number of steps taken per day.

Results: The TUG test was strongly associated with other valid outcome measures of ambulatory mobility (Spearman rank correlation, rs=.71-.90) and disability status (rs=.80), moderately to strongly associated with balance confidence (rs=.66), and weakly associated with postural control (ie, balance) (rs=.31). The TUG test was moderately associated with cognitive processing speed (rs=.59), but not associated with other nonambulatory measures (ie, Late-Life Function and Disability Instrument-upper extremity function).

Conclusions: Our findings support the validity of the TUG test as a measure of functional mobility. This warrants its inclusion in patients' assessment alongside other valid measures of functional mobility in both clinical and research practice in persons with MS.