Validity of the 30-Second Sit-to-Stand test as a measure of lower extremity function in persons with multiple sclerosis: Preliminary evidence.

BACKGROUND:The 30-Second Sit-To-Stand (30SSTS) is a quick, inexpensive, safe, and widely used clinical measure of lower extremity function. To date, there is limited evidence regarding the use of 30SSTS in multiple sclerosis (MS). The purpose of this study was to examine the construct validity of the 30SSTS test in persons with MS compared with non-MS healthy controls. METHODS:Twenty ambulatory persons with MS and twenty age- and sex-matched healthy controls completed the 30SSTS, Timed 25-Foot Walk (T25FW), Timed Up and Go (TUG), Six-Minute Walk (6MW), and Godin Leisure-Time Exercise Questionnaire (GLTEQ). Persons with MS also completed the Patient Determined Disease Steps (PDDS) and 12-item MS Walking Scale (MSWS-12). RESULTS:Persons with MS had significantly worse performance on the TUG (mean difference [95% confidence interval] = 1.4 [0.5, 2.3] sec) and 6MW (-259.2 [-450.8, -67.6] ft), but not on the 30SSTS (-1.6 [-1.5, 4.6] reps) and T25FW (-0.59 [-0.1, 1.2] ft/sec) compared with controls. There were significant moderate-to-strong correlations between the 30SSTS with T25FW, TUG, and 6MW scores in persons with MS (r = 0.48, -0.65 and 0.61, respectively), whereas the 30SSTS was only significantly associated with 6MW scores (r = 0.43) in controls. The 30SSTS was negatively associated with MS-related walking disability assessed by the PDDS and MSWS-12 (rs = -0.52 and -0.64, respectively), but was not significantly associated with the GLTEQ in MS and controls (r = 0.30 and 0.17, respectively). CONCLUSION:This study provides initial support for the construct validity of the 30SSTS as a measure of lower extremity function in persons with MS. Our findings warrant the inclusion of the 30SSTS as a feasible and valid measure of physical function in clinical research and practice involving persons with MS.