Further validation of the Six-Spot Step Test as a measure of ambulation in multiple sclerosis.

BACKGROUND

There is preliminary evidence regarding the validity of the Six-Spot Step Test (SSST) as a promising measure of ambulatory function in persons with multiple sclerosis (MS). To date, this assessment has not been subject to the same rigor and extent of psychometric evaluation as other widely-accepted measures of ambulatory (e.g., timed 25-foot walk (T25FW)).

OBJECTIVE

This study aimed to provide additional validity evidence for the SSST in 96 persons with MS, based on construct validity and precision. Construct validity involves examining the pattern of associations between the SSST and other measures, and precision involves comparing SSST performance relative to other valid measures of ambulation for differentiating between levels of disability status, MS clinical course, and fall risk based on balance confidence.

METHODS

All participants completed the SSST, T25FW, Timed Up-and-Go (TUG), six-minute walk, Multiple Sclerosis Walking Scale-12, Late-Life Function and Disability Inventory, Activities-specific Balance Confidence, and Paced Auditory Serial Addition Test. All participants further underwent a neurological examination for generating EDSS scores, and then wore an ActiGraph accelerometer for the waking hours of a 7-day period.

RESULTS

SSST performance was strongly associated with other valid measures of ambulation (|ρ| = .65-.90) and disability status (ρ = .73), moderately-to-strongly associated with balance confidence (ρ = .58), and weakly-to-moderately associated with cognitive processing speed and non-ambulatory measures (|ρ| = .35-.39). The SSST demonstrated stronger relative precision in discriminating between levels of disability status, MS clinical course, and fall risk based on balance confidence than the T25FW and TUG.

CONCLUSIONS

We provide comprehensive validity evidence for the SSST that supports its consideration for inclusion alongside other highly-regarded objective measures of ambulatory function for clinical research and practice in persons with MS.