Test-retest agreement and reliability of the Six Spot Step Test in persons with multiple sclerosis

The Six Spot Step Test (SSST) extends traditional walking outcomes in persons with multiple sclerosis (PwMS) by further challenging components of coordination and balance. Nonetheless, the test-retest agreement of the SSST has not been investigated.

To determine the within-day, day-to-day, and inter-rater agreement and reliability of the SSST in PwMS. A secondary aim was to investigate the validity of handheld timing.

A total of 38 PwMS with an Expanded Disability Status Scale (EDSS) <6.5 completed two SSSTs with a 5-minute break in-between. After 2 days, this procedure was repeated. Bland-Altman analysis was performed to determine the 95% Limits of Agreement (LOA) and Intraclass Correlation Coefficient (ICC) was calculated. In a subgroup of 18 PwMS, the SSSTs were video-recorded and timed by a second investigator.

The relative LOA within and between days were ±15% and ±19%, while ICC were 0.987 and 0.983, respectively. A minor learning effect was found over four tests. The handheld timing error was ±0.5 seconds when compared to video-based timing.

The SSST has an acceptable within- and between-day agreement and reliability. For interventional purposes, a change of >19% can be regarded as a real change. Valid timing can be performed by a handheld stopwatch.