Construct validity and intrasession intra-rater reliability of the stair and step tests in individuals with multiple sclerosis

Objective This research aimed to establish the test–retest reliability, agreement, measurement precision, and construct validity of the Stair and Step Tests in individuals with Multiple Sclerosis (MS).Methods One hundred patients with MS were evaluated using the Stair Test, Step Test, Timed Up and Go (TUG), 30-Second Chair Stand Test (30-s CSTS), Modified Four Square Step Test (mFSST), and 12-Item MS Walking Scale (MSWS-12). For test–retest reliability, the Stair and Step Tests were repeated after a 60-minute rest. Data were analyzed for reliability (ICC2,1), agreement (Bland-Altman), measurement precision (SEM95, MDC95), and construct validity (Pearson correlations).Results Both assessments demonstrated excellent test–retest reliability. The Stair Test achieved an ICC2,1 of 0.997 (95% CI: 0.996–0.998), while the Step Test reached 0.955 (95% CI: 0.933–0.969). Regarding measurement precision, SEM95 and MDC95 were 0.15; 0.41 for the Stair Test, and 0.58; 1.61 for the Step Test. Bland-Altman analysis revealed tight agreement with negligible bias for the Stair (−0.003) and Step (0.030) tests. The Stair Test correlated strongly with TUG, mFSST, MSWS-12, and EDSS (all r = 0.979), and inversely with 30-s CSTS (r = −0.957) (p < .01). The Step Test showed positive associations with 30-s CSTS (r = 0.908) and inverse links to TUG (r = −0.929), mFSST (r = −0.929), MSWS-12 (r = −0.927), and EDSS (r = −0.928) (p < .01).Conclusion The Stair and Step Tests offer a clinically practical, fast, and low-fatigue solution for monitoring mobility in MS, bridging the gap between psychometric precision and the time constraints of routine physiotherapy practice.