Test-retest and inter-rater reliability and construct validity of the 2-minute step test in individuals with Parkinson's disease

Abstract

ObjectiveTo evaluate the test-retest and inter-rater reliability and construct validity of the 2-minute step test (2MST) in individuals with Parkinson's disease (PD). MethodsTwo previously trained examiners applied the 2MST in two moments. Clinical measurements of PD were obtained using the following instruments: Berg Balance Scale (BBS), Unified Parkinson's Disease Rating Scale (UPDRS), modified Hoehn and Yahr Scale (H&Y), gait speed and cadence, 5-time Sit-to-Stand Test (5TSST) and Timed Up and Go (TUG). For reliability, the intraclass correlation coefficient (ICC), standard error of measurement (SEM) and minimal detectable change (MDC) were calculated. For construct validity, Pearson's and Spearman's correlation coefficient were used. The agreement between the measurement in person and via recorded video was assessed by means of Bland-Altman plots. ResultsThe 2MST showed adequate test-retest reliability (ICC = 0.80, SEM = 10.59, MDC = 29.35) and excellent inter-rater reliability (ICC = 0.93, SEM = 4.49, MDC = 12.46). There was acceptable agreement between assessments made with in person and via video. A correlation magnitude above 0.50 was found between 2MST and gait speed, and a correlation magnitude between 0.30 and 0.50 with BBS, gait cadence, UPDRS and TUG. ConclusionThe 2MST presents adequate test-retest and inter-rater reliability and a valid construct to evaluate the aerobic endurance of individuals with PD.