Psychometric Properties of Three Functional Mobility Tests for People With Parkinson Disease.

Standardized outcome measures with high clinical utility are of the greatest importance for clinical practice. The aim of this study was to examine interrater and intrarater reliability, construct validity, discriminant ability, and smallest detectable differences of the sit-to-stand test (STS), Timed “Up & Go” Test (TUG), and bed mobility test for people with Parkinson disease. The authors conducted a cross-sectional, psychometric evaluation study composed of a group of individuals with PD (PD group) and a group of individuals who were healthy (control group) who recruited through local Parkinson disease groups and assessed in a movement laboratory in their “on” phase. Measurements of time to perform one STS, TUG, and bed mobility test were collected based on video recordings of that single performance. Thirty-eight participants with PD (Hoehn and Yahr stages I-IV) and 19 age-matched control participants were recruited. Intraclass correlation coefficients for interrater and intrarater reliability for the PD group ranged from .95 to .99. Bland-Altman plots showed mean differences close to zero and narrow confidence intervals. Construct validity was established by means of moderate to good Spearman rho correlation coefficients with part III of the Unified Parkinson’s Disease Rating Scale and the Hoehn and Yahr stage (range=.51-.63). Timings of all tests discriminated participants in the PD group from those in the control group and participants in the PD group in Hoehn and Yahr stages I and II from those in Hoehn and Yahr stages III and IV, but did not discriminate “nonfallers” or those with single falls from repeat “fallers” or “nonfreezers” from “freezers.” Applicable smallest detectable differences were established. The authors not that the findings aren’t generalizable to people within the late stage of PD (Hoehn and Yahr stage IV: n=3).
The study found that timings of videos of three functional mobility tests possessing high clinical utility showed good psychometric properties for community-dwelling, ambulatory people with PD.