Reliability of impairment and physical performance measures for persons with Parkinson's disease

Background and Purpose. Parkinson's disease (PD) is characterized by rigidity, postural instability, bradykinesia, and tremor, as well as other musculoskeletal impairments and functional limitations. The purpose of this investigation was to determine the reliability and stability of measures of impairments and physical performance for people in the early and middle stages of PD. Subjects. Thirteen men and 2 women in Hoehn and Yahr stages 2 and 3 of PD participated. Their mean age was 74.5 years (SD=5.7, range=64-84). Methods. Thirteen impairment-level variables and 8 physical performance variables were measured. Measurements were taken on two consecutive days and again a week later on the corresponding two consecutive days. Reliability and stability were assessed using analysis of variance and intraclass correlation coefficients (ICCs). Results. Test-retest reliability (ICCs) of variables ranged from .69 (hamstring muscle length) to .97 (lumbar flexion). Intraclass correlation coefficients were .85 or greater for 10 of the variables. Conclusions and Discussion. The results suggest that in the early and middle stages of PD, many of the measures of impairment and physical performance are relatively stable.