Test-retest Reliability of the Physical Performance Test for Persons with Parkinson Disease

Abstract

Background and Purpose: Reliable measures are needed to document functional status and disease progression for people with Parkinson disease (PD). We, therefore, evaluated the reliability of the Physical Performance Test (PPT) for people with PD. Methods: Fourteen community-dwelling subjects with PD participated: 8 males, 6 females; modified Hoehn and Yahr Stages 2 and 2.5; mean age 62.4 years (±6.3). The test was administered twice, 1 week apart. The 7-item and 9-item summary scores of the PPT were each compared between sessions using repeated measures analysis of variance (ANOVA). The intraclass correlation coefficient (ICC) and method error (ME) were calculated to further assess reliability. Results: Between sessions, 7- and 9-item summed scores were not statistically different. The range of summed scores fell in the midst of the available score range for both the 7- and 9-item tests suggesting resistance to floor and ceiling effects. The ICCs showed good agreement (7-item = 0.818; 9-item = 0.895) indicating test reliability for this population. Based on the ME, an examiner can expect a 6% variation for the 7-item summary score and a 4% variation for the 9-item score summary between testing sessions. Conclusions: The 7- and 9-item PPTs were demonstrated to be reliable objective measures in individuals with PD. Simple props and brief administration time (10–15 minutes) make the test practical to use.