Objective: To determine which test for postural instability in Parkinson's disease (PD) is reliable, valid, and easy to perform in a clinical setting.
Design: Cross-sectional reliability and validity study.
Setting: Academic center for movement disorders.
Participants: Forty-two patients with PD and 15 controls. Based on the results of a structured interview, the patients were divided in PD-unstable (n=22) and PD-stable (n=20) groups.
Interventions: Not applicable.
Main outcome measures: Several variants of the retropulsion test with differences in execution and scoring. Responses were scored on 5 different rating scales (ratings of Nutt, Bloem, Pastor; the Unified Parkinson's Disease Rating Scale [UPDRS]; the Short Parkinson Evaluation Scale). These tests were compared with steady-stance positions.
Results: The interrater reliability was high for most ratings, with weighted kappa ranging from.63 for the UPDRS to.98 for both the Pastor rating and steady-stance positions. Most ratings distinguished between the groups. However, the Nutt rating had the highest overall predictive accuracy, with a sensitivity of.63 and a specificity of.88.
Conclusions: The most valid test for postural stability in PD was an unexpected shoulder pull, executed once, with taking more than 2 steps backward considered abnormal. This retropulsion test is easy to use in a clinical setting.