Purpose: The objectives of this study were to examine (1) the intrarater, interrater, and test-retest reliability of the timed 360° turn test in people with Parkinson's Disease (PwPD); (2) the minimum detectable change in the timed 360° turn test times; (3) the concurrent and discriminant validity of the timed 360° turn test; (4) the cut-off times which best discriminate PwPD from healthy people and fallers from non-fallers with Parkinson's Disease (PD).
Methods: Fifty-four PwPD and 32 healthy people were included. The timed 360° turn test was administered along with Timed Up and Go Test, Berg Balance Scale, Four Square Step Test, Unified Parkinson's Disease Rating Scale, and Hoehn and Yahr Scale. In addition, PwPD were categorized into fallers and non-fallers based on fall history. Reliability analyses were assessed using intraclass correlation coefficients in a subgroup of 38 PwPD.
Results: The timed 360° turn test had excellent intrarater, interrater, and test-retest reliability. It was strongly correlated with other outcome measures (p < 0.001). In both sides, significant differences in the timed 360° turn test times were found between PwPD and healthy people and between fallers and non-fallers with PD (p < 0.001 and p < 0.001, respectively). The timed 360° turn test times of 3.76-3.89 s were found to best discriminate PwPD from healthy people, while 5.46-5.74 s were found to best discriminate fallers from non-fallers with PD. The minimum detectable change in the timed 360° turn test times were 1.98 s for dominant side and 1.48 s for non-dominant side in PwPD.
Conclusions: The timed 360° turn test is a reliable, valid, and clinically available tool for assessing turning ability in PwPD.
Keywords: Parkinson’s Disease; Rehabilitation; Reliability; Turning ability; Validity.