Background and Purpose:
People with Parkinson disease
(PD) present phenotypes that are characterized as tremor-dominant (TD) or postural instability/gait difficulty (PIGD) subtypes. Differentiation of subtypes allows clinicians to predict disease course and adjust treatment. We examined whether brief mobility and balance measures can discriminate PIGD from TD phenotypes.
We performed a cross-sectional study with individuals with PD (n = 104). Blinded raters assessed participants with the Unified Parkinson's Disease Rating Scale (UPDRS) or Movement Disorders Society revision (MDS-UPDRS), and balance assessments: 360° turn test, one-leg stance, a reactive postural control test, and tandem walk. Participants were classified as PIGD or TD based on the UPDRS or MDS-UPDRS assessment results. Differences in balance variables between subtypes were assessed with univariate analyses. Receiver operating characteristic (ROC) curve analyses were performed to investigate the ability of balance variables to differentiate PD subtypes.
No differences between subtypes were observed for tandem walk or reactive postural control. Participants with PIGD performed worse on number of steps and time to complete the 360° turn test and on one-leg stance time. ROC curves showed only the 360° turn test discriminated PIGD from TD with high specificity (0.84). Post hoc analyses revealed that the 360° turn test is the most discriminatory for classifying PD subtypes in early stages of the disease. ROC analyses based on combined models including both the 360° test and tandem walk test performance increased the specificity to 0.97.
Discussion and Conclusions:
The 360° turn test requires minimal time to administer and may be useful in mild-moderate PD for distinguishing PIGD from TD subtypes.
Video Abstract available for more insights from the authors (see the Video, Supplemental Digital Content 1, available at: http://links.lww.com/JNPT/A295).