A summary index derived from Kinect to evaluate postural abnormalities severity in Parkinson's Disease patients

Postural abnormalities are common disabling motor complications affecting patients with Parkinson's disease (PD). We proposed a summary index for postural abnormalities (IPA) based on Kinect depth camera and explored the clinical value of this indicator. Seventy individuals with PD and thirty age-matched healthy controls (HCs) were enrolled. All participants were tested using a Kinect-based system with IPA automatically obtained by algorithms. Significant correlations were detected between IPA and the Movement Disorder Society-Sponsored Revision of the Unified Parkinson's Disease Rating Scale (MDS-UPDRS) total score (r_s = 0.369, p = 0.002), MDS-UPDRS-III total score (r_s = 0.431, p < 0.001), MDS-UPDRS-III 3.13 score (r_s = 0.573, p < 0.001), MDS-UPDRS-III-bradykinesia score (r_s = 0.311, p = 0.010), the 39-item Parkinson's Disease Questionnaire (PDQ-39) (r_s = 0.272, p = 0.0027) and the Berg Balance Scale (BBS) score (r_s = -0.350, p = 0.006). The optimal cut-off value of IPA for distinguishing PD from HCs was 12.96 with a sensitivity of 97.14%, specificity of 100.00%, area under the curve (AUC) of 0.999 (0.997-1.002, p < 0.001), and adjusted AUC of 0.998 (0.993-1.000, p < 0.001). The optimal cut-off value of IPA for distinguishing between PD with and without postural abnormalities was 20.14 with a sensitivity, specificity, AUC and adjusted AUC of 77.78%, 73.53%, 0.817 (0.720-0.914, p < 0.001), and 0.783 (0.631-0.900, p < 0.001), respectively. IPA was significantly correlated to the clinical manifestations of PD patients, and could reflect the global severity of postural abnormalities in PD with important value in distinguishing PD from HCs and distinguishing PD with postural abnormalities from those without.