Determination of the optimal threshold value that can be discriminated by dysphonia measurements for unified Parkinson´s Disease rating scale

Recently, there is an increasing motivation to develop telemonitoring systems that enable cost-effective screening of Parkinson´s Disease (PD) patients. These systems are generally based on measuring the motor system disorders seen in PD patients by the help of non-invasive data collection tools. Vocal impairments one of the most commonly seen PD symptoms in the early stages of the disease, and building such telemonitoring systems based on detecting the level of vocal impairments results in reliable motor UPDRS tracking systems. In this paper, we aim to determine the optimal UPDRS threshold value that can be discriminated by the vocal features extracted from the sustained vowel phonations of PD patients. For this purpose, we used an online available PD telemonitoring dataset consisting of speech recordings of 42 PD patients. We converted the UPDRS prediction problem into a binary classification problem for various motor UPDRS threshold values, and fed the features to k-Nearest Neighbor and Support Vector Machines classifiers to discriminate the PD patients whose UPDRS is less than or greater than the specified threshold value. The results indicate that speech disorders are more significantly seen in the patients whose UPDRS exceeds the experimentally determined threshold value (15). Besides, considering that the motor UPDRS ranges from 0 to 108, relatively low UPDRS threshold of 15 validates that vocal impairments can be used as early indicators of the disease.