 The study aimed to establish the test retest reliability and longitudinal stability of digital biomarkers, DB, captured using sensors embedded in smart devices for home-based sign and symptom monitoring in Parkinson disease, PD. The results showed that only a few tapping and voice features had good to excellent test retest reliability and medium to large effect sizes, while other features performed poorly. Additionally, the longitudinal analyses revealed significant alterations over time across a variety of features, particularly for the tapping task. These findings suggest the need for further development of more standardized, sensitive, and reliable DB for application and self-administered remote studies in patients with PD, while considering motivational, learning, and other confounders that may cause variations in performance. This article was authored by Mehran Sahandifar, Simon B. Iqaf, Maria Goni, and others.