Fig. 2

Potential screening strategies for target populations for disease-modification trials in the general community assuming three different target populations (PPV > 60%). First column: individuals with hyposmia and DAT-Deficit; real numbers from the PARS study that used olfactory testing as first remote screening step and DAT-Scan as a second screen are presented [43]. These include losses to follow up. Second column: patients with idiopathic RBD and further marker(s) that indicate increased risk for early conversion as hyposmia, abnormal color vision, or subtle motor dysfunction (approximately one third of idiopathic RBD patients) [13, 44]; the identification of idiopathic RBD patients from the general community is modeled using a questionnaire as a first remote screening step (assuming a prevalence of probable RBD of 5%) [46, 48] and polysomnography as a second screening step (assuming that approximately one sixth of probable RBD cases are confirmed as having idiopathic RBD) [45, 46]. Third column: Individuals with probable prodromal PD according to the MDS research criteria as modeled from data of the prospective population-based Bruneck Study [34]; remote screening includes a questionnaire-based assessment and brief odor-identification test. The model envisages that all participants reaching a post-test probability for prodromal PD of > 10% (one quarter of participants) are invited for the in person screening including a motor examination and transcranial sonography. Estimated numbers necessary for remote screening are derived from the prevalence of probable prodromal PD (i.e. 2.2%). Please note that only multipliers in the first column account for losses to follow-up, whereas the ones in the second and third columns do not