Over 80% of patients with isolated REM sleep behavior disorder (RBD) will subsequently convert to Parkinson’s disease, Lewy body dementia or multiple system atrophy within 10-15 years. RBD is therefore considered to be an early warning sign of neurodegenerative disease affecting the central nervous system. RBD is characterized in part by the presence of alpha-synuclein seeds within the olfactory mucosa which can be detected using an amyloid amplification method called real-time quaking-induced conversion (RT-QuIC). The study included 163 participants: 63 with RBD, 41 with Parkinson’s disease and 59 healthy controls. Alpha-synuclein RT-QuIC was positive for 47.6% in RBD, 61% in Parkinson’s disease and 10.2% controls. The overall sensitivity and specificity was 45.2% and 89.8%. Patients with RBD and olfactory dysfunction were more likely to test positive.

A separate study demonstrated an increase in sensitivity of the RT-QuIC assay from 45% to 84% by modifying the sampling technique in patients with Parkinson’s disease (https://doi.org/10.1186/s40035-022-00311-3).

The University of Innsbruck in Austria is conducting a clinical trial to screen individuals for alpha-synuclein seeding in the olfactory mucosa following recovery from COVID-19 infection. They will be using RT-QuIC as a diagnostic tool. 200 participants will be enrolled: a group of COVID-19 patients with and without olfactory dysfunction; a group of patients with Parkinson’s disease; and a group of healthy controls. The study will be completed by the end of 2023 (https://clinicaltrials.gov/ct2/show/NCT05401773).