A method is provided for distinguishing between and/or diagnosing Parkinson's disease (PD) or multiple system atrophy (MSA) in a subject who is exhibiting symptoms associated with both PD and MSA. The method comprises: (A) contacting a biological sample obtained from the subject and comprising soluble, misfolded alpha-synuclein (αS) protein with a pre-incubation mixture comprising a monomeric αS substrate and an indicator to form an incubation mixture; (B) conducting an incubation cycle two or more times on the incubation mixture to form misfolded αS aggregates; (C) subjecting the incubation mixture to excitation and detecting via indicator fluorescence emission the misfolded αS aggregates; and (D) diagnosing the subject has having PD or MSA depending on the fluorescence emission intensity. In some aspects, the incubation cycles are conducted in the presence of a bead.
DISCRIMINATING PARKINSON'S DISEASE FROM MULTIPLE SYSTEM ATROPHY USING ALPHA-SYNUCLEIN PMCA