Detection of phosphorylated α-synuclein in skin

We read the Review by Julian Agin-Liebes and colleagues on the α-synuclein biomarker assays,1 and disagree with the authors’ interpretation of the false-positive rate of immunostaining with an anti-pS129-α-synuclein antibody. The Review concludes that this method had false-positive rates as high as 20% in healthy controls, which could lead to one in every five healthy individuals being incorrectly diagnosed with Parkinson's disease. To support this statement, the authors cite only one study.2 Their statement of a high rate of false positives is not supported by other studies discussed in the Review nor by several pioneer studies in the field published before 2019, which indicate that the positivity rate in healthy controls ranges from 0% to 3·3%.3–5