Following a similar approach of exosomal quantitation [48] but using a different technology, single-molecule array (SiMoA) assays, Shi and colleagues evaluated the possibility of using tau as a PD biomarker, measuring its concentration both in whole plasma and L1CAM+ plasma exosomes in pwPD, Alzheimer’s disease (AD), and healthy controls [45]. The gene discussed is L1CAM; the disease is Alzheimer disease.