SNCA and Parkinson disease: Likewise, another large study of 334 healthy controls, 333 PD and 114 MSA patients, erythrocyte α-synuclein oligomers or o-α-syn were found to be much elevated in PD patients compared to that in other two groups, and apparently, this measurement could differentiate PD patients from control or MSA subjects with good sensitivity and specificity (Li et al., 2019).