Table 2.
Summary of techniques of synuclein species quantification in different specimens and findings in PD.
| Specimen | Methods | Analyte | Diagnostic meaning |
|---|---|---|---|
| CSF | • ELISA, Electrochemiluminescence, xMAP technology, Single-molecule array technology |
t-α-syn p-α-syn o-α-syn |
↓ in synucleinopathies, ↑ as aspecific marker of synaptic damage ↑ in PD than controls, better diagnostic yield if combined with other α-syn species ↑ in PD than controls, better diagnostic yield if combined with other α -syn species |
| • Real-Time Quaking-Induced Conversion (RT-QuIC), Protein-Misfolding Cyclic Amplification (PMCA) | misfolded α-syn |
Can accurately detect α-syn seeding activity across the spectrum of LB-related disorders Higher seeding activity of pathologically aggregated α -syn in DLB than PD |
|
| • Nanoscale flow cytometry | α-syn–containing extracellular vesicles (EVs) | Total α-syn–positive and aggregated α-syn–positive EV are significantly lower in patients with PD than controls | |
| Blood | • ELISA |
t-α-syn plasma o-α-syn plasma p-α-syn |
Not conclusive results for differentiating controls from diseased groups, possible utility as a marker of disease progression ↑ in PD ↑ in PD |
| • Nanoscale flow cytometry | α-syn–containing extracellular vesicles (EVs) | ↑ in PD | |
| Saliva, tears | • ELISA |
t-α-syn o-α-syn o-α-syn/t-α-syn |
Not statistically significant in distinguishing PD from controls ↑ in PD than controls, correlates with disease duration ↑ in PD than controls, increased in advanced stages |
| Skin | • Immunohistochemical analysis |
t-α-syn p-α-syn |
↑ in PD and synucleinopathies than tauopathies and controls Skin α-syn deposits differ in clinical variants of synucleinopathy |
| Retina | • Fluorescence immunohistochemistry | p-α-syn |
in the retina of PD patients in parallel with that in the brain, including before clinical onset of the disease. It correlates with clinical disease severity |
| Gut mucosa | • Immunohistochemical analysis |
t-α-syn p-α-syn |
Conflicting results. More recent studies do not find significant diagnostic value in discriminating PD patients from controls |
| Gonadal tissue | • Immunohistochemical analysis | p-α-syn | Abundance of p-α-syn in the testicular and ovarian tissue of two PD patients |