Table 4 -.
Candidate biomarkers for Parkinson’s disease
| Modality | Biomarker | Diagnostic Potential | Comments | |||
|---|---|---|---|---|---|---|
| Prodromal PD | Manifest PD | DD Non-PD |
Progression | |||
| MRI | Substantia nigra neuromelanin 68,70,71 | +? | + | - | + | Insufficiently studied in prodromal PD |
| Dorsolateral nigral hyperintensity74,75 | +? | + | - | - | Insufficiently studied in prodromal PD No differentiation PD vs atypical PD |
|
| Quantitative Susceptibility Mapping (QSM) 69,72,73 | ? | + | - | ? | Limited number of studies Use in DD unclear No progression data |
|
| Tensor Imaging (Free Water MRI; NODDI) 76,77 | ? | + | + | ? | Role in early/prodromal Dx unclear No progression data |
|
| Automated Volumetry 78,79 | - | - | + | + | Insufficiently studied in prodromal PD | |
| Mutlimodal MRI80 | ? | - | + | ? | Insufficiently studied in prodromal PD No progression data |
|
| Radiotracer Imaging | A-syn | + | + | +/− | + | Tracers not yet available |
| Tau-protein 97 | - | - | + | - | Mostly studied in AD & PSP/CBD, limited data for PD | |
| Blood | Nfl 98 | - | - | + | - | Non-specific marker for neurodegeneration. Insufficiently studied in prodromal PD. |
| CSF |
a-syn seeding activity (RTQuiC, PMCA) 89–92,94,95 |
+ | + | + | - | May distinguish different a-syn strains in PD vs MSA |
| Nfl 99 | - | - | + | - | Non-specific marker for neurodegeneration. May differentiate PD from Atypical parkinsonism at group level Insufficiently studied in prodromal PD. |
|
| Tissue Biopsies | Dermal a-syn 86 (IHC) | + | + | - | ? | Requires multi-site sampling, limited sensitivity, not specific to PD vs other synucleinopathies |
| Dermal a-syn seeding activity (RT-QuIC; PMCA) 93 | ? | + | + | ? | Limited in-vivo information | |
| Olfactory Mucosa a-syn seeding activity (RT-QuIC) 96 | +? | + | ? | ? | Limited number of studies | |
| GI a-syn 87 | ? | +/− | - | ? | Invasive, Requires multi-site sampling, limited sensitivity | |
| Salivary gland a-syn 87,88 | + | + | - | - | Invasive, limited sensitivity | |
| Faeces | Gut microbiota | ? | +/− | - | - | Variable results ref different composition of bacterial microbiome between PD and controls |
| Digital biomarkers | Multiple motor and non-motor assessments / wearable devices100 | +? | - | - | + | Insufficiently studied in prodromal PD No differentiation PD vs atypical PD |
Abbreviations: DD: differential diagnosis; MRI magnetic resonance imaging; NODDI: neurite orientation dispersion and density imaging; a-syn: alpha-synuclein; Nfl neurofilament; RT-QuIC: Real-time quaking-induced conversion; PMCA: protein misfolding cyclic amplification; IHC: Immunohistochemistry; GI gastrointestinal