A perspective of persons with Parkinson's disease on the contribution of alpha-synuclein seed amplification assay biomarker to the diagnosis of Parkinson's disease

Alpha-synuclein is a normal protein, but misfolded forms in the cerebrospinal fluid can be detected using the alpha-synuclein seed amplification assay (alpha Syn-SAA), a potential biomarker for Parkinson's disease (PD). Some experts consider this assay a 'game changer' for redefining and reclassifying PD. In this article, we, three individuals with PD, share our perspective on the suitability of alpha Syn-SAA as the basis for a new classification and staging system for PD. We also discuss other biomarkers and their relevance to those with PD, drawing on our research and the scientific background of two authors. We aim to clarify complex media reports and study findings for the PD community. We argue that while alpha Syn-SAA can identify the presence of pathology, it cannot explain the underlying cause for such pathology or predict the progression of PD. Given the varied biological pathways leading to PD, using alpha Syn-SAA as a unified biological definition for a new classification system is premature. Further research is needed before it can serve as the foundation for defining and staging Parkinson's disease. Although alpha Syn-SAA has its place, like the DAT scan, it should be seen as a tool for confirming diagnoses rather than defining them.