Seeding amplification assay: Limitations and insights for enhanced clinical and research applications

The accurate diagnosis of synucleinopathies—neurodegenerative diseases marked by misfolded α-synuclein protein aggregates, such as Parkinson's disease, dementia with Lewy bodies, and multiple system atrophy—remains a critical challenge. Conventional clinical criteria, frequently verified only through postmortem examination, results in diagnostic delays that impede timely intervention. Seeding amplification assay (SAA) has emerged as a promising diagnostic tool, offering high sensitivity for detecting α-synuclein aggregates even in early disease stages. While SAA enables early diagnosis by amplifying misfolded α-synuclein in biological samples, several barriers exist, including a lack of assay standardization, technical complexity, and difficulty differentiating among synucleinopathies. Additionally, the current SAA is primarily qualitative, limiting their ability to correlate with disease severity or progression. This review addresses these limitations by examining pre-analytical and analytical factors influencing SAA performance and exploring emerging quantitative approaches. Recent advancements include the integration of SAA with quantitative methodologies, which hold promise for enhanced diagnostic accuracy and clinical applicability. SAA's potential as a diagnostic and monitoring tool is significant and can be further improved by validation in longitudinal studies. The clinical implementation of SAA could revolutionize the early detection and management of synucleinopathies, ultimately improving patient outcomes through earlier diagnosis and tailored therapeutic strategies.