pEAβ in AD demonstrated the largest variant-specific signature with 31 unique proteins, pan-Aβ showed 11 unique proteins in AD, and 14 unique proteins in CN, 16 proteins were shared between AD pEAβ and AD pan-Aβ, with PCSK1N shared across AD pEAβ, and AD/CN pan-Aβ. Here, PCSK1N is linked to Alzheimer disease.