Plasma Aβ42/Aβ40 ratio values measured by ABtest-IA correlate directly with cerebrospinal fluid Aβ42 levels and inversely with cortical amyloid burden measured by PET scanning. (https://pubmed.ncbi.nlm.nih.gov/31787105)
The Aβ42/Aβ40 ratio measured by ABtest-IA is lower in individuals with cortical amyloid burden above the normal level in Amyloid-PET (Aβ+) than in individuals with a burden below the threshold (Aβ-) (https://pubmed.ncbi.nlm.nih.gov/32179698).
Plasma Aβ42/Aβ40 ratio predicts brain amyloid burden and can discriminate normal amyloid PET-positive vs. negative individuals with an AUCROC of 0.896 among people without symptoms of cognitive impairment. (https://pubmed.ncbi.nlm.nih.gov/32179698).