{"id":"amyloid-beta-42-40-ratio","name":"Amyloid Beta 42/40 Ratio, Plasma","shortName":"Aβ42/40 ratio","aliases":["ABeta 42/40 Ratio","Aβ42/40","Abeta 42/40","Amyloid Beta 42/40 Ratio","AB42/40","Aβ42/Aβ40","Amyloid Beta 42/40","A-beta 42/40 Ratio","Amyloid Beta 42/40 Ratio, Plasma","Abeta42/40 Ratio","Plasma Aβ42/40","Beta-Amyloid 42/40 Ratio","Amyloid beta 42/amyloid beta 40 ratio"],"abbreviations":["Aβ42/40","Aβ42/Aβ40","AB42/40"],"loinc":[{"code":"106941-8","primary":true}],"specimen":"plasma","units":[{"ucum":"{ratio}","display":"ratio"}],"referenceRanges":[{"population":"Adults","low":0.095,"high":null,"unit":"{ratio}","unitDisplay":"ratio","note":"C2N Diagnostics' own cutoff (mass spectrometry), as printed in the Mayo Clinic Laboratories catalog: a ratio of 0.095 or higher is 'consistent with absence of amyloid plaques'. It applies to that method only. Other methods use other cutoffs (a research mass-spectrometry method used 0.1218), and immunoassay ratios are on a different scale. The test is meant for adults with signs or symptoms of cognitive impairment, not for people without symptoms.","sources":[{"title":"PrecivityAD2, Plasma (Mayo test ID C2AD2, performed by C2N Diagnostics)","url":"https://www.testcatalog.org/show/C2AD2","publisher":"Mayo Clinic Laboratories Extended Catalog (testcatalog.org)","year":2026},{"title":"PrecivityAD, Plasma (Mayo test ID C2NAD, performed by C2N Diagnostics)","url":"https://www.testcatalog.org/show/C2NAD","publisher":"Mayo Clinic Laboratories Extended Catalog (testcatalog.org)","year":2026}]}],"review":{"status":"ai-verified","label":"AI-verified against cited sources. Awaiting expert review","lastReviewed":"2026-10-03"},"summary":"The ratio of two amyloid peptides in blood plasma. A lower ratio can be a sign of amyloid build-up in the brain, and each lab method has its own cutoff.","url":"https://bloodtesttracker.com/markers/amyloid-beta-42-40-ratio","notice":"Information, not medical advice. Ranges differ between labs, so the range on your own report is the one your result is judged against."}