Alzheimer's disease (AD) is the most common cause of dementia, but cognitive decline also occurs in other neurological conditions, such as Parkinson's disease, Lewy body dementia, vascular dementia, and frontotemporal dementia.

Elecsys Phospho-Tau (181P) Plasma (Roche), a blood-based diagnostic test, has been cleared by the FDA to aid in the initial assessment of amyloid plaque pathology associated with Alzheimer's disease (AD) in patients ≥55 years old with signs of cognitive decline. It is the second blood test for AD biomarkers to be cleared by the FDA; the Lumipulse G pTau217/β-Amyloid 1-42 Plasma Ratio test was cleared in 2025 (see Table 1).