Assessment of a Plasma Amyloid Probability Score to Estimate Amyloid Positron Emission Tomography Findings Among Adults With Cognitive Impairment

Key Points Question Is an amyloid probability score based on a mass spectrometry–based blood test measuring plasma amyloid β 42:40 ratio and apoE proteotype plus age, associated with identifying brain amyloidosis among patients with cognitive impairment? Findings In this cohort study of 686 participants from 2 separate studies, the developed Amyloid Probability Score showed high concordance with amyloid PET status, with an area under the curve of 0.88 and overall accuracy of 81%. The test’s findings were significantly associated with the presence or absence of brain amyloidosis as determined by positron emission tomography. Meaning These findings suggest that this blood test had robust performance in detecting brain amyloidosis and could aid clinicians in the diagnosis of Alzheimer disease among patients with cognitive impairment.