Is the p-tau217 plasma test used as a surrogate for amyloid PET scan or CSF testing when considering starting Leqembi in patients with Alzheimer's disease?

P-tau127 is an excellent surrogate for amyloid, though it is not yet standard practice. Currently, there are no best practice guidelines on whether p-tau217 alone is sufficient or if it needs to be combined with Aβ42/Aβ40 or APOE4. These are available clinically but not yet FDA-approved. The FDA-approved CSF assays are Aβ42 and p-tau181. Initially, they were mistakenly thought to represent amyloid and tau levels in the brain, but it turns out they both represent amyloid. The gold standard for as...