Scientists have developed p-tau217 plasma assays to create a clock that predicts the onset of Alzheimer's disease symptoms in cognitively intact individuals.[1] This clock makes it possible to estimate when such persons will develop the first symptoms of the disease.[1] The study was published in Nature Medicine on February 19, 2026.[1] p-tau217 tests achieve high accuracy in predicting Alzheimer's disease, ranging from 81% to 92–94% in different studies.[1][2] Plasma p-tau217 is strongly associated with amyloid PET positivity in asymptomatic individuals and helps identify the risk of progression to MCI.[2] Levels of p-tau217 rise with disease progression and distinguish Alzheimer's disease from other conditions.[3][4] The test is safe, although there is a risk of false positives.[1]