AbstractINTRODUCTIONWe set out to identify tau PET‐positive (A+T+) individuals among amyloid‐beta (Aβ) positive participants using plasma biomarkers.METHODSIn this cross‐sectional study we assessed 234 participants across the AD continuum who were evaluated by amyloid PET with [¹⁸F]AZD4694 and tau‐PET with [¹⁸F]MK6240 and measured plasma levels of total tau, pTau‐181, pTau‐217, pTau‐231, and N‐terminal tau (NTA‐tau). We evaluated the performances of plasma biomarkers to predict tau positivity in Aβ+ individuals.RESULTSHighest associations with tau positivity in Aβ+ individuals were found for plasma pTau‐217 (AUC [CI_95%] = 0.89 [0.82, 0.96]) and NTA‐tau (AUC [CI_95%] = 0.88 [0.91, 0.95]). Combining pTau‐217 and NTA‐tau resulted in the strongest agreement (Cohen's Kappa = 0.74, CI_95% = 0.57/0.90, sensitivity = 92%, specificity = 81%) with PET for classifying tau positivity.DISCUSSIONThe potential for identifying tau accumulation in later Braak stages will be useful for patient stratification and prognostication in treatment trials and in clinical practice.Highlights We found that in a cohort without pre‐selection pTau‐181, pTau‐217, and NTA‐tau showed the highest association with tau PET positivity. We found that in Aβ+ individuals pTau‐217 and NTA‐tau showed the highest association with tau PET positivity. Combining pTau‐217 and NTA‐tau resulted in the strongest agreement with the tau PET‐based classification.