Janelidze, ShorenaPalmqvist, SebastianLeuzy, AntoineStomrud, ErikVerberk, Inge M.W.Zetterberg, HenrikAshton, Nicholas J.Pesini, PedroSarasa, LeticiaAllué, José AntonioTeunissen, Charlotte E.Dage, Jeffrey L.Blennow, KajMattsson-Carlgren, NiklasHansson, Oskar2022-11-162022-11-162022-02Janelidze S, Palmqvist S, Leuzy A, et al. Detecting amyloid positivity in early Alzheimer's disease using combinations of plasma Aβ42/Aβ40 and p-tau. Alzheimers Dement. 2022;18(2):283-293. doi:10.1002/alz.12395https://hdl.handle.net/1805/30569Introduction: We studied usefulness of combining blood amyloid beta (Aβ)42/Aβ40, phosphorylated tau (p-tau)217, and neurofilament light (NfL) to detect abnormal brain Aβ deposition in different stages of early Alzheimer's disease (AD). Methods: Plasma biomarkers were measured using mass spectrometry (Aβ42/Aβ40) and immunoassays (p-tau217 and NfL) in cognitively unimpaired individuals (CU, N = 591) and patients with mild cognitive impairment (MCI, N = 304) from two independent cohorts (BioFINDER-1, BioFINDER-2). Results: In CU, a combination of plasma Aβ42/Aβ40 and p-tau217 detected abnormal brain Aβ status with area under the curve (AUC) of 0.83 to 0.86. In MCI, the models including p-tau217 alone or Aβ42/Aβ40 and p-tau217 had similar AUCs (0.86-0.88); however, the latter showed improved model fit. The models were implemented in an online application providing individualized risk assessments (https://brainapps.shinyapps.io/PredictABplasma/). Discussion: A combination of plasma Aβ42/Aβ40 and p-tau217 discriminated Aβ status with relatively high accuracy, whereas p-tau217 showed strongest associations with Aβ pathology in MCI but not in CU.en-USAttribution-NonCommercial 4.0 InternationalAlzheimer's diseaseAβ42/Aβ40AmyloidBlood biomarkersNeurofilament lightp-tau217Article