INTRODUCTION: Plasma phosphorylated tau (p-tau)217 is a leading blood-biomarker for the detection of amyloid beta (Aβ) pathology. We assessed the performance of a fully automated plasma p-tau217 immunoassay to detect Aβ pathology in mild cognitive impairment (MCI)/mild dementia. METHODS: Paired plasma and cerebrospinal fluid (CSF) samples were obtained at time of diagnostic lumbar puncture (LP) in a specialist memory service. Plasma p-tau217 was measured using the Lumipulse immunoassay platform and ability to detect CSF-defined Aβ positivity assessed. RESULTS: Of 148 participants (69.4 ± 6.5 years
54.1% female), 101 had MCI and 47 mild dementia. Median plasma p-tau217 was >
4-fold higher in Aβ+ vs Aβ- individuals with an area under the curve of 0.92 (0.87-0.97). Application of 90%, 95%, and 97.5% sensitivity/specificity thresholds for plasma p-tau217 may have obviated the need for more than half of LPs. DISCUSSION: Our real-world data support the clinical use of fully automated plasma p-tau217 immunoassays, although further studies in more diverse cohorts are required. HIGHLIGHTS: Plasma phosphorylated tau (p-tau)217 was measured using a fully automated immunoassay (Lumipulse).P-tau217 was >
4-fold higher in amyloid beta (Aβ)+ versus Aβ- individuals.Plasma p-tau217 had an area under the curve of 0.92 for detection of Aβ status.Using a previously proposed two-threshold approach may avoid more than half of lumbar punctures.