Abstract
BACKGROUND: In recent years, plasma levels of phosphorylated tau species, particularly p-tau217, have emerged as reliable indicators of amyloid-β (Aβ) pathology in the brain. However, real-world data on plasma biomarkers across diverse populations remain limited. We conducted a prospective multicenter study under real-world clinical settings to evaluate diagnostic performance of plasma biomarkers, including p-tau217, in discriminating amyloid status among a Japanese population. METHODS: A total of 332 participants were recruited from seven memory clinics across Japan. Participants were categorized into four clinical subgroups: cognitively unimpaired (CU), mild cognitive impairment (MCI), Alzheimer’s disease dementia (ADD), and non-ADD. We measured Aβ40, Aβ42, p-tau181, total-tau, and neurofilament light chain (NfL) in CSF and Aβ40, Aβ42, p-tau217, p-tau181, glial fibrillary acidic protein (GFAP) and NfL in plasma using the LUMIPULSE platform. Amyloid status was determined by amyloid PET imaging and/or CSF Aβ42/40 ratio. RESULTS: Significant differences were observed in plasma biomarker levels, including Aβ42/40, p-tau217, p-tau181, GFAP, and NfL across clinical categories. Plasma p-tau217 and p-tau217/Aβ42 achieved high diagnostic accuracy, with areas under the curve (AUC) exceeding 0.9 with PET amyloid status as the reference, demonstrating comparable performance to the in vitro diagnostic (IVD)-approved CSF Aβ42/40 ratio. The two-cutoff approach using plasma p-tau217 and p-tau217/Aβ42 to achieve 90% sensitivity and 90% specificity provided high negative and positive predictive values. The intermediate range defined by these two-cutoff points was narrower for p-tau217/Aβ42 than for p-tau217. The predefined U.S. Food and Drug Administration (FDA)-approved two-cutoff points were applicable to this cohort with good accuracy. Concordance of plasma p-tau217 or p-tau217/Aβ42 with PET or CSF Aβ42/40 status ranged from 87% to 93%, although larger discordant results were observed in the non-ADD group. CONCLUSIONS: This study demonstrates the clinical utility of plasma p-tau217 and p-tau217/Aβ42 ratio for real-world diagnostic evaluations of dementia. However, careful interpretation of plasma biomarker is warranted in cases showing discordant results with PET or CSF findings. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13195-026-01997-7.