Abstract
Clin Chem Lab Med. 2026 Apr 29. doi: 10.1515/cclm-2026-0370. Online ahead of print.
ABSTRACT
OBJECTIVES: Plasma p-tau217 is a leading blood-based biomarker for Alzheimer's disease (AD), offering high diagnostic accuracy and potential utility for treatment eligibility and monitoring. However, real-world data on concordance between cerebrospinal fluid (CSF) Aβ42/40 and plasma p-tau217 in routine clinical laboratory settings remain limited.
METHODS: We retrospectively evaluated all plasma p-tau217 tests performed in the Clinical Neurochemistry Laboratory at Sahlgrenska University Hospital between August 2025 and March 2026. De-identified plasma p-tau217, additional blood biomarkers, and available CSF results were extracted from the laboratory information system. Concordance between plasma p-tau217 and CSF Aβ42/40 was evaluated by calculating positive and negative percent agreement, with CSF Aβ42/40 used as the reference standard. In addition, diagnostic accuracy for brain amyloid positivity was assessed using two predefined clinical cutoffs for plasma p-tau217 (<0.22 vs. >0.34 ng/L). Internal analytical performance was monitored over a six-month period using commercial quality control materials, with additional evaluation of lot-to-lot consistency for plasma p-tau217.
RESULTS: Among 1,352 plasma p-tau217 measurements, paired CSF Aβ42/40 data were available for 121 individuals. Based on plasma p-tau217 probability categories, 541 samples (40.0 %) were classified as low probability, 228 (16.9 %) as intermediate probability, and 583 (43.1 %) as high probability for amyloid pathology. Using CSF Aβ42/40 as the reference standard, plasma p-tau217 demonstrated a positive percent agreement of 84.5 % (95 % CI: 72.6-92.7 %) and a negative percent agreement of 87.5 % (95 % CI: 73.2-95.8 %). Internal quality control analyses showed good within-batch precision, with coefficients of variation below 7.3 %. Batch-dependent bias was observed in QC measurements, most notably for one batch (+14.4-18.4 %); however, subsequent QC investigations indicated that this deviation originated from the QC material rather than from assay-related performance. Lot-to-lot consistency assessment did not reveal systematic reagent lot-dependent effects during the study period.
CONCLUSIONS: Lumipulse plasma p-tau217 demonstrated stable analytical performance and consistent concordance with CSF Aβ42/40 in routine clinical practice. The observed agreement supports the feasibility of plasma p-tau217 as a supportive tool in the clinical evaluation of AD, while underscoring the need for continued quality control monitoring and prospective evaluation of assay performance.
PMID:42053135 | DOI:10.1515/cclm-2026-0370
UK DRI Authors
