Implementation and clinical concordance of a plasma pTau217 RUO assay within an in-house IVD/LDT workflow

Abstract Objectives To describe implementation of an automated plasma phosphorylated tau 217 (pTau217) reagent in a laboratory-defined workflow and evaluate concordance with cerebrospinal fluid (CSF) amyloid status. Methods We analyzed 73 matched CSF-plasma pairs from a memory-clinic cohort using CSF Aβ42/40 as reference. Published thresholds defined three classification zones. Renal analyses within this plasma-only cohort were exploratory and included amyloid-status adjustment. Analytical observations comprised one plasma dilution series, single-sample stability testing, and serum/CSF precision data. Results Plasma pTau217 discriminated CSF Aβ-positive status with an area under the curve (AUC) of 0.918 (95 % CI 0.825–0.987). Exploratory AUC estimates were 0.957 (95 % CI 0.889–0.999) for estimated glomerular filtration rate (eGFR) ≥60 and 0.692 (95 % CI 0.250–1.000) for eGFR <60 mL/min/1.73 m 2 . The latter subgroup comprised 13 Aβ-positive and four Aβ-negative patients; no formal AUC comparison was performed. At the rule-out threshold, 25/73 patients were classified as negative, including two Aβ-positive cases (negative predictive value 0.920). The rule-in zone comprised 39/73 patients, including three Aβ-negative cases (positive predictive value 0.923); nine patients (12.3 %) were intermediate. Conclusions Plasma pTau217 showed strong concordance with CSF Aβ42/40 status and potential for three-zone triage in memory-clinic patients. Exploratory renal findings warrant confirmation in larger cohorts.