Development and validation of a high‐sensitivity assay for measuring p217+tau in plasma

Abstract

Introduction Diagnosis of Alzheimer's disease (AD) based on amyloid beta (A), pathologic tau (T), and neurodegeneration (N) biomarkers in peripheral fluids promises to accelerate clinical trials and intercept disease earlier. Methods Qualification of a Simoa plasma p217+tau assay was performed, followed by clinical utility evaluation in a cohort of 227 subjects with broad A and T spectrum. Results The p217+tau plasma assay was accurate, precise, dilution linear, and highly sensitive. All measured samples were within linear range of the assay, presented higher concentration in AD versus healthy controls ( P < .0001), and plasma and cerebrospinal fluid levels correlated (r 2 = 0.35). The plasma p217+tau results were predictive of central T and A status (area under the curve = 0.90 and 0.90, respectively) with low false +/– rates. Discussion The assay described here exhibits good technical performance and shows potential as a highly accurate peripheral biomarker for A or T status in AD and cognitively normal subjects.

Plasma p217+tau versus NAV4694 amyloid and MK6240 tau PET across the Alzheimer's continuum

“…Plasma ptau217+ assay was performed on a SIngle MOlecular Array (Simoa) HD‐X platform blinded to all subject data using the technique described previously. 14 Samples were measured in duplicate, yielding average precision of 12% CV (87% of the samples measured with CV < 20%). Functional assay range (after accounting for sample dilution) was: lower limit of detection (LLOD) = 1 fg/mL, lower limit of quantification (LLOQ) = 10 fg/mL, upper limit of quantification (ULOQ) = 20,000 fg/mL.…”

“… 13 The recognized epitope is thus referred to as “p217+tau” and its measurement in plasma has demonstrated good concordance with CSF markers of AD in a validation cohort of 227 subjects with an area under the curve (AUC) of 0.90 versus CSF Aβ42/40 and 0.95 versus CSF P‐tau181. 14 …”

Plasma p217+tau vs NAV4694 amyloid and MK6240 tau PET across the Alzheimer continuum

“…Plasma from K 2 -EDTA tubes (7.5 mL S-monovette 01.1605.008, Sarstedt) containing pre-added prostaglandin E1 (33 ng/mL of whole blood, Sapphire Biosciences) to prevent platelet activation, a potential source of peripheral amyloid-β, was centrifuged at room temperature at 200g for 10 mins to collect platelet-rich plasma, and then at 800g for 10 mins to provide plasma that was snap frozen within 2 hr of collection was stored in vapour phase liquid nitrogen prior to shipping on dry ice from Australia to Janssen R&D, La Jolla, CA, USA. Plasma ptau217+ assay was performed on a SIngle MOlecular Array (Simoa) HD-X platform blinded to all subject data using the technique previously described [13]. Data analysis was then performed by AIBL investigators.…”

“…More recently a high sensitivity Simoa assay has been developed using a capture antibody (pT3) that was raised against tau in paired helical filaments (PHF) of AD brain [12,13]. The core requirement for this antibody binding is phosphorylation at aa217 (p217) with enhanced binding when other nearby phosphorylated sites are present, predominantly at aa212 [12].…”

“…The core requirement for this antibody binding is phosphorylation at aa217 (p217) with enhanced binding when other nearby phosphorylated sites are present, predominantly at aa212 [12]. The recognised epitope is thus referred to as “p217+tau” and its measurement in plasma has demonstrated good concordance with CSF markers of AD in a validation cohort of 227 subjects with Area Under the Curve (AUC) of 0.90 vs CSF Aβ42/40 and 0.95 vs CSF P-tau181 [13].…”