Session: Parallel session 9 - Complex mixtures - polymers - microplastics

Standardisation of Measurements of Neurodegenerative Disease Biomarkers: tau protein from CSF to plasma

Chiara GIANGRANDE¹, Vincent DELATOUR¹, Johan GOBOM⁵, Zetterberg HENRIK⁵, Hélène VANEECKHOUTTE¹, Samy MESSAOUDI^1,2, Christophe HIRTZ³, Sylvain LEHMANN³, Joelle VINH², Yann VERDIER ², Kaj BLENNOW⁵, Andreas JEROMIN⁴

¹LNE - Direction de la Métrologie Scientifique et Industrielle, Paris, France
²Ecole Superieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI Paris) – Université Paris sciences et lettres, Paris, France
³Plateforme de Prot´eomique Clinique de Montpellier (PPC) – BioCampus, Centre de Recherche Inserm – Institute for Regenerative Medicine and Biotherapy (IRMB) Hôpital Saint Eloi, Montpellier, France
⁴AlzPath, Carlsbad, United States
⁵Department of Psychiatry and Neurochemistry, Institute of Neuroscience and Physiology, the Sahlgrenska Academy at the University of Gothenburg, Mölndal, Gothenburg, Sweden

Introduction

Tau hyper-phosphorylation is one of the main hallmarks of Alzheimer’s disease (AD) and its measurement provides higher accuracy to discriminate AD from other forms of dementia and to stratify patients at an early-stage.

Here we describe fit for purpose reference measurement procedures (RMPs) to standardise t-tau and p-tau quantification in CSF and plasma by using targeted mass spectrometry.

Methodology

Candidate SI-traceable protein and peptide primary calibrators were fully characterised by using amino acid analysis and high resolution mass spectrometry for impurity profiling. Different tau peptides were measured in CSF pools and patients single donations in order to validate LC-MS candidate reference methods by exploiting the potential of PRM and isotopic dilution.

Results

An SI-traceable candidate protein primary calibrator was developed for total tau (t-tau) and a LC-IDMS candidate reference method quantification was validated. Three CSF pools were successfully quantified with a relative expanded uncertainty below 10%. 13 matrix-based certified reference materials (CRMs) and 40 CSF single donations were also measured within an intercomparison involving 8 immunoassays from 5 IVD providers to assess the commutability of the CRMs. Similar activities were initiated on the clinically-relevant phosphorylated epitopes of tau, p-tau(181), p-tau(217) and p-tau(231), where multiple phosphopeptide primary calibrators were sourced and characterized as well as a GSK3beta-phosphorylated protein primary calibrator.

Conclusion

Targeted mass spectrometry coupled to isotopic dilution was successfully used to establish a calibration hierarchy to SI for tau protein and its phosphorylated forms. This work will allow the transfer of tau measurement from CSF to plasma within an EU-funded project, NEuroBioStand, coordinated by LNE, aiming at standardising biomarkers measurements for the early diagnosis of neurodegenerative diseases through the use of SI-traceable materials.