Validation of a plasma GFAP immunoassay and establishment of age-related reference values: bridging analytical performance and routine implementation
Year: 2025
Type: article
Abstract: Objectives Glial fibrillary acidic protein (GFAP) is a well-established biomarker of astrocytic activation associated with neurodegenerative diseases, neuroinflammatory disorders, and traumatic brain injury. With increasing interest in blood-based biomarkers, the need for analytically validated assays and reliable reference intervals is critical for routine clinical implementation. This study aimed to analytically validate the MSD S-Plex ® GFAP immunoassay for plasma and to establish age-stratified reference intervals in an apparently healthy population. Methods This study was conducted in two phases. First, key analytical validation parameters – including repeatability, intermediate precision, measurement range, interferences, and sample stability – were evaluated following Clinical and Laboratory Standards Institute (CLSI) and published protocol guidelines. Second, reference intervals were derived from 579 apparently healthy individuals aged 17–91 years using a right-sided non-parametric percentile method. Age-specific upper reference limits were calculated for three predefined age groups, and a continuous age-dependent centile model was applied. Results MSD S-Plex ® GFAP assay demonstrated strong analytical performance, with coefficients of variation for repeatability and intermediate precision below 12 %. After accounting for the 1:2 dilution ratio, the validated measurement range was 0.425–1760 ng/L, with all calibration residuals remaining within ±15 %. GFAP concentrations were unaffected by hemolysis (p=0.85) and remained stable for up to 7 days at 4 °C and under frozen storage conditions. Age-stratified upper reference limits for plasma GFAP were established as 38 pg/mL (18–<50 years), 73 pg/mL (≥50–<70 years), and 156 pg/mL (≥70 years). Additionally, sex-related differences were observed after age 50, with females showing higher absolute GFAP levels than males. A strong positive correlation between age and plasma GFAP levels was observed (Spearman’s r=0.832, p<0.0001). Conclusions This study demonstrates the robust analytical performance of the MSD S-Plex ® GFAP assay and establishes age-related reference values for plasma GFAP. These findings support its suitability for routine clinical use and enhance its applicability in the diagnosis and monitoring of central nervous system (CNS) pathologies, such as neurodegenerative diseases, neuroinflammatory disorders, and acute brain injuries, within biomarker-supported clinical algorithms.
Institutions: Sahlgrenska University Hospital, University of Gothenburg, Region Västra Götaland, University Hospital of North Norway, Akershus University Hospital, UiT The Arctic University of Norway, University of Oslo, University of Science and Technology of China, Sorbonne Université, Pitié-Salpêtrière Hospital, Institut du Cerveau, University of Wisconsin–Madison, UCL Queen Square Institute of Neurology, University College London
Language: English
Subfield: Physiology
Field: Medicine
Domain: Health Sciences
Open Access status: hybrid
Estimated APC paid: $2,712
Funders: Alzheimer's Association, Amgen, Alzheimer's Drug Discovery Foundation, Eli Lilly and Company, Sanofi, Biogen, Teva Pharmaceutical Industries, Familjen Erling-Perssons Stiftelse, Cure Alzheimer's Fund, Stiftelsen för Gamla Tjänarinnor, EU Joint Programme – Neurodegenerative Disease Research, Prothena, Argenx, Apellis Pharmaceuticals, European Partnership on Metrology, National Institute for Health and Care Research, University College London, European Commission, Eisai, Hjärnfonden, Novo Nordisk, Vetenskapsrådet, Sahlgrenska Universitetssjukhuset, Göteborgs Universitet, Siemens Healthineers, Julius Clinical, UK Dementia Research Institute, Olav Thon Stiftelsen, HORIZON EUROPE Framework Programme
Awards: G1057200632, G1088883541, G1253720191, The Alzheimer’s Association quality control (QC) program for CSF and plasma biomarkers - Continuation, G150733400, G1551449788, G1588116593, G1771944843, G1802301745, G1833008592, G201353144, G2057385626, G2108271864, G237833635, G2543812357, G2799940023, G2841269746, G2879339865, G292763017, Trajectories of neuronal degeneration and vascular pathology in preclinical Alzheimer`s disease, G3241251457, Fluid biomarkers for neurodegenerative dementias, G3903502641, G3914690605, G4181470480, G4234328627, G4260843567, G432431387, G434337789, G4377393254, G5040492720, G506008078, G516766298, G5193057828, Fluid biomarkers for neurodegenerative dementias, CASCADE: CAuSe or Consequence in Alzheimer DiseasE?, G6158734006, G6289970089, G6422975485, Multi-omics Interdisciplinary Research Integration to Address DEmentia diagnosis, G6745400708, G691317373
OpenAlex ID: W4413436453