Pre-Analytical Variables Influencing Stability of Blood-Based Biomarkers of Neuropathology

Article type: Research Article

Authors: Panikkar, Daniel^a | Vivek, Sithara^b | Crimmins, Eileen^c | Faul, Jessica^d | Langa, Kenneth M.^{d; e; f} | Thyagarajan, Bharat^{b; *}

Affiliations: [a] Department of Neuroscience, University of Minnesota, Minneapolis, MN, USA | [b] Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, MN, USA | [c] Davis School of Gerontology, University of Southern California, Los Angeles, CA, USA | [d] Institute for Social Research, Survey Research Center, University of Michigan, Ann Arbor, MI, USA | [e] Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA | [f] Veterans Affairs Ann Arbor Center for Clinical Management Research, Ann Arbor, MI, USA

Correspondence: [*] Correspondence to: Dr. Bharat Thyagarajan, Department of Laboratory Medicine and Pathology, University of Minnesota, MMC 609, 420 Delaware Street, Minneapolis, MN 55455, USA. Tel.: +1 612 624 1257; E-mail: thya0003@umn.edu; ORCID ID: 0000-0001-6968-6985

Abstract: Background:Sample collection and preanalytical protocols may significantly impact the results of large-scale epidemiological studies incorporating blood-based biomarkers of neuropathology. Objective:To evaluate the stability and assay variability of several blood-based biomarkers of neuropathology for common preanalytical conditions. Methods:We collected serum and plasma samples from 41 participants and evaluated the effect of processing delay of up to 72 h when stored at 4∘C, three freeze-thaw cycles, and a combination of 48-h processing delay when stored at 4∘C and three freeze-thaw cycles on biomarker stability. Using the Simoa assay (Quanterix Inc.), we measured amyloid-β 40 (Aβ40), amyloid-β 42 (Aβ42), neurofilament light (NfL), glial fibrillary acidic protein (GFAP), and phosphorylated tau 181 (p-tau-181). Results:We found that Aβ40 and Aβ42 levels significantly decreased after a 24-h processing delay in both plasma and serum samples, and a single freeze-thaw cycle (p < 0.0001). Nevertheless, serum Aβ42/40 ratio remained stable with a processing delay up to 48 h while plasma Aβ42/40 ratio showed only small but significant increase with a delay up to 72 h. Both plasma and serum GFAP and NfL levels were only modestly affected by processing delay and freeze-thaw cycles. Plasma p-tau-181 levels notably increased with a 24-, 48-, and 72-h processing delay, but remained stable in serum. Intra-individual variation over two weeks was minimal for all biomarkers and their levels were substantially lower in serum when compared with plasma. Conclusion:These results suggest that standardizing preanalytical variables will allow robust measurements of biomarkers of neuropathology in population studies.

Keywords: Alzheimer’s disease, amyloid-β , blood-based biomarkers, pre-analytical variables, Simoa assay, stability

DOI: 10.3233/JAD-230384

Journal: Journal of Alzheimer's Disease, vol. 95, no. 2, pp. 735-748, 2023