Equivalence of serum and plasma neurofilament light chain levels using highly sensitive automated immunoassay

Abstract Background Neurofilament light chain (NfL) in blood is a promising new biomarker for neurogenerative disease1 and clinical progression in presymptomatic Alzheimer disease2. Well established standardization of assays and collection methods are necessary before acceptance for clinical use. Data supporting equivalence of plasma and serum NfL testing are not yet widely published. In this study, we compared three blood collection specimen types, two for plasma and one for serum. Method Matched serum, heparin‐treated plasma, and EDTA‐treated plasma from 40 individual donors were acquired. NfL concentration was determined using an automated immunoassay developed at Siemens Healthcare Laboratory, LLC3. Sample equivalence was analyzed with Deming regression. Result All two way comparisons resulted in strong correlation: NfL concentrations in serum and lithium heparin plasma (slope=1.004, R=0.971), serum and K2EDTA plasma (slope=1.065, R=0.961), and lithium heparin plasma and K2EDTA plasma (slope=1.059, R=0.979). Conclusion Individual to individual variability was noted to be higher in plasma than with serum. With a well‐optimized automated immunoassay, NfL concentrations in plasma and serum were equivalent. References: (1) Zetterberg, H., Burnham, S.C. Blood‐based molecular biomarkers for Alzheimer’s disease. Mol Brain 12, 26 (2019) doi:10.1186/s13041‐019‐0448‐1. (2) Preische O, et al, Serum neurofilament dynamics predicts neurodegeneration and clinical progression in presymptomatic Alzheimer's disease, Nat Med. 2019 Feb;25(2):277‐283. doi: 10.1038/s41591‐018‐0304‐3. (3) Plavina, et al, Development of a Sensitive Serum Neurofilament Light Assay on Siemens Routine Immunoassay Platforms, poster presentation, ECTRIMS, 2019.