Cerebrospinal fluid neurofilament light chain profiling and quantitation in neurological diseases

Abstract Neurofilament light chain (NfL) is an established marker of neuroaxonal injury that is elevated in cerebrospinal fluid (CSF) and blood across various neurological diseases. It is increasingly used in clinical practice to aid diagnosis and monitor progression, and as an outcome measure to assess safety and efficacy of disease-modifying therapies across the clinical translational neuroscience field. Quantitative methods for NfL in human biofluids have relied on immunoassays, which have limited capacity to describe the structure of the protein in CSF, and how this might vary in different neurodegenerative diseases. In this study we characterised and quantified NfL species in CSF across neurodegenerative and neuroinflammatory diseases and healthy controls using targeted mass spectrometry. We show that the quantitative immunoprecipitation-tandem mass spectrometry (IP-MS/MS) method developed in this study strongly correlates to single-molecule array (Simoa) measurements in CSF across the broad spectrum of neurodegenerative diseases and was replicable across mass spectrometry methods and centres. In summary, we have created an accurate and cost-effective assay for measuring a key biomarker in translational neuroscience research and clinical practice, which can be easily multiplexed and translated into clinical laboratories for the screening and monitoring of neurodegenerative disease or acute brain injury.