Serum and cerebrospinal fluid neurofilament light chains measured by SIMOA™, Ella™, and Lumipulse™ in multiple sclerosis naïve patients

Background Neurofilament light chains (NfL) are cytoskeletal biomarkers of axonal damage, about 40-fold higher in cerebrospinal fluid (CSF) compared to serum, and requiring ultrasensitive techniques to be measured in this latter fluid. Objectives To compare CSF and serum NfL levels in multiple sclerosis (MS) patients using different platforms. Methods 60 newly diagnosed relapsing-remitting MS patients (38 females; median age: 36.5 years, range: 15-60) were enrolled before steroid or disease-modifying treatments. CSF and serum NfL were measured with: the commercial Ella (TM) microfluidic platform (Bio-Techne), the Lumipulse (TM) Chemiluminescent Enzyme ImmunoAssay (Fujirebio), and the SIMOA (TM) on the SR-X instrument using NF-light assays (Quanterix). Results CSF and serum NfL absolute levels strongly correlated between assays, although being more elevated with Ella (TM). Passing-Bablok regression showed high agreement in measuring CSF NfL between assays (with greater proportional difference using Ella (TM)), and very high agreement for serum comparing SIMOA (TM) and Lumipulse (TM). Similarly, the Bland-Altman comparison evidenced lower biases for Lumipulse (TM) for both fluids. Conclusions CSF and serum NfL in naive MS patients are reliably measured with all assays. Although not interchangeable, SIMOA (TM) and Lumipulse (TM) showed high agreement for serum and CSF values.