Additionally, we sought to correlate CHI3L1 blood and cerebrospinal fluid (CSF) levels and identified its cellular source in peripheral blood mononuclear cells (PBMCs) from MS patients.<h4>Methods</h4>We used an in-house Single Molecule Array (Simoa) assay to measure CHI3L1 levels in serum, plasma, and CSF from MS patients and controls. This evidence concerns the gene CHI3L1 and myeloid sarcoma.