CXCL13 and in situ carcinoma: On the base CXCL13 concentrations in the CSF of HC, we found a cutoff value of 6.8 pg/mL (μ + 4δ) that allowed the identification of two groups of CIS/eRRMS patients having CSF CXCL13 values below (CXCL13−, 20 patients) or above (CXCL13+, 20 patients) this limit.