The CSF/serum ratio of CXCL8 (median 33.59, ranged from 0.51 to 220.1) in neurosyphilis patients was significantly higher than that in non-neurosyphilis patients (median 6.1, ranged from 0.02 to 43.3, p = 0.000) (Fig. 2N). Here, CXCL8 is linked to neurosyphilis.