The AUC of Model 2 was not statistically different from that of the ratio of CSF/serum CXCL13 and CSF VDRL (p = 0.3968, p = 0.1386, respectively), but it was higher than that of the ratio of CSF/serum CXCL8 and CXCL10 (p < 0.0001, p = 0.007, respectively) for all neurosyphilis. Here, CXCL13 is linked to neurosyphilis.