For the HIV-infected patients with concurrent syphilis, those who had neurological symptoms when performing lumbar puncture, CD4 cell counts <350 per μL, and with serological TRUST titer ≥16 was 4.9-, 4.3-, and 4.1-fold, respectively, more likely to be diagnosed as having neurosyphilis (Table 2). Here, CD4 is linked to neurosyphilis.