For the total group with CNS infection (encephalitis, VM and ABM), CSF levels correlated with serum levels for 3-HK (Rho 0.6, p < 0.001), QA (0.4, p = 0.04), and PIC (0.7, p < 0.001), for all other KP metabolites, there was no significant correlation between CSF and serum levels. Here, NPPA is linked to viral encephalitis.