Chronic HIV encephalitis--I. Cerebrospinal fluid diagnosis.

To establish a reliable procedure for the early detection of central nervous system involvement in HIV infection, paired cerebrospinal fluid and serum samples of 59 patients were analysed. Fifteen were HIV antibody positive without clinical symptoms (stage I), 12 had lymphadenopathy syndrome or AIDS-related complex (stage II), and 32 had AIDS (stage III). Intrathecal synthesis of HIV antibodies was determined by a modified ELISA. Antibodies in CSF and serum were evaluated at identical immunoglobulin G levels to correct for the actual blood-CSF-barrier permeability. A CSF/serum quotient above 1.5 is indicative of intrathecal antibody synthesis, which was found in 47% of the patients in stage I, 67% in stage II, and 84% in stage III. These findings indicate an early and frequent invasion of the CNS.