Background:  Symptoms suggesting aseptic meningitis (fever, headache, meningismus) are relatively common during primary HIV infection (PHI), and other central nervous system (CNS) infections can complicate the course of chronic HIV disease. The proportion of patients presenting with meningitis who have undiagnosed HIV infection is not known. Determining the prevalence of HIV infection in this population may impact HIV testing recommendations.

Methods:  Residual cerebrospinal fluid (CSF) specimens from patients aged 16 to 65 years who had herpes simplex virus (HSV) polymerase chain reaction (PCR) testing requested between January 1, 1999 and September 30, 2005 were retrospectively tested for HIV RNA using the UltraSensitive COBAS Amplicor HIV-1 Monitor Test. Transplant recipients and those with known HIV infection were excluded. After medical and laboratory records were reviewed, all identifiers were removed from the database and specimens prior to testing. A CSF pooling strategy that combined 0.1-mL aliquots from 10 separate patients was used for sample analysis. When HIV RNA was detected in a pool, each of the 10 component samples were retested individually. The study was approved by the Duke Institutional Review Board.

Results:  Of 288 patient samples, 72 tested for HIV RNA (25%) had abnormal CSF indices (>5 nucleated cells/mm³ and protein >50 mg/dL). Among the 72 patients with inflammatory CSF, 57 (79%) had documented symptoms of meningitis or encephalitis. HIV RNA was detected in the CSF of 3 of 57 patients (5%) with clinical and laboratory findings indicative of CNS infection. Of the 3 patients, 2 presented to the emergency department with a syndrome suggestive of PHI (fever, headache, malaise, and CSF lymphocytic pleocytosis with negative cultures and HSV PCR). Both had high levels of HIV RNA detected in CSF (157,000 and 106,000 copies/mL, respectively). The third patient was hospitalized with invasive pneumococcal disease and had a CSF HIV RNA of 124 copies/mL. HIV infection was not diagnosed prospectively in any of the 3. Of the 57 patients with clinical and laboratory findings of meningitis/encephalitis, 33 (58%) had an HIV antibody test during their evaluation, but only 4 (7%) also had an HIV PCR.

Conclusions:  Unsuspected HIV infection, including PHI, is relatively common among patients with acute meningitis. Patients with clinical and laboratory findings suggestive of meningoencephalitis should have HIV testing, including a nucleic acid test, performed as a part of the diagnostic evaluation.