Cerebrospinal fluid testing for the diagnosis of central nervous system infection

The central nervous system (CNS) is susceptible to bacterial, viral, and fu ngal infections, and prion diseases. Examination of the cerebrospinal fluid (CSF) is crucial in diagnosing these infections. Cerebrospinal tests may d irectly identify an organism and its nucleic acid and surface constituents by culture, polymerase chain reaction (PCR), or antigen detection. Alternat ively, antibody to an organism may be identified in CSF by enzyme-linked im munosorbent assay (ELISA), Western blot, or complement fixation assay. This article discusses how these CSF tests are performed and addresses the sens itivity and specificity of such tests for the diagnosis of selected CNS inf ections.