Assessment of an immunoassay for interferon-alpha in cerebrospinal fluid as a diagnostic aid in infections of the central nervous system.

A highly sensitive and specific immunoradiometric assay, based upon a monoclonal antibody, was used to measure interferon-alpha (IFN-alpha) in the cerebrospinal fluid (CSF) of patients with central nervous system infections and in controls with non-infectious neurological disorders. IFN-alpha was detected in all 21 patients with viral meningitis but in only one of four patients with non-viral aseptic meningitis. It was also present in the CSF of three of four patients with herpes encephalitis and five of seven patients with acute bacterial meningitis. By contrast, IFN-alpha was present in the CSF in low concentrations in only five (7%) of 71 neurological controls. This rapid test is positive in viral meningitis and may help in distinguishing viral infection from other causes of aseptic meningitis. It is usually negative in non-infective disorders but will not distinguish between viral and bacterial infections.