Diagnosis of tuberculous meningitis confirmed by means of an immunoblot method

In order to define the mycobacterial antigens that may be specifically associated with human tuberculous infection, the cerebrospinal fluid (CSF) specimens of 30 patients with tuberculous meningitis (TBM) and of an equal number of patients with non-tuberculous meningitis (controls) were compared by means of an immunoblot method for detecting antibody to Mycobacterium tuberculosis. In the CSF of controls, mycobacterial antibody was either absent or, when present, was found to react with 27, 30 and 45 KDa antigens of M. tuberculosis. Among patients with TBM, the numbers as well as intensities of the immunostained bands in the nitrocellulose membranes (NCM) were greater than among controls. Furthermore, a unique disease-associated mycobacterial antigen, 35 KDa of M. tuberculosis, was found to react with a specific antibody in the CSF of patients with TBM but was not detected in the CSF of any of the controls. This 35 KDa antigen could be easily identified in the NCM. The immunoblot method showed 100% sensitivity in all the culture-positive patients with TBM. Because of the high degree of specificity as well as sensitivity of the immunoblot method, we consider that this method is of value for confirming the diagnosis of TBM.