Diagnostic Value of Early Secreted Antigenic Target-6 for the Diagnosis of Tuberculous Meningitis Patients

Abstract

The early diagnosis of tuberculous meningitis (TBM) is very crucial, since delayed diagnosis can lead to various neurological manifestations. We have previously developed an in-house indirect enzyme-linked immunosorbent assay (ELISA) for TBM diagnosis using the Antigen 85 (Ag 85) complex. It has been suggested that the Ag 85 complex might give false-positive reactions for individuals vaccinated with Bacillus Calmette-Guérin (BCG). In the present study, we describe a prospective evaluation demonstrating that early secreted antigenic target- 6 (ESAT-6), which is absent in Mycobacterium bovis BCG strains, is in the cerebrospinal fluid (CSF) of TBM patients. We used an indirect ELISA to detect ESAT-6 antigens in the CSF of TBM patients using polyclonal antibodies against ESAT-6. Using the indirect ELISA method, we demonstrated a sensitivity and specificity of 80% and 94%, respectively, for the diagnosis of TBM. The detection of ESAT-6 in the CSF of TBM patients by indirect ELISA is a promising method and can be used to develop an immunodiagnostic assay with increased sensitivity and specificity.