Mycobacterium-specific Cerebrospinal Fluid Smear Immunocytochemistry:a Novel Method For The Diagnosis Of Tuberculous Meningitis

BackgroundEarly and reliable diagnosis of tuberculous meningitis (TBM) still poses a great challenge.One of the underlying difficulties is due to the fact that Mycobacterium tuberculosis (Mtb)are mainly not present in the cerebrospinal fluid (CSF) but in the immune cells, especiallyin the phagocytotic macrophages. The present study was designed to demonstrate thepresence of early secretory antigenic target6(ESAT-6), a mycobacterium-specific antigen,in the immune cells in infected CSF samples and to compare the efficiency of thisantigen-based approach in the laboratory diagnosis of TBM.Methods203consecutive patients with clinically suspected TBM within the previous four weekswere prospectively recruited at tweleve centers in China. Routine biochemical, cytologicaland microbiological examinations of CSF were performed. CSF smears were stained bystandard immunocytological method to demonstrate the presence of ESAT-6antigen.ResultsWe enrolled203subjects.135patients satisfied the diagnostic criteria for definite TBM, in which Mtb was isolated from CSF samples in33patients and acid-fast bacilli wasdetected in135patients. The adjudicated final diagnosis were24patients with probableTBM,26patients with possible TBM, and18patients with non-TBM. The proportion ofESAT-6positively-stained immune cells in the definite, probable, and possible TBMgroups were significantly higher than that of the patients with non-TBM. Sensitivity andspecificity of the test were98.5%(95%CI98.4%to98.6%) and77.8%(75.9%to79.7%)and ESAT-6appeared to be helpful in the diagnosis of TBM.ConclusionsCSF smear immunocytochemistry with antibodies to ESAT-6is rapid, sensitive, andspecific for establishing an early etiological diagnosis of TBM.