Study on the early diagnostic value of T-SPOT.TB assay detecting mononuclear cells in cerebrospinal fluid of patients with tuberculous meningitis

Abstract

Background Tuberculous meningitis (TBM) is a worldwide central nervous system infectious disease and is seriously harmful to human beings. The traditional normal assay of cerebrospinal fluid (CSF) and radiological examination always delay the clinical treatment because of low sensitivity and specificity. Therefore, a more sensitive method for the clinical diagnosis of TBM is badly in need. This article uses T lymphocytes enzyme-linked immunospot assay (ELISPOT) to detect mononuclear cells in peripheral blood (PB) and CSF of TBM patients, and compares the sensitivity and specificity in the diagnosis of TBM between the two methods, for the purpose of providing effective examination method for the early diagnosis of TBM. Methods PB and CSF samples were collected from 30 cases of TBM (case group) and 30 cases of non-TBM (control group) respectively, and mononuclear cells were separated and extracted through cryopreservation and rapid thawing. A spot test using T lymphocytes infected with tubercle bacillus (T-SPOT.TB) was applied to check T lymphocytes secreted by interferon⁃γ in PB and CSF, so that the sensitivity and specificity for diagnosing TBM by this method were evaluated. Results CSF mononuclear cells ELISPOT assay showed that 28 cases in the case group were diagnosed as TBM and other 2 cases were diagnosed as non-TBM, with the positive rate being 93.33% (28/30); as for control group, 1 case was diagnosed as TBM, and 29 cases were diagnosed as non-TBM, with the positive rate being 3.33% (1/30). In CSF mononuclear cells ELISPOT assay, the sensitivity and specificity were 93.33% and 96.67%; false positive rate was 3.33%; false negative rate was 6.67%; positive likelihood ratio was 28.33; negative likelihood ratio was 0.07. PB mononuclear cells ELISPOT assay showed that 23 cases in the case group were diagnosed as TBM and 7 cases were diagnosed as non⁃TBM, with the positive rate being 76.67% (23/30); as for control group, 4 cases were diagnosed as TBM, and 26 cases were diagnosed as non-TBM, with the positive rate being 13.33% (4/30). In PB mononuclear cells ELISPOT assay, the sensitivity and specificity were 76.67% and 86.67% ; false positive rate was 13.33% ; false negative rate was 23.33% ; positive likelihood ratio was 5.79; negative likelihood ratio was 0.15. Fisher exact probability test showed the difference between the TBM positive rate of PB and CSF ELISPOT assay was not statistically significant (P = 0.254). Conclusion PB and CSF mononuclear cells ELISPOT assay can be effectively favorable for the current diagnosis of TBM as an auxiliary diagnostic method. Besides, CSF mononuclear cells ELISPOT assay is more efficient than PB assay.