| Objective:Tuberculous meningitis(TBM),a chronic central nervous system infection disease caused by Mycobacterium tuberculosis, has high rates of case fatality and mutilation. Patients'prognosis is strongerly associated with early diagonosis and treatment in time. It is also well recognized that early diagnosis and institution of appropriate treatment in patients with TBM will lead to complete neurological recovery, whereas a delay in diagnosis and treatment often leads to irreversible neurological sequelae or death. But it is easy to make a misdiagnosis in early stage, because of diversify clinical manifestation. The misdiagnosis rate of TBM described in the exterior and interior literatures were 31.6%, while the diagnosis rate was only 10% in early stage (within one week). A confirmatory ("gold standard") laboratory diagnosis of TBM depends upon the demonstration of the causative agent of the disease, i.e., Mycobacterium tuberculosis (M.TB), in the cerebrospinal fluid (CSF) specimens by bacteriological methods, which poses less sensitivity. So their values of earlier diagnosis in clinical are limited. Early diagnosis and effective chemotherapy reduces the mortality and morbidity in patients with TBM. During the past few years, various immunological and molecular biological methods, especially PCR have been developed for rapid diagnosis of TBM. All these techniques are still considered investigational, and very few are routinely used in the management of individual cases of TBM. In addition, the techniques do show considerable variation in sensitivity and specificity. The host response to infection of M.TB is a typical cell-mediated immunity, along with fairly stronge humoral immune reaction. So it is maybe helpful to make a rapid diagnosis through demonstration of mycobacterial antigen and specific antibody in CSF specimens of patients with TBM. Whereas, M.TB is intracellular autoecious bacteria , and primarily lived in macrophages, which also the effector cells in immune reaction. The function of these monocytes is to phagocytose the tubercle bacilli and process the antigenic component of the bacilli. Thus, the cytoplasm of the monocytes in patients with TBM during the active stages contain mycobacterial antigen. In this study, upon the foundation of CSF routine examination, anti-M.tuberculosis antibodies in CSF and mycobacterial antigen in monocytes (macrophages) are detected. The purpose of this study is to find an effective method for early diagnosis of TBM.Methods:CSF samples were collected from 159 patients with definite diagnosis. All these patients were from the Second Hospital of Hebei Medical University during the period of 2004 October~2006 October. These patients were divided into three groups. (1)TBM group: Totally 67 patients. Among them 47 patients were pure TBM, 20 patients combined tuberculosis outside of skull. (2)Other central nervous system infection diseases: Of the 63 patients, 37 had meningoencephalitis of viral, 13 had pyogenic meningitis, 7 had cryptococcal meningitis, 6 had brain cysticercosis; (3)non-infection of central nervous diseases: 29 patients, including Guillain-Barre syndrome (GBS), myelitis, blood disorders, et al.CSF was collected by lumbar puncture in all patients, and analyzed by routine test, biochemical, cytology (MGG dye), Indian ink and aricine blue staining. Besides these, antibodies to M.tuberculosis in CSF and immunocytological demonstration of mycobacterial antigen in monocytes (macrophages) are carried out at the same time. All indexes were developed test, and continuously detected 2 times or more every 5~7 days.Results:1 CSF routine test: In most of the CSF samples of patients with TBM, the parameters showed elevated protein and cell population, reduced glucose concentration and chloridum .2 CSF Cytology: The CSF-cytospin smears from TBM group showed a mixture of monocytoid cells, lymphocytes and neutrophils (56/67, 83.6%). In disease control groups, meningoencephalitis of viral was dominate of lymphoid-cell response; pyogenic meningitis showed neutrophil response; Cryptococcal was detected in CSF with cryptococcal meningitis, and aricine blue and Indian ink staining were all positive. Neurocysticercosis disease showed eosinophilosis. While the reactions in CNS non-infection diseases were non-specificity. After statistical treatment, there was a statistical significance in cytologic diagnosis between groups. At the dynamic observation, neutrophil would last a long time and gradually reduced when the condition of TBM patients become better after treatment, the monocyte and lymphoid cells increased at the same time. 3 The demostration of antigens in monocytes: At the early stage of disease, the antigens of M tuberculosis could be detected in the cytoplasm of monocytes in the CSF by the immunocytological method, and the positive staining would keep for a long time with developed test. The sensitivity was 81.2%, and specificity did 95.7%.4 Detection of antibody to Mycobacterium tuberculosis: All cerebrospinal fluid samples from 20 TBM showed none positive.5 Comparisons of positive rates between different methods: it didn't have significant difference (X2=0.052, P=0.819>0.05) between CSF Cytology(mixed-cell response) and antigens demonstration. But the specificity of antigens demonstration is higher.Conclusions:1 CSF routine test, biochemical and cytology are considerable adjuncts for the laboratory diagnosis of TBM.2 The study showed that the antigens of M.tuberculosis can be detected in the cytoplasm of the monocytes in CSF by immunocytological method at the early stage of disease. The technical aspects are simple, rapid, and sensitive, as well as specific, and therefore can be applied for the early diagnosis of TBM.3 Detection of antibody to Mycobacterium tuberculosis has less sensitivity. Maybe it is not enough to clinical diagnosis, and a further research is essential.4 The presence of M.TB antigen were helpful to elevate the diagnosis rate, associated with dynamic observation on cerebrospinal fluid cytology.
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