Comparative Evaluation of Early Diagnosis of Tuberculous Meningitis by Different Assays

Abstract

Cerebrospinal fluid (CSF) and peripheral blood (PBL) were sampled multiple times from 25 patients with a clinical diagnosis of tuberculous meningitis (TBM) and 49 controls, including 27 patients with other infectious diseases of the central nervous system and 22 patients with other noninfectious neurological diseases. We used an enzyme-linked immunospot assay (ELISPOT) to detect anti-Mycobacterium bovis BCG antibody-secreting cells in CSF and PBL, PCR to detect a repeated insertion sequence (IS6110) specific for Mycobacterium tuberculosis in CSF, and an enzyme-linked immunosorbent assay (ELISA) to detect anti-BCG antibodies in CSF and PBL. In the meantime, culture of CSF from every TBM and control patient was done on Lowenstein-Jensen medium. ELISPOT proved to be the most valuable test, with a sensitivity of 84.0% and a specificity of 91.8%, and showed a sensitivity of 100.0% with the CSF specimens obtained within 4 weeks after the onset of TBM. The numbers of CSF anti-BCG immunoglobulin-secreting cells tested by ELISPOT were even higher in the early phase of TBM and declined while the disease was going on (P ‫؍‬ 0.008), which allowed an early diagnosis to be made. The sensitivities of PCR and ELISA were only 75.0% and 52.3%, respectively; and the specificities were 93.7% and 91.6%, respectively. Culture of CSF on Lowenstein-Jensen medium was the least sensitive (16%) compared to the sensitivities of the other three assays. Our results demonstrate that the ELISPOT technique is worthy for routine use in the laboratory to support the clinical diagnosis of TBM.In the past several years there has been a global increase in the incidence of tuberculosis along with the prevalence of AIDS and the emergence of multidrug-resistant strains. Tuberculous meningitis (TBM) is a major global health problem and is the most severe form of extrapulmonary tuberculosis, with a high rate mortality. TBM is diagnosed on the basis of clinical features, cerebrospinal fluid (CSF) studies, and radiological findings. Due to the variable clinical presentations and CSF findings, which can be confused with those of other chronic infections of the central nervous system (CNS), TBM is sometimes difficult to diagnosis with certainty, especially in its early phase (about 1 to 2 weeks after onset, according to our clinical observations). During this time period, the typical clinical manifestations of TBM have not fully developed. The polymorphonuclear pleocytosis in CSF can occur early and may give an erroneous impression of bacterial meningitis. Also during this time period, the antibiotic or antituberculous treatment has lasted for just a short time, and the effect of therapy is not obvious enough to be able to make a judgment. The contrast enhancement of the basal cisterns, hydrocephalus, or lesions in the brain parenchyma on a computed tomography (CT) image or a magnetic resonance imaging image specific for TBM may not occur so early. Previous clinical studies have clearly demonstrated that the timing of the onset of chemotherapy is the most cr...

Central Nervous System Tuberculosis: Pathogenesis and Clinical Aspects

“…In a study among patients with a clinical diagnosis of TBM that compared a dot immunobinding assay for an M. tuberculosis-specific 14-kDa protein antigen with PCR to detect IS6110, specific for M. tuberculosis in the CSF, the immunobinding assay was more sensitive than the PCR method (75% versus 40.5%, respectively) (204). Among the advantages of either antibody or antigen detection methods is that these methods are more applicable to laboratories based in the developing world, where the majority of the TBM burden remains, than more costly PCR-based methods (164,204 (146). In at least one study, the use of the MTD test was not helpful in diagnosing tuberculoma (9).…”

“…These assays have been evaluated specifically in HIV-coinfected patients (59,180) and also as a means to monitor therapy (180,210). While many of those studies demonstrated improved sensitivity over traditional smear and culture methods, several other studies highlighted the low sensitivities associated with these PCR assays (25,68,112,164,206). Looking at the utility of applying PCR assays to the (206).…”

“…An example of a more recent study shows that measuring antibodies against a 30-kDa protein that is a specific antigen of M. tuberculosis (88) yielded a more promising sensitivity of 92% (89). One technique that has emerged to address the suboptimal sensitivity of detecting M. tuberculosis-specific antibodies in the CSF is the use of immunospot assays to detect anti-M. bovis BCG antibody-secreting cells directly rather than quantifying the antibody itself (117,164). In a study of patients with a clinical diagnosis of TBM that compared the utility of detecting anti-M. bovis BCG antibodysecreting cells in the CSF by enzyme-linked immunospot (ELISPOT) assay, PCR to detect an insertion sequence (IS6110) specific for M. tuberculosis in the CSF, and an enzyme-linked immunosorbent assay (ELISA) to detect anti-BCG antibodies, the ELISPOT method was more sensitive than (84% versus 75% and 52.3%, respectively) and as specific as (91.8% versus 93.7% and 91.6%, respectively) the other methods tested (164).…”

“…One technique that has emerged to address the suboptimal sensitivity of detecting M. tuberculosis-specific antibodies in the CSF is the use of immunospot assays to detect anti-M. bovis BCG antibody-secreting cells directly rather than quantifying the antibody itself (117,164). In a study of patients with a clinical diagnosis of TBM that compared the utility of detecting anti-M. bovis BCG antibodysecreting cells in the CSF by enzyme-linked immunospot (ELISPOT) assay, PCR to detect an insertion sequence (IS6110) specific for M. tuberculosis in the CSF, and an enzyme-linked immunosorbent assay (ELISA) to detect anti-BCG antibodies, the ELISPOT method was more sensitive than (84% versus 75% and 52.3%, respectively) and as specific as (91.8% versus 93.7% and 91.6%, respectively) the other methods tested (164). Those authors also emphasized that the sensitivity of the ELISPOT method was better earlier in the clinical course of TBM and that the sensitivity improved to 100% among those tested within 4 weeks of onset of TBM symptoms (164).…”

Evaluation of Lionex TB kits and mycobacterial antigens for IgG and IgA detection in cerebrospinal fluid from tuberculosis meningitis patients

“…TB meningitis (TBM) is a common clinical manifestation involving infection of the central nervous system with Mycobacterium tuberculosis. Delay in diagnosis and treatment leads to neurologic handicap and mortality (Quan et al 2006). Usually, TBM diagnosis is made by clinical suspicion associated with cerebrospinal fluid (CSF) biochemical findings and protein concentration measurement is an important tool for early recognition of neurological disease; however, abnormalities may suggest TBM but do not differ significantly from those observed in other types of infectious meningitis (Thompson 1995).…”