The potential contribution of the polymerase chain reaction to the diagnosis of tuberculous meningitis

Diagnostic accuracy of the interferon-gamma release assay (IGRA) for cases of feline mycobacteriosis

The aim of this study was to evaluate the sensitivity and specificity of the interferon-gamma release assay (IGRA) for diagnosing infections with members of the Mycobacterium (M.) tuberculosis-complex (MTBC) and non-tuberculous mycobacteria (NTM) in domestic cats, and to generate defined feline-specific cut-off values using receiver operating characteristic (ROC) curve analysis to improve test performance. Records of 594 cats that had been tested by IGRA were explored to identify individuals that had a culture and/or polymerase chain reaction (PCR)-confirmed case of mycobacterial disease, and those that had a final diagnosis of non-mycobacterial disease. A total of 117 cats - 80 with mycobacterial disease and 37 diagnosed with a condition other than mycobacteriosis - were identified for further detailed analysis. This population was used to estimate test sensitivity and specificity, as well as likelihood ratios for the IGRA to correctly identify a cat with or without mycobacterial disease. Agreement between IGRA results and culture/PCR using current and proposed new cut-off values was also determined. ROC analysis of defined confirmed infected and non-mycobacterial disease control cats allowed an adjustment of current test cut-offs that increased the overall test sensitivity for MTBC infections from 83.1 % (95 % confidence interval [CI]: 71.5-90.5 %) to 90.2 % (95 % CI: 80.2-95.4%), and M. bovis infection from 43 % (95 % CI: 28.2-60.7%) to 68 % (95 % CI: 51.4-82.1%) while maintaining high test specificity (100 % in both cases). Overall agreement between IGRA results and culture/PCR, while recognising that neither culture nor PCR tests have perfect sensitivity, improved from weak (κ = 0.57) to moderate (κ = 0.71) using new proposed IGRA test cut-off values. Application of these results, based upon the statistical analysis of accumulated test data, can improve the diagnostic performance of the feline IGRA, particularly for identifying infections with M. bovis, without compromising specificity.

A Systematic Review and Meta-analysis of the Diagnostic Accuracy of Nucleic Acid Amplification Tests for Tuberculous Meningitis

The diagnosis of tuberculous meningitis (TBM) is difficult and poses a significant challenge to physicians worldwide. Recently, nucleic acid amplification (NAA) tests have shown promise for the diagnosis of TBM, although their performance has been variable. We undertook a systematic review and meta-analysis to evaluate the diagnostic accuracy of NAA tests with cerebrospinal fluid (CSF) samples against that of culture as the reference standard or a combined reference standard (CRS) for TBM. We searched the Embase, PubMed, Web of Science, and Cochrane Library databases for the relevant records. The QUADAS-2 tool was used to assess the quality of the studies. Diagnostic accuracy measures (i.e., sensitivity and specificity) were pooled with a random-effects model. All statistical analyses were performed with STATA (version 14 IC; Stata Corporation, College Station, TX, USA), Meta-DiSc (version 1.4 for Windows; Cochrane Colloquium, Barcelona, Spain), and RevMan (version 5.3; The Nordic Cochrane Centre, the Cochrane Collaboration, Copenhagen, Denmark) software. Sixty-three studies comprising 1,381 cases of confirmed TBM and 5,712 non-TBM controls were included in the final analysis. These 63 studies were divided into two groups comprising 71 data sets (43 in-house tests and 28 commercial tests) that used culture as the reference standard and 24 data sets (21 in-house tests and 3 commercial tests) that used a CRS. Studies which used a culture reference standard had better pooled summary estimates than studies which used CRS. The overall pooled estimates of sensitivity, specificity, positive likelihood ratio (PLR), and negative likelihood ratio (NLR) of the NAA tests against culture were 82% (95% confidence interval [CI], 75 to 87%), 99% (95% CI, 98 to 99%), 58.6 (95% CI, 35.3 to 97.3), and 0.19 (95% CI, 0.14 to 0.25), respectively. The pooled sensitivity, specificity, PLR, and NLR of NAA tests against CRS were 68% (95% CI, 41 to 87%), 98% (95% CI, 95 to 99%), 36.5 (95% CI, 15.6 to 85.3), and 0.32 (95% CI, 0.15 to 0.70), respectively. The analysis has demonstrated that the diagnostic accuracy of NAA tests is currently insufficient for them to replace culture as a lone diagnostic test. NAA tests may be used in combination with culture due to the advantage of time to result and in scenarios where culture tests are not feasible. Further work to improve NAA tests would benefit from the availability of standardized reference standards and improvements to the methodology.

Diagnostic efficacy of adenosine deaminase levels in cerebrospinal fluid in patients of tubercular meningitis: A comparison with PCR for Mycobacterium Tuberculosis

Background

The rapid diagnosis of Tubercular meningitis (TBM) is fundamental to clinical outcome. The key to diagnosis lies in Cerebrospinal fluid (CSF) analysis and radiological investigations. There are numerous lacunae in the confirmation of diagnosis of TBM from CSF.

Purpose

The aim of present study was to compare the efficacy of CSF adenosine deaminase (ADA) level assays and Polymerase chain reaction (PCR) for Mycobacterium tuberculosis (M. tuberculosis) in the diagnosis of TBM.

Methods

Fifty four adult patients with suspected TBM and 37 controls were included in the study and CSF analyzed for ADA and PCR for M. tuberculosis. The cases were subdivided into definite (5), highly probable (22), probable (22) and possible TBM (5) as per previously validated criteria. The first two were grouped as "most likely" TBM (27) and last two as "unconfirmed" TBM (27).

Results

The mean ADA of the "most likely" TBM was 29±24, "unconfirmed" TBM was 21 ± 15 and controls were 4.8±2.2 U/L. The ADA levels correlated with CSF proteins, absolute lymphocyte count and the staging of the disease. Using a cut off level of >L10 U/L, CSF ADA had a sensitivity of 92.5% and specificity of 97%. PCR for M. tuberculosis was positive in 12 out of 27 "most likely" TBM cases, 5 out of 27 "unconfirmed" TBM cases and 3 out of 37 controls. PCR for M. tuberculosis had a sensitivity of 44.5% and specificity of 92% in the "most likely" TBM cases. Conclusions: ADA is a rapid, inexpensive and sensitive test in the diagnosis of TBM. It is more sensitive than AFB smear and culture. PCR is another rapid test in the diagnosis of TBM with a good specificity, even in those patients already on presumptive anti-tuberculous treatment. However, despite the sensitivity and specificity of CSF ADA, it should be corroborated with AFB smear and CSF PCR.

Adenosine deaminase activity in cerebrospinal fluid and serum for the diagnosis of tuberculous meningitis

OBJECTIVE

To evaluate the usefulness of serum and CSF adenosine deaminase (ADA) activity for the diagnosis of tuberculous meningitis (TBM) from other meningitis.

METHODS

We studied CSF and serum ADA activity for 83 cases of TBM, 148 of bacterial meningitis (BM), and 262 of viral or aseptic meningitis.

RESULTS

The mean ADA activities (IU/L) in CSF and serum were higher in TBM (11.80 ± 2.50, 30.28 ± 7.30) than in other types of meningitis (8.52 ± 3.60, 17.90 ± 9.20 in BM; 5.26 ± 1.90, 8.56 ± 5.9 in viral or aseptic meningitis). When we accepted a serum ADA activity cut-off value of 15 IU/L for the differential diagnosis of TBM and non-TBM with ROC analysis, the sensitivity was 84% and specificity was 82%. Combining CSF (≥ 10) and serum (≥ 15) ADA activity significantly increased overall specificity from 92% to 97% for the diagnosis of TBM.

CONCLUSIONS

The determination of CSF and serum ADA activity is a simple and reliable test for differentiating TBM from other types of meningitis.

Childhood tubercular meningitis: an institutional experience and analysis of predictors of outcome

Tubercular meningitis constitutes an important cause of morbidity and mortality in developing countries, and various factors determine its outcome. We studied demographic and clinical profiles of childhood tubercular meningitis, and identified predictors of outcome. This prospective study was performed in 65 children aged ≤ 18 years, hospitalized with a diagnosis of tubercular meningitis. Boys outnumbered girls. Most patients presented with a poor clinical grade. Headache and vomiting comprised common features. Cerebrospinal fluid was characterized by predominant lymphocytosis. Many patients were diagnosed for Mycobacterium tuberculosis via polymerase chain reaction. Hydrocephalus comprises a common finding via computed tomography. Low Glasgow Coma Scores, seizures, basal exudates, and infarcts predict outcomes. Children with headaches, fevers, and altered sensorium should be investigated promptly for tubercular meningitis. Timely intervention may lead to early diagnoses and reductions in morbidity and mortality.

Comparison of real time IS6110-PCR, microscopy, and culture for diagnosis of tuberculous meningitis in a cohort of adult patients in Indonesia

BACKGROUND

Bacteriological confirmation of tuberculous (TB) meningitis is difficult. Culture is slow and microscopy has insufficient sensitivity. We evaluated real time PCR targeting insertion sequence IS6110 among 230 consecutive adult patients with subacute meningitis in a referral hospital in Indonesia.

METHODS

Cerebrospinal fluid (CSF) samples were examined using microscopy, solid and liquid culture, and real time IS6110-PCR with a fluorescence-labeled probe using DNA extracted from CSF. CSF samples from 40 non-infectious neurology patients were used as negative controls. IS6110-PCR results were linked with clinical and CSF characteristics.

RESULTS

Most patients presented with subacute meningitis, after a median of 14 days of symptoms (range 7-30). After exclusion of cryptococcal and bacterial meningitis, 207 patients were classified as definite or probable TB meningitis; 17.9% with HIV infection. Among this group IS6110-PCR gave the highest positivity rate (68%, 95% CI 62-74%) compared with microscopy of ZN-stained slides (11%, 95% CI 7-15%), and mycobacterial culture using solid (36%, 95% CI 29-42%) and liquid (44%, 95% CI 37-51%) media. IS6110-PCR was positive in 92% of patients with culture-positive and 42% of patients with culture-negative probable TB meningitis. Among culture-negative patients, a positive PCR was associated with a history of TB treatment, a longer duration of illness, a higher CSF cell count and protein, and a lower CSF glucose. IS6110-PCR was negative in all CSF samples from non-meningitis control patients.

CONCLUSIONS

Real time IS6110-PCR is a quick, sensitive, and specific test for diagnosing of TB meningitis in this setting. Its performance in other (less-developed) settings needs further study.

Neurosarcoidosis: guidance for the general neurologist

Neurosarcoidosis (NS) more commonly occurs in the setting of systemic disease. The diagnosis is based on a clinical history suggestive of NS, presence of noncaseating granulomas, and supportive evidence of sarcoid pathology, laboratory, and imaging studies. NS could involve any part of the nervous system and often demands high doses of steroids for symptom control. It presents low response to isolated steroids administration and frequently requires immunosuppressive agents. In NS, lymphocytes are polarized toward an excessive Th1 response, leading to overproduction of TNF-alpha and INF-gama, as well as lL-2 and IL-15. Infliximab, a chimeric monoclonal antibody that neutralizes the biological activity of TNF-alpha, is a new option in the NS treatment. We revised pathophysiology, clinical manifestations, diagnostic work up, and treatment of NS as guidance for the general neurologist.

The PCR-Based Diagnosis of Central Nervous System Tuberculosis: Up to Date

Central nervous system (CNS) tuberculosis, particularly tuberculous meningitis (TBM), is the severest form of Mycobacterium tuberculosis (M.Tb) infection, causing death or severe neurological defects in more than half of those affected, in spite of recent advancements in available anti-tuberculosis treatment. The definitive diagnosis of CNS tuberculosis depends upon the detection of M.Tb bacilli in the cerebrospinal fluid (CSF). At present, the diagnosis of CNS tuberculosis remains a complex issue because the most widely used conventional “gold standard” based on bacteriological detection methods, such as direct smear and culture identification, cannot rapidly detect M.Tb in CSF specimens with sufficient sensitivity in the acute phase of TBM. Recently, instead of the conventional “gold standard”, the various molecular-based methods including nucleic acid amplification (NAA) assay technique, particularly polymerase chain reaction (PCR) assay, has emerged as a promising new method for the diagnosis of CNS tuberculosis because of its rapidity, sensitivity and specificity. In addition, the innovation of nested PCR assay technique is worthy of note given its contribution to improve the diagnosis of CNS tuberculosis. In this review, an overview of recent progress of the NAA methods, mainly highlighting the PCR assay technique, was presented.

Sensitivity and specificity of immunocytochemical staining of mycobacterial antigens in the cytoplasm of cerebrospinal fluid macrophages for diagnosing tuberculous meningitis

The sensitivity and specificity of immunocytochemical staining of mycobacterial antigens in the cytoplasm of cerebrospinal fluid (CSF) macrophages for diagnosis of tuberculous meningitis (TBM) was prospectively compared with Ahuja criteria from 393 consecutive CSF specimens. The assay can play an important role for the diagnosis of TBM, with sensitivity of 73.5% and specificity of 90.7%.

Multiplex PCR for rapid diagnosis of tuberculous meningitis

Rapid and specific diagnosis of tubercular meningitis is of paramount importance to decrease morbidity and mortality. The aim of the study was to evaluate multiplex PCR using protein b, MPB 64, and IS6110 primers directed against M. tuberculosis complex for the diagnosis of tuberculous meningitis (TBM). Multiplex PCR was performed on 18 TBM confirmed cases (culture was positive), 92 clinically suspected TBM cases and 100 non-TBM (control group) patients. Multiplex PCR had a sensitivity of 94.4% for confirmed cases and specificity of 100% for confirmed TBM cases. In 92 clinically diagnosed but unconfirmed TBM cases, multiplex PCR was positive in 84.78% cases. The overall sensitivity of microscopy, culture and multiplex cases were 1.81, 16.73, and 86.63% and specificity was 100, 100, and 100% respectively. Multiplex PCR using protein b, MPB 64, and IS6110 primers has a high sensitivity and specificity in diagnosis of tubercular meningitis.

Does multiplex polymerase chain reaction increase the diagnostic percentage in osteoarticular tuberculosis? A prospective evaluation of 80 cases

PURPOSE

Multiplex Polymerase Chain Reaction (MPCR) is a technique in which two or more gene targets are amplified in a single reaction. This has increased sensitivity of diagnosis as a single gene target may be absent in some Mycobacterium tuberculosis strains.

METHODS

MPCR using two target genes specific for Mycobacterium tuberculosis, that is, IS6110 and MPB 64, ZN staining and Mycobacterial culture were performed on synovial fluid/pus samples of 80 (three confirmed, 77 suspected) patients of osteoarticular tuberculosis and 25 non tuberculosis patients.

RESULTS

MPCR had a sensitivity of 100% in confirmed cases and 81.8% in clinically suspected cases. AFB was positive in one patient and Mycobacterial culture was positive in three patients. MPCR also had 100% specificity; MPB64 was positive in five patients in which IS6110 was negative whereas IS6110 was positive in two patients in which MPB64 was negative.

CONCLUSIONS

MPCR is a sensitive and specific method for diagnosis of paucibacilliary conditions such as osteoarticular tuberculosis.

Foot ulcer caused by multidrug-resistant Mycobacterium tuberculosis in a diabetic patient

Osteoarticular tuberculosis is the fourth leading type of extrapulmonary tuberculosis. The disease has a progressive course and the diagnosis is often made in the later stages of bone destruction. We describe a case of a foot ulcer caused by drug-resistant Mycobacterium tuberculosis in a patient with known diabetes where the diagnosis was not suspected initially. Although tuberculous foot ulcers are rare, they should be included in the differential diagnosis of unknown foot ulcers. A greater awareness of this rare clinical entity may help in commencing specific evidence-based therapy quickly and preventing undue morbidity and mortality.

To compare CSF adenosine deaminase levels and CSF-PCR for tuberculous meningitis

This study was planned to compare the adenosine deaminase (ADA) levels and polymerase chain reaction (PCR) in cerebrospinal fluid (CSF) as a rapid method to diagnose tuberculosis meningitis (TBM). Fifty-four adult patients with suspected TBM and 37 controls were included in this study. The median ADA level was 21U/L of most likely TBM, 14U/L of unconfirmed TBM and 5U/L of controls. PCR for Mycobacterium tuberculosis was positive in 12 out of 27 most likely TBM cases, 5 out of 27 unconfirmed TBM cases and 3 out of 37 controls. Using a cut off level of >10U/L, CSF-ADA had a sensitivity of 92.5% and specificity of 97% for the diagnosis of TBM. PCR for M. tuberculosis had a sensitivity of 44.5% and specificity 92% in the most likely TBM cases. This study shows that CSF-ADA is a more sensitive indicator than PCR for the diagnosis of M. tuberculosis.

Lumbar puncture and cerebrospinal fluid analysis

Examination of the CSF is the gold standard for the diagnosis of meningitis. There are a number of laboratory tests. in addition to CSF cell count, glucose concentration, Gram's stain, and bacterial culture, that are useful in identifying the organism and differentiating between bacterial and viral meningitis. These laboratory tests can be used in combination with the clinical presentation to determine which patient should be treated for bacterial meningitis while awaiting the result of CSF Gram's stain and bacterial culture.

Efficient diagnosis of tuberculous meningitis by detection of Mycobacterium tuberculosis DNA in cerebrospinal fluid filtrates using PCR

Tuberculous meningitis (TBM) is the most devastating form of meningitis and prompt diagnosis holds the key to its management. Conventional microbiology has limited utility and nucleic acid-based methods have not been widely accepted for various reasons. In view of the paucibacillary nature of cerebrospinal fluid (CSF) and the recent demonstration of free Mycobacterium tuberculosis DNA in clinical specimens, the present study was designed to evaluate the utility of CSF 'filtrates' for the diagnosis of TBM using PCR. One hundred and sixty-seven CSF samples were analysed from patients with 'suspected' TBM (n=81) and a control group including other cases of meningitis or neurological disorders (n=86). CSF 'sediments' and 'filtrates' were analysed individually for M. tuberculosis DNA by quantitative real-time PCR (qRT-PCR) and conventional PCR. Receiver-operating characteristic curves were generated from qRT-PCR data and cut-off values of 84 and 30 were selected for calling a 'filtrate' or 'sediment' sample positive, respectively. Based on these, TBM was diagnosed with 87.6% and 53.1% sensitivity (P<0.001) in 'filtrates' and 'sediments', respectively, and with 92% specificity each. Conventional devR and IS6110 PCR were also significantly more sensitive in 'filtrates' versus 'sediments' (sensitivity of 87.6% and 85.2% vs 31% and 39.5%, respectively; P<0.001). The qRT-PCR test yielded a positive likelihood ratio of 11 and 6.6 by analysing 'filtrate' and 'sediment' fractions, respectively, which establishes the superiority of the 'filtrate'-based assay over the 'sediment' assay. PCR findings were separately verified in 10 confirmed cases of TBM, where M. tuberculosis DNA was detected using devR PCR assays in 'sediment' and 'filtrate' fractions of all samples. From this study, we conclude that (i) CSF 'filtrates' contain a substantial amount of M. tuberculosis DNA and (ii) 'filtrates' and not 'sediments' are likely to reliably provide a PCR-based diagnosis in 'suspected' TBM patients.

Newer methods over the conventional diagnostic tests for tuberculous meningitis: do they really help?

Rapid diagnosis of tuberculous meningitis (TBM) is crucial as the disease outcome depends on the stage at which the treatment is initiated. The reliability of the available tests has not been established; thus, the present study was conducted to evaluate the conventional diagnostic tests as compared to the newer methods. Cerebrospinal fluid was collected from 100 children, and analyzed for various biochemical and cytological tests. The samples were subjected to Ziehl-Neelsen (Z-N) staining, Lowenstein-Jensen (L-J) culture, BACTEC culture and polymerase chain reaction (PCR). Twenty-two patients could be identified as definitive TBM based on the demonstration of Mycobacterium tuberculosis by BACTEC culture and PCR. Of these 22 cases, Z-N staining was positive in only two and L-J culture in six cases. Both the BACTEC culture and PCR had 100% agreement in the diagnosis of TBM. However, BACTEC culture could be a better diagnostic test as drug sensitivity can also be performed by this method.

Central nervous system tuberculosis: pathogenesis and clinical aspects

Tuberculosis of the central nervous system (CNS) is a highly devastating form of tuberculosis, which, even in the setting of appropriate antitubercular therapy, leads to unacceptable levels of morbidity and mortality. Despite the development of promising molecular diagnostic techniques, diagnosis of CNS tuberculosis relies largely on microbiological methods that are insensitive, and as such, CNS tuberculosis remains a formidable diagnostic challenge. Insights into the basic neuropathogenesis of Mycobacterium tuberculosis and the development of an appropriate animal model are desperately needed. The optimal regimen and length of treatment are largely unknown, and with the rising incidence of multidrug-resistant strains of M. tuberculosis, the development of well-tolerated and effective antibiotics remains a continued need. While the most widely used vaccine in the world largely targets this manifestation of tuberculosis, the BCG vaccine has not fulfilled the promise of eliminating CNS tuberculosis. We put forth this review to highlight the current understanding of the neuropathogenesis of M. tuberculosis, to discuss certain epidemiological, clinical, diagnostic, and therapeutic aspects of CNS tuberculosis, and also to underscore the many unmet needs in this important field.

Improved diagnosis of central nervous system tuberculosis by MPB64-Target PCR

Central nervous system (CNS) tuberculosis is a serious clinical problem, the treatment of which is sometimes hampered by delayed diagnosis. Clearly, prompt laboratory diagnosis is of vital importance as the spectrum of disease is wide and abnormalities of the cerebrospinal fluid (CSF) are incredibly variable. Since delayed hypersensitivity is the underlying immune response, bacterial load is very low. The conventional bacteriological methods rarely detect Mycobacterium tuberculosis in CSF and are of limited use in diagnosis of tuberculous meningitis (TBM). This double blind study was, therefore, directed to the molecular analysis of CNS tuberculosis by an in-house-developed PCR targeted for amplification of a 240bp nucleotide sequence coding for MPB64 protein specific for Mycobacterium tuberculosis. Based on the clinical criteria, 47 patients with CNS tuberculosis and a control group of 10 patients having non-tubercular lesions of the CNS were included in the study. Analyses were done in three groups; one group consisting of 27 patients of TBM, a second group of 20 patients with intracranial tuberculomas and a third group of 10 patients having nontubercular lesions of the CNS acted as control. There were no false positive results by PCR and the specificity worked out to be 100%. In the three study groups, routine CSF analysis (cells and chemistry), CSF for AFB smear and culture were negative in all cases. PCR was positive for 21/27 patients (77.7% sensitivity) of the first group of TBM patients, 6/20 patients (30% sensitivity) of the second group with intracranial tuberculomas were positive by PCR and none was PCR-positive (100% specificity) in the third group. Thus, PCR was found to be more sensitive than any other conventional method in the diagnosis of clinically suspected tubercular meningitis.

Evaluation of the IS6110 PCR assay for the rapid diagnosis of tuberculous meningitis

Background

Tuberculous meningitis (TBM) is one of the common clinical manifestations of extra-pulmonary tuberculosis. It is difficult to diagnose due to a lack of rapid, sensitive, and specific tests. Newer methods, which are easy and reliable, are required to diagnose TBM at an early stage. Thus our aim was to evaluate the polymerase chain reaction (PCR) technique, using primers directed against the IS6110 gene, for the detection of Mycobacterium tuberculosis in the CSF, for the diagnosis of TBM patients.

Methods

An in-house IS6110 PCR method using a specific pair of primers designed to amplify the insertion sequence, IS6110, in the M. tuberculosis genome was used to analyze CSF. A total of 80 CSF samples from different groups of patients were studied (confirmed TBM n = 35, clinically suspected TBM n = 16, non-TBM infectious meningitis n = 12, non infectious neurological diseases n = 17).

Results

PCR gave a sensitivity of 91.4% and specificity of 75.9% for the diagnosis of TBM in patients with TBM confirmed by culture. In 16 clinically diagnosed, but unconfirmed, TBM cases PCR was positive in 10 (62.5%) cases. There were seven (24.1%) PCR-positive cases among the 29 patients with non-TBM and non-infectious neurological disease.

Conclusion

We conclude that the performance of an in-house IS6110 PCR assay is valuable in the rapid diagnosis of tuberculous meningitis.

Diagnosis of tuberculous meningitis: clinical and laboratory parameters

BACKGROUND

Confirming the clinical suspicion of tuberculous meningitis (TBM) has always been problematic. Whilst smear and culture positivity are diagnostic, these tests have low sensitivity. The polymerase chain reaction (PCR) assay has given variable results.

AIM

This study attempted to improve the diagnostic yield by: (a) increasing the cerebrospinal fluid (CSF) volumes; (b) testing the yield from three specimens of CSF assumed to represent lumbar, cervico-thoracic cord, and base of brain CSF samples; (c) undertaking PCR assays using multiple primer sets; and (d) using real-time PCR.

METHOD

Patients suspected of having cranial or spinal meningeal tuberculosis were entered into the study. Three aliquots of CSF were subjected to smear, culture, and conventional and real-time PCR. Three sets of primers - IS6110, MPB64, and PT8/9 - were used. Patients were retrospectively classified into four categories: 'definite TB' (culture positive), 'probable TB' (clinical and other tests suggestive of TB), 'not TB', and 'uncertain diagnosis'.

RESULTS

A total of 68 patients were studied. There were 20 patients classified as definite TB, 24 probable TB, 17 not TB, and seven uncertain diagnosis. Forty-eight of 57 (84.2%) patients tested were HIV seropositive. The IS6110 PCR was positive in 27 patients which included 18/20 culture positive cases, six in the probable TB group, and three in the not TB group. The MPB64 and PT8/9 primers did not increase the yield. Real-time PCR was positive in seven additional patients. Combining the definite and probable TB, the sensitivity of all PCR assays was 70.5% (31/44) and specificity 87.5% (21/24).

CONCLUSION

Targeting multiple sites of the TB genome using conventional PCR did not increase the number of positive cases. Real-time PCR was more sensitive. However, all the current techniques are still too insensitive to confidently exclude the diagnosis on laboratory grounds.

Rapid diagnosis of tuberculous meningitis: a comparative evaluation of in-house PCR assays involving three mycobacterial DNA sequences, IS6110, MPB-64 and 65 kDa antigen

A PCR was standardized for amplifying three different mycobacterial--IS6110, MPB-64, 65 kDa DNA sequences. A comparative evaluation of the three PCR assays was carried out for the rapid diagnosis of tuberculous meningitis (TBM) using cerebrospinal fluid (CSF) specimens. While the IS6110 PCR was a single-step amplification reaction, the MPB-64 and 65 kDa antigen PCR assays were nested reactions. A total of 176 cerebrospinal fluid (CSF) samples from 176 patients were subjected to amplification of the three different mycobacterial sequences. Amongst them, 45 samples were obtained from confirmed cases of TBM (culture positive) and 56 samples were obtained from clinically suspected cases of TBM which were culture-negative. The remaining 75 CSF samples were categorized under the non-infectious and infectious illness of the central nervous system (CNS). Against a gold standard of culture, a sensitivity of 98% (NPV=99%) and a specificity of 100% (PPV=100%) was observed with the IS6110 PCR. Among the nested PCRs, a sensitivity of 91% (NPV=94%) and a specificity of 91% (PPV=85%) was observed with the MPB-64 assay, while the 65 kDa protocol had an associated sensitivity of 51% (NPV=76%) and a specificity of 92% (PPV=79%). These findings suggest that among the nested PCR assays, the MPB-64 PCR assay was associated with an enhanced degree of sensitivity and was comparable in terms of specificity. Our study also demonstrates that the IS6110 assay, while being a single-step PCR had the advantage of being a rapid test for the diagnosis of TBM, with increased sensitivity and enhanced specificity as compared to the nested PCR protocols.

Utility of the polymerase chain reaction in the diagnosis of tuberculous meningitis

Due to inconsistent clinical presentations and the lack of a rapid, sensitive and specific test, tuberculous meningitis (TBM) is particularly difficult to diagnose. The present study was carried out to determine the utility of the polymerase chain reaction (PCR) using INS primers in the diagnosis of TBM and to compare the efficacy of two different DNA extraction protocols. Fifty-seven cerebrospinal fluid (CSF) samples from suspected cases of meningitis -- 30 definitive/possible TBM and 27 non-TBM -- were processed for microscopy, culture and PCR. Results of computer tomographic (CT) scan findings were noted. The results of smear, culture and PCR were compared using culture and/or clinical response to treatment as the gold standard. The sensitivity of microscopy, culture, CT scan and PCR was 3.3%, 26.7%, 60.0% and 66.7%, respectively. PCR following QIAmp DNA extraction had a sensitivity of 66.7% compared to PCR following a DNA extraction protocol based on the use of cetyl trimethyl ammonium bromide (CTAB) (50%). PCR was positive in all culture-positive CSF samples using either extraction method. PCR is a rapid and sensitive technique; above all, it can diagnose tuberculous meningitis at a very early stage.

Interferon γ quantification in cerebrospinal fluid compared with PCR for the diagnosis of tuberculous meningitis

PURPOSE

To assess the utility of interferon gamma (INF-gamma) levels in cerebrospinal fluid (CSF), for the diagnosis of tuberculous meningitis (TBM), and compare these results with aPCR technique.

METHODS

We studied CSF samples from patients with proven or probable TBM and a control group, composed by patients with other causes of meningitis and without meningitis. INFgamma levels were measured by radioimmunoassay. A PCR technique was performed using IS6110 primers.

RESULTS

Of the 127 patients studied, 20 (15.6%) had TBM, 59 (46%) had meningitis of another aetiology and 49 (38.4%) had were HIV and non-HIV patients with normal CSF. The area below the ROC curve for interferon gamma levels in the diagnosis of TBM was 0.94. A cut-off of 6.4 IU/mL yielded a sensitivity of 70% and a specificity of 94%. False positive results were observed in 7 of the 59 patients (11.8%) with non-TB meningitis, (patients with herpetic meningoencephalitis and meningitis due to intracellular microorganisms). INF-gamma sensitivity was higher than PCR (70% vs. 65%). Both tests performed together showed higher sensitivity (80%) and specificity (92.6%).

CONCLUSION

CSF INF-gamma levels (> 6.4 IU/mL) are very valuable in TBM diagnosis. PCR and INF-gamma could be simultaneously used to increase the diagnostic yield.

Evaluation of an in-house-developed PCR for the diagnosis of tuberculous meningitis in Indian children

Early and rapid detection of the causative organism is necessary in tuberculosis, particularly tuberculous meningitis, as the disease affects mainly children and if untreated or improperly treated can cause severe central nervous system disorders and can often be fatal. An in-house-developed PCR technique was developed for the detection ofMycobacterium tuberculosisDNA, in which the target for amplification was a 340 bp nucleotide sequence located within the 38 kDa protein gene. The test can detect as small an amount of DNA as 10 fg, which is equivalent to two to three organisms, and is highly specific. Amplified product was detected by ethidium bromide staining after electrophoresis and Southern hybridization. Evaluation of test sensitivity and specificity was carried out using acid-fast bacilli-positive sputum samples from patients with pulmonary tuberculosis and an equal number of non-tuberculosis patient samples as negative controls. In a double-masked study 30 cerebrospinal fluid samples from tuberculous meningitis patients and 30 samples from non-tuberculous meningitis patients were investigated. Out of the 30 samples 22 were positive by ethidium bromide-stained gel electrophoresis and 27 gave positive results by Southern hybridization. All of the 30 control samples showed negative results. The sensitivity of this PCR was 90 % and specificity, 100 %.

[Neuromeningeal tuberculosis: the contribution of genetic amplification to diagnosis]

Neurological manifestations of tuberculosis are rare, especially in immunocompetent subjects. The heterogeneity of clinical and radiological features induces frequently a delay for diagnosis. The aim of the study was to describe clinical and radiological presentation of 11 cases of neuro-tuberculosis and to evaluate clinical outcome. We performed clinical, CSF, MRI and outcome evaluation in all patients. We also performed a mycobacterium analysis by polymerase chain reaction (PCR). Patients were 6 men and 5 women with a mean age of 45.4 years. Clinical presentations were meningeal symptoms in 9 cases and focal manifestations in 4 cases. CSF was abnormal in 82 p.cent of cases (protein increase in 73 p.cent, pleiocytosis in 73 p.cent, hypoglycorrhachia in 45 p.cent and hypochlorrhachia in 36 p.cent). The best diagnostic test was PCR (positive in 45 p.cent of cases). CSF cultures were positive in only 2 cases (18 p.cent). Only 2 patients had chest involvement. MRI was abnormal in 64 p.cent of cases showing pseudo-tumor, arachnoiditis, vascular lesions or medullar involvement. Outcome was good in all cases but two (one patient died and one patient had paraplegia possibly related to late diagnosis). Neurological manifestations of tuberculosis are extremely various in terms of clinical and radiological presentation. The best diagnostic test seems to be tuberculosis PCR. Outcome is frequently favorable if late diagnosis is avoided.

Diagnostic accuracy of nucleic acid amplification tests for tuberculous meningitis: a systematic review and meta-analysis

Conventional tests are not always helpful in making a diagnosis of tuberculous meningitis. We did a systematic review and meta-analysis to establish the summary accuracy of nucleic acid amplification (NAA) tests for tuberculous meningitis. We searched six electronic databases and contacted authors, experts, and manufacturers. Measures of diagnostic accuracy were pooled using a random effects model. 49 studies met our inclusion criteria. The summary estimates in 14 studies with commercial NAA tests were: sensitivity 0.56 (95% CI 0.46, 0.66), specificity 0.98 (0.97, 0.99), positive likelihood ratio 35.1 (19.0, 64.6), negative likelihood ratio 0.44 (0.33, 0.60), and diagnostic odds ratio 96.4 (42.8, 217.3). In the 35 studies with in-house ("home-brew") tests, the summary accuracy could not be established with confidence because of wide variability in test accuracy. On current evidence, commercial NAA tests show a potential role in confirming tuberculous meningitis diagnosis, although their overall low sensitivity precludes the use of these tests to rule out tuberculous meningitis with certainty.

Nested polymerase chain reaction for Mycobacterium tuberculosis DNA detection in aqueous and vitreous of patients with uveitis

BACKGROUND

Tuberculosis may be a lethal disease. Its ocular manifestations are commonly associated with severe difficulties in diagnosis and therapy; furthermore, it may cause blindness. DNA amplification methods may allow early detection of small amounts of Mycobacterium tuberculosis DNA to afford the possibility of prompt diagnosis. We evaluated a nested polymerase chain reaction (nPCR) assay for detection of Mycobacterium tuberculosis DNA in aqueous and vitreous.

METHODS

In a case-control study, 22 cases of diagnosed TB uveitis (three HIV-infected patients) and 38 controls (18 HIV-infected patients) with other types of uveitis (syphilis, nine; cytomegalovirus, seven; toxoplasmosis, five; herpes simplex, one; autoimmune vasculitis, eight; Vogt-Koyanagi-Harada, four; pars planitis, one; serpinginous choroiditis, one; Wegener granulomatosis, one; and Fuchs iridocyclitis, one studied). Samples from aqueous or vitreous were cultured and analyzed by nPCR for presence of M. tuberculosis nucleic acids. We used two sets of primers corresponding to IS6110 region coding for 219 bp and 123 bp DNA sequences.

RESULTS

Results were confirmed by Southern blot. All samples were tested by PCR simultaneously for Herpes simplex I, Herpes zoster, cytomegalovirus (CMV) and Toxoplasma gondii. nPCR was positive in 17 cases (77.2%) and only in three controls (8.8%) p = 0.022. All cultures were negative. Southern blot confirmed all positive nPCR tests. According to our definition of cases, there were five false negative results: two in patients with pulmonary tuberculosis; two in patients with tuberculous lymphadenitis, and one with positive skin test and hematuria. There were three cases considered false positives for nPCR: one with autoimmune vasculitis, and two with toxoplasmic uveitis.

CONCLUSIONS

nPCR for TB in ocular fluids was positive in the majority of cases of ocular TB. This method is useful in early confirmation of ocular tuberculosis.

[Central nervous tuberculosis in patients non-VIH: seven case reports]

PURPOSE

Tuberculosis involving the central nervous system (CNS) is rarely observed in non immuno-compromised hosts. We report herin the various clinical, biological and radiological manifestations observed in 7 patients with CNS tuberculosis.

METHODS

Clinical and biological records of 7 patients with CNS tuberculosis were retrospectively studied. All patients had encephalic CT-scan and MRI in the course of the disease.

RESULTS

5 women and 2 men with a mean age of 38.4 years initially initially presented with headache (n = 6), fever (n = 5), meningeal irritation (n = 3), localizing neurological signs (n = 1). Lumbar punction revealed lymphocytic meningitis (n = 6/7). Mycobacterium tuberculosis or bovis was isolated in 3 patients only. Cerebral tomodensitography or magnetic resonance imaging were initially normal in most of cases (n = 4/7), but discovered in the course of disease basilar meningitis (n = 6), hydrocephalus (n = 6), abcess or tuberculoma (n = 4). In all the patients, initiation of the treatment was complicated by clinical and/or biological deterioration, called paradoxal reaction, leading in all cases to glucocorticoid adjunction, with various final results. Indeed, 4 patients developed neurological sequelae. No patient died.

CONCLUSION

CNS tuberculosis is a rare disease in non immunocompromised patients whose diagnostic may be difficult due to the absence of specific clinical symptoms, negative initial radiological examination, as well as delayed and often negative bacterial isolation. Paradoxal reaction appeared to be frequent despite specific antibiotherapy and underlines the beneficial effects of addictive corticosteroids.

Early detection of central nervous system tuberculosis with the gen-probe nucleic Acid amplification assay: utility in an inner city hospital

Central nervous system tuberculosis is a serious clinical problem, the treatment of which is sometimes hampered by delayed diagnosis. We investigated the utility of the Gen-Probe nucleic acid amplification assay for the rapid diagnosis of tuberculous meningitis and as a noninvasive method of identifying intracranial tuberculoma.

A comparative evaluation of dot immunobinding assay (Dot-Iba) and polymerase chain reaction (PCR) for the laboratory diagnosis of tuberculous meningitis

The results of a Dot immunobinding assay (Dot Iba) for the detection of mycobacterial antigen in the cerebrospinal fluid (CSF) of 45 patients with tuberculous meningitis (TBM) were compared with the results of a polymerase chain reaction (PCR) for the detection of Mycobacterium tuberculosis. In eight patients with culture proven TBM, Dot-Iba gave positive results, while PCR yielded positive results only in six patients. The overall sensitivities of Dot-Iba and PCR in 37 patients with culture negative (probable) TBM were 75.67% and 40.5% respectively. Dot-Iba, in contrast to PCR is a rapid and relatively easier method. More importantly, Dot-Iba is suitable for the routine application for the laboratory diagnosis of TBM and therefore best suited to laboratories in the developing world.

Tuberculous meningoencephalitis in HIV-seronegative patients: variety of clinical presentation and impact on diagnostics and treatment

Tuberculous meningoencephalitis (TBM), an infrequent disease in Western European countries, shows a wide heterogeneity of clinical symptoms.

MATERIAL AND METHODS

We present 4 patients (age range 42-72 years) with the definite diagnosis of isolated TBM. All patients were HIV-seronegative, only 1 patient was known to be immunoincompetent on admission due to acute myelocytic leukemia; other reasons for immune suppression were detected in 2 other patients (leukemia and idiopathic CD4+ T-lymphocytopenia, respectively).

RESULTS

The diagnosis of TBM was confirmed in 3 cases by culture from CSF, in 1 case Mycobacterium tuberculosis was proven only in tracheal aspirate. In 1 patient M. bovis was found, which is an extremely rare cause of TBM in Germany. We report the contributions of different diagnostic tools (CSF analysis, neuroimaging) in reaching the presumptive diagnosis and in monitoring the further course. All patients developed neurological complications despite prompt tuberculostatic treatment. Three of the patients presented a chronic severe loss of consciousness of unclear origin.

CONCLUSION

The possible causative relationships of these complications and their impact on the prognosis are discussed.

Low sensitivity of polymerase chain reaction for diagnosis of tuberculous meningitis in southeastern Brazil

Two polymerase chain reaction (PCR) protocols showed low sensitivity (36% and 53% for TB AMPLICOR and MPB64 nested PCR, respectively), when compared with classic microbiological methods (73% and 54% for Ziehl-Neelsen staining and culture, respectively), in the diagnosis of tuberculous meningitis in 91 patients in southeastern Brazil. Only three PCR-positive, microbiologically negative patients were found. Analysis of sequential cerebrospinal fluid samples by nested PCR detected Mycobacterium tuberculosis DNA up to 29 days after the introduction of antituberculosis chemotherapy.

TB PCR in the early diagnosis of tuberculous meningitis: evaluation of the Roche semi-automated COBAS Amplicor MTB test with reference to the manual Amplicor MTB PCR test

SETTING

Cecilia Makiwane Hospital, Mdantsane, Eastern Cape, Republic of South Africa.

OBJECTIVE

To assess the role of the semi-automated Roche COBAS AMPLICOR(TM)Mycobacterium tuberculosis PCR test in the diagnosis of tuberculous meningitis (TBM).

DESIGN

Eighty-three specimens of cerebrospinal fluid (CSF) were collected prospectively from 69 patients with suspected TBM. The COBAS AMPLICOR TB PCR test was compared with the manual AMPLICOR(TM)TB PCR test, clinical and cerebrospinal fluid (CSF) findings, direct ZN smear and radiometric TB culture.

RESULTS

CSF from 7/40 (17.5%) patients treated for TBM were positive by TB COBAS AMPLICOR(TM). The sensitivity of the test was not significantly different (p=0.375) from the manual TB AMPLICOR(TM)PCR test. The comparative sensitivities of the TB COBAS AMPLICOR(TM)PCR and the manual AMPLICOR PCR for detecting cases of definite and probable TBM from CSF collected within 9 days of commencing antituberculosis treatment were 40% and 60% respectively. All 29 patients not treated for TBM were negative by COBAS AMPLICOR(TM), giving a specificity of 100%.

CONCLUSION

The COBAS AMPLICOR(TM)TB PCR test is a rapid and highly specific diagnostic test for TBM. However, there was a non-significant trend favouring slightly greater sensitivity using the manual AMPLICOR(TM)TB PCR test.

The clinical, radiological and pathological profile of tuberculous meningitis in patients with and without human immunodeficiency virus infection

BACKGROUND

As human immunodeficiency virus (HIV) infection primarily impairs cellular immunity, the immune responses of HIV-infected individuals to tuberculous bacilli may be inadequate. The features of pulmonary and abdominal tuberculosis evident in HIV-positive (HIV-P) patients with severe immunosuppression are markedly different from those seen in HIV-negative (HIV-N) patients. However, such differences have not been reported in tuberculous meningitis (TBM). Here, we therefore compared the clinical, radiological and pathological features of TBM in patients with and without HIV infection.

METHODS AND RESULTS

Twenty-two HIV-P patients with TBM, seen over 5 years, were studied and compared with 31 HIV-N patients with TBM. Although clinical features were similar, cognitive dysfunction was more common amongst the HIV-P group. Pathological features were markedly different in the HIV-P group reflecting severely reduced and atypical inflammatory response, and extensive vasculopathy. This manifested as absence or minimal meningeal enhancement and absence of communicating hydrocephalus on CT scan in HIV-P patients. Mortality was higher within the HIV-P group and depressed levels of consciousness and hemiplegia were associated with poor prognosis.

CONCLUSION

The clinical, radiological and pathological features of TBM in HIV-P patients are distinctly different from those without HIV infection; a finding previously unreported.

Comparison of in house polymerase chain reaction with conventional techniques for the detection of Mycobacterium tuberculosis DNA in granulomatous lymphadenopathy

AIMS

To evaluate the usefulness of the devR based polymerase chain reaction (PCR) in the detection of Mycobacterium tuberculosis in lymph node aspirates and tissues of lymphadenitis and to compare PCR with conventional diagnostic techniques.

SUBJECTS AND METHODS

Coded specimens of fine needle aspirates and biopsies from 22 patients with tuberculous lymphadenitis, 14 patients with non-tubercular lymphadenitis, and nine patients with granulomatous lymphadenitis were processed and subjected to analysis by PCR, smear microscopy, M tuberculosis culture, histology, and cytology.

RESULTS

Tuberculous lymphadenitis was correctly diagnosed by PCR in 18 patients, by culture in five patients, by histology in 13 patients, and by cytology in seven patients. PCR gave two false positive results in 14 patients with non-tubercular lymphadenitis. The sensitivity of the conventional techniques was significantly higher with biopsies (17 of 22 specimens; 77%) than with fine needle aspirates (nine of 22 specimens; 41%). However, the sensitivity of PCR was not significantly higher with biopsies (68%) in comparison with fine needle aspirates (55%). The sensitivity of either biopsy PCR or fine needle aspirate PCR was not significantly different from that of either histology combined with culture or cytology combined with culture. The overall combined specificity of PCR was 86%. Mycobacterium tuberculosis DNA was detected in six of nine patients with granulomatous lymphadenitis.

CONCLUSION

PCR is the most sensitive single technique available to date for the demonstration of M tuberculosis in specimens derived from patients with a clinical suspicion of tuberculous lymphadenitis. The value of PCR lies in its use as an adjunct test in the diagnosis of tuberculous lymphadenitis, particularly in those patients where conventional methods fail. Because fine needle aspiration is not an invasive procedure, it is the procedure of choice, and PCR should be performed initially on these samples. Excisional biopsy histology and PCR should be recommended only for patients in whom fine needle aspirate PCR is negative or when there is discrepancy with the clinical impression.

Central nervous system tuberculosis

Involvement of the central nervous system (CNS) by Mycobacterium tuberculosis, particularly meningitis, is the most severe form of tuberculous infection. Parenchymal CNS involvement can occur in the form of tuberculoma or, more rarely, abscess. Although surgery was initially advocated as the mainstay of therapy, more recent evidence suggests that parenchymal forms of CNS tuberculosis can be cured with medical treatment alone. Also, damage of the spinal cord, roots, and spine can occur in the form of spinal meningitis, radiculomyelitis, spondylitis, or spinal cord infarction.

Tuberculosis of the central nervous system

Tuberculous involvement of the brain and spinal cord are common neurological disorders in developing countries and have recently shown a resurgence in developed ones. Tuberculous meningitis is an important manifestation and is associated with high morbidity and mortality. Diagnosis is based on clinical features, cerebrospinal fluid changes, and imaging characteristics. Bacteriological confirmation is not possible in all cases as serological tests do not have sufficient sensitivity and specificity. The polymerase chain reaction shows promise for the future. Appropriate chemotherapeutic agents should be administered as early as possible, although there is no unanimity concerning chemotherapeutic regimens or optimal duration of treatment. The patient's clinical stage at presentation is the most important prognostic factor. The role of corticosteroids is controversial but they should be administered to all patients presenting in stage III. Surgical procedures are directed at management of the hydrocephalus. Focal lesions, intracranial tuberculomas, and tuberculous abscesses, are usually located in cerebral or cerebellar hemispheres, uncommonly in brainstem and very rarely in spinal cord. They do not usually require surgical intervention and respond well to antituberculous treatment, along with corticosteroids.