Xpert MTB/RIF Ultra and Xpert MTB/RIF assays for extrapulmonary tuberculosis and rifampicin resistance in adults

BACKGROUND

Xpert MTB/RIF Ultra (Xpert Ultra) and Xpert MTB/RIF are World Health Organization (WHO)-recommended rapid nucleic acid amplification tests (NAATs) widely used for simultaneous detection of Mycobacterium tuberculosis complex and rifampicin resistance in sputum. To extend our previous review on extrapulmonary tuberculosis (Kohli 2018), we performed this update to inform updated WHO policy (WHO Consolidated Guidelines (Module 3) 2020).

OBJECTIVES

To estimate diagnostic accuracy of Xpert Ultra and Xpert MTB/RIF for extrapulmonary tuberculosis and rifampicin resistance in adults with presumptive extrapulmonary tuberculosis.

SEARCH METHODS

Cochrane Infectious Diseases Group Specialized Register, MEDLINE, Embase, Science Citation Index, Web of Science, Latin American Caribbean Health Sciences Literature, Scopus, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform, the International Standard Randomized Controlled Trial Number Registry, and ProQuest, 2 August 2019 and 28 January 2020 (Xpert Ultra studies), without language restriction.

SELECTION CRITERIA

Cross-sectional and cohort studies using non-respiratory specimens. Forms of extrapulmonary tuberculosis: tuberculous meningitis and pleural, lymph node, bone or joint, genitourinary, peritoneal, pericardial, disseminated tuberculosis. Reference standards were culture and a study-defined composite reference standard (tuberculosis detection); phenotypic drug susceptibility testing and line probe assays (rifampicin resistance detection).

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed risk of bias and applicability using QUADAS-2. For tuberculosis detection, we performed separate analyses by specimen type and reference standard using the bivariate model to estimate pooled sensitivity and specificity with 95% credible intervals (CrIs). We applied a latent class meta-analysis model to three forms of extrapulmonary tuberculosis. We assessed certainty of evidence using GRADE.

MAIN RESULTS

69 studies: 67 evaluated Xpert MTB/RIF and 11 evaluated Xpert Ultra, of which nine evaluated both tests. Most studies were conducted in China, India, South Africa, and Uganda. Overall, risk of bias was low for patient selection, index test, and flow and timing domains, and low (49%) or unclear (43%) for the reference standard domain. Applicability for the patient selection domain was unclear for most studies because we were unsure of the clinical settings. Cerebrospinal fluid Xpert Ultra (6 studies) Xpert Ultra pooled sensitivity and specificity (95% CrI) against culture were 89.4% (79.1 to 95.6) (89 participants; low-certainty evidence) and 91.2% (83.2 to 95.7) (386 participants; moderate-certainty evidence). Of 1000 people where 100 have tuberculous meningitis, 168 would be Xpert Ultra-positive: of these, 79 (47%) would not have tuberculosis (false-positives) and 832 would be Xpert Ultra-negative: of these, 11 (1%) would have tuberculosis (false-negatives). Xpert MTB/RIF (30 studies) Xpert MTB/RIF pooled sensitivity and specificity against culture were 71.1% (62.8 to 79.1) (571 participants; moderate-certainty evidence) and 96.9% (95.4 to 98.0) (2824 participants; high-certainty evidence). Of 1000 people where 100 have tuberculous meningitis, 99 would be Xpert MTB/RIF-positive: of these, 28 (28%) would not have tuberculosis; and 901 would be Xpert MTB/RIF-negative: of these, 29 (3%) would have tuberculosis. Pleural fluid Xpert Ultra (4 studies) Xpert Ultra pooled sensitivity and specificity against culture were 75.0% (58.0 to 86.4) (158 participants; very low-certainty evidence) and 87.0% (63.1 to 97.9) (240 participants; very low-certainty evidence). Of 1000 people where 100 have pleural tuberculosis, 192 would be Xpert Ultra-positive: of these, 117 (61%) would not have tuberculosis; and 808 would be Xpert Ultra-negative: of these, 25 (3%) would have tuberculosis. Xpert MTB/RIF (25 studies) Xpert MTB/RIF pooled sensitivity and specificity against culture were 49.5% (39.8 to 59.9) (644 participants; low-certainty evidence) and 98.9% (97.6 to 99.7) (2421 participants; high-certainty evidence). Of 1000 people where 100 have pleural tuberculosis, 60 would be Xpert MTB/RIF-positive: of these, 10 (17%) would not have tuberculosis; and 940 would be Xpert MTB/RIF-negative: of these, 50 (5%) would have tuberculosis. Lymph node aspirate Xpert Ultra (1 study) Xpert Ultra sensitivity and specificity (95% confidence interval) against composite reference standard were 70% (51 to 85) (30 participants; very low-certainty evidence) and 100% (92 to 100) (43 participants; low-certainty evidence). Of 1000 people where 100 have lymph node tuberculosis, 70 would be Xpert Ultra-positive and 0 (0%) would not have tuberculosis; 930 would be Xpert Ultra-negative and 30 (3%) would have tuberculosis. Xpert MTB/RIF (4 studies) Xpert MTB/RIF pooled sensitivity and specificity against composite reference standard were 81.6% (61.9 to 93.3) (377 participants; low-certainty evidence) and 96.4% (91.3 to 98.6) (302 participants; low-certainty evidence). Of 1000 people where 100 have lymph node tuberculosis, 118 would be Xpert MTB/RIF-positive and 37 (31%) would not have tuberculosis; 882 would be Xpert MTB/RIF-negative and 19 (2%) would have tuberculosis. In lymph node aspirate, Xpert MTB/RIF pooled specificity against culture was 86.2% (78.0 to 92.3), lower than that against a composite reference standard. Using the latent class model, Xpert MTB/RIF pooled specificity was 99.5% (99.1 to 99.7), similar to that observed with a composite reference standard. Rifampicin resistance Xpert Ultra (4 studies) Xpert Ultra pooled sensitivity and specificity were 100.0% (95.1 to 100.0), (24 participants; low-certainty evidence) and 100.0% (99.0 to 100.0) (105 participants; moderate-certainty evidence). Of 1000 people where 100 have rifampicin resistance, 100 would be Xpert Ultra-positive (resistant): of these, zero (0%) would not have rifampicin resistance; and 900 would be Xpert Ultra-negative (susceptible): of these, zero (0%) would have rifampicin resistance. Xpert MTB/RIF (19 studies) Xpert MTB/RIF pooled sensitivity and specificity were 96.5% (91.9 to 98.8) (148 participants; high-certainty evidence) and 99.1% (98.0 to 99.7) (822 participants; high-certainty evidence). Of 1000 people where 100 have rifampicin resistance, 105 would be Xpert MTB/RIF-positive (resistant): of these, 8 (8%) would not have rifampicin resistance; and 895 would be Xpert MTB/RIF-negative (susceptible): of these, 3 (0.3%) would have rifampicin resistance.

AUTHORS' CONCLUSIONS

Xpert Ultra and Xpert MTB/RIF may be helpful in diagnosing extrapulmonary tuberculosis. Sensitivity varies across different extrapulmonary specimens: while for most specimens specificity is high, the tests rarely yield a positive result for people without tuberculosis. For tuberculous meningitis, Xpert Ultra had higher sensitivity and lower specificity than Xpert MTB/RIF against culture. Xpert Ultra and Xpert MTB/RIF had similar sensitivity and specificity for rifampicin resistance. Future research should acknowledge the concern associated with culture as a reference standard in paucibacillary specimens and consider ways to address this limitation.

Xpert® MTB/RIF assay for extrapulmonary tuberculosis and rifampicin resistance

BACKGROUND

Tuberculosis (TB) is the world's leading infectious cause of death. Extrapulmonary TB accounts for 15% of TB cases, but the proportion is increasing, and over half a million people were newly diagnosed with rifampicin-resistant TB in 2016. Xpert^® MTB/RIF (Xpert) is a World Health Organization (WHO)-recommended, rapid, automated, nucleic acid amplification assay that is used widely for simultaneous detection of Mycobacterium tuberculosis complex and rifampicin resistance in sputum specimens. This Cochrane Review assessed the accuracy of Xpert in extrapulmonary specimens.

OBJECTIVES

To determine the diagnostic accuracy of Xpert a) for extrapulmonary TB by site of disease in people presumed to have extrapulmonary TB; and b) for rifampicin resistance in people presumed to have extrapulmonary TB.

SEARCH METHODS

We searched the Cochrane Infectious Diseases Group Specialized Register, MEDLINE, Embase, Science Citation Index, Web of Science, Latin American Caribbean Health Sciences Literature (LILACS), Scopus, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform, the International Standard Randomized Controlled Trial Number (ISRCTN) Registry, and ProQuest up to 7 August 2017 without language restriction.

SELECTION CRITERIA

We included diagnostic accuracy studies of Xpert in people presumed to have extrapulmonary TB. We included TB meningitis and pleural, lymph node, bone or joint, genitourinary, peritoneal, pericardial, and disseminated TB. We used culture as the reference standard. For pleural TB, we also included a composite reference standard, which defined a positive result as the presence of granulomatous inflammation or a positive culture result. For rifampicin resistance, we used culture-based drug susceptibility testing or MTBDRplus as the reference standard.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data, assessed risk of bias and applicability using the QUADAS-2 tool. We determined pooled predicted sensitivity and specificity for TB, grouped by type of extrapulmonary specimen, and for rifampicin resistance. For TB detection, we used a bivariate random-effects model. Recognizing that use of culture may lead to misclassification of cases of extrapulmonary TB as 'not TB' owing to the paucibacillary nature of the disease, we adjusted accuracy estimates by applying a latent class meta-analysis model. For rifampicin resistance detection, we performed univariate meta-analyses for sensitivity and specificity separately to include studies in which no rifampicin resistance was detected. We used theoretical populations with an assumed prevalence to provide illustrative numbers of patients with false positive and false negative results.

MAIN RESULTS

We included 66 unique studies that evaluated 16,213 specimens for detection of extrapulmonary TB and rifampicin resistance. We identified only one study that evaluated the newest test version, Xpert MTB/RIF Ultra (Ultra), for TB meningitis. Fifty studies (76%) took place in low- or middle-income countries. Risk of bias was low for patient selection, index test, and flow and timing domains and was high or unclear for the reference standard domain (most of these studies decontaminated sterile specimens before culture inoculation). Regarding applicability, in the patient selection domain, we scored high or unclear concern for most studies because either patients were evaluated exclusively as inpatients at tertiary care centres, or we were not sure about the clinical settings.Pooled Xpert sensitivity (defined by culture) varied across different types of specimens (31% in pleural tissue to 97% in bone or joint fluid); Xpert sensitivity was > 80% in urine and bone or joint fluid and tissue. Pooled Xpert specificity (defined by culture) varied less than sensitivity (82% in bone or joint tissue to 99% in pleural fluid and urine). Xpert specificity was ≥ 98% in cerebrospinal fluid, pleural fluid, urine, and peritoneal fluid.Xpert testing in cerebrospinal fluidXpert pooled sensitivity and specificity (95% credible interval (CrI)) against culture were 71.1% (60.9% to 80.4%) and 98.0% (97.0% to 98.8%), respectively (29 studies, 3774 specimens; moderate-certainty evidence).For a population of 1000 people where 100 have TB meningitis on culture, 89 would be Xpert-positive: of these, 18 (20%) would not have TB (false-positives); and 911 would be Xpert-negative: of these, 29 (3%) would have TB (false-negatives).For TB meningitis, ultra sensitivity and specificity against culture (95% confidence interval (CI)) were 90% (55% to 100%) and 90% (83% to 95%), respectively (one study, 129 participants).Xpert testing in pleural fluidXpert pooled sensitivity and specificity (95% CrI) against culture were 50.9% (39.7% to 62.8%) and 99.2% (98.2% to 99.7%), respectively (27 studies, 4006 specimens; low-certainty evidence).For a population of 1000 people where 150 have pleural TB on culture, 83 would be Xpert-positive: of these, seven (8%) would not have TB (false-positives); and 917 would be Xpert-negative: of these, 74 (8%) would have TB (false-negatives).Xpert testing in urineXpert pooled sensitivity and specificity (95% CrI) against culture were 82.7% (69.6% to 91.1%) and 98.7% (94.8% to 99.7%), respectively (13 studies, 1199 specimens; moderate-certainty evidence).For a population of 1000 people where 70 have genitourinary TB on culture, 70 would be Xpert-positive: of these, 12 (17%) would not have TB (false-positives); and 930 would be Xpert-negative: of these, 12 (1%) would have TB (false-negatives).Xpert testing for rifampicin resistanceXpert pooled sensitivity (20 studies, 148 specimens) and specificity (39 studies, 1088 specimens) were 95.0% (89.7% to 97.9%) and 98.7% (97.8% to 99.4%), respectively (high-certainty evidence).For a population of 1000 people where 120 have rifampicin-resistant TB, 125 would be positive for rifampicin-resistant TB: of these, 11 (9%) would not have rifampicin resistance (false-positives); and 875 would be negative for rifampicin-resistant TB: of these, 6 (1%) would have rifampicin resistance (false-negatives).For lymph node TB, the accuracy of culture, the reference standard used, presented a greater concern for bias than in other forms of extrapulmonary TB.

AUTHORS' CONCLUSIONS

In people presumed to have extrapulmonary TB, Xpert may be helpful in confirming the diagnosis. Xpert sensitivity varies across different extrapulmonary specimens, while for most specimens, specificity is high, the test rarely yielding a positive result for people without TB (defined by culture). Xpert is accurate for detection of rifampicin resistance. For people with presumed TB meningitis, treatment should be based on clinical judgement, and not withheld solely on an Xpert result, as is common practice when culture results are negative.

Diagnostic accuracy of the loop-mediated isothermal amplification assay for extrapulmonary tuberculosis: A meta-analysis

Background

Loop-mediated isothermal amplification (LAMP) is used to detect pulmonary tuberculosis (PTB); however, the diagnostic accuracy of the LAMP assay for extrapulmonary tuberculosis (EPTB) is unclear. We performed a meta-analysis to evaluate the performance of LAMP in the detection of EPTB.

Methods

We searched PubMed, EMBASE, the Cochrane Library, China National Knowledge Infrastructure (CNKI), and the Wanfang database for studies published before Sep 16, 2017. We reviewed studies and compared the performance of LAMP with that of a composite reference standard (CRS) and culture for clinically suspected EPTB. We used a bivariate random-effects model to perform meta-analyses and used meta-regression and subgroup analysis to analyze sources of heterogeneity.

Results

Fourteen articles including 24 independent studies (16 compared LAMP to CRS, 8 to culture) of EPTB were identified. LAMP showed a pooled sensitivity of 77% (95% confidence interval (CI) 68–85), specificity of 99% (95% CI 96–100), and area under SROC curves (AUC) of 0.96 (95% CI 0.94–0.97) against CRS. It showed a pooled sensitivity of 93% (95% CI 88–96), specificity of 77% (95% CI 64–86), and AUC of 0.94 (95% CI 0.92–0.96) against culture. The pooled sensitivity, specificity, and AUC of MPB64 LAMP were 86% (95% CI 86–86), 100% (95% CI 100–100), and 0.97 (95% CI 0.95–0.98), respectively, and those of IS6110 LAMP were 75% (95% CI 64–84), 99% (95% CI 90–100), and 0.91 (95% CI 0.88–0.93), respectively, compared with CRS.

Conclusions

These results suggest good diagnostic efficacy of LAMP in the detection of EPTB. Additionally, the diagnostic efficacy of MPB64 LAMP was superior to that of IS6110 LAMP.

Apoptosis, production of MMP9, VEGF, TNF-alpha and intracellular growth of M. tuberculosis for different genotypes and different pks5/1 genes

BACKGROUND

A previous study of IS6110 RFLP and spoligotyping of M. tuberculosis isolates from 152 Thai patients with tuberculous meningitis revealed a significantly higher percentage (57%) of the Beijing genotype as compared to isolates obtained from pulmonary tuberculosis. We postulated that the M. tuberculosis Beijing genotype is likely to be more virulent than others.

OBJECTIVES

Ten M. tuberculosis cerebrospinal fluid (CSF) isolates from five RFLP groups, together with different characteristics of pks15/1, M. tuberculosis H37Rv and M. bovis BCG, were investigated for their virulence in vitro.

METHODS

In this study, THP-1 cells were used as host cells to determine the intracellular growth and the induction of MMP9, VEGF, TNF-alpha and apoptosis. Determinations of the cytokine production and apoptosis were based on available commercial kits using ELISA techniques.

RESULTS

No significant difference in intracellular multiplication was found between the M. tuberculosis CSF isolates. Three isolates, consisting of 2 Nonthaburi and 1 heterogeneous isolate, were found to stimulate high TNF-alpha and MMP-9 production during the early infection period.They were isolated from 3 different patients, 2 of whom died with initial stages II and III. This result suggested that there might be an association between TNF-alpha and MMP-9 production that could account for the specific virulent nature of Nonthaburi strains. VEGF production was determined and comparable levels were found in all isolates. No significant apoptosis was detected in M. tuberculosis CSF isolates. No significant differences suggesting that the 2 Beijing strains are more virulent than the others were observed.

CONCLUSION

The predominance of the Beijing strains in cases of tuberculous meningitis (TBM) in Thai patients is not a result of their hypervirulence.

Detection of M. tuberculosis in clinical samples of diversified nature by IS6110 based PCR

Performance of the polymerase chain reaction technique based on IS6110 sequence was evaluated in clinical samples obtained from pulmonary and extrapulmonary cases of tuberculosis. One hundred and seventy two samples were processed for detection of M. tuberculosis by ZN stained smear examination, LJ medium culture, BACTEC radiometric culture and PCR tests amplifying 123bp region of IS6110 sequence. A significant difference was seen in the sensitivities of different tests, the figures being 83% for PCR test, 35.2% for smear examination, 47.16% for LJ culture and 53.45% for BACTEC culture (p < 0.05). However, no significant difference was found as far as specificity was concerned. PCR test sensitivity in. pulmonary and extrapulmonary clinical samples were 90.14% and 77.27% respectively and found to be significantly higher (p < 0.05) when compared with those of other tests. The mean detection time for M. tuberculosis was 24.03 days by LJ medium culture, 12.89 days by BACTEC culture and less than one day by PCR test. PCR based on IS6100 sequence is highly sensitive method for the early diagnosis of pulmonary and extrapulmonary tuberculosis.

[Antimycobacterial antibody level in pleural, pericardial and cerebrospinal fluid of patients with tuberculosis]

The goal of the study was to evaluate IgG, IgA and IgM mediated humoral immune response against 38kDa and 16 kDa or 38kDa and LAM mycobacterial antigens in pleural, pericardial or cerebrospinal fluid from patients with tuberculosis (TB) and to compare to non-tuberculous controls (NTB). 30 cerebrospinal fluids (CSF) (16 TB pts and 14 NTB pts), 17 pericardial fluids (6 TB and 11 NTB) and 20 pleural fluids (7 TB and 13 NTB) were examined. Commercially available ELISA-based assays (Pathozyme Tb complex plus, Myco G, A and M--Omega Diagnostic) were used. Tests were performed and cut off established according to manufacturer instruction. Mean IgG level against 38 + 16kDa was significantly higher in neurotuberculosis group compared to control (p<0.05). Sensitivity of the test in detecting neurotuberculosis was of 42% and specificity of 96%. Mean IgG, IgA and IgM against 38kDa + LAM level was higher in TB group compared to NTB in CSF. No difference was observed between TB and NTB group in pleural effusion. Antimycobacterial antibody levels were non-significantly increased in pericardial fluid in TB. The findings of the study indicate that TB is associated with the presence of detectable levels of antibodies in the CSF and pericardial effusion. Anti 38kDa + 16kDa IgG test can be used in combination with other diagnostic methods to increase diagnostic accuracy of neurotuberculosis.

The Cobas Amplicor MTB test for detection of Mycobacterium tuberculosis complex from respiratory and non-respiratory clinical specimens

The Cobas Amplicor MTB test is a polymerase chain reaction (PCR) technique commonly used for direct detection of Mycobacterium tuberculosis in clinical samples. This assay is only validated for respiratory specimens, but many physicians also request PCR analyses for non-respiratory ones. 877 respiratory and 564 non-respiratory specimens were analysed by this test. Using culture results as standard, the sensitivity, specificity, positive (PPV) and negative predictive values (NPV) of the PCR were, respectively, 97.9%, 100%, 100% and 94.4% for smear-positive respiratory specimens, 68.8%, 99.2%, 87.5% and 97.5% for smear-negative respiratory samples, 57.8%, 98.6%, 78.8% and 96.4% for all non-respiratory specimens, and 42.4%, 98.6%, 66.7% and 96.4% for smear-negative non-respiratory specimens. 154 cerebrospinal fluid samples were analysed and the sensitivity, specificity, PPV and NPV were 55.6%, 97.2%, 55.6% and 97.2%, respectively. These results indicate that the Cobas Amplicor MTB test enables detection of tuberculosis in respiratory specimens, but does not perform well enough in non-respiratory specimens. The method fails particularly in cases where a reliable and rapid test is urgently needed, e.g. in tuberculous meningitis.

[Tuberculous otitis media. Report of 3 cases]

Tuberculous otitis media (TOM) is a rare cause of chronic suppurative infection of the middle ear. Due to that the symptoms and signs are often indistinguishable from those of nontuberculosis chronic otitis media and the fact that the index of suspicion is low, there is frequently a considerable delay prior to diagnosis. This can lead to irreversible complications such as facial nerve paralysis and labyrinthitis. Medical therapy with antituberculous drugs is usually effective. We report three cases with TOM diagnosticated and followed up in our Service from january 1993 to july 2001. Their charts were retrospectively reviewed for relevant historical data, physical findings, complementary studies, treatment and clinical response. We performed a review of the literature, emphasizing that TOM should be considered in the differential diagnosis of chronic otitis media.

[Diagnosis of tuberculosis by immunocapture of the tuberculous bacillus (using magnetic beads)]

Tuberculosis is worldwide considered as a major health problem with high morbidity and mortality rates. Diagnosis of tuberculosis can be problematic. Microscopy, as the basic diagnostic method, stands inadequately alone due to a low sensitivity, and culture suffers from being time-consuming. A rapid, sensitive and simple diagnostic test, applicable in the field is therefore highly needed. A diagnostic method for the detection of M. tuberculosis by immunocapture technique has been developed using magnetic beads coated with polyclonal anti-M. tuberculosis. The detection of captured bacilli using biotinylated anti-APA monoclonal antibody (APA is a minor secreted antigen) was found more sensitive than microscopy. The results suggest that the development of a rapid strip test to detect major antigen could be a useful tool for the control of tuberculosis.

Rapid and efficient detection of extra-pulmonary Mycobacterium tuberculosis by PCR analysis

SETTING

The diagnosis of extra-pulmonary tuberculosis (EPTB) remains an important clinical problem, primarily because of the inadequate sensitivity of conventional bacteriologic methods for detecting Mycobacterium tuberculosis in extra-pulmonary specimens.

OBJECTIVE

To evaluate whether a IS6110-based polymerase chain reaction (PCR) method can be utilized to detect M. tuberculosis in non-pulmonary specimens.

DESIGN

Specimens from 286 Mexican patients with a presumptive clinical diagnosis of EPTB were prospectively examined by Ziehl-Neelsen staining, mycobacterial culture on Löwenstein-Jensen slants, and by PCR. The DNA for PCR was extracted by the buffer lysis method and phenol-guanidine thiocyanate-chloroform. Primers that amplify a 200 bp fragment from the insertion-like M. tuberculosis sequence element IS6110 were utilized.

RESULTS

Our results demonstrate that this PCR method is highly specific (100%) for identifying M. tuberculosis from a variety of specimens including cerebrospinal fluid (CSF), pleural fluid, ascitic fluid, pericardial fluid, urine, and lymph node exudate. Moreover, the sensitivity of PCR for detecting M. tuberculosis in CSF (94%), pleural fluid (94%), ascitic fluid and other extrapulmonary specimens (93%) greatly exceeds the sensitivity of conventional smear and culture methods.

CONCLUSION

These results demonstrate that PCR can be a highly specific and sensitive aid in the detection of M. tuberculosis from extra-pulmonary specimens.

Detection of rifampin resistance by single-strand conformation polymorphism analysis of cerebrospinal fluid of patients with tuberculosis of the central nervous system

Mutations in a 69-bp region of the rpoB gene of Mycobacterium tuberculosis are associated with rifampin resistance (Rif[r]). These have been detected with mycobacterial DNA extracted from bacterial suspensions or respiratory specimens that were acid-fast smear positive. We experimented with a strategy for the rapid detection of Rif(r) in cerebrospinal fluid (CSF) samples. The strategy involves the amplification of the 69-bp region of rpoB by means of PCR and the identification of nucleotide mutations by single-strand conformation polymorphism (SSCP) analysis of the amplification products. Sixty-five CSF specimens collected from 29 patients (19 patients were coinfected with human immunodeficiency virus) with culture or autopsy-confirmed (22 patients) or highly probable (7 patients) tuberculosis of the central nervous system (CNS-TB) were processed. Amplified products suitable for evaluation by SSCP analysis were obtained from 37 CSF specimens from 25 subjects (86.2%). PCR-SSCP of CSF correctly identified the rifampin susceptibility phenotype of isolates from all 17 patients for whom the results of susceptibility tests carried out with strains cultured from CSF or respiratory samples were available. Moreover, this assay revealed the rifampin susceptibility genotype of isolates from the eight patients (three patients with culture-confirmed CNS-TB and five patients in whom CNS-TB was highly probable) for whom no susceptibility test results were available; the PCR-SSCP data obtained for these patients were concordant with the outcome after a standard antituberculosis treatment. The evolution of a mutation in the rpoB gene was documented in a patient during the course of treatment. PCR-SSCP analysis of CSF seems to be an efficacious method of predicting Rif(r) and would reduce the time required for susceptibility testing from approximately 4 to 8 weeks to a few days.

Diagnostic performance of amplified Mycobacterium tuberculosis direct test with cerebrospinal fluid, other nonrespiratory, and respiratory specimens

The Gen-Probe Amplified Mycobacterium tuberculosis Direct Test (MTD) was adapted to be used for cerebrospinal fluid (CSF) and a large variety of other nonrespiratory specimens. Standardized with artificially spiked dilution series of CSF, the modified MTD procedure consists of (i) increasing the amount of sample 10-fold, (ii) pretreating the specimen with a detergent, and (iii) increasing the amplification time from 2 to 3 h. Performance of MTD in a clinical mycobacteriology laboratory was tested over an extended period of time, involving a total of 322 nonrespiratory as well as 1,117 respiratory specimens from 998 patients. Results from MTD were compared with those from microscopy, culture, analysis of tuberculostearic acid by gas-liquid chromatography-mass spectrometry (CSF only), and the final clinical diagnosis. When MTD results were compared with resolved data, the sensitivity, specificity, and positive and negative predictive values for MTD were 93.1, 97.7, 90.0, and 98.5%, respectively, for nonrespiratory specimens and 86.6, 96.4, 76.8, and 98.1%, respectively, for respiratory specimens. Our data demonstrate that (i) MTD is a robust, highly sensitive and specific technique for the rapid detection of M. tuberculosis complex in all types of clinical specimens, (ii) there was no statistically significant difference (P > 0.005) in sensitivity and specificity for nonrespiratory compared with respiratory specimens, and (iii) repeating all MTDs which yield a result between 30,000 and 200,000 relative light units would help prevent a large number of false positives and, thus, enhance test specificity.

Assessment of a possible imbalance between tumor necrosis factor (TNF) and soluble TNF receptor forms in tuberculous infection of the central nervous system

Distributions of tumor necrosis factor (TNF) and its soluble receptor forms, R55-BP and R75-BP, were analyzed in the cerebrospinal fluid of patients with severe acute or chronic central nervous system infections. Tuberculous infections were associated with high ratios of R55-BP and R75-BP to TNF, 27.2 and 28.0, respectively, suggesting a small biologically active fraction of TNF. The opposite was found in subjects with acute bacterial meningitis. They had large fractions of biologically active TNF and thus low ratios of R55-BP and R75-BP to TNF, 3.7 and 4.0, respectively. It is hypothesized that chronic infectious diseases, such as tuberculous infections, may be associated with inadequate production of TNF and a concomitant relative increase of soluble TNF receptors, which may prolong the disease.

[Observation on application of solid phase indirect hemadsorption assay for detection IgM antibodies to tuberculosis in non-serum specimens]

We used solid phase indirect hemadsorption assay (SPIHA) to detect specific IgM antibodies in specimens from cerebrospinal fluid, pleural fluid and ascitic fluid in patients with tuberculosis and compared with the enzyme linked immunosorbent assay (ELISA) and indirect hemagglutination assay (IHA). The result showed that detection of tuberculous specific IgM antibodies in cerebrospinal fluid by SPIHA is important for diagnosing the tuberculous meningitis.

The cerebrospinal fluid in the diagnosis of tuberculous meningoencephalitis: review of the literature

We review the literature on the biochemical, cytological and immunological changes in the cerebrospinal fluid (CSF) in tuberculous meningoencephalitis, emphasizing the inconsistency and low specificity of the CSF findings described in classic accounts of this disease. We consider separately the possible causes of yellow or bloody fluid. The development of accurate techniques of analysis does not diminish the importance of the clinical findings and history in the early diagnosis of this disease.

Evidence for an informal clinical policy resulting in high use of a very-low-yield test

The actual and self-reported practice regarding the use of cerebrospinal fluid cultures for Mycobacterium tuberculosis was examined. All neurology house staff members surveyed, 62 percent of internal medicine house staff members, and none of pediatric house staff members reported that they would order mycobacterial cultures of cerebrospinal fluid routinely. The actual practice was comparable, with 71 percent of cerebrospinal fluid specimens being subjected to culture for mycobacteria on the neurology service, 65 percent on the internal medicine service, and 6 percent on the pediatric service. In this practice, medicine and neurology house staff differ significantly from their pediatric colleagues (p less than 0.001) and from the stated practice of their respective faculties (p less than 0.01). For at least six years, most medicine and neurology house staff have commonly applied an informal clinical policy of routinely culturing cerebrospinal fluid specimens for mycobacteria, despite a low suspicion of disease, lack of faculty support for the practice, and a zero yield for the test. Informal clinical policies such as this may be an important contributor to the problem of technology overuse.

Cerebrospinal fluid C-reactive protein in infective meningitis in childhood

The value of cerebrospinal fluid C-reactive protein (CSF CRP) determination as a diagnostic aid in infective meningitis has been investigated in four groups of children. In a "no meningitis" group of 10 children, a median CSF CRP value of 0.08 micrograms/ml was obtained (range 0 to 0.31 micrograms/ml); in a viral meningitis group of 21 children a median value of 0.01 micrograms/ml (range 0 to 3.06 micrograms/ml); in a bacterial meningitis group of 27 children a median value of 9.6 micrograms/ml (range 0 to 31.5 micrograms/ml); and in a tuberculous meningitis group of 18 children a median value of 0.29 micrograms/ml (range 0 to 4.9 micrograms/ml). CSF CRP values in the bacterial meningitis group differed significantly from those of each of the other groups (P less than 0.01), but considerable overlap between the groups detracted from the diagnostic value of the test. In six patients with bacterial meningitis with ambiguous conventional CSF chemistry results, normal CSF CRP values were found. Simultaneous serum CRP was determined in nine patients with tuberculous meningitis and 11 with bacterial meningitis, and the CRP response in both the serum and CSF appears subdued in tuberculous meningitis in comparison with bacterial meningitis. CSF CRP and total protein values were determined intermittently during a 24-hour period in ventricular CSF from two children with tuberculous meningitis who underwent temporary direct ventricular drainage. A considerable and apparently parallel diurnal variation in both values was seen. CSF CRP values have limited application in the etiologic diagnosis of meningitis.

99mTc-sodium pertechnetate permeation into cerebrospinal fluid

The integrity of the blood-brain barrier may be reflected by the blood and cerebrospinal fluid (CSF) if these two compartments are sampled at an appropriate interval after the administration of certain substances. After reading through the controversial literature, this study was undertaken to determine the frequency with which 99mTc-sodium pertechnetate entered the CSF to an abnormal extent, and to see whether this was related to any particular pathology. The plasma-to-CSF ratios were determined in 51 patients 4 hours following the intravenous administration of 0.5-10 mCi 99mTc-sodium pertechnetate. In 23 patients with active CNS tuberculosis, the mean value of the pertechnetate plasma-to-CSF ration was 32.12. In contradistinction, the plasma-to-CSF pertechnetate in 28 nontuberculous subjects was considerably higher (144.63). For the purpose of correlation, a 82Br partition test was also done on each subject 48 hours following the oral administration of NH82Br. The 48-hour study in each of these cases was generally in agreement with the pertechnetate studies: the plasma-to-CSF ratio mean value was 1.25 in patients with active CNS tuberculosis, while for the nontuberculous patients it was 3.32.