Diagnostic accuracy of nucleic acid amplification based assays for tuberculous meningitis: A meta-analysis.

BACKGROUND: Numerous in-house and commercial nucleic acid amplification tests (NAAT) have been evaluated using variable reference standards for diagnosis of TBM but their diagnostic potential is still not very clear. METHODS: We conducted a meta-analysis to assess the diagnostic accuracy of different NAAT based assays for diagnosing TBM against 43 data sets of confirmed TBM (n = 1066) and 61 data sets of suspected TBM (n = 3721) as two reference standards. The summary estimate of the sensitivity and the specificity were obtained using the bivariate model. QUADAS-2 tool was used to perform the Quality assessment for bias and applicability. Publication bias was assessed with Deeks' funnel plot. RESULTS: Studies with confirmed TBM had better summary estimates as compared to studies with clinically suspected TBM irrespective of NAAT and index tests used. Among in-house assays, MPB as the gene target had best summary estimates in both confirmed [sensitivity:90%(83-95), specificity:97-%(87-99), DOR:247 (50-1221), AUC:99%(97-100), PLR:38.8-(6.6-133), NLR:0.11(0.05-0.18), I2 = 15%] and clinically suspected [sensitivity:69%(47-85), specificity:96%(90-98), DOR:62(16.8-232), AUC:94%(92-97), PLR:16.9(6.5-36.8), NLR:0.33(0.16-0.56), I2:15.3%] groups. GeneXpert revealed good diagnostic accuracy only in confirmed TBM group [sensitivity = 57%(38-74), specificity = 98%(89-100), DOR = 62(7-589), AUC = 87%(79-96), PLR = 33.2(3.8-128), NLR = 0.45(0.26-0.68), I2 = 0%]. CONCLUSIONS: This meta-analysis identified potential role of MPB gene among in-house assays and GeneXpert as commercial assay for diagnosing TBM.

Isoniazid and rifampicin heteroresistant Mycobacterium tuberculosis isolated from tuberculous meningitis patients in India.

BACKGROUND: Heteroresistant Mycobacterium tuberculosis (mixture of susceptible and resistant subpopulations) is thought to be a preliminary stage to full resistance and timely detection, initiation of correct treatment is vital for successful anti tubercular therapy. The aim of this study was to detect multi drug resistant (MDR) and heteroresistant M. tuberculosis with the associated gene mutations from patients of tuberculous meningitis. METHODS: A total of 197 M. tuberculosis isolates from 478 patients of TBM were isolated from July 2012 to July 2015 and subjected to drug susceptibility testing (DST) by BACTEC MGIT and Genotype MTBDR line probe assay (LPA). Heteroresistance was defined as presence of both WT and mutant genes in LPA. RESULTS: Of 197 M. tuberculosis isolates, 11 (5.6%) were MDR, 23 (11.6%), 1 (0.5%) were mono resistant to isoniazid (INH) and rifampicin (RMP) respectively. Heteroresistance was detected in 8 (4%), 2 (1%) isolates to INH and RMP respectively. INH heteroresistant strains had WT bands with mutation band S315T1 whereas RMP heteroresistant strains had WT bands with mutation band S531L. CONCLUSION: The prevalence of MDR M. tuberculosis was 5.6% in TBM patients with the most common mutation being ΔWT band with S315T1 for INH and ΔWT band with S531T for RMP. MGIT DST was found to be more sensitive for detecting overall resistance in M. tuberculosis but inclusion of LPA not only reduced time for early initiation of appropriate treatment but also enabled detection of heteroresistance in 8 (4%), 2 (1%) isolates for INH and RMP respectively.

Predictors of adverse outcome in patients of tuberculous meningitis in a multi-centric study from India.

INTRODUCTION: This study aimed to investigate the factors which may predict mortality and neurological disability at one year follow up in patients of tuberculous meningitis (TBM) in India. METHODOLOGY: Patients with TBM were prospectively enrolled from July 2012 to September 2014 from four tertiary care hospitals of Delhi. The demographic characteristics, clinical features and laboratory findings were collected and patients were followed up till 1 year. These were analyzed by univariate and multivariate multinomial logistic regression analysis to identify predictors of adverse patient outcome at 1 year follow up. RESULTS: Out of 478 patients enrolled, 391 patients could be followed up to 1 year. Sixty-four patients (16.3%) died and 150 patients (39%) survived with one or more neurological disability. Altered sensorium, motor deficit, cranial nerve palsy, seizures, isolation of M. tuberculosis and presence of multi-drug resistance were independently associated with any adverse outcome (death or disability) but by multivariate analysis only motor deficit, altered sensorium and isolation of M. tuberculosis on culture produced a statistically significant model for prediction of patient outcome. CONCLUSION: The three-predictor model with motor deficit, altered sensorium and isolation of M. tuberculosis produced a statistically significant model with correct prediction rate of 60.4%. These three variables predicted death with odds ratio of 39.2, 6.7 and 2.1 respectively in comparison to recovery whereas only motor deficit and isolation of M. tuberculosis predicted neurological disability at 1 year with odds ratio of 3.9, 2.4 respectively.

Evaluation of Geno Type MTBDRplus Line Probe Assay for Early Detection of Drug Resistance in Tuberculous Meningitis Patients in India.

BACKGROUND: Molecular methods which allow for rapid and reliable detection of drug resistance have yet not been sufficiently evaluated for timely management of patients with tuberculous meningitis. AIMS: We aimed to evaluate Geno Type MTBDRplus line probe assay for early detection of drug resistance in Mycobacterium tuberculosis isolates and CSF samples of confirmed tuberculous meningitis patients. SETTINGS AND DESIGN: This was a multicentric prospective study carried out from July 2011 to December 2013 in tertiary care hospitals of Delhi. MATERIALS AND METHODS: The assay was performed on 89 M. tuberculosis isolates and 31 direct CSF samples from microbiologically confirmed tuberculous meningitis patients. The sensitivity and specificity of this assay was calculated in comparison to drug susceptibility testing by BACTEC MGIT 960 system. RESULTS: The sensitivity, specificity for detection of resistance to Isoniazid was 93%, 97% and to Rifampicin was 80%, 98.8%, respectively by this assay in comparison with the phenotypic drug susceptibility testing. The line probe assay could detect M. tuberculosis in 55% of CSF samples from patients with microbiologically confirmed tuberculous meningitis. Only 5/89 isolates (5.6%) were resistant to both Isoniazid and Rifampicin while 9/89 (10%) isolates were additionally resistant to Isoniazid. Resistance to any of the drugs, namely Isoniazid, Rifampicin, Streptomycin or Ethambutol, was seen in 24.7% of strains. CONCLUSION: The line probe assay has a good sensitivity and specificity for detection of drug resistance to Isoniazid and Rifampicin in M. tuberculosis culture isolates. However, this assay has limited role in detection of M. tuberculosis and drug resistance from direct samples with confirmed diagnosis of tuberculous meningitis.