Evaluation of Capilia TB assay for rapid identification of Mycobacterium tuberculosis complex in BACTEC MGIT 960 and BACTEC 9120 blood cultures

<p>Abstract</p> <p>Background</p> <p>Capilia TB is a simple immunochromatographic assay based on the detection of MPB64 antigen specifically secreted by the <it>Mycobacterium tuberculosis </it>complex (MTC). Capilia TB was evaluated for rapid identification of MTC from BACTEC MGIT 960 and BACTEC 9120 systems in Kampala, Uganda. Since most studies have mainly dealt with respiratory samples, the performance of Capilia TB on blood culture samples was also evaluated.</p> <p>Methods</p> <p>One thousand samples from pulmonary and disseminated tuberculosis (TB) suspects admitted to the JCRC clinic and the TB wards at Old Mulago hospital in Kampala, Uganda, were cultured in automated BACTEC MGIT 960 and BACTEC 9120 blood culture systems. BACTEC-positive samples were screened for purity by sub-culturing on blood agar plates. Two hundred and fifty three (253) samples with Acid fast bacilli (AFB, 174 BACTEC MGIT 960 and 79 BACTEC 9120 blood cultures) were analyzed for presence of MTC using Capilia TB and in-house PCR assays.</p> <p>Results</p> <p>The overall Sensitivity, Specificity, Positive and Negative Predictive values, and Kappa statistic for Capilia TB assay for identification of MTC were 98.4%, 97.6%, 97.7%, 98.4% and 0.96, respectively. Initially, the performance of in-house PCR on BACTEC 9120 blood cultures was poor (Sensitivity, Specificity, PPV, NPV and Kappa statistic of 100%, 29.3%,7%, 100% and 0.04, respectively) but improved upon sub-culturing on solid medium (Middlebrook 7H10) to 100%, 95.6%, 98.2%, 100% and 0.98, respectively. In contrast, the Sensitivity and Specificity of Capilia TB assay was 98.4% and 97.9%, respectively, both with BACTEC blood cultures and Middlebrook 7H10 cultured samples, revealing that Capilia was better than in-house PCR for identification of MTC in blood cultures. Additionally, Capilia TB was cheaper than in-house PCR for individual samples ($2.03 vs.$12.59, respectively), and was easier to perform with a shorter turnaround time (20 min vs. 480 min, respectively).</p> <p>Conclusion</p> <p>Capilia TB assay is faster and cheaper than in-house PCR for rapid identification of MTC from BACTEC MGIT 960 and BACTEC 9120 culture systems in real-time testing of AFB positive cultures.</p

Use of Colorimetric Culture Methods for Detection of Mycobacterium Tuberculosis Complex Isolates from Sputum Samples in Resource-Limited Settings

Despite recent advances, tuberculosis (TB) diagnosis remains imperfect in resource-limited settings due to its complexity and costs, poor sensitivity of available tests, or long times to reporting. We present a report on the use of colorimetric methods, based on the detection of mycobacterial growth using colorimetric indicators, for the detection of Mycobacterium tuberculosis in sputum specimens. We evaluated the nitrate reductase assay (NRA), a modified NRA using para-nitrobenzoic acid (PNB) (NRAp), and the resazurin tube assay using PNB (RETAp) to differentiate tuberculous and nontuberculous mycobacteria. The performances were assessed at days 18 and 28 using mycobacterium growth indicator tube (MGIT) and Löwenstein-Jensen (LJ) medium culture methods as the reference standards. We enrolled 690 adults with suspected pulmonary tuberculosis from a regional referral hospital in Uganda between March 2010 and June 2011. At day 18, the sensitivities and specificities were 84.6% and 90.0% for the NRA, 84.1% and 92.6% for the NRAp, and 71.2% and 99.3% for the RETAp, respectively. At day 28, the sensitivity of the RETAp increased to 82.6%. Among smear-negative patients with suspected TB, sensitivities at day 28 were 64.7% for the NRA, 61.3% for the NRAp, and 50% for the RETAp. Contamination rates were found to be 5.4% for the NRA and 6.7% for the RETAp, compared with 22.1% for LJ medium culture and 20.4% for MGIT culture. The median times to positivity were 10, 7, and 25 days for colorimetric methods, MGIT culture, and LJ medium culture,respectively. Whereas the low specificity of the NRA/NRAp precludes it from being used for TB diagnosis, the RETAp might provide an alternative to LJ medium culture to decrease the time to culture results in resource-poor settings

Development of treatment-decision algorithms for children evaluated for pulmonary tuberculosis: an individual participant data meta-analysis.

Background: Many children with pulmonary tuberculosis remain undiagnosed and untreated with related high morbidity and mortality. Recent advances in childhood tuberculosis algorithm development have incorporated prediction modelling, but studies so far have been small and localised, with limited generalisability. We aimed to evaluate the performance of currently used diagnostic algorithms and to use prediction modelling to develop evidence-based algorithms to assist in tuberculosis treatment decision making for children presenting to primary health-care centres. Methods: For this meta-analysis, we identified individual participant data from a WHO public call for data on the management of tuberculosis in children and adolescents and referral from childhood tuberculosis experts. We included studies that prospectively recruited consecutive participants younger than 10 years attending health-care centres in countries with a high tuberculosis incidence for clinical evaluation of pulmonary tuberculosis. We collated individual participant data including clinical, bacteriological, and radiological information and a standardised reference classification of pulmonary tuberculosis. Using this dataset, we first retrospectively evaluated the performance of several existing treatment-decision algorithms. We then used the data to develop two multivariable prediction models that included features used in clinical evaluation of pulmonary tuberculosis-one with chest x-ray features and one without-and we investigated each model's generalisability using internal-external cross-validation. The parameter coefficient estimates of the two models were scaled into two scoring systems to classify tuberculosis with a prespecified sensitivity target. The two scoring systems were used to develop two pragmatic, treatment-decision algorithms for use in primary health-care settings. Findings: Of 4718 children from 13 studies from 12 countries, 1811 (38·4%) were classified as having pulmonary tuberculosis: 541 (29·9%) bacteriologically confirmed and 1270 (70·1%) unconfirmed. Existing treatment-decision algorithms had highly variable diagnostic performance. The scoring system derived from the prediction model that included clinical features and features from chest x-ray had a combined sensitivity of 0·86 [95% CI 0·68-0·94] and specificity of 0·37 [0·15-0·66] against a composite reference standard. The scoring system derived from the model that included only clinical features had a combined sensitivity of 0·84 [95% CI 0·66-0·93] and specificity of 0·30 [0·13-0·56] against a composite reference standard. The scoring system from each model was placed after triage steps, including assessment of illness acuity and risk of poor tuberculosis-related outcomes, to develop treatment-decision algorithms. Interpretation: We adopted an evidence-based approach to develop pragmatic algorithms to guide tuberculosis treatment decisions in children, irrespective of the resources locally available. This approach will empower health workers in primary health-care settings with high tuberculosis incidence and limited resources to initiate tuberculosis treatment in children to improve access to care and reduce tuberculosis-related mortality. These algorithms have been included in the operational handbook accompanying the latest WHO guidelines on the management of tuberculosis in children and adolescents. Future prospective evaluation of algorithms, including those developed in this work, is necessary to investigate clinical performance. Funding: WHO, US National Institutes of Health

Treatment outcomes and tolerability of the revised WHO anti-tuberculosis drug dosages for children

BACKGROUND: In 2010, the World Health Organization (WHO) revised the paediatric dosages of anti-tuberculosis drugs, increasing rifampicin to 15 mg/kg, isoniazid to 10 mg/kg and pyrazinamide to 35 mg/kg. We assessed treatment outcomes, safety and adherence among children treated with the new recommended dosages. METHODS : Prospective cohort of children started on anti-tuberculosis treatment in Uganda with 12 months of follow-up, including alanine aminotransferase (ALT) monitoring. Treatment intake was observed. RESULTS : Of 144 treated children, 81 were male (56.3%), 106 (73.6%) were aged,5 years, 30 (22%) had moderate to severe malnutrition and 48 (33.3%) had human immunodeficiency virus infection. Treatment outcomes were as follows: 117 (81.3%) successes, 3 (2.1%) failures, 4 (2.8%) lost to follow-up, 19 (13.2%) deaths and 1 (0.7%) transferred out. There was no relapse. Severe malnutrition (adjusted hazard ratio 8.76, 95% confidence interval [CI] 1.59-48.25) was the only predictor of death. Two serious adverse events were attributed to treatment: one case of increased ALT and one with peripheral neuropathy. Median ALT values at baseline and at weeks 2, 4 and 8 were respectively 24 (interquartile range [IQR] 16-39), 26 (IQR 18-38), 28 (IQR 21-40) and 27 (IQR 19-38) international units/l. Treatment adherence was above 85% on all visits. CONCLUSION: We confirm the good tolerability of and adherence to the new treatment recommendations. The increased risk of fatal outcome among severely malnourished children requires attention

Asymptomatic Plasmodium Infections in Children in Low Malaria Transmission Setting, Southwestern Uganda

A survey of asymptomatic children in Uganda showed Plasmodium malariae and P. falciparum parasites in 45% and 55% of microscopy-positive samples, respectively. Although 36% of microscopy-positive samples were negative by rapid diagnostic test, 75% showed P. malariae or P. ovale parasites by PCR, indicating that routine diagnostic testing misses many non–P. falciparum malarial infections

Evaluation of OMNIgene sputum and ethanol reagent for preservation of sputum prior to xpert and culture testing in Uganda

Xpert MTB/RIF (Xpert) and culture are the most reliable methods for tuberculosis diagnosis but are still poorly accessible in many low-resource countries. We aimed to assess the effects of OMNIgene Sputum (OM-S) and ethanol in preserving sputum for Xpert and OM-S for mycobacterial growth indicator tube (MGIT) testing over periods of 15 and 8 days, respectively. Sputum samples were collected from newly diagnosed smear-positive patients. For Xpert, pooled samples were split into 5 aliquots: 3 for Xpert on days 0, 7, and 15 without additive and 2 with either OM-S or ethanol at day 15. For MGIT, 2 aliquots were tested without preservative and 2 with OM-S at 0 and 8 days. Totals of 48 and 47 samples were included in the analysis for Xpert and culture. With Xpert, using day 0 as a reference, untreated samples stored for 7 and 15 days showed concordances of 45/46 (97.8%) and 46/48 (95.8%). For samples preserved with OM-S or ethanol for 15 days compared with untreated samples processed at day 0 or after 15 days, OM-S concordances were 46/48 (95.8%) and 47/48 (97.9%), while those of ethanol were 44/48 (91.7%) and 45/48 (93.8%). With MGIT, concordances between untreated and OM-S-treated samples were 21/41 (51.2%) at day 0 and 21/44 (47.7%) at day 8. In conclusion, Xpert equally detected tuberculosis in OM-S-treated and untreated samples up to 15 days but showed slightly lower detection in ethanol-treated samples. Among OM-S-treated samples, MGIT positivity was significantly lower than in untreated samples at both time points