TB LAMP assay, a beneficial tool for the diagnosis of Tubercular meningitis in resource-limited settings.

INTRODUCTION: Tubercular meningitis (TBM) is a serious public health problem in developing countries as it leads to significant mortality and residual neurological sequelae. The estimated mortality due to TBM in India is 1.5 per 100,000 population. In resource-limited settings, only the Ziehl-Neelsen (ZN) stain, which has very little sensitivity, is available. The World Health Organization recommended the Loop Mediated Isothermal Amplification (TB LAMP) assay for pulmonary tuberculosis only. We evaluated this test for tubercular meningitis as well. METHODOLOGY: In a cross-sectional study of 2-year duration, we have taken 239 cerebrospinal fluid samples from suspected cases of tubercular meningitis patients. ZN staining along with Mycobacteria Growth Indicator Tube (MGIT) TB culture, Xpert MTB/RIF Ultra assay, and commercial TB LAMP assay were performed for each sample. RESULTS: Out of 239 samples, 40 samples (16.73%) were found TB LAMP assay positive, 48 samples (20.08%) were found Xpert ultra-assay positive, 12 samples (5.02%) were MGIT TB culture positive and acid-fast bacillus smear positive in ten samples (4.18 %). Out of 12 MGIT-positive samples, all samples (100%) were TB LAMP and Xpert ultra positive and one sample (8.33%) was ZN smear positive. In 199 negative samples from the TB LAMP assay, eight samples were positive by Xpert, none by MGIT TB culture and AFB smear. Sensitivity and specificity were found as 100% and 87.66%, respectively, for the TB LAMP assay. CONCLUSION: TB LAMP assay is a rapid, cost-effective, sensitive, and specific test for tubercular meningitis infection in resource-limited settings.

Evaluation of kit-based loop-mediated isothermal amplification (TB-LAMP) assay in the diagnosis of tubercular lymphadenitis.

Background: The rapid and accurate diagnosis of tubercular lymphadenitis remains a challenging task today. The World Health Organization (WHO) endorsed the LoopAMP MTBC kit (TB-LAMP) as a replacement for sputum smear microscopy in the diagnosis of pulmonary tuberculosis (PTB). However, no prospective diagnostic accuracy study of TB-LAMP for tubercular lymphadenitis in adults has been performed yet. The current study evaluated the diagnostic performance of TB-LAMP in tubercular lymphadenitis (LNTB). Methods: In a prospective observational study conducted at a tertiary care hospital in India, 90 subjects (age >18 years) suspected of LNTB were recruited consecutively and followed up for 6 months between January 2019 and December 2020. Samples were processed for microscopy, culture, GeneXpert, histopathology and TB-LAMP. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of TB-LAMP against the composite reference standard (CRS) and culture were determined. Results: TB-LAMP showed a sensitivity of 83.78 % (95 % CI, 73.76-90.47) and a specificity of 81.25 % (95 % CI, 56.99-93.41), respectively, against the CRS. The PPV and NPV were 95.38 % (95 % CI, 87.29-98.42) and 52.00 % (95 % CI, 33.50-69.97), respectively. TB-LAMP showed a sensitivity of 88.89 % (95 % CI, 71.94-96.15) and a specificity of 36.17 % (95 % CI, 23.97-50.46), respectively, against culture. The PPV and NPV were 44.44 % (95 % CI, 32-57.62) and 85 % (95 % CI, 63.96-94.76), respectively. Conclusion: TB-LAMP can be used instead of conventional microscopy for the diagnosis of TB in lymph node specimens at primary healthcare centres. It provides rapid and cost-effective diagnosis of LNTB in resource-limited settings due to good sensitivity and NPV.

Tuberculosis-loop-mediated isothermal amplification implementation in Cameroon: Challenges, lessons learned and recommendations.

Background: Until 2016, microscopy was the main tool for the early detection of pulmonary tuberculosis in Cameroon, especially in remote settings. Due to the poor sensitivity of microscopy, there was a need to implement a molecular assay in order to improve tuberculosis case detection. Intervention: In 2017, tuberculosis loop-mediated isothermal amplification (TB-LAMP), a molecular rapid diagnostic test recommended by the World Health Organization, was implemented in Cameroon as a replacement test of microscopy for initial diagnosis of pulmonary tuberculosis and also as a follow-on test to microscopy for smear-negative sputum specimens. A roll out plan for TB-LAMP implementation in Cameroon had been developed from January 2017 to April 2017, followed by initial implementation at four sites in May 2017. Additional sites were added progressively. Lessons learnt: The use of TB-LAMP as a follow-on test to microscopy for smear-negative sputum specimens helped in the detection of tuberculosis in 14.77% of those who were sputum-smear negative in 2019. Tuberculosis-loop-mediated isothermal amplification usage as an initial test, followed by testing with Xpert MTB/RIF for rapid tuberculosis and rifampicin resistance detection during tuberculosis mass screening campaigns, reduced the turn-around time by 73.23% as compared to when the Gene Xpert instrument was used alone. Recommendations: The implementation and scaling up of TB-LAMP in Cameroon contributed to increase access to tuberculosis molecular diagnosis in remote settings and as such improved tuberculosis case notification. However, to better enhance this notification and optimise the use of a TB-LAMP instrument, a suitable sample transport system is recommended.

A cost-benefit algorithm for rapid diagnosis of tuberculosis and rifampicin resistance detection during mass screening campaigns.

BACKGROUND: Active tuberculosis (TB) case finding is important as it helps detect pulmonary TB cases missed by the other active screening methods. It requires periodic mass screening in risk population groups such as prisoners and refugees. Unfortunately, in these risk population groups periodic mass screening can be challenging due to lengthy turnaround time (TAT), cost and implementation constraints. The aim of this study was to evaluate a diagnostic algorithm that can reduce the TAT and cost for TB and Rifampicin resistance (RR) detection. The algorithm involves testing with TB-LAMP followed by Xpert MTB/RIF for positive TB-LAMP cases to diagnose TB during mass campaigns in prisons and refugee camps. METHODS: The National Tuberculosis Control Program (NTCP) organized routine TB mass-screening campaigns in 34 prisons and 3 villages with refugees camps in Cameroon in 2019. TB LAMP was used for initial TB diagnosis and all TB-LAMP positive cases tested with the Xpert MTB/RIF assay to determine RR. TAT and cost benefits analysis of the combined use of TB-LAMP and Xpert MTB/RIF assays was determined and compared to the Xpert MTB/RIF assay when used only. RESULTS: A total of 4075 sputum samples were collected from TB presumptive, 3672 cases in 34 prisons and 403 samples in 3 villages. Of the 4,075 samples screened with TB-LAMP, 135 were TB positive (3.31%) and run on the Xpert MTB/RIF. Of the 135 positives cases, Xpert MTB/RIF revealed 3 were RR (2.22%). The use of TB-LAMP followed by testing with Xpert MTB/RIF for TB and RR detection reduced the TAT by 73.23% in prisons and 74.92% in villages. In addition to a reduced TAT, the two molecular tests used in synergy is cost benefit from year 2 onwards. CONCLUSION: This study demonstrates the advantages of a diagnostic algorithm based on an initial testing with TB-LAMP followed by testing with Xpert MTB/RIF for TB diagnosis. This approach improved early and rapid TB detection with an added advantage of providing RR status. The proposed algorithm is effective and less costly from the second year of implementation and should be used by TB control programs.

Cost-Utility Analysis of Molecular Testing for Tuberculosis Diagnosis in Suspected Pulmonary Tuberculosis in Thailand.

PURPOSE: Given the lack of economic evaluation study of molecular testing in Thailand, this study aimed to evaluate the cost-utility of molecular testing algorithms including Xpert MTB/RIF and the loop-mediated isothermal amplification (TB-LAMP) in the general population suspected of having pulmonary TB based on a societal perspective. METHODS: A hybrid decision tree Markov model using a 1-month cycle length was used to evaluate costs and outcomes of five TB diagnostic algorithms: 1) sputum smear microscopy (SSM) with culture and drug susceptibility testing (DST), 2) Xpert MTB/RIF add-on, 3) Xpert MTB/RIF initial, 4) TB-LAMP add-on, and 5) TB-LAMP initial during a lifetime period. All costs were calculated in 2021 Baht, and results were presented as an incremental cost-effectiveness ratio (ICER) for molecular testing compared with SSM with culture. One-way sensitivity and probability analyses were used to evaluate uncertainty input parameters. RESULTS: TB-LAMP was less expensive overall (6565 Baht) than Xpert MTB/RIF (7010 Baht) and SSM with culture (6845 Baht). Molecular testing was projected to improve quality adjusted life year (QALY) by 0.53 to 0.94 years. In comparison to SSM with culture and DST, providing an initial TB-LAMP test was the most preferred choice. Xpert MTB/RIF Initial had the lowest ICER (197 Baht per QALY gained), followed by TB-LAMP Add-on (993 Baht per QALY gained) and Xpert MTB/RIF Add-on (3940 Baht per QALY gained). One-way sensitivity analysis uncovered that sensitivity of TB-LAMP was greater than that of other parameters. CONCLUSION: Providing molecular testing including Xpert MTB/RIF and TB-LAMP as either initial or add-on test for TB diagnosis was more cost-effective than SSM with culture and DST in the general population with suspected pulmonary TB in Thailand. Our study could provide useful evidence to policymakers advocating for inclusion of molecular testing in the universal health coverage benefit package in Thailand.

Diagnostic accuracy of TB-LAMP assay in patients with pulmonary tuberculosis...a case-control study in northern India.

SETTING: A tertiary care hospital in North India. OBJECTIVE: Tuberculosis (TB) remains a major public health problem in developing countries. The diagnosis of tuberculosis is still challenging in primary care settings in endemic countries like India. WHO has endorsed loop mediated isothermal amplification assay (LAMP) for TB as a replacement for smear microscopy for peripheral settings, however, more data is required to establish the specificity of this modality for the diagnosis of TB. In this study we aim to determine the diagnostic accuracy of the TB-LAMP assay in pulmonary tuberculosis. DESIGN: A total of 236 patients (117 cases suspected of TB and 119 patients with non-TB pulmonary disease) were enrolled between February to July, 2018. Microbiological workups consisting of mycobacterial smear microscopy, culture, Xpert MTB/Rif and TB-LAMP were performed. RESULTS: From 236 samples, 18 (7.6%) were excluded from the study. TB-LAMP and Xpert MTB/RIF were positive in 46 (21.1%) and 49 (22.5%) of the samples, respectively. The sensitivity of Xpert MTB/RIF and TB-LAMP, when culture was taken as a reference standard, was 90% (95%CI: 78.2-96.7) and 82% (95%CI: 68.6...91.4), respectively. The specificity, positive predictive value (PPV), and negative predictive value (NPV) of TB-LAMP assay were 96.8% (95%CI: 92.8...98.9), 89.1% (95%CI: 77.4...95.2), and 94.4% (95%CI: 90.4...96.5), respectively. CONCLUSION: The TB-LAMP assay showed a good specificity and sensitivity for detection ofM. tuberculosis in adults, however, for programmatic implementation, more studies are required to be conducted at peripheral level healthcare settings.

Diagnostic accuracy of screening algorithms to identify persons with active pulmonary tuberculosis at prison entry: protocol of a systematic review and network meta-analysis.

Prison inmates are a high-risk group for tuberculosis (TB) infection and disease due to the increasing number of vulnerable fringe groups, risk factors (e.g., alcohol and drug addictions), contagious diseases (HIV, hepatitis), and their high-risk behavior. Compared to the general population, TB incidence and prevalence rates are significantly higher among prison inmates. Early identification of potentially infectious pulmonary TB (PTB) and targeted care of sick inmates are essential to effectively control TB within the prison system. The WHO recommends combining active and passive case-finding in prisons. No study has been published comparing the broad spectrum of screening tools using a diagnostic accuracy network meta-analysis (NMA). We aim to identify the most accurate TB case-finding algorithm at prison entry that is feasible in resource-limited prisons of high-burden TB countries and ensures continuous comprehensive TB detection services in such settings. Evidence generated by this NMA can provide important decision support in selecting the most (cost-) effective algorithms for screening methods for resource-limited settings in the short, medium, and long terms.

Diagnostic Accuracy of Loop-Mediated Isothermal Amplification (TB-LAMP) for Tuberculosis in Children.

BACKGROUND: Diagnosing tuberculosis (TB) in children is challenging due to its paucibacillary nature. Loop-mediated isothermal amplification (TB-LAMP) is a simple, rapid, and specific point-of-care molecular diagnostic test. However, evaluation of its performance remains limited in children. This study aimed to evaluate the diagnostic performance of Eiken TB-LAMP among children with presumed tuberculosis disease. METHODS: Pulmonary and extrapulmonary specimens were collected from children under 18 years with presumed TB. Each specimen was tested by using TB-LAMP, acid-fast bacilli (AFB) smear microscopy, and one of the two molecular assays (polymerase chain reaction [PCR] or Xpert MTB/RIF). Sensitivity and specificity were estimated compared to mycobacterial culture as reference standard. RESULTS: From January 2020 to January 2021, 75 participants with presumed TB were enrolled with median age of 7 years (IQR 2-12). Seventeen specimens from 16 (21.3%) children had bacteriologically confirmed TB: 10 pulmonary and 7 extrapulmonary specimens. Overall sensitivity and specificity of TB-LAMP was 76.5% (95% CI 50.1%-93.2%) and 100% (95% CI 94.3%-100%), respectively. It had significantly higher sensitivity than AFB (52.9%, 95% CI 27.8%-77.0%) and similar to other molecular assays; PCR 82.4% (95% CI 56.6%-96.2%), Xpert MTB/RIF 70.0% (95% CI 34.8%-93.3%). Sensitivity of TB-LAMP for pulmonary, lymph node tissue, and extrapulmonary fluid was 80% (95% CI 44.4%-97.5%), 100% (95% CI 39.8-100), and 33.3% (95% CI 0.8-90.6), respectively. TB-LAMP detected all smear-positive (N = 9) and 50% of smear-negative (N = 8) specimens. CONCLUSIONS: TB-LAMP had higher sensitivity than AFB microscopy and accuracy similar to other molecular assays in both pulmonary and extrapulmonary specimens. These findings support using TB-LAMP as a point-of-care test in children.

Evaluation of TB-LAMP assay for detection of Mycobacterium tuberculosis in children.

BACKGROUND: Paediatric tuberculosis remains a major public health problem in developing countries. The diagnosis of tuberculosis in children is challenging because of the paucibacillary nature of the disease, due to which more sensitive nucleic acid amplification tests are needed. In this study, we determined the accuracy of WHO endorsed TB-LAMP assay for detection of Mycobacterium tuberculosis in children. METHODS: This was a prospective study conducted between March to July, 2018. A total of 177 samples from consecutive suspected TB children were received for microbiological diagnosis of TB. All tests for Mycobacterium tuberculosis detection were performed in parallel (smear microscopy, mycobacterial culture, Xpert MTB/RIF and TB-LAMP). The diagnostic accuracy of index test i.e. TB LAMP were determined using mycobacterial culture as a reference standard. RESULTS: Of the 177 samples, 2 (1.1%) were excluded from the study. Among 175 samples, TB-LAMP and Xpert MTB/RIF were positive in 27 (15.4%) and 25 (14.3%) samples, respectively. The sensitivity of both Xpert MTB/RIF and TB-LAMP was same, i.e. 84% (95%CI: 63.9-95.5%), when culture was considered as the reference standard. The specificity, positive predictive value and negative predictive value of TB-LAMP assay was 96% (95%CI: 91.5-98.5%), 77.8% (95%CI: 61.1-88.6%) and 97.3% (95%CI: 93.6-98.9%), respectively. CONCLUSION: For the detection of M. tuberculosis in paediatric samples, TB-LAMP showed a sensitivity and specificity comparable to Xpert MTB/RIF.

Diagnostic Yield of Oral Swab Testing by TB-LAMP for Diagnosis of Pulmonary Tuberculosis.

OBJECTIVE: A prospective study was conducted to ascertain the accuracy of oral swab specimens collected in the early morning, spot and at night for detecting pulmonary tuberculosis (TB). METHODS: We prospectively enrolled patients with symptoms suggestive of pulmonary TB in Beijing Chest Hospital. An early morning sputum specimen was collected from each patient for GeneXpert MTB/RIF (Xpert) and mycobacterial culture. In addition, three oral swabs were collected for TB-LAMP testing. RESULTS: With the combined results of three oral swab specimens, the proportion of Mycobacterium tuberculosis (MTB)-positive cases achieved 40.6%, which was comparable to results for Xpert and MGIT (P=0.603). Using Xpert plus MGIT as reference, the sensitivity of OS-LAMP on a single specimen ranged from 32.6% on the night oral swab to 50.0% on the morning swab. The combination of three oral swab specimens correctly identified 38 MTB-positive cases, indicating an overall sensitivity of 82.6%, which was significantly higher than that of a single oral swab specimen (P<0.001, P=0.001). CONCLUSION: Oral swab can be used as an alternative specimen for diagnosis of pulmonary TB using TB-LAMP. Morning oral swab exhibits the highest sensitivity, and the inclusion of more specimens at different time points provides compensation in diagnostic sensitivity with single oral swab.

Comparison of Diagnostic Yield of Tuberculosis Loop-Mediated Isothermal Amplification Assay With Cartridge-Based Nucleic Acid Amplification Test, Acid-Fast Bacilli Microscopy, and Mycobacteria Growth Indicator Tube Culture in Children With Pulmonary Tuberculosis.

BACKGROUND: Cartridge-based nucleic acid amplification test (CB-NAAT) has been recommended for diagnosis of tuberculosis (TB) in children, but its wide use is limited by high cost and the need for well-equipped laboratories. This study was conducted in children with pulmonary TB to compare the diagnostic yield of TB-LAMP (loop-mediated isothermal amplification test) with CB-NAAT and other conventional methods. METHODS: Patients ≤ 14 years of age diagnosed with probable pulmonary TB were included in the study. Induced sputum/gastric aspirate was obtained and subjected to acid-fast bacilli (AFB) microscopy, mycobacteria growth indicator tube (MGIT) culture, CB-NAAT, and TB-LAMP. The TB-LAMP assay was performed using 2 different primers, IS6110 and mpb64, for detection of Mycobacterium tuberculosis (MTB). TB-LAMP assays were compared to other assays using appropriate statistical tests. RESULTS: One hundred fourteen subjects were recruited in the study. AFB microscopy, MGIT culture, CB-NAAT, TB-LAMP IS6110, and TB-LAMP mpb64 showed positivity of 32 (28.1%), 59 (51.7%), 66 (57.9%), 75 (65.8%), and 81 (71%), respectively. TB-LAMP IS6110 showed significantly higher MTB detection in comparison to AFB microscopy and MGIT culture (P = .0001 and P = .03, respectively), and showed no significant difference in MTB detection in comparison with CB-NAAT (P = .219). TB-LAMP mpb64 showed significantly higher MTB detection as compared to AFB microscopy, MGIT culture, and CB-NAAT (P = .0001, P = .003, and P = .037, respectively). TB-LAMP mpb64 and IS6110 showed sensitivity of 94.9% (95% confidence interval [CI], 85.9%-98.9%) and 89.8% (95% CI, 79.7%-96.2%), respectively, in reference to MGIT culture. The degree of agreement between TB-LAMP (mpb64 and IS6110) with CB-NAAT showed κ values of 0.718 and 0.834, respectively. CONCLUSIONS: TB-LAMP assay can be a useful alternative test in diagnosis of pulmonary TB in children.

The Role of TB-LAMP Method in Detecting Mycobacterium tuberculosis from Sputum of Patients Suspected of Having Pulmonary Tuberculosis.

BACKGROUND: Indonesia is one of the countries with the highest incidence of tuberculosis (TB) in the world. Appropriate diagnosis is an effort to control TB. The World Health Organization has recommended loop-mediated isothermal amplification (LAMP). In order to be applied routinely, it is necessary to do research to evaluate the LAMP method. METHODS: the research was a cross-sectional study and was carried out at the Clinical Microbiology Laboratory of the Faculty of Medicine, Universitas Indonesia, for 100 patients suspected of having pulmonary TB. Each patient handed over two direct sputum specimens. For each direct sputum specimen, an acid-fast bacilli (AFB) smear was carried out. Two direct sputum specimens from each patient were combined to produce mixed sputum. For each mixed sputum specimen, an AFB smear, Lowenstein-Jensen culture, and TB-LAMP were carried out. RESULTS: the percentage of LAMP (+) cells in mixed sputum that was AFB (-) was 32.78%. The TB-LAMP showed a sensitivity of 100% (95% CI 89.56-100%), a specificity of 69.64% (95% CI 55.74-80.84%), positive predictive value of 71.19% (95% CI 57.73-81.86%), and negative predictive value of 100% (95% CI 88.83-100%). CONCLUSION: TB-LAMP has both high sensitivity and negative predictive value.

Challenges and Progress with Diagnosing Pulmonary Tuberculosis in Low- and Middle-Income Countries.

Case finding and the diagnosis of tuberculosis (TB) are key activities to reach the World Health Organization's End TB targets by 2030. This paper focuses on the diagnosis of pulmonary TB (PTB) in low- and middle-income countries. Sputum smear microscopy, despite its many limitations, remains the primary diagnostic tool in peripheral health facilities; however, this is being replaced by molecular diagnostic techniques, particularly Xpert MTB/RIF, which allows a bacteriologically confirmed diagnosis of TB along with information about whether or not the organism is resistant to rifampicin within two hours. Other useful diagnostic tools at peripheral facilities include chest radiography, urine lipoarabinomannan (TB-LAM) in HIV-infected patients with advanced immunodeficiency, and the loop-mediated isothermal amplification (TB-LAMP) test which may be superior to smear microscopy. National Reference Laboratories work at a higher level, largely performing culture and phenotypic drug susceptibility testing which is complemented by genotypic methods such as line probe assays for detecting resistance to isoniazid, rifampicin, and second-line drugs. Tuberculin skin testing, interferon gamma release assays, and commercial serological tests are not recommended for the diagnosis of active TB. Linking diagnosis to treatment and care is often poor, and this aspect of TB management needs far more attention than it currently receives.

Comparative Evaluation of the Loop-Mediated Isothermal Amplification Assay for Detecting Pulmonary Tuberculosis.

BACKGROUND: Early detection of tuberculosis (TB) is challenging in resource-poor settings because of limited accessibility to molecular diagnostics. The aim of this study was to evaluate the performance of the loop-mediated isothermal amplification kit (TB-LAMP) for TB diagnosis compared with conventional and molecular tests. METHODS: A total of 290 consecutive sputum samples were collected from May till September, 2015. All samples were processed using the N-Acetyl-L-cysteine (NALC) NaOH method and tested by smear microscopy, solid and liquid culture, real-time PCR, and TB-LAMP. RESULTS: The sensitivity of TB-LAMP for smear-positive and smear-negative samples with culture positivity was 92.0% and 58.8%, respectively. TB-LAMP was positive in 14.9% of TB culture-negative samples; however, all those samples were also positive by real-time PCR. In addition, none of the samples positive for nontuberculous mycobacteria by culture were positive by TB-LAMP. The overall agreement between TB-LAMP and real-time PCR was good; however, the concordance rate was significantly lower for real-time PCR positive samples with Ct values of 30-35. CONCLUSIONS: TB-LAMP could replace smear microscopy and increase TB diagnostic capacity when Xpert MTB/RIF is not feasible because of poor infrastructure.

Evaluation of Loopamp™MTBC detection kit for diagnosis of pulmonary tuberculosis at a peripheral laboratory in a high burden setting.

The Loopamp™MTBC detection kit (TB-LAMP) was designed to replace the sputum smear microscopy for the diagnosis of pulmonary tuberculosis. We evaluated its performance at a peripheral laboratory in Vietnam. The sensitivity of TB-LAMP was 45.5% (28.1%-63.6%), which was equal to 3-sputum smear microscopy but lower than that of Xpert MTB/RIF (87.8% [71.8%-96.6%]). In patients with culture-confirmed TB, sensitivity was 80% (51.9%-95.7%) in smear-positive and 16.7% (3.5%-41.4%) in smear-negative cases. The specificity of TB-LAMP was 95.1% (92.7%-96.9%), which was lower than that of smear microscopy (98.9% [97.5%-99.7%]) and Xpert MTB/RIF (99.3% [98.1%-99.9%]) (P<0.05). The probability of TB detection by TB-LAMP was more influenced by sample quality and viscosity than were smear microscopy, Xpert MTB/RIF, and culture. The present data do not support the use of TB-LAMP as a replacement test for smear microscopy in peripheral laboratories.

Conventional and Molecular Methods for the Diagnosis of Smear Negative Pulmonary TB and Concordance of Empirical TB Diagnosis with Culture Assay.

BACKGROUND: Ethiopia is among high TB burden countries. The proportion of smear negative patients among pulmonary TB cases was 51%. Nevertheless, microscopy is still a primary tool for TB diagnosis. In the absence of sensitive diagnostic methods, clinicians often make the diagnosis of smear-negative pulmonary TB with information obtained through the clinical history, physical examination and chest X-ray. The treatment of smear negative TB patients with those criteria largely depends on the treating clinician. There is limited data on the utilization of clinical criteria commonly used to initiate TB treatment empirically when culture is used as the reference method. Beside this, there are a number of sensitive diagnostic methods that have a substantial contribution for the diagnosis of smear negative TB patients, but only few studies were conducted in Ethiopia to address this issue. OBJECTIVE: To assess the contribution of conventional and molecular methods for smear-negative patients and describe the concordance rate of empiric TB treatment with culture assay. METHODS: A cross-sectional study was designed on smear negative TB presumptive patients referred to St. Peter's TB Specialized Hospital from December 2014 to June 2015. Consecutive smear negative TB presumptive patients, aged greater or equal to 15 and willing to participate were included in the study. Socio-demographic and clinical data were collected using the data collection form designed for the study purpose. The data collection form was designed to capture patient demographic data, signs and symptoms, chest X-ray findings and empirical TB treatment initiations. Spot-Moring-spot sputum was collected using sterile falcon tubes for routine diagnostic purpose. Direct ZN examination was done on Spot-Moring-spot sputum at St. Peter's TB Specialized Hospital. The morning sputum was used for culture (LJ and MGIT), TB-LAMP, Xpert MTB/RIF assay and fluorescent microscopy examination. Data were captured and analyzed using SPSS. RESULTS: This study enrolled 459 smear negative presumptive TB patients. Most (57%) of the study participants were female; with median age of 40 IQR (28-55) years. HIV test results were available for 41% of the study participants and the prevalence of HIV among the study participants was 30%. Three hundred eighty three cases were having both treatment and lab results. Forty six cases were treated empirically. The sensitivity and specificity of empiric TB treatment when compared to culture were 45.8% and 90% respectively. The overall culture positivity rate was 6.8% (30/439), of which 6.6% (26/391) was by MGIT and 5.3% (23/436) was by LJ method. Direct and concentrated fluorescent microscopy adds 0.9% and 1.3% detection rate compared to the direct ZN. The overall sensitivity and specificity of TB-LAMP was 61.5% (16/26) and 96.6% respectively. The overall sensitivity and specificity of Xpert MTB/RIF was 70.8% (17/24) and 97.2% respectively. CONCLUSION: TB-LAMP and Xpert MTB/RIFassaycan provide confirmatory results for at least two third of TB cases.

Comparison of TB-LAMP, GeneXpert MTB/RIF and culture for diagnosis of pulmonary tuberculosis in The Gambia.

BACKGROUND: Diagnosis of tuberculosis (TB) remains difficult, particularly in resource-limited settings. The development of nucleic acid-based tests for detection of Mycobacterium tuberculosis complex (MTBC) has significantly increased sensitivity compared to conventional smear microscopy and provides results within a matter of hours compared to weeks for the current gold-standard, liquid culture. METHODS: In this study we performed side-by-side comparison of mycobacterial detection assays on sputum samples from 285 subjects presenting with symptoms suggestive of TB in The Gambia and a cross-sectional cohort of 156 confirmed TB patients with a median of 2 months of treatment. A novel assay, Loop-Mediated Amplification test for TB (TB-LAMP), was compared to smear microscopy, MGIT culture and GeneXpert MTB/RIF for all samples. RESULTS: When culture was used as the reference standard, we found an overall sensitivity for TB-LAMP of 99% (95% CI: 94.5-99.8) and specificity of 94% (95% CI: 89.3-96.7). When latent class analysis was performed, TB-LAMP had 98.6% (95% CI: 95.9-100) sensitivity and 99% (95% CI: 98.2-100) specificity compared to 91.1% (95% CI: 86.1-96) sensitivity and 100% (95% CI: 98.2-100) specificity for MGIT culture. GeneXpert had the highest sensitivity 99.1% (95% CI: 97.1-100) but the lowest specificity 96% (95% CI: 92.6-98.3). Both TB-LAMP and GeneXpert showed high sensitivity and specificity regardless of age or strain of infection. CONCLUSION: Our findings show the diagnostic utility of both GeneXpert and TB-LAMP in The Gambia. Whilst TB-LAMP requires less infrastructure, it is unable to detect drug-resistant patterns and therefore would be most suitable as a screening test for new TB cases in peripheral health clinics.

Rapid detection of Mycobacterium tuberculosis complex in sputum Samples using PURE TB-LAMP assay.

OBJECTIVE/BACKGROUND: Lack of rapid and accurate diagnostic testing is a critical obstacle to global tuberculosis (TB) control. Sensitivity of sputum smear microscopy (SSM) is not optimal; however, it remains the most prevalent tool for TB confirmation in poor countries. As a part of passive case finding of TB detection, this study was conducted to determine the clinical performance of PURE TB-LAMP assay using liquid culture medium as the gold standard. METHODS: Centre Antituberculeux de Yopougon is one of the 17 intermediate Tuberculosis centers in Côte d'Ivoire. A standardized questionnaire was submitted to patients with signs and symptoms consistent with tuberculosis by a trained caregiver. After obtaining signed consent forms, sputum samples were collected according to National TB Control Programme guidelines (spot-morning). SSM after Ziehl-Neelsen staining and TB-LAMP assay were blindly performed on the first sample. Samples transported to Institut Pasteur de Côte d'Ivoire were decontaminated according to the N-acetyl-L-Cystein method. In Mycobacteria Growth Indicator Tube (MGIT), 500mL of pellets were inoculated and incubated in the MGIT 960 system. MPT64 antigen was detected in positive cultures. RESULTS: Of the 500 patients enrolled, 469 (232men and 239 women) patients were included. The mean ages of men and women were 36.9 (15-86) and 37.3 (15-37.3) years, respectively. There were 56 (12.2%) HIV-infected patients, including 14 women. Clinical isolates of M. tuberculosis complex were detected for 157 (33.5%) patients. Compared with culturing, the overall sensitivity and specificity of SSM were 86% (95% confidence interval [CI]=81-91) and 96% (95% CI=94-98), respectively. The overall sensitivity and specificity for TB-LAMP was 92% (95% CI=0.88-0.96) and 94% (95% CI=0.91-0.97), respectively. Positive likelihood ratios for TB-LAMP and SSM were 15.3 and 21.5, respectively, and negative likelihood ratios for TB-LAMP and SSM were 0.09 and 0.15, respectively. Among the 469 patients, active tuberculosis was detected using TB-LAMP assay and SSM in 162 (34.5%) and 147 (31.3%) patients, respectively. CONCLUSION: For accurate diagnostic of pulmonary TB, TB-LAMP could be used as a tool of the first intention.