Assay For Diagnosis Of Tuberculosis Research Articles

Evaluation of the IP-10 mRNA release assay for diagnosis of TB in HIV-infected individuals.

HIV-infected individuals are susceptible to Mycobacterium tuberculosis (M.tb) infection and are at high risk of developing active tuberculosis (TB). Interferon-gamma release assays (IGRAs) are auxiliary tools in the diagnosis of TB. However, the performance of IGRAs in HIV-infected individuals is suboptimal, which limits clinical application. Interferon-inducible protein 10 (IP-10) is an alternative biomarker for identifying M.tb infection due to its high expression after stimulation with M.tb antigens. However, whether IP-10 mRNA constitutes a target for the diagnosis of TB in HIV-infected individuals is unknown. Thus, we prospectively enrolled HIV-infected patients with suspected active TB from five hospitals between May 2021 and May 2022, and performed the IGRA test (QFT-GIT) alongside the IP-10 mRNA release assay on peripheral blood. Of the 216 participants, 152 TB patients and 48 non-TB patients with a conclusive diagnosis were included in the final analysis. The number of indeterminate results of IP-10 mRNA release assay (13/200, 6.5%) was significantly lower than that of the QFT-GIT test (42/200, 21.0%) (P = 0.000026). IP-10 mRNA release assay had a sensitivity of 65.3% (95%CI 55.9% - 73.8%) and a specificity of 74.2% (95%CI 55.4% - 88.1%), respectively; while the QFT-GIT test had a sensitivity of 43.2% (95%CI 34.1% - 52.7%) and a specificity of 87.1% (95%CI 70.2% - 96.4%), respectively. The sensitivity of the IP-10 mRNA release assay was significantly higher than that of QFT-GIT test (P = 0.00062), while no significant difference was detected between the specificities of these two tests (P = 0.198). The IP-10 mRNA release assay showed a lower dependence on CD4+ T cells than that of QFT-GIT test. This was evidenced by the fact that the QFT-GIT test had a higher number of indeterminate results and a lower sensitivity when the CD4+ T cells counts were decreased (P < 0.05), while no significant difference in the number of indeterminate results and sensitivity were observed for the IP-10 mRNA release assay among HIV-infected individuals with varied CD4+T cells counts (P > 0.05). Therefore, our study suggested that M.tb specific IP-10 mRNA is a better biomarker for diagnosis of TB in HIV-infected individuals.

Accuracy of Xpert MTB/RIF assay in diagnosis of tuberculosis a comparison to culture

Culture method is the most sensitive and specific method for the detection of Mycobacterium tuberculosis. Despite this, cultures are highly prone to contamination and the process can still take several days and does require expensive equipment, strict biosafety practices and well trained technical staff .Among the currently available Nucleic Acid Amplification Tests (NAAT), the Xpert MTB/RIF Assay (CB-NAAT), the LINE Probe Assay (LPA) and the Loop-Mediated Isothermal Amplification (LAMP) are endorsed by WHO for in vitro diagnosis of TB. The present study was carried out to assess the performance of CB-NAAT (Cepheid GeneXpert®) system for the diagnosis of MTB in both pulmonary and extra pulmonary specimens, within the demographic area of south Kashmir, India. Materials and methods: In this study Pulmonary &amp; extra pulmonary specimens received at the Microbiology laboratory, from the new clinically suspected tuberculosis patients were used. The samples received at the laboratory were divided into three portions, one part each was used for AFB direct smear preparation, CB-NAAT and culture, respectively. A smear was reported positive if either the direct or the concentrated smear showed the presence of AFB. The concentrates were cultured on LJ media and incubated for up to 8 weeks.

Low-cost 3D-printed inverted microscope to detect Mycobacterium tuberculosis in a MODS culture

MODS, an assay for diagnosis of tuberculosis and drug-susceptibility, is based in the microscopic observation of the characteristic cords of Mycobacterium tuberculosis colonies grown in liquid media. An inverted optical microscope (100× magnification) is required to observe and interpret MODS cultures. Unfortunately, the cost of commercial inverted microscopes is not affordable in low resource settings. To perform a diagnosis of tuberculosis using the MODS assay, images with modest quality are enough for proper interpretation. Therefore, the use of a high cost commercial inverted optical microscope is not indispensable.In this study, we designed a prototype of an optical inverted microscope created by 3D-printing and based on a smartphone. The system was evaluated with 226 MODS TB positive and 207 MODS TB negative digital images. These images were obtained from 10 sputum samples MODS positive and 10 sputum samples MODS negative. The quality of all images was assessed by a qualified technician, in terms of adequacy to interpret and classify them as positive or negative for tuberculosis.The quality of the images was considered appropriate for MODS interpretation. All the 20 samples were correctly classified (as TB positive/negative) by reading with the prototype 3D-printed inverted microscope.

Lipoarabinomannan as a Point-of-Care Assay for Diagnosis of Tuberculosis: How Far Are We to Use It?

Tuberculosis (TB) is still a severe public health problem; the current diagnostic tests have limitations that delay treatment onset. Lipoarabinomannan (LAM) is a glycolipid that is a component of the cell wall of the bacillus Mycobacterium tuberculosis, the etiologic agent of TB. This glycolipid is excreted as a soluble form in urine. The World Health Organization has established that the design of new TB diagnostic methods is one of the priorities within the EndTB Strategy. LAM has been suggested as a biomarker to develop diagnostic tests based on its identification in urine, and it is one of the most prominent candidates to develop point-of-care diagnostic test because urine samples can be easily collected. Moreover, LAM can regulate the immune response in the host and can be found in the serum of TB patients, where it probably affects a wide variety of host cell populations, consequently influencing the quality of both innate and adaptive immune responses during TB infection. Here, we revised the evidence that supports that LAM could be used as a tool for the development of new point-of-care tests for TB diagnosis, and we discussed the mechanisms that could contribute to the low sensitivity of diagnostic testing.

Evaluation of the Xpert MTB/RIF test accuracy for rapid diagnosis of pulmonary tuberculosis in a tuberculosis endemic area

Aim and objectives: Mycobacterium tuberculosis (MTB) is a causative agent of tuberculosis (TB) which remains as an endemic disease in Iran. One of the most significant steps for control of TB is the fast and accurate diagnosis of patients. Examination of sputum smears is the primary method for TB diagnosis, and the culture method remains as the gold standard. Recently, a molecular assay that named Xpert MTB/RIF assay (Xpert), was introduced for rapid diagnosis of TB. The aim of this study was to evaluate the performance of the Xpert assay for diagnosis of TB in Golestan province. Methods: The TB suspected cases which referred to Tuberculosis Reference laboratory, Gorgan, Iran, from March 2018 to February 2019 were included to this study. The sputum specimens were examined using smear microscopy after Ziehl–Neelsen staining and graded according to the International Union Against Tuberculosis and Lung Disease scale (scanty, 1+, 2+, 3+ and 4+). The Xpert analysis was performed according to the manufacturer's instructions and the provided semi-quantitative results for positive specimens (very low, low, medium and high) were documented. The specimens were cultured into Lowenstein-Jensen (LJ) culture media after decontamination by Petroff's method. Sensitivity and specificity of Xpert and smear microscopy were calculated using a culture as reference standard. Results: Of 102 presumptive TB cases, 17 (16.7%) had culture proven TB. The set of 16 (94·1%) culture-confirmed TB cases were equivalently detected using smear microscopy and Xpert. Compared to the culture method, specificity of Xpert and smear microscopy was 100% (85/85) and 97.6% (83/85), respectively. Both tests had a sensitivity of 94.1% (16/17). When the semi-quantitative results of Xpert were compared with smear microscopy, there was 92.3% agreement for specimens with medium/high results, with those that had 1+ to 3+ scales. Conclusion: The rapid and accurate laboratory diagnosis of TB is one of the most important steps for TB control programs. In this study, the Xpert was effectively used to early and accurate diagnosis of TB in the study area. In the other hand, correlation between the Xpert semi-quantitative results and smear microscopy showed that Xpert could help in evaluation of patient's transmission potential.

ASSESSMENT OF THE MICROSCOPIC– OBSERVATION- DRUG - SUSCEPTIBLITY ASSAY (MODS) AND GENEXPERT ASSAY FOR DIAGNOSIS OF PULMONARY TUBERCULOSIS

Background: Tuberculosis (TB) is considered the most common and highly contagious disease worldwide. Early and accurate diagnosis of TB with detection of multidrug-resistant Mycobacterium tuberculosis (M.TB) is of primary importance for both patient management and infection control. Objectives: To evaluate the performance of Microscopic-Observation Drug-Susceptibility (MODS) assay and GeneXpert MTB/RIF( GeneXpert ) assay in diagnosis of TB and detection of MDR-TB directly from sputum specimens in comparison to the convential diagnostic methods (direct Ziehl-Neelsen "Z-N" stained smear and culture on Lowenstein-Jenson media "LJ"). Patients and Methods: After approval of institutional ethical committee a total of 120 suspected pulmonary TB patients admitted to chest hospitals and dispensaries in Egypt (Giza, Cairo, Alexandria, Dakahlia, Suez, Beheira, Monufia, Qena). Their age was more than 16 years; all of them did not receive any anti tubercular drugs. Sputum samples were collected from each patient and subjected to direct ZN smear, culture and sensitivity of M.TB on LJ and Middlebrook 7H9 medium for MODS assay. Finally Genexpert M.TB/RIF assay was done directly for all sputum samples. Results: Infection rate among males was higher than female (81.7% & 18.7%). Also, it was observed that 56.7% of sputum samples gave positive direct Z-N smear, while 64.2% were positive for both LJ culture &MODS assay. On the other hand, by Genexpert, 68% of cases were positive. The sensitivity and specificity of the various diagnostic methods were studied in relation to LJ culture (gold standard). It was found that MODS assay was rapid that results were obtained in a median of 8 days ranged from (7– 21 days), while median time of LJ was 21dayes ranged from (21– 60). MODS had 100% sensitivity and specificity. Direct smear was less sensitive (88.3%), and GeneXpert was less specific (88.4%), but more rapid results were obtained in 2 hours. Finally, detection of MDR-TB using various methods for 77 isolated M.TB strains ranged from 16.9-19.5% to isoniazid (INH) and 9.8%-18.2% to rifampicin (RMP) by various diagnostic methods with statistically insignificant difference between them. Conclusion: MODS was an optimal alternative rapid diagnostic technique for TB and detection of M.TB and MDR-TB in resource limited settings, results were obtained in a median of 8 days. On the other hand, Gene Xpert was a novel integrated diagnostic PCR analysis in a single hand free step for rapid diagnosis of TB and detection of RMP resistance in clinical specimens in 2 hours but it was expensive.

ASSESSMENT OF THE MICROSCOPIC– OBSERVATION- DRUG - SUSCEPTIBLITY ASSAY (MODS) AND GENEXPERT ASSAY FOR DIAGNOSIS OF PULMONARY TUBERCULOSIS

Background: Tuberculosis (TB) is considered the most common and highly contagious disease worldwide. Early and accurate diagnosis of TB with detection of multidrug-resistant Mycobacterium tuberculosis (M.TB) is of primary importance for both patient management and infection control. Objectives: To evaluate the performance of Microscopic-Observation Drug-Susceptibility (MODS) assay and GeneXpert MTB/RIF( GeneXpert ) assay in diagnosis of TB and detection of MDR-TB directly from sputum specimens in comparison to the convential diagnostic methods (direct Ziehl-Neelsen stained smear and culture on Lowenstein-Jenson media LJ). Patients and Methods: After approval of institutional ethical committee a total of 120 suspected pulmonary TB patients admitted to chest hospitals and dispensaries in Egypt (Giza, Cairo, Alexandria, Dakahlia, Suez, Beheira, Monufia, Qena). Their age was more than 16 years; all of them did not receive any anti tubercular drugs. Sputum samples were collected from each patient and subjected to direct ZN smear, culture and sensitivity of M.TB on LJ and Middlebrook 7H9 medium for MODS assay. Finally Genexpert M.TB/RIF assay was done directly for all sputum samples. Results: Infection rate among males was higher than female (81.7% & 18.7%). Also, it was observed that 56.7% of sputum samples gave positive direct Z-N smear, while 64.2% were positive for both LJ culture &MODS assay. On the other hand, by Genexpert, 68% of cases were positive. The sensitivity and specificity of the various diagnostic methods were studied in relation to LJ culture (gold standard). It was found that MODS assay was rapid that results were obtained in a median of 8 days ranged from (7– 21 days), while median time of LJ was 21dayes ranged from (21– 60). MODS had 100% sensitivity and specificity. Direct smear was less sensitive (88.3%), and GeneXpert was less specific (88.4%), but more rapid results were obtained in 2 hours. Finally, detection of MDR-TB using various methods for 77 isolated M.TB strains ranged from 16.9-19.5% to isoniazid (INH) and 9.8%-18.2% to rifampicin (RMP) by various diagnostic methods with statistically insignificant difference between them. Conclusion: MODS was an optimal alternative rapid diagnostic technique for TB and detection of M.TB and MDR-TB in resource limited settings, results were obtained in a median of 8 days. On the other hand, Gene Xpert was a novel integrated diagnostic PCR analysis in a single hand free step for rapid diagnosis of TB and detection of RMP resistance in clinical specimens in 2 hours but it was expensive.

EFFICACY OF GENE XPERT MTB/RIF ASSAY AND AFB CULTURE IN DIAGNOSIS OF MYCOBACTERIUM TB COMPLEX ON EBUS TBNA

SESSION TITLE: Tuesday Abstract Posters SESSION TYPE: Original Investigation Posters PRESENTED ON: 10/22/2019 01:00 PM - 02:00 PM PURPOSE: Rationale – Tuberculosis and Sarcoidosis are two clinical entity that share same clinical, radiological and pathological features and differentiating between two might be an arduous task. As cultures for M. Tuberculosis in tissue specimens have prolonged turn-around times, rapid molecular methods such as MTB. Rif system has shown great promise in rapid diagnosis of tuberculosis through detection of DNA of M. Tuberculosis and concurrent identification of major mutation that confers rifampicin resistance. We aim to evaluate both efficacy and role of Xpert MTB / RIF Assay and Mycobacterium TB Culture for diagnosis of TB using EBUS TBNA samples in patients with intra-thoracic granulomatous lymphadenopathy. METHODS: This was a retrospective study of randomly selected 100 patients who underwent EBUS TBNA for intra-thoracic granulomatous lymphadenitis with Gene Xpert MTB / RIF Assay and diagnosed with either Tuberculosis or Sarcoidosis RESULTS: EBUS TBNA procedures were performed and a diagnosis of Sarcoidosis (n 17) or Tuberculosis (n 83) was made in 100 patients. Histological results with grades I to II were seen in 74 patients and grade III in 26 patients respectively. Necrotising granulomas were found in 26 / 83 (31.32%) while Non-necrotising granulomas were found in 57 / 83 (68.67%) patients diagnosed with Tuberculosis. Mycobacterium TB Culture was performed in 72 patients diagnosed with Tuberculosis and was positive in 11 patients – 09 / 26 Necrotising Granuloma vs 02 / 57 Non-necrotising Granuloma (34.61% vs 3.5%, P = 0.010). Gene Xpert MTB / RIF Assay were performed in 20 / 83 patients diagnosed with Tuberculosis and was positive in 4 patients – 01 / 07 Necrotising Granuloma vs 03 / 13 Non-necrotising Granuloma (14.30% vs 23.10%, P = 0.547). The Diagnostic Accuracy of Xpert MTB / RIF Assay in diagnosis of Tuberculosis was 70% (95% CI 45.72% to 88.10%), Sensitivity 40%, Specificity 100%, Disease Prevalence 50%, PPV 100%, NPV 62.50%. Of 2 patients finally diagnosed with Sarcoidosis also showed a positive result of Xpert MTB / RIF Assay which possibly suggests casual link between TB and Sarcoidosis CONCLUSIONS: Gene Xpert MTB / RIF Assay can be useful in patients with suspected Pulmonary TB either AFB smear negative or positive due to its rapid and simultaneous detection of Rifampicin resistance and especially beneficial in patients with MDR TB and HIV associated TB. Xpert MTB / RIF Assay has good sensitivity and PPV in context of culture positive intra-thoracic TB lymphadenopathy and can provide immediate diagnosis of likely drug resistance specially in highly endemic area like India CLINICAL IMPLICATIONS: Positive Xpert MTB / RIF Assay with very low MTB detection but culture negative results need to be read cautiously and should be well correlated with clinical and treatment history of patient since Gene Xpert Assay amplifies any DNA, of live or dead bacilli and required to avoid false positive result DISCLOSURES: No relevant relationships by UMANG SHAH, source=Web Response

Development and evaluation of rapid and specific sdaA LAMP-LFD assay with Xpert MTB/RIF assay for diagnosis of tuberculosis

There is need for rapid and cost-effective diagnostic test for tuberculosis. The present study was carried out to design a Loop-mediated isothermal amplification (LAMP) assay combined with lateral flow dipstick (LFD) as a point-of-care method for diagnosis of TB. LAMP assay targeting sdaA gene combined with LFD for sequence specific detection was standardized in user friendly and rapid format. It does not require sophisticated instruments and shows visual results instantly. The LAMP-LFD assay was validated using culture confirmed specimens. The assay was evaluated in a cross-sectional study using respiratory specimens collected from patients in Delhi, India and it showed high concordance with GeneXpert MTB/RIF assay. Lateral flow dipstick method has provided an excellent detection format with LAMP method. The LAMP-LFD assay showed high diagnostic accuracy in comparison to other methods and can be used as a point-of-care test in cost-effective manner.

Feasibility of using Determine TB-LAM to diagnose tuberculosis in HIV-positive patients in programmatic conditions: a multisite study

ABSTRACTBackground: Determine TB-LAM is a urine-based point-of-care assay for diagnosis of tuberculosis (TB).Objective: To assess the feasibility of using LAM to diagnose TB in adult HIV-positive patients in resource-limited settings.Methods: We performed a multi-centric mixed-methods cross-sectional descriptive study in the Democratic Republic of Congo, Malawi, and Mozambique. We used the study and program monitoring tools to estimate user workload, turn-around time (TAT), and proportion of patients with LAM and sputum-based results. We conducted semi-structured interviews to assess the user acceptability of the LAM.Results: The duration of the LAM testing activity per patient was 27 min (IQR 26–29); staff continued with other duties whilst waiting for the result. More patients had a LAM versus a sputum-based result: 168/213 (78.9%) vs 77/213 (36.1%), p < 0.001 in DRC; 691/695 (99.4%) vs 429/695 (61.7%), p < 0.001 in Malawi; and 646/647 (99.8%) vs 262/647 (40.5%), p < 0.001 in Mozambique. The median TAT in minutes when LAM was performed in the consultation room was 75 (IQR 45–188) in DRC, 29 (IQR 27–39) in Malawi, and 36 (IQR 35–41) in Mozambique. In comparison, the overall median TAT for sputum-based tests (smear or GeneXpert) was 2 (IQR 1–3) days. The median time to the first anti-TB drug dose for LAM-positive patients was 155 (IQR 90–504) minutes in DRC and 90 (IQR 60–117) minutes in Mozambique. The overall inter-reader agreement for the interpretation of the LAM result as positive or negative was 98.9%, kappa 0.97 (95%CI 0.96–0.99). Overall, LAM users found the test easy to perform. Major concerns were use of the reading card and the prior requirement of CD4 results before LAM testing.Conclusion: It is feasible to implement the LAM test in low resource settings. The short TAT permitted same day initiation of TB treatment for LAM-positive patients.

The implementation of Xpert MTB/RIF assay for diagnosis of tuberculosis in Nepal: A mixed-methods analysis.

BackgroundTuberculosis (TB) is a major public health problem in low and middle-income countries. Early detection and enrolment of TB cases is a challenge for National TB Programs.ObjectiveTo understand the performance and feasibility for scale-up of Xpert MTB/RIF assay for the TB diagnosis in Nepal.DesignImplementation research employed mixed-method sequential explanatory design. The results of Xpert MTB/RIF assay were analysed in 26 TB diagnostic centres where Xpert machines had been installed before 2015. In-depth interviews and focus group discussions were conducted with stakeholders, purposively selected to represent experiences in centres that were functioning well, poorly or not functioning.ResultsDuring a one-year period in 2015/16, 23,075 Xpert MTB/RIF assays were performed in 21 diagnostic centres with 22,288 people also tested by sputum microscopy. Among these, 77% had concordant (positive or negative) results, demonstrating fair agreement (Kappa score, 0.3) between test results. Test failure and positivity rates in diagnostic centres ranged from 2.6% to 13.4% and 6.5% to 49%, respectively. The number of cartridges per positive result varied from 2.3 to 10.2. Xpert assay was positive in 3314 (15% of all cases) sputum smear microscopy negative cases. Of 4280 bacteriologically confirmed cases by Xpert assay, 355 (8%) were rifampicin resistant. Xpert machines were no longer functioning regularly throughout the year in 5 diagnostic centres. The main barriers for effective implementation of Xpert in Nepal were the lack of: timely supply of cartridges; replacement of damaged modules; maintenance of Xpert machines; and stock verification for timely procurement of cartridges. Inadequate laboratory infrastructure for maintaining functional Xpert equipment further challenges implementation and scale-up.ConclusionThe implementation of Xpert MTB/RIF assay has increased case-finding of TB and MDR-TB in Nepal. However, there is a need to improve laboratory performance and strengthen laboratory infrastructure for optimal utilisation and scale-up of Xpert.

Synthetic Peptides are Better Than Native Antigens for Development of ELISA Assay for Diagnosis of Tuberculosis

Immunodiagnosis of both pulmonary tuberculosis (PTB) and extrapulmonary tuberculosis has remained challenging. In the present work, in-house developed synthetic peptide based antibody detection assay was assessed and validated with antigen based assay for effective diagnosis of tuberculosis (TB). The study population included both tuberculous meningitis (TBM) (n = 60) admitted to Neurology IPD wards of our Institute hospital and PTB cases (n = 57) recruited from high TB endemic zones. Peptides of five highly immunogenic Mycobacterium tuberculosis (MTB) proteins (Ag85B, 45 kDa, HSP-16, CFP-10 and ESAT-6) were designed and synthesized. The designed peptides were evaluated in samples of both TBM and PTB cases, respectively, using in-house developed antibody detection method. The developed tests were further compared and validated with MTB native proteins based antibody detection ELISA. Sensitivity and specificity of peptide assay were significantly higher or almost similar (p < 0.05) in TBM and PTB as compared to native proteins based ELISA. Among all peptides, diagnostic reliability of Ag 85B peptide A1 was higher for both forms of TB. Peptide-based antibody assay is cost effective, simple and may be interchangeable with conventional Antigen based ELISA assays for effective diagnosis of TB in the developing world.

Purified protein derivative immunotherapy for viral warts and interpretation of tuberculin skin tests and interferon gamma release assay for diagnosis of tuberculosis in India

Purified protein derivative immunotherapy for viral warts and interpretation of tuberculin skin tests and interferon gamma release assay for diagnosis of tuberculosis in India

Serial testing of interferon-gamma release assay for diagnosis of tuberculosis in HIV-infected adults

Serial testing of interferon-gamma release assay for diagnosis of tuberculosis in HIV-infected adults

Evaluation of the Xpert MTB/RIF assay for diagnosis of tuberculosis and rifampin resistance in county-level laboratories in Hunan province, China

Background The Xpert MTB/RIF showed high sensitivity and specificity in previous studies carried out in different epidemiological and geographical settings and patient populations in high-burden tuberculosis (TB) countries. However, there were little data obtained by validation or demonstration study of the assay in China. In this study, the performance of Xpert MTB/RIF was investigated in two county-level laboratories in Hunan Province, China. Methods Consecutive patients with suspected pulmonary tuberculosis (PTB) and suspicion for multidrug-resistant tuberculosis (MDR-TB) were enrolled. For each patient suspected to have PTB, three sputum specimens (one spot sputum, one night sputum, and one morning sputum) were collected and each sputum was tested with smear microscopy, Löwenstein-Jensen (LJ) culture, and Xpert MTB/RIF test. For comparison across subgroups and testing methods, 95% confidence intervals were calculated. All analyses were done with SPSS 16.0, and P &lt;0.05 was regarded as significant. Results For case detection, the sensitivity of Xpert MTB/RIF was 100% for smear- and culture-positive TB and 88.6% for smear-negative and culture-positive TB; the overall sensitivity was 94.5% for all culture-positive patients. The specificity was 99.8%. The sensitivity of Xpert MTB/RIF assay was 22.0% in clinical TB patients and the specificity reached 100.0% in the group of patients who are infected with nontuberculous mycobacteria. For the detection of rifampin resistance, the sensitivity of MTB/RIF RIF-resistance detection was 92.9%, and the specificity was 98.7%. Of the 26 Xpert MTB/RIFpositive and RIF-resistant patients confirmed by LJ proportion tests, 20 (76.9%) patients were infected by MDR-TB. Conclusions The Xpert MTB/RIF assay is a highly sensitive and specific method for diagnosis of TB and RIF resistance, which will enable it to have the potential to be used in county-level laboratories and lead to the reduction of the infectious pool and improvements in TB control in China. Further evaluations in county-level laboratories for implementing the assay are still required.

Evaluation of the specificity of intradermal tuberculin and serological tests for diagnosis of tuberculosis in alpaca (Vicugna pacos) and llama (Lama glama) herds under field conditions in Peru

Diagnosis of tuberculosis (TB) in camelids is still a challenge mainly due to the lack of standardised diagnostic assays and the limitations regarding sensitivity (Se) and specificity (Sp) of the...

Xpert MTB/RIF: a game changer for the diagnosis of pulmonary tuberculosis in children?

Xpert MTB/RIF: a game changer for the diagnosis of pulmonary tuberculosis in children?

Comparative study between using QuantiFERON and tuberculin skin test in diagnosis of Mycobacterium tuberculosis infection

AimStudy degree of sensitivity and specificity of IFN-γ as QuantiFERON-TB Gold In-Tube assay in diagnosis of tuberculosis instead of tuberculin test. Subjects and methodsForty patients were included in this study subdivided into two groups. First included 20 patients with sputum positive for tuberculosis, while the second included 20 patients suspected to catch TB infection, guided by: clinical and radiological examinations with smear negative for TB. Control group included 10 clinical and radiological healthy controls previously vaccinated by BCG with positive tuberculin test. All subjects were submitted for full clinical history physical examination routine laboratory tests, plain chest X-ray, sputum study for acid fast Bacilli by Ziehl–Neelsen stain, tuberculin test using Mantoux technique, sputum culture on Lowenstein-Jensen Medium and QuantiFERON-TB Gold In-Tube (QFT-Gold IT) assay. ResultsQFT-Gold IT test sensitivity=100% specificity=100% predictive value positive=100% which means that 100% of the disease positive patients gave positive QFT-Gold IT test and predictive value negative=100% which means that 100% of the disease negative patients gave negative QFT-Gold IT test. Agreement between tuberculin test and QFT-Gold IT test was good agreement where the ‘κ’ was 0.65 (CI=0.39–0.91). Study revealed positive correlation between QuantiFERON level and severity of infection in sputum, which was statistically significant, where ‘r’ was 0.92 and P-value was <0.05. ConclusionQFT-Gold IT, has excellent sensitivity and specificity unaffected by BCG vaccination. Tuberculin test specificity is high in non-BCG-vaccinated populations but low and variable in BCG vaccinated populations.

Assessment of the Xpert MTB/RIF assay for diagnosis of tuberculosis with gastric lavage aspirates in children in sub-Saharan Africa: a prospective descriptive study

Rapid and accurate diagnosis of pulmonary tuberculosis in children remains challenging because of difficulties in obtaining sputum samples and the paucibacillary nature of the disease. The Xpert MTB/RIF assay is useful for rapid diagnosis of childhood tuberculosis with sputum and nasopharyngeal samples. We assessed this assay for the detection of tuberculosis and multidrug resistant (MDR) tuberculosis with gastric lavage aspirate (GLA) samples in children admitted to hospital. We did a prospective study to assess the sensitivity and specificity of the Xpert MTB/RIF assay with GLA samples for the detection of pulmonary tuberculosis and MDR tuberculosis in new paediatric inpatient admissions at the University Teaching Hospital, Lusaka, Zambia. Children aged 15 years or younger were recruited between June, 2011, and May, 2012. GLA and sputum were analysed by standard smear-microscopy, mycobacterial growth indicator tube (MGIT) culture, MGIT drug-susceptibility testing, and the Xpert MTB/RIF assay. Sensitivity of the Xpert MTB/RIF assay was assessed with the Pearson χ(2) or Fishers exact test. Of 930 children, 142 produced sputum and GLA was obtained from 788 non-sputum producers. Culture-positive tuberculosis was identified in 58 (6·2%) of 930 children: ten from sputum producers and 48 from GLA of non-sputum producers. The sensitivity and specificity of the Xpert MTB/RIF assay were similar: sensitivity was 68·8% (95% CI 53·6-80·9) for GLA versus 90·0% (54·1-99·5; p=0·1649) for sputum samples; specificity was 99·3% (98·3-99·8) for GLA and 98·5% (94·1-99·7; p=0·2871) for sputum samples. The Xpert MTB/RIF assay detected an extra 28 tuberculosis cases compared with smear microscopy and was significantly more sensitive than smear microscopy for both sputum (90·0% [54·1-99·5] vs 30·0% [8·1-64·6], p=0·01) and GLA (68·8% [53·6-80·9] vs 25·0% [14·1-40·0], p<0·0001). The assay load did not differ significantly by sample type (p=0·791). 22 children were infected with HIV and tuberculosis and significant differences in assay performance could not be detected when stratifying by HIV status for either sample type. The Xpert MTB/RIF assay detected rifampicin resistance in three GLA samples: two confirmed as MDR tuberculosis and one false positive. Analyses of GLA samples with the Xpert MTB/RIF assay is a sensitive and specific method for rapid diagnosis of pulmonary tuberculosis in children who cannot produce sputum. The single site nature of our study invites caution. European Commission, European Developing Countries Clinical Trials Partnership, and UBS Optimus Foundation.

Comparison of acid-fast bacilli smear and chromatographic immunoassay in patients with active tuberculosis

The aim of this study was to compare acid-fast bacilli smear and chromatographic immunoassay in patients with active tuberculosis (TB). The ability to rapidly detect tubercle bacilli in respiratory secretions was determined for the acid-fast bacilli (AFB) smear in comparison with chromatographic immunoassay in serum samples. A total of 96 respiratory specimens and 96 serum samples were evaluated. The chromatographic immunoassay and AFB were positive in six patients (6.25%) and negative in 90 of 96 specimens (93.75%). The sensitivity, specificity, positive predictive value and negative predictive value of chromatographic immunoassay and AFB were 100%. These results demonstrated the clinical usefulness of chromatographic immunoassay assay for the rapid diagnosis of TB in serum. And compared with the AFB smear, the chromatographic immunoassay assay gives a successful diagnosis. Key words: Tuberculosis, chromatographic immunoassay, acid-fast bacilli smear.