Detection Of Rifampicin Resistance Research Articles

Discordance of the Repeat GeneXpert MTB/RIF Test for Rifampicin Resistance Detection Among Patients Initiating MDR-TB Treatment in Uganda.

BackgroundThe Global Laboratory Initiative (GLI) guidelines recommend repeat for GeneXpertMTB/RIF (XpertMTB/RIF) in patients with a low pretest probability of rifampicin resistance (RR).MethodsThis was a cross-sectional study using results of sputum specimens collected from participants screened for the STREAM 2 trial. We recruited all patients with XpertMTB/RIF RR-TB detected who were referred for RR/multidrug-resistant (MDR) TB treatment initiation at Mulago National Referral Hospital, Kampala, between September 2017 and October 2019. At baseline, smear microscopy, repeat XpertMTB/RIF, Xpert Ultra, and MTBDRplus assays were done on sputum specimens. Culture-based drug susceptibility testing (DST) was performed on discordant specimens. We analyzed the prevalence and factors associated with discordance between initial and repeat XpertMTB/RIF RR and false XpertMTB/RIF RR. False XpertMTB/RIF RR was defined as no RR detected by any of Xpert Ultra, LPA, or culture DST (reference comparator).ResultsA total of 126/130 patients had repeat XpertMTB/RIF results, of whom 97 (77.0%) had M. tuberculosis detected, 81 (83.5%) had RR detected, and 1 (1.0%) had RR indeterminate. The prevalence of discordant XpertMTB/RIF RR was 15/96 (15.6%), whereas false XpertMTB/RIF RR prevalence was 10/96 (10.4%).Low–bacillary load sputum specimens were more likely to have discordant XpertMTB/RIF RR and false XpertMTB/RIF RR results (adjusted odds ratio [aOR], 0.04; 95% CI, 0.00–0.37; P = .01; aOR, 0.02; 95% CI, 0.01–0.35; P = .01, respectively).ConclusionsOur findings show a high false-positive rifampicin resistance rate in low–TB burden patients, which calls for repeat testing in order to prevent unnecessary prescription of anti-MDR-TB therapy.

Xpert MTB/RIF and Xpert Ultra assays for screening for pulmonary tuberculosis and rifampicin resistance in adults, irrespective of signs or symptoms.

Xpert MTB/RIF and Xpert Ultra assays for screening for pulmonary tuberculosis and rifampicin resistance in adults, irrespective of signs or symptoms.

What is the accuracy of the Xpert® MTB/RIF assay for detecting rifampicin resistance?

What is the accuracy of the Xpert® MTB/RIF assay for detecting rifampicin resistance?

Performance of cytology, acid-fast bacilli smear, gene Xpert and mycobacterial cultures in endobronchial ultrasound-transbronchial needle aspiration aspirate in diagnosing mediastinal tuberculous lymphadenitis.

Background:Diagnosis of isolated mediastinal tuberculosis (TB) can be challenging. Endobronchial ultrasound (EBUS) increases the diagnostic yield by direct sonographic visualization of mediastinal and hilar lymph nodes. With the advent of molecular techniques such as Gene Xpert, their addition to the cytology and cultures increases the diagnostic yield and detection of rifampicin resistance (RR) which helps change the effective therapeutic regimen immediately.Materials and Methods:Prospective analysis of all patients undergoing EBUS-guided transbronchial needle aspiration (EBUS-TBNA) with a clinical possibility of TB in isolated mediastinal lymphadenopathy patients at a tertiary care referral center between June 2016 and January 2018. All patients had at least five passes from each node of which two passes from each lymph node sampled in 2 ml of saline for culture and Gene Xpert for microbiologic, pathologic, and molecular analysis as per hospital protocol.Results:Out of 60 patients, 44 were diagnosed to have mediastinal tuberculous lymphadenitis, 8 sarcoidosis, 2 malignancies, and 6 reactive lymphadenitis. TBNA cytology was positive in 40/44 patients (90.9%), out of which 18 patients were culture positive with the sensitivity of 100%, specificity 47.6%, positive predictive value (PPV) 45%, and negative predictive value (NPV) 100%, (P value 0.011). TBNA acid-fast bacilli (AFB) smear was positive in 20/44 patients (45.45%) out of which 12 were culture positive, with sensitivity of 67%, specificity 80.95%, PPV 60%, NPV 85% (P value 0.011). TBNA Gene Xpert was positive in 30/44 patients (68.2%), out of which 6 (13.63%) showed RR-TB and two were cytology negative. Sixteen patients where culture positive with sensitivity of 88.89%, specificity 66.67%, PPV 53.33%, NPV 93.33% (P value of 0.005). TBNA AFB culture was positive in 18/44 patients (40.9%).Conclusion:EBUS-TBNA is an effective and safe diagnostic tool for intrathoracic TB, especially for mediastinal tuberculous lymphadenitis. The combination of various tests increases the diagnostic yield. Mediastinal nodal aspirates traditionally believed to be paucibacillary can still be captured by Gene Xpert.

Spectrum of Drug Resistance in Musculoskeletal Tuberculosis.

Very few studies report resistance pattern exclusively in musculoskeletal tuberculosis (MSK-TB). This study of 100 pus samples from patients of MSK-TB with active disease in whom Mycobacterium tuberculosis (MTB) was detected by cartridge-based nucleic acid amplification test (CBNAAT), revealed the pattern of resistance among newly diagnosed and previously treated cases. Liquid culture and drug susceptibility testing (DST) using MGIT 960 was done for 11 anti-tubercular drugs. Among these 100 cases; 22% were AFB positive; MGIT 960 detected MTB in 58.33% (35/60) new cases and 30.0% (12/40) previously treated cases. Five new and 10 previously treated cases had drug resistance and 12 were detected rifampicin resistance (Rif-R) by CBNAAT. Among new cases MGIT-DST detected mono-INH resistant in 2.86% (1/35), mono-STR resistant in 2.86% (1/35), MDR-TB in 5.7% (2/35) and pre-XDR in 2.9%(1/35).Among previously treated cases Rif-R was found in 10% (4/40) where MTB was not detected by MGIT and MGIT-DST detected mono-INH resistant in 8.33% (1/12); MDR-TB in 8.33% (1/12) and pre-XDR in 33.3%. There were no cases of XDR-TB. High disease burden of various type drug resistance were seen more commonly in previously treated cases and was not uncommon in new cases of MSK-TB. Both CBNAAT and DST are essential for detecting resistance pattern in MSK-TB.

The simple direct slide method is comparable to indirect Lowenstein Jensen proportion culture for detecting rifampicin resistant tuberculosis.

Introduction. Drug resistant tuberculosis remains a worldwide problem that requires prompt diagnosis.Hypothesis/Gap statement. The WHO recommended direct, rapid Xpert MTB/RIF is prohibitively costly, therefore, there is a need to validate a rapid, affordable DST for use in low- and middle-income settings.Aim. The technical performance and time to results of a simple, direct microscopy-based slide DST (SDST) assay for diagnosis of rifampicin-resistant TB was evaluated in Uganda.Methodology. Sputum samples from 122 smear-positive re-treatment TB patients presenting to the TB treatment centre at Uganda's National Referral Hospital, Mulago, Kampala, Uganda were examined. The sputum samples were tested by the direct SDST which was compared to the indirect Lowenstein Jensen Proportion Method (LJDST) method as the gold standard. The time to results was defined as the time from DST setting to results interpretation. The results were further analysed for sensitivity and specificity as well as agreement between LJDST and SDST for rifampicin resistance determination.Results. A total of 117 smear positive sputum samples with valid results for both tests were compared. The median time to results for SDST was 14 days with an interquartile range (IQR) of 10-14 days compared to 60 days with IQR of 60-75 days for LJDST. The number for rifampicin resistance by the gold standard LJDST was 26. The SDST had a sensitivity of 96 % (95 %; CI 81-99 %) and a specificity of 97.8 % (95 %; CI 93-100 %). The Positive Predictive and Negative Predictive values for SDST were 92.3 % (95 %; CI 76.8-99 %) and 98.9 % (95 %; CI 94-100 %), respectively. The kappa agreement between SDST and LJDST was 92.3 %.Conclusion. The SDST was found to be a rapid and accurate direct test for the detection of rifampicin resistance among retreatment TB cases in low-income settings.

Xpert Ultra versus Xpert MTB/RIF for pulmonary tuberculosis and rifampicin resistance in adults with presumptive pulmonary tuberculosis.

Xpert Ultra versus Xpert MTB/RIF for pulmonary tuberculosis and rifampicin resistance in adults with presumptive pulmonary tuberculosis.

The MTB/MDR ELITe MGB® Kit: Performance Assessment for Pulmonary, Extra-Pulmonary, and Resistant Tuberculosis Diagnosis, and Integration in the Laboratory Workflow of a French Center.

A rapid and reliable diagnostic for tuberculosis, including the detection of both rifampicin (RIF) and isoniazid (INH) resistance, is essential for appropriate patient care. Nucleic acid amplification tests are a fast alternative to methods based on Mycobacterium tuberculosis complex (MTB) cultures. Thus, the performance of the MDR/MTB ELITe MGB® Kit on the ELITe InGenius® platform was retrospectively evaluated for MTB detection on pulmonary and extra-pulmonary samples and for RIF/INH resistance detection on MTB strains. The sensitivity and specificity of the kit for MTB detection compared to the MTB culture were 80.0% and 100.0%, respectively. For the antimicrobial susceptibility prediction, the agreement with phenotypic antimicrobial susceptibility testing (AST) was 92.0%. For RIF, the sensitivity was 100.0% and the specificity was 95.5%. For INH, the sensitivity and specificity were 75.0% and 100.0%, respectively. A single RIF false-positive result was obtained for a strain with a low level of RIF resistance that was not detected by phenotypic AST, but carrying a rpoB L452P mutation. INH false-negative results (3) were due to mutations on the katG gene that were not probed by the test. Overall, the MTB/MDR ELITe MGB® Kit presents a strong performance for MTB detection and for the detection of both RIF and INH resistance, with an easy integration in laboratory workflow thanks to its fully automatized system.

USE OF CARTRIDGE BASED NUCLEIC ACID AMPLIFICATION TEST FOR RAPID DETECTION OF MYCOBACTERIUM TUBERCULOSIS IN PULMONARY AND EXTRAPULMONARY TUBERCULOSIS

Objective: Tuberculosis is an airborne infection caused by Mycobacterium tuberculosis. Timely diagnosis and treatment are important to prevent the spread of infection. Cartridge-based nucleic acid amplification test (CBNAAT) provides a valuable tool in the early detection of TB. This study is undertaken to evaluate the utility of CBNAAT for the detection of MTB. Comparison of cartridge-based nucleic acid amplification testing with ZN staining.
 Methods: This prospective observational study was carried out in the Department of Microbiology, BLDEDU’s Shri B. M. Patil Medical College, Hospital and RC and Dr. Karigoudar Diagnostic Laboratory, Vijayapur. A total of 129 samples from patients with the presumptive diagnosis of TB based on history, clinical presentation, and radiological findings were included in the study. All samples were subjected to ZN staining, and Cartridge-based nucleic acid amplification test and data were analyzed.
 Results: The present study showed ZN smear positivity of 7.75% and CBNAAT positivity of 19.38%. CBNAAT sensitivity and specificity were 90% and 86.55, respectively, compared with ZN staining with a significant P value of <0.001.
 Conclusion: CBNAAT helps diagnose TB and detect rifampicin resistance within 2-3 h with high sensitivity and specificity. Rifampicin resistance detection is of great concern, which otherwise leads to treatment failure and on time spread of multidrug resistance TB, leading to increased morbidity and mortality.

Xpert MTB/RIF combined with T-SPOT.TB in the diagnostic value of drug-resistant tuberculous pleurisy

Objective To investigate the diagnostic value of Xpert MTB/RIF combined with T-SPOT.TB in the drug-resistant tuberculous pleurisy. Methods Sixty-two patients with drug-resistant tuberculous pleurisy were selected as tuberculous pleurisy group, and 60 patients with other diseases and pleural effusion admitted to Hebei Province Chest Hospital from January 2014 to December 2019 were selected as the control. General clinical data were collected and analyzed, two groups of pleural effusion samples were collected for detection of Xpert MTB/RIF, T-SPOT.TB and tubercle bacillus culture and drug sensitivity, etc, tubercle bacillus culture of pleural effusion was used as the gold standard for the diagnosis of tuberculous pleurisy. Results The sensitivity of Xpert MTB/RIF, T-SPOT.TB and two parallel methods was 79.0%, 88.7%, 96.8% respectively, the specificity was 90.0%, 81.7%, 95.0% respectively, the diagnostic sensitivity, specificity were significantly higher than those of ADA and acid fast staining (all P <0.05). Taking the tuberclebacillus drug sensitivity as the gold standard, the sensitivity of Xpert MTB/RIF test for rifampicin resistance was 89.47%, and the consistency between the two methods was good ( Kappa =0.900). Conclusion Xpert MTB/RIF combined with T-SPOT.TB in the diagnosis of tuberculous pleurisy can improve the sensitivity and specificity, reduce the misdiagnosis rate, at the same time, Xpert MTB/RIF can quickly detect rifampicin resistance of Mycobacterium tuberculosis in pleural effusion, be conducive to the early diagnosis and treatment of drug-resistant tuberculous pleurisy. 摘要：目的 探讨结核分枝杆菌/利福平耐药基因检测(Xpert MTB/RIF)联合结核感染T细胞斑点检测(T-SPOT.TB)对耐药性结核性胸膜炎诊断及治疗的价值。 方法 选取2014年1月至2019年12月河北省胸科医院收治的62例结 核性胸膜炎患者为结核性胸膜炎组, 选择同期来河北省胸科医院院救治的非结核性胸膜炎患者60例为对照组。分析 比较两组一般资料, 留取两组胸腔积液样本进行Xpert MTB/RIF、T-SPOT.TB、结核菌培养+药敏等检测, 胸腔积液结核 菌培养阳性作为诊断结核性胸膜炎的金标准。 结果 Xpert MTB/RIF、T-SPOT.TB、两种方法并联检测结核性胸膜炎的 灵敏度分别为79.0%、88.7%、96.8%, 特异度分别为90.0%、81.7%、95.0%, 均明显髙于ADA及抗酸染色诊断的敏感度及 特异度, 差异有统计学意义( P 均<0.05)。以结核菌药敏检测为金标准, XpertMTB/RIF检测利福平耐药的敏感度为 89.47%, 两者一致性较好( Kappa =0.900)。 结论 Xpert MTB/RIF联合T-SPOT.TB检测提髙了结核性胸膜炎诊断的敏感 度和特异度, 降低误诊率, 同时XpertMTB/RIF可快速检测出胸水中耐利福平的结核分枝杆菌感染, 有利于耐药结核性 胸膜炎的早期诊断及治疗。

Integrating Xpert MTB/RIF for TB diagnosis in the private sector: evidence from large-scale pilots in Patna and Mumbai, India

BackgroundXpert MTB/RIF (Xpert) has been recommended by WHO as the initial diagnostic test for TB and rifampicin-resistance detection. Existing evidence regarding its uptake is limited to public health systems and corresponding resource and infrastructure challenges. It cannot be readily extended to private providers, who treat more than half of India’s TB cases and demonstrate complex diagnostic behavior.MethodsWe used routine program data collected from November 2014 to April 2017 from large-scale private sector engagement pilots in Mumbai and Patna. It included diagnostic vouchers issued to approximately 150,000 patients by about 1400 providers, aggregated to 18,890 provider-month observations. We constructed three metrics to capture provider behavior with regards to adoption of Xpert and studied their longitudinal variation: (i) Uptake (ordering of test), (ii) Utilization for TB diagnosis, and (iii) Non-adherence to negative results. We estimated multivariate linear regression models to assess heterogeneity in provider behavior based on providers’ prior experience and Xpert testing volumes.ResultsUptake of Xpert increased considerably in both Mumbai (from 36 to 60.4%) and Patna (from 12.2 to 45.1%). However, utilization of Xpert for TB diagnosis and non-adherence to negative Xpert results did not show systematic trends over time. In regression models, cumulative number of Xpert tests ordered was significantly associated with Xpert uptake in Patna and utilization for diagnosis in Mumbai (p-value< 0.01). Uptake of Xpert and its utilization for diagnosis was predicted to be higher in high-volume providers compared to low-volume providers and this gap was predicted to widen over time.ConclusionsPrivate sector engagement led to substantial increase in uptake of Xpert, especially among high-volume providers, but did not show strong evidence of Xpert results being integrated with TB diagnosis. Increasing availability and affordability of a technically superior diagnostic tool may not be sufficient to fundamentally change diagnosis and treatment of TB in the private sector. Behavioral interventions, specifically aimed at, integrating Xpert results into clinical decision making of private providers may be required to impact patient-level outcomes.

Low Cycle Threshold Value in Xpert MTB/RIF Assay May Herald False Detection of Tuberculosis and Rifampicin Resistance: A Study of Two Cases.

We report 2 cases for whom Xpert MTB/RIF falsely signaled rifampicin-resistant tuberculosis, based on unusually low cycle threshold and 3 of 5 probes missing. Other mycobacterial tests were negative. Further optimization of the Xpert MTB/RIF algorithm is warranted.

Accuracy of molecular drug susceptibility testing amongst tuberculosis patients in Karakalpakstan, Uzbekistan.

In this retrospective study, we evaluated the diagnostic accuracy of molecular tests (MT) for the detection of DR-TB, compared to the gold standard liquid-based drug susceptibility testing (DST) in Karakalpakstan. A total of 6670 specimens received in the Republican TB No 1 Hospital Laboratory of Karakalpakstan between January and July 2017 from new and retreatment patients were analysed. Samples were tested using Xpert MTB/RIF and line probe assays (LPA) for the detection of mutations associated with resistance. The sensitivity and specificity of MTs were calculated relative to results based on DST. The accuracy of MT for detection of rifampicin resistance was high, with sensitivity and specificity over 98%. However, we observed reduced sensitivity of LPA for detection of resistance; 86% for isoniazid (95% CI 82-90%), 86% for fluoroquinolones (95% CI 68-96%), 70% for capreomycin (95% CI 46-88%) and 23% for kanamycin (95% CI 13-35%). We show that MTs are a useful tool for rapid and safe diagnosis of DR-TB; however, clinicians should be aware of their limitations. Although detection of rifampicin resistance was highly accurate, our data suggest that resistance mutations circulating in the Republic of Karakalpakstan for other drugs were not detected by the methods used here. This merits further investigation.

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

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

DIAGNOSTIC PERFORMANCE OF ZIEHL-NEELSEN &amp; CBNAAT TECHNIQUES IN PULMONARY TUBERCULOSIS, A RETROSPECTIVE ANALYSIS AT TERTIARY CARE HOSPITAL IN JHALAWAR, RAJASTHAN.

Introduction: Tuberculosis (TB) remains a leading cause of death among infectious diseases worldwide. The advent of the CBNAAT was a revolution in the diagnosis of tuberculosis, especially with high incidence and resource poor regions. It can be used close to the point of care by operators with minimal technical expertise, enabling diagnosis of TB and rifampicin&#x0D; Resistance (RIF) concurrently using unprocessed clinical specimens, in less than 2h.&#x0D; Aim: To evaluate the diagnostic performances of Ziehl-Neelsen &amp; CBNAAT techniques in detection of Pulmonary Tuberculosis.&#x0D; Materials and Methods: We retrospectively reviewed the 2414 sputum samples of suspected pulmonary TB. Sputum samples were subjected for ZN staining and CBNAAT.RIF resistance was detected by CBNAAT.&#x0D; Results: Out of 2414 samples, 751 sputum samples were positive by smear microscopy. 1127 Samples were confirmed positive by CBNAAT examination. Majority of cases, 43.57% were in 21-40 yrs age group.24.40% were females and 75.59% were males. Sensitivity of CBNAAT was 100% for sputum positive cases and sensitivity was 22.6% for sputum negative cases. Overall RIF resistance was detected in 49 (4.4%) cases in present study.&#x0D; Conclusion: CBNAAT provide sensitive detection of tuberculosis and rifampicin resistance directly from untreated sputum in less than 2 hours with minimal hands-on time.&#x0D; Keywords: Cartridge-based nucleic acid amplification tests (CBNAAT), Rifampicin(RIF)

Neurotuberculosis: an update.

Tuberculous (TB) meningitis (TBM), accounting for 70-80% of cases of neurotuberculosis, is one of the most severe forms of extrapulmonary tuberculosis. Two-thirds of new TB cases come from eight countries. Polymorphisms in toll-interleukin-1 receptor domain and in leukotriene A4 hydrolase (LTA4H) gene, affect the risk of inflammation in TBM. The common site of tuberculoma in children is cerebellum, and they may rarely develop tuberculous encephalopathy which has a high mortality. Young females with a high cerebrospinal fluid (CSF) protein have an increased predisposition to develop optochiasmatic arachnoiditis. Spinal TB meningitis may mimic transverse myelitis or Guillain-Barre syndrome. An extra-neural focus of TB should be sought clinically and radiologically as it may indicate safer and more accessible sites for diagnostic samplings. Cartridge-based nucleic acid amplification test (CBNAAT), also known as Genexpert test, is a polymerase chain reaction (PCR)-based method for detection of TB which also detects rifampicin resistance as it targets the rpob gene of mycobacteria. Line probe assays, based on PCR and reverse hybridization methods, identify mutations associated with drug resistance within a week. TBM being a paucibacillary disease, often evades a definite diagnosis and empirical treatment for a minimum of 9months is warranted based on clinical judgement. All TBM patients should receive adjunctive corticosteroids, even those with HIV infection. Drug resistance is strongly associated with previous treatment and bedaquiline as well as delamanid have received approvals for multidrug resistant (MDR) TB. The key principle of managing MDR TB is never to add a single drug to a failing regimen. Correct combination and duration of most effective second line drugs in MDR TB require further modifications. Early shunting should be considered in those with hydrocephalus failing medical management. The single most important determinant of outcome is the stage of TBM at which treatment has been started.

Genexpert rapid detection of rifampicin resistance among patients with pulmonary tuberculosis

The routine conventional phenotypic bacteriological tests available for pulmonary tuberculosis (PTB) diagnosis, such as microscopy by Ziehl Neelsen staining, and Lowenstein Jensen method of solid culture, requires a long time for revealing positivity, resulting in a delayed diagnosis. After Mycobacterium tuberculosis (MTB) genome was discovered, nucleic acid amplification techniques were developed with more rapid detection and identification of rifampicin resistance in respiratory and extra-pulmonary specimens. GeneXpert is a DNA-polymerase chain reaction technique based on NAA, which allows an accurate genotypic method for a quick diagnosis of PTB diagnosis. The aim of the study was to assess retrospectively the yield of genotypic assay GeneXpert in revealing multidrug resistant TB compare to phenotypic confirmation by solid culture. 512 patients with positive and negative smears of suspected PTB were investigated by conventional phenotypic assays. PTB diagnosis assessed by positive genotypic assay and confirmed by phenotypic conventional solid culture method was 78.12%. The yield of GeneXpert in revealing rifampicin resistance was high (n=79/512; 15.43%) with 12.5% additional resistance against isoniazid revealed by positive solid cultures and drug susceptibility test. GeneXpert assay is a very useful method for rapid detection of MTB and drug resistance, which facilitates timely diagnosis and appropriate management of pulmonary tuberculosis.

Extra-pulmonary tuberculosis (EPTB): Study of clinico-demographic profile, and comparison of microbiological diagnostic modalities with special emphasis on role of CBNAAT in detecting rifampicin resistance in fluid specimens

The purpose of our study was to evaluate the place of CBNAAT in the diagnosis of extra-pulmonary TB in fluid specimens, and also detecting drug resistance in comparison to the Gold Standard - MGIT Bactec Culture. Material and Methods: In prospective observational study of 2 yrs. among 165 EPTB cases, we studied the clinical presentation, compared the results of microbiological diagnostic modalities (ZN smear, CBNAAT, MGIT Culture) and evaluated the drug resistance. Statistics: Used Chi square test via software STATA 15 and calculated p value.Results: The positivity rate of CBNAAT (31.30%) was higher than ZN smear (23.92%), which was in turn higher than MGIT culture (9.9%) and CBNAAT was able to detect Rifampicin resistance in 16.66% EPTB cases. Conclusion: We concluded that, the role of CBNAAT in fluid specimens should not be undermined and should be preferred over the “Gold standard” MGIT culture.

Study of diagnostic role of GeneXpert test in patients with pulmonary tuberculosis at El-Mahalla Chest Hospital

Background Tuberculosis (TB) is a serious health problem in middle-income and low-income countries and needs rapid diagnosis and treatment. Xpert MTB/RIF assay provides early results by simultaneous detection of Mycobacterium tuberculosis (MTB) and rifampicin (RIF) resistance. Aim To evaluate the performance of GeneXpert MTB/RIF technique in diagnosing patients with pulmonary TB at El-Mahalla Chest Hospital, Egypt. Patients and methods Data of pulmonary TB were retrospectively analyzed between February 2017 and February 2018 from patient files and included laboratory results regarding Ziehl–Neelsen (ZN) smear microscopy, GeneXpert assay, and culture. Patients were divided into group I, having confirmed TB, where MTB was detected, and group II, having unconfirmed and unlikely TB, where MTB was not detected. Results A total of 150 patients were recruited. Overall, 80% were males, and the median age was 45.2±15.1 years. Positivity of ZN smear for TB bacilli was 61.1%, positivity of GeneXpert MTB was 65.9%, and culture positivity was 67.3%. GeneXpert sensitivity and negative predictive value were 96 and 96%, respectively, and were found to be higher when compared with ZN smear with 89 and 90%, respectively. Specificity of both techniques was 100%. Previous history of TB was an independent predictor for GeneXpert positivity, whereas both previous history of TB and positive sputum smear were independent predictors of RIF resistance. Conclusion GeneXpert has a higher diagnostic value compared with ZN smear, providing a faster diagnosis for pulmonary TB than culture, and it can detect RIF resistance.

GeneXpert: A new tool for the rapid detection of rifampicin resistance in mycobacterium tuberculosis

Background: present study was planned to evaluate the diagnostic accuracy of GeneXpert assay for the detection of rifampicin resistance in mycobacterium tuberculosis using conventional drug susceptibility testing as gold standard. Methods and materials: This cross-sectional study was conducted at Jinnah Hospital, Lahore,/Allama Iqbal Medical College, Lahore, Pakistan, from January 2012 to December 2014, and comprised clinically and radiologically diagnosed tuberculosis suspected cases. Pulmonary and extra-pulmonary specimens were collected from strong tuberculosis suspects. All specimens were processed for Ziehl Neelsen staining, Lowenstein-Jensen culture and GeneXpert assay. All mycobacterium tuberculosis positive cases on Lowenstein-Jensen culture were further processed for drug susceptibility testing. Results: Of the 2,200 cases, 840(49.46%) were positive for mycobacterium tuberculosis on GeneXpert assay. Of them, 134(15.6%) cases showed rifampicin resistance on GeneXpert assay. The sensitivity, specificity, positive predictive value and negative predictive value of GeneXpert assay for rifampicin resistance were 127(98.3%), 704(99.1%), 127(94.7%) and 704(99.4%), respectively, by comparing the results with drug susceptibility testing. Conclusion: GeneXpert assay was an extremely helpful diagnostic tool for the detection of rifampicin resistance in tuberculosis suspects with fairly high sensitivity and specificity along with short turnout time