Comparison of Xpert MTB/RIF Assay and the Conventional Sputum Microscopy in Detecting Mycobacterium tuberculosis in Northern Thailand

Early detection of tuberculosis: a systematic review

Tuberculosis remains a significant global health challenge. Tuberculosis affects millions of individuals worldwide. Early detection of tuberculosis plays a relevant role in the management of treatment of tuberculosis. This systematic review will analyze the findings of several published studies on the topic of the early detection of tuberculosis. This systematic review highlights their methodologies and limitations as well as their contributions to our understanding of this pressing issue. Early detection of tuberculosis can be achieved through tuberculosis screening for contacts. Comprehensive health education for household contacts can be used as early detection. The in-house deep learning models can be used in the X-ray used for automatic detection of tuberculosis. Interferon gamma release assay, routine passive and active case detection, portable X-ray and nucleic acid amplification testing, and highly sensitive enzyme-linked immunosorbent assay tests play critical roles in improving tuberculosis detection.

Evaluation of the GeneXpert MTB/RIF to diagnose tuberculosis in a public health laboratory

OBJECTIVES

To evaluate the performance of geneXpert MTB/Rif versus conventional methods (bacilloscopy and culture) in the diagnosis of tuberculosis in a Central Public Health Laboratory (LACEN, Tocantins), Northern Brazil.

METHODS

Retrospective study, with information from 1,973 suspected cases of tuberculosis from patients treated from January 2015 to December 2020.

RESULTS

From the culture (reference standard), the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of the geneXpert MTB/Rif were 100%, 97%, 74%, 100%, and 97%, respectively, against 85%, 98%, 80%, 98%, and 97% of bacilloscopy.

CONCLUSIONS

The geneXpert MTB/Rif performed similarly to culture and better than bacilloscopy. Although positive cases with negative culture should be evaluated with caution, its routine use is important for the early detection of tuberculosis.

Performance of GeneXpert MTB/RIF for Diagnosing Tuberculosis Among Symptomatic Household Contacts of Index Patients in South Africa

BACKGROUND

We describe the performance of GeneXpert MTB/RIF (Xpert) for diagnosing tuberculosis (TB) among symptomatic household contacts (HHCs) of rifampicin-resistant and drug-sensitive index cases.

METHODS

We conducted a cross-sectional study among HHCs of recently diagnosed (<2 weeks) smear-positive and Xpert-positive index cases in the Bojanala District, South Africa. The HHCs were screened for TB symptoms; persons with ≥1 TB symptom provided 1 sputum for smear microscopy, Xpert, and mycobacterial growth indicator tube (MGIT) culture. Diagnostic test performance of Xpert was determined using MGIT as the reference standard.

RESULTS

From August 2013 to July 2015, 619 HHCs from 216 index cases were enrolled: 60.6% were female, median age was 22 years (interquartile range, 9-40), and 126 (20.4%) self-reported/tested human immunodeficiency virus positive. A total of 54.3% (336 of 619) of contacts had ≥1 TB symptom (cough, fever, night sweats, weight loss), 297 of 336 (88.4%) of which provided a sputum; 289 (97.3%) had complete testing and 271 were included in the analysis. In total, 42 (6.8%) of 619 HHCs had microbiologically confirmed TB. The MGIT identified 33 HHCs as positive for Mycobacterium tuberculosis; of these, 7 were positive on Xpert resulting in a sensitivity of 21.2% (95% confidence interval [CI], 9.0-38.9), specificity of 98.3% (95% CI, 95.6-99.5), positive predictive value of 63.6% (95% CI, 30.8-89.1), and negative predictive value of 90.0 (95% CI, 85.7-93.4).

CONCLUSIONS

Among symptomatic HHCs investigated for TB, Xpert performed suboptimally compared with MGIT culture. The poor performance of Xpert for diagnosing TB suggests that a more sensitive test, such a Xpert Ultra or culture, may be needed to improve yield of contact investigation, where feasible.

Evaluation of Xpert MTB/RIF with microscopy and culture for the diagnosis of tuberculosis in a referral laboratory in Nepal

Sputum microscopy and Xpert MTB/RIF are the primary rapid diagnostic methods for tuberculosis (TB) in Nepal. Disagreements among Xpert, microscopy, and culture, for example, cases with Xpert positive and microscopy negative, were frequently observed in Nepal including in our reference laboratory. The objective of this study was to compare the effectiveness of Xpert with culture and microscopy for TB diagnosis in Nepal. A total of 125 TB suspected sputum samples were processed for Xpert, microscopy, and culture. The Xpert results when compared with culture showed 100% sensitivity and 97.4% specificity with an excellent agreement (kappa = 0.96), whereas microscopy showed the sensitivity and specificity of 43.2% and 98.7%, respectively, with a moderate agreement (kappa = 0.4). The sensitivity and specificity of microscopy, when compared with Xpert, were 43.5% and 100%, respectively. The majority of Xpert positive samples of a medium MTB detection and all samples of low and very low MTB detection were missed by microscopy. Our study showed that Xpert MTB/RIF is a reliable tool for the diagnosis and management of TB in Nepal. Because of its high cost and sustainability, alternative simple and rapid diagnostic methods with a similar efficiency would be helpful for TB control in Nepal.

Epidemiology of molecular probes in Xpert MTB/RIF assay in Khyber Pakhtunkhwa, Pakistan

Regardless of a plethora of advanced diagnostics, TB and drug resistance remains a principal killer. We proposed gold nanoparticles (AuNPs) attached with probes to enhance the efficiency of GeneXpert MTB/RIF assay instead of conventional dye probes for molecular detection. A total of 15,000 samples were collected from TB suspects and subjected to Xpert MTB/RIF assay, where 6800 (45.3%) were detected as MTB positive, 280 (4.3%) were detected to harbor mutations in the RRDR, while invalid /errors were found in 690 (4.6%) cases. The mutations were detected by probe E, 199 (71.1%), while probes B and D, 30 and 26 (10% and 9%), respectively. In the Xpert MTB/RIF Assay were found mutations picked by probes E and B codons 529-533 (71%) and 512-518 (10%), respectively. The fast-rising works of TB nano-diagnostics, of Xpert probes, may improve by the applications of gold nanoparticle probes.

Prevalence of rifampicin resistance tuberculosis among HIV/TB coinfected patients in Benue State, Nigeria

Introduction

the emergence of HIV/TB co-infection has changed the global health landscape globally, particularly in sub-Saharan Africa and Asia with a high prevalence rate. It has further worsened and compound patient diagnosis, treatment/management approach and infection control. Rifampicin resistance TB (RR-TB) is a good indicator of treatment failure and infection control in the community. This study determines the prevalence of RR-TB among HIV/TB coinfected patients in Benue State, Nigeria.

Methods

the case-control study was carried out at Federal Medical Centre, Makurdi and General Hospital, Otupko, between January 2017 and February 2018. One thousand and ten suspected tuberculosis and HIV patients were enrolled in the study, diagnosed according to WHO guidelines. Sputum samples were collected and then analyzed by acid-fast bacilli smear test and GeneXpert MTB/RIF assay.

Results

overall prevalence of tuberculosis by acid-fast test was 74 (7.3%), 171 (16.93%) by GeneXpert assay and 2.18% by RR-TB test respectively. Significant difference was observed between the detection technique and demographic variables, high prevalence among urban patient compared to rural (8.85%vs 5.40%; X²= 4.38; P = 0.036) and ethnic background of the patients (X²= 23.21; P = 0.000) by acid fast test. With GeneXpert, high prevalence recorded among patient within age-group15-45years (X²= 8.01; P = 0.046) and ethnic group (X²= 6.30; P = 0.044). The occurrence of HIV/TB co-infection was less associated with Idoma ethnic group (COR; 0.440; 95% C.I; 0.246 - 0.786).

Conclusion

the relatively high prevalence of HIV/TB co-infection and RR-TB is a tremendous public health threat, considering society's attendant implication. Further surveillance studies are needed to evaluate the situation in Benue State better.

Diagnostic performance of GeneXpert in tuberculosis-HIV co-infected patients at Asella Teaching and Referral Hospital, Southeastern Ethiopia: A cross sectional study

BACKGROUND

GeneXpert is a new introduction in the diagnostic modality to fight tuberculosis (TB) among people living with HIV (PLHIV) under the program of intensified TB case finding. This study aimed to evaluate the diagnostic performance of GeneXpert under the program of intensified TB cases finding among PLHIV.

METHODS

Cross-sectional study was conducted by recruiting individuals attending an HIV clinic from February 2018 to January 2019. Data on clinical parameters were collected using a standardized tool. Two-morning sputum samples were collected and processed for smear microscopy and GeneXpert. SPSS 21 used for data analysis. Proportion, percentage, and mean with SD were used to describe variables. Univariate and multivariable logistic regressions were used to assess factors associated with the GeneXpert. Values for which the 95% CI interval not includes 1 and for which P<0.05 were considered significant.

RESULT

A total of 384 presumptive TB-HIV co-infection cases were included, of which 166 (43%) were diagnosed to have TB. Fifty-four (32.5%) TB cases were smear AFB positive while 79 (47.7%) TB cases were GeneXpert positive. The GeneXpert detection rate was almost two-fold of that of smear microscopy and all smear positive TB cases were detected by GeneXpert. Moreover, GeneXpert was able to detect an additional third of TB confirmed cases among smear AFB negative cases. Advanced stage of the disease, high viral load and presence of anemia were significantly associated with TB. The WHO TB screening tool remained least sensitive with the lowest positive predictive value.

CONCLUSION

GeneXpert demonstrated two-fold case detection rate compared to the sputum smear microscopy and additional third TB case detection rate among smear AFB negative cases. Clinical screening tool for evaluation of TB-HIV co-infection showed poor performance in TB case notification.

Which sample type is better for Xpert MTB/RIF to diagnose adult and pediatric pulmonary tuberculosis?

Objective: This review aimed to identify proper respiratory-related sample types for adult and pediatric pulmonary tuberculosis (PTB), respectively, by comparing performance of Xpert MTB/RIF when using bronchoalveolar lavage (BAL), induced sputum (IS), expectorated sputum (ES), nasopharyngeal aspirates (NPAs), and gastric aspiration (GA) as sample.

Methods: Articles were searched in Web of Science, PubMed, and Ovid from inception up to 29 June 2020. Pooled sensitivity and specificity were calculated, each with a 95% confidence interval (CI). Quality assessment and heterogeneity evaluation across included studies were performed.

Results: A total of 50 articles were included. The respective sensitivity and specificity were 87% (95% CI: 0.84–0.89), 91% (95% CI: 0.90–0.92) and 95% (95% CI: 0.93–0.97) in the adult BAL group; 90% (95% CI: 0.88–0.91), 98% (95% CI: 0.97–0.98) and 97% (95% CI: 0.95–0.99) in the adult ES group; 86% (95% CI: 0.84–0.89) and 97% (95% CI: 0.96–0.98) in the adult IS group. Xpert MTB/RIF showed the sensitivity and specificity of 14% (95% CI: 0.10–0.19) and 99% (95% CI: 0.97–1.00) in the pediatric ES group; 80% (95% CI: 0.72–0.87) and 94% (95% CI: 0.92–0.95) in the pediatric GA group; 67% (95% CI: 0.62–0.72) and 99% (95% CI: 0.98–0.99) in the pediatric IS group; and 54% (95% CI: 0.43–0.64) and 99% (95% CI: 0.97–0.99) in the pediatric NPA group. The heterogeneity across included studies was deemed acceptable.

Conclusion: Considering diagnostic accuracy, cost and sampling process, ES was a better choice than other sample types for diagnosing adult PTB, especially HIV-associated PTB. GA might be more suitable than other sample types for diagnosing pediatric PTB. The actual choice of sample types should also consider the needs of specific situations.

Can the High Sensitivity of Xpert MTB/RIF Ultra Be Harnessed to Save Cartridge Costs? Results from a Pooled Sputum Evaluation in Cambodia

Despite the World Health Organization recommending the use of rapid molecular tests for diagnosing tuberculosis (TB), uptake has been limited, partially due to high cartridge costs. Other infectious disease programs pool specimens to save on diagnostic test costs. We tested a sputum pooling strategy as part of a TB case finding program using Xpert MTB/RIF Ultra (Ultra). All persons were tested with Ultra individually, and their remaining specimens were also grouped with 3–4 samples for testing in a pooled sample. Individual and pooled testing results were compared to see if people with TB would have been missed when using pooling. We assessed the potential cost and time savings which different pooling strategies could achieve. We tested 584 individual samples and also grouped them in 153 pools for testing separately. Individual testing identified 91 (15.6%) people with positive Ultra results. One hundred percent of individual positive results were also found to be positive by the pooling strategy. Pooling would have saved 27% of cartridge and processing time. Our results are the first to use Ultra in a pooled approach for TB, and demonstrate feasibility in field conditions. Pooling did not miss any TB cases and can save time and money. The impact of pooling is only realized when yield is low.

Isolation and Immunological Detection of Mycobacterium Tuberculosis from HIV and Non-HIV Patients in Benue State, Nigeria

BACKGROUND

Immunological techniques are important tools for tuberculosis epidemiology; although its use is underutilized in Nigeria. In this study, we report the epidemiological outlook of Mycobacterium tuberculosis among HIV patients in Benue State, Nigeria.

METHODS

Sputum samples were collected from 425 suspected TB patients from July 2016 to February 2018 and subjected to acid-fast microscopy, GeneXpert MTB/RIF, processed using NALC-NaOH and cultured on Lowenstein-Jensen media. The isolates obtained were identified by SD-Bioline® assay.

RESULTS

The prevalence of TB by acid-fast microscopy was 35(15.9%). The prevalence of TB by acid-fast bacilli was significantly (χ2 = 8.458; P = 0.003) highest among the 15-34 years age group (22.0%) compared with other age groups. TB prevalence was significantly (χ2 = 4.751; P = 0.029) higher among patients from rural areas than those from urban center (23.8% vs 14.1%). GeneXpert assay detected 64(15.1%) TB cases of which patients from rural areas had significantly (χ2 = 8.104; P = 0.017) higher prevalence of TB than patients from urban areas (23.8% vs 12.9%). The overall rifampicin resistance TB was 3.1%. Also, patients from rural areas had significantly (χ2 = 10.625; P = 0.005) higher rifampicin resistance compared with patient from urban areas (8.3% vs 1.3%). Of the 126(29.7%) mycobacterial isolates, 42(33.33%) were identified as MTBC and 84 (66.67%) as NTM by SD-Bioline® assay.

CONCLUSIONS

The study revealed that Mycobacterium tuberculosis infection is still a major public health problem, with relatively high prevalence rate of rifampicin resistance among HIV positive patients. Further studies are needed for early detection and treatment intervention necessary for infection control.

Xpert MTB/RIF assay for the diagnosis of rifampicin resistance in different regions: a meta-analysis

Background

To estimate the diagnostic accuracy of Xpert MTB/RIF for rifampicin resistance in different regions, a meta-analysis was carried out.

Methods

Several databases were searched for relevant studies up to March 3, 2019. A bivariate random-effects model was used to estimate the diagnostic accuracy.

Results

We identified 97 studies involving 26,037 samples for the diagnosis of rifampicin resistance. The pooled sensitivity, specificity and AUC of Xpert MTB/RIF for rifampicin resistance detection were 0.93 (95% CI 0.90–0.95), 0.98 (95% CI 0.96–0.98) and 0.99 (95% CI 0.97–0.99), respectively. For different regions, the pooled sensitivity were 0.94(95% CI 0.89–0.97) and 0.92 (95% CI 0.88–0.94), the pooled specificity were 0.98 (95% CI 0.94–1.00) and 0.98 (95% CI 0.96–0.99), and the AUC were 0.99 (95% CI 0.98–1.00) and 0.99 (95% CI 0.97–0.99) in high and middle/low income countries, respectively. The pooled sensitivity were 0.91 (95% CI 0.87–0.94) and 0.91 (95% CI 0.86–0.94), the pooled specificity were 0.98 (95% CI 0.96–0.99) and 0.98 (95% CI 0.96–0.99), and the AUC were 0.98 (95% CI 0.97–0.99) and 0.99 (95% CI 0.97–0.99) in high TB burden and middle/low prevalence countries, respectively.

Conclusions

The diagnostic accuracy of Xpert MTB/RIF for rifampicin resistance detection was excellent.

Xpert MTB/RIF and Xpert MTB/RIF Ultra for pulmonary tuberculosis and rifampicin resistance in adults

BACKGROUND

Xpert MTB/RIF (Xpert MTB/RIF) and Xpert MTB/RIF Ultra (Xpert Ultra), the newest version, are the only World Health Organization (WHO)-recommended rapid tests that simultaneously detect tuberculosis and rifampicin resistance in persons with signs and symptoms of tuberculosis, at lower health system levels. A previous Cochrane Review found Xpert MTB/RIF sensitive and specific for tuberculosis (Steingart 2014). Since the previous review, new studies have been published. We performed a review update for an upcoming WHO policy review.

OBJECTIVES

To determine diagnostic accuracy of Xpert MTB/RIF and Xpert Ultra for tuberculosis in adults with presumptive pulmonary tuberculosis (PTB) and for rifampicin resistance in adults with presumptive rifampicin-resistant tuberculosis.

SEARCH METHODS

We searched the Cochrane Infectious Diseases Group Specialized Register, MEDLINE, Embase, Science Citation Index, Web of Science, Latin American Caribbean Health Sciences Literature, Scopus, the WHO International Clinical Trials Registry Platform, the International Standard Randomized Controlled Trial Number Registry, and ProQuest, to 11 October 2018, without language restriction.

SELECTION CRITERIA

Randomized trials, cross-sectional, and cohort studies using respiratory specimens that evaluated Xpert MTB/RIF, Xpert Ultra, or both against the reference standard, culture for tuberculosis and culture-based drug susceptibility testing or MTBDRplus for rifampicin resistance.

DATA COLLECTION AND ANALYSIS

Four review authors independently extracted data using a standardized form. When possible, we also extracted data by smear and HIV status. We assessed study quality using QUADAS-2 and performed meta-analyses to estimate pooled sensitivity and specificity separately for tuberculosis and rifampicin resistance. We investigated potential sources of heterogeneity. Most analyses used a bivariate random-effects model. For tuberculosis detection, we first estimated accuracy using all included studies and then only the subset of studies where participants were unselected, i.e. not selected based on prior microscopy testing.

MAIN RESULTS

We identified in total 95 studies (77 new studies since the previous review): 86 studies (42,091 participants) evaluated Xpert MTB/RIF for tuberculosis and 57 studies (8287 participants) for rifampicin resistance. One study compared Xpert MTB/RIF and Xpert Ultra on the same participant specimen.Tuberculosis detectionOf the total 86 studies, 45 took place in high tuberculosis burden and 50 in high TB/HIV burden countries. Most studies had low risk of bias.Xpert MTB/RIF pooled sensitivity and specificity (95% credible Interval (CrI)) were 85% (82% to 88%) and 98% (97% to 98%), (70 studies, 37,237 unselected participants; high-certainty evidence). We found similar accuracy when we included all studies.For a population of 1000 people where 100 have tuberculosis on culture, 103 would be Xpert MTB/RIF-positive and 18 (17%) would not have tuberculosis (false-positives); 897 would be Xpert MTB/RIF-negative and 15 (2%) would have tuberculosis (false-negatives).Xpert Ultra sensitivity (95% confidence interval (CI)) was 88% (85% to 91%) versus Xpert MTB/RIF 83% (79% to 86%); Xpert Ultra specificity was 96% (94% to 97%) versus Xpert MTB/RIF 98% (97% to 99%), (1 study, 1439 participants; moderate-certainty evidence).Xpert MTB/RIF pooled sensitivity was 98% (97% to 98%) in smear-positive and 67% (62% to 72%) in smear-negative, culture-positive participants, (45 studies). Xpert MTB/RIF pooled sensitivity was 88% (83% to 92%) in HIV-negative and 81% (75% to 86%) in HIV-positive participants; specificities were similar 98% (97% to 99%), (14 studies).Rifampicin resistance detectionXpert MTB/RIF pooled sensitivity and specificity (95% Crl) were 96% (94% to 97%) and 98% (98% to 99%), (48 studies, 8020 participants; high-certainty evidence).For a population of 1000 people where 100 have rifampicin-resistant tuberculosis, 114 would be positive for rifampicin-resistant tuberculosis and 18 (16%) would not have rifampicin resistance (false-positives); 886 would be would be negative for rifampicin-resistant tuberculosis and four (0.4%) would have rifampicin resistance (false-negatives).Xpert Ultra sensitivity (95% CI) was 95% (90% to 98%) versus Xpert MTB/RIF 95% (91% to 98%); Xpert Ultra specificity was 98% (97% to 99%) versus Xpert MTB/RIF 98% (96% to 99%), (1 study, 551 participants; moderate-certainty evidence).

AUTHORS' CONCLUSIONS

We found Xpert MTB/RIF to be sensitive and specific for diagnosing PTB and rifampicin resistance, consistent with findings reported previously. Xpert MTB/RIF was more sensitive for tuberculosis in smear-positive than smear-negative participants and HIV-negative than HIV-positive participants. Compared with Xpert MTB/RIF, Xpert Ultra had higher sensitivity and lower specificity for tuberculosis and similar sensitivity and specificity for rifampicin resistance (1 study). Xpert MTB/RIF and Xpert Ultra provide accurate results and can allow rapid initiation of treatment for multidrug-resistant tuberculosis.

Naked eye detection of the Mycobacterium tuberculosis complex by recombinase polymerase amplification-SYBR green I assays

BACKGROUND

Rapid diagnosis of Mycobacterium tuberculosis (Mtb) is key to controlling the spread of tuberculosis, which is a global health concern. In this study, isothermal recombinase polymerase amplification (RPA) was developed to detect specific targets of Mtb, IS6110 and IS1081. Additionally, SYBR Green I was used for endpoint detection of the RPA products by the naked eye.

METHOD

A total of 146 genomic Mtb DNA samples and 24 genomic nontuberculous mycobacteria (NTM) DNA samples were amplified at IS6110 and IS1081 by RPA. After a complete amplification, the RPA amplicons were examined by agarose gel electrophoresis (RPA-AGE) and SYBR Green I (RPA-S) assays. The performance of the RPA assays was evaluated by comparing them to a conventional PCR.

RESULTS

The RPA assay demonstrated to have a good capability to differentiate Mtb from NTM with a very short turnaround time at a constant temperature. Compared to conventional PCR, the sensitivities and specificities of RPA-AGE for IS6110 and IS1081 were 100%. The specificity of RPA-S was 100% for both targets; however, its sensitivities for IS6110 and IS1081 were 97.95% and 99.32%, respectively. The limits of detection of IS6110 RPA-AGE and RPA-S were 0.05 and 0.5 ng, respectively, while the LODs of IS1081 RPA-AGE and RPA-S were 0.00005 and 0.05 ng, respectively. Both RPA assays showed a satisfying diagnostic specificity, with no cross-reaction with other bacteria.

CONCLUSION

A rapid, sensitive, naked eye RPA assay can be integrated into point-of-care diagnosis for Mtb detection, especially in remote areas where laboratory instrument resources are limited.

High HIV and active tuberculosis prevalence and increased mortality risk in adults with symptoms of TB: a systematic review and meta-analyses

INTRODUCTION

HIV and tuberculosis (TB) remain leading causes of preventable death in low- and middle-income countries (LMICs). The World Health Organization (WHO) recommends HIV testing for all individuals with TB symptoms, but implementation has been suboptimal. We conducted a systematic literature review and meta-analyses to estimate HIV and TB prevalence, and short-term (two to six months) mortality, among adults with TB symptoms at community- and facility level.

METHODS

We searched Embase, Global Health and MEDLINE databases, and reviewed conference abstracts for studies reporting simultaneous HIV and TB screening of adults in LMICs published between January 2003 and December 2017. Meta-analyses were performed to estimate prevalence of HIV, undiagnosed TB and mortality risk at different health system levels.

RESULTS

Sixty-two studies including 260,792 symptomatic adults were identified, mostly from Africa and Asia. Median HIV prevalence was 19.2% (IQR: 8.3% to 40.4%) at community level, 55.7% (IQR: 20.9% to 71.2%) at primary care level and 80.7% (IQR: 73.8% to 84.6%) at hospital level. Median TB prevalence was 6.9% (IQR: 3.3% to 8.4%) at community, 20.5% (IQR: 11.7% to 46.4%) at primary care and 36.4% (IQR: 22.9% to 40.9%) at hospital level. Median short-term mortality was 22.6% (IQR: 15.6% to 27.7%) among inpatients, 3.1% (IQR: 1.2% to 4.2%) at primary care and 1.6% (95% CI: 0.45 to 4.13, n = 1 study) at community level.

CONCLUSIONS

Adults with TB symptoms have extremely high prevalence of HIV infection, even when identified through community surveys. TB prevalence and mortality increased substantially at primary care and inpatient level respectively. Strategies to expand symptom-based TB screening combined with HIV and TB testing for all symptomatic individuals should be of the highest priority for both disease programmes in LMICs with generalized HIV epidemics. Interventions to reduce short-term mortality are urgently needed.

Evaluation of the Xpert® MTB/RIF assay and microscopy for the diagnosis of Mycobacterium tuberculosis in Namibia

BACKGROUND

Tuberculosis (TB) kills approximately two million people and infects around nine million worldwide annually. Its proper management, especially in resource-limited settings, has been hindered by the lack of rapid and easy-to-use diagnostic tests. Sputum smear microscopy remains the cheapest, readily available diagnostic method but it only identifies less than half of the patients with a HIV/TB co-infection because the bacilli would have disseminated from the lungs to other areas of the body. The fully automated Xpert® MTB/RIF assay is a promising innovation for diagnosing TB and detecting resistance to rifampicin. This study aimed to evaluate the use of Xpert® MTB/RIF assay and microscopy in the diagnosis of Mycobacterium tuberculosis in Namibia, by determining the disease's epidemiology and calculating the proportion of cases infected just with TB and those with a resistance to rifampicin among the total suspected cases of TB in the country.

METHODS

This retrospective study analysed TB cases that were diagnosed using both the Xpert® MTB/RIF assay and microscopy. Data were collected from patient records from the Meditech laboratory information system of the Namibia Institute of Pathology for the time period of July 2012-April 2013. Data from 13 regions were collected.

RESULTS

The total number of specimens collected from patients with symptoms of pulmonary TB was 1 842. Of these, 594 (32.20%) were found to be positive for MTB by Xpert® MTB/RIF assay, out of which 443 (24.05%) were also found to be positive by microscopy. The remainder was negative. The male patients were more resistant to rifampicin when compared to the female patients.

CONCLUSIONS

Tuberculosis is widely distributed throughout Namibia, with slightly more males infected than females. Most TB patients are also co-infected with HIV. Both microscopy and Xpert® MTB/RIF assay are crucial for the diagnosis of TB in the country. Screening diagnostic efforts should focus on the sexually active HIV positive male population who could be the source of more RIF-resistant TB than females to prevent its spread.

Rifampicin-resistance pattern of Mycobacterium tuberculosis and associated factors among presumptive tuberculosis patients referred to Debre Markos Referral Hospital, Ethiopia: a cross-sectional study

BACKGROUND

Prevailing data on rifampicin-resistant M. tuberculosis is essential for early management of MDR-TB. Therefore, this study was conducted to determine the prevalence of rifampicin-resistant Mycobacterium tuberculosis and associated factors among presumptive TB cases in Debre Markos Referral Hospital, Ethiopia.

METHODS

A cross-sectional study was conducted from September 2014 to March 2015. Detection of M. tuberculosis and resistance to rifampicin was performed using Gene Xpert MTB/RIF assay. Data was collected using structured questionnaire by face to face interview. Logistic regression analysis was computed to determine the associated factors of rifampicin-resistant M. tuberculosis.

RESULTS

A total of 505 presumptive TB patients included in the study. The prevalence of M. tuberculosis confirmed cases was 117 (23.2%) (95% CI 19.7-27%). It was higher among males (27.9%) than females (17.9%) (AOR: 2.17; CI 1.35-3.49). Of the 117 M. tuberculosis confirmed cases, 12 (10.3%) (95% CI 6.0-17.1%) were resistant to rifampicin. Rifampicin-resistant M. tuberculosis was noticed in 7 previously treated TB patients (17.1%) and 5 treatment naive patients (6.7%) (AOR: 4.16; CI 1.04-16.63). The prevalence of rifampicin-resistant M. tuberculosis was 6 (9.8%) and 6 (11.3%) in pulmonary and extra-pulmonary infections, respectively. Of the 30, MTB/HIV co-infection, 3 (10%) were rifampicin-resistant M. tuberculosis.

CONCLUSION

Rifampicin-resistant M. tuberculosis is prevalent in both pulmonary and extra-pulmonary tuberculosis patients. Previous treatment with anti-TB drugs was significantly associated with rifampicin resistance. Therefore, the use of Gene Xpert should be scaled up across the country for rapid detection and management of drug resistant M. tuberculosis.