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Background: Early detection of multidrug-resistant Mycobacterium tuberculosis (MDR-TB) is of primary importance for both patient management and infection control. Optimal methods for identifying MDR-TB in a timely and affordable manner in resource-limited settings are not yet available.
Objectives: To evaluate the performance of a low-technology b...
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... characteristics, using the MGIT re- sult as the reference standard, are shown in Table 3. Specifi city, i.e., the ability to detect true susceptibility, was 92.9% for INH, 96.9% for RMP and 98.6% for MDR-TB detection, while sensitivity, i.e., the ability to detect true resistance, was respectively 92.9%, 93.6% and 95.3. ...
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Citations
... The DST findings are obtained within seven days using this method. 86 ...
Tuberculosis (TB) is a significant public health challenge, especially in developing nations. Developing a TB eradication strategy is hampered by the global health concern of drug-resistant (DR) TB. Effective patient treatment, preventing TB transfer and avoiding the upsurge of DR strains depend primarily on the timely and accurate identification of DR TB. Due to inadequate sensitivity, the necessity of trained laboratory personnel, the sluggish growth pattern of Mycobacterium bacilli in culture, and the small number of bacilli that are usually found in extrapulmonary TB samples, TB diagnosis is still tricky in clinical practice. Although mycobacterial culture is the gold standard to identify TB and determine drug resistance, it takes 2 to 8 weeks to develop. Despite their high cost, nucleic acid amplification tests (NAATs) and whole-genome sequencing (WGS) are the commonly employed molecular-based methods for diagnosing and identifying TB. The WHO suggested the GeneXpert MTB/RIF to identify TB and detect resistance to rifampicin. In comparison, numerous molecular techniques were developed, including allele-specific PCR (MAS-PCR), solid-phase hybridization, real-time PCR (RT-PCR) and droplet digital PCR-based technique (DDPCR). This manuscript is intended to overview the current approaches for the phenotypic and genotypic diagnosis of TB disease and identifying resistance to antitubercular drugs depending on recently published articles, WHO and CDC reports, and commercially available diagnostic tools.
... MODS can provide susceptibility results simultaneously with culture results. The performance of MODS assay in detecting INH and RIF resistance was investigated in various studies and two meta-analysis (6,11,12,(16)(17)(18)(19)(20)(21), and MODS assay was found to be an accurate method for detecting drug resistance. According to the pooled estimates of the meta-analysis (16,19), sensitivity and specificity of the assay ranged between 96-98% and 96-99.4%, ...
... Most of the earlier studies used proportion method as the reference DST (16,19). However, only a few studies used automated MGIT system as the reference method for DST, and the sensitivity and specificity of MODS in these studies ranged between 75-93.8% and 92.9-97.4% for detecting INH and 93.6-100% and 96.9-100% for detecting RIF resistance, respectively (17,20,21). In our study, the sensitivity of MODS for detection of INH and RIF resistance was slightly lower compared with most of these earlier studies; however, the specificity was similar. ...
... In the studies that used automated MGIT system as reference, MODS assay detected MDR-TB with high sensitivity (range 85.7-95.3%) and the specificity (range 97.5-100%) (17,20,21), which was consistent with our results. Moreover, the TAT of MODS culture was similar with MGIT culture and shorter than LJ culture as expected. ...
... The microscopic observation drug susceptibility (MODS) assay is a low-cost, liquid culture-based diagnostic assay for TB (7,8). With accuracy comparable to that of other culture techniques (7,9,10), MODS is faster (7), provides simultaneous DST (10-13), and has World Health Organization (WHO) approval for direct testing of sputum specimens in low-resource settings (14, 15). MODS accurately diagnoses TB from cerebrospinal fluid (16) and pleural specimens (17), but its role in the diagnosis of solid tissue TB remains unknown. ...
... The microscopic observation drug susceptibility (MODS) assay is a low-cost, liquid culture-based diagnostic assay for TB (7,8). With accuracy comparable to that of other culture techniques (7,9,10), MODS is faster (7), provides simultaneous DST (10)(11)(12)(13), and has World Health Organization (WHO) approval for direct testing of sputum specimens in low-resource settings (14,15). MODS accurately diagnoses TB from cerebrospinal fluid (16) and pleural specimens (17), but its role in the diagnosis of solid tissue TB remains unknown. ...
... The microscopic observation drug susceptibility (MODS) assay is a low-cost, liquid culture-based diagnostic assay for TB (7,8). With accuracy comparable to that of other culture techniques (7,9,10), MODS is faster (7), provides simultaneous DST (10)(11)(12)(13), and has World Health Organization (WHO) approval for direct testing of sputum specimens in low-resource settings (14,15). MODS accurately diagnoses TB from cerebrospinal fluid (16) and pleural specimens (17), but its role in the diagnosis of solid tissue TB remains unknown. ...
In this study, 132 patients with lymphadenopathy were investigated. Fifty-two (39.4%) were diagnosed with tuberculosis (TB). The microscopic observation drug susceptibility (MODS) assay provided rapid (13 days), accurate diagnosis (sensitivity, 65.4%) and reliable drug susceptibility testing (DST). Despite its lower sensitivity than that of other methods, its faster results and simultaneous DST are advantageous in resource-poor settings, supporting the incorporation of MODS into diagnostic algorithms for extrapulmonary TB.
... More recently, the diagnostic accuracy of MODS was estimated against a reference standard including Löwenstein-Jensen (LJ) media and BACTEC MGIT culture. Overall MODS sensitivity for MTB detection was 85% and specificity was 93%; the authors also demonstrated that diagnostic accuracy did not significantly differ by HIV infection status [17]. The NRA is based on the ability of MTB to reduce nitrate to nitrite by the action of the nitrate reductase enzyme, which is indicated by the development of a dark rose to purple-rose color after the addition of the reagent. ...
... For example, MODS, NRA, or LRP were evaluated both for identification of MTB and determination of resistance to anti-tuberculosis drugs. Results of several studies have shown that the sensitivity of the MODS assay in detecting MDR varies from 72% to 100% [16,17,36]. Recently, the performance of NRA on Middlebrook 7H11 agar for detection of isoniazid and rifampin resistance has been evaluated and compared with the direct proportion method on LJ medium directly on smear-positive sputum specimens. ...
Tuberculosis remains one of the major causes of global death from a single infectious agent. This situation is worsened by the HIV/AIDS pandemic because one-third of HIV/AIDS patients are co-infected with Mycobacterium tuberculosis. Failure to control the spread of tuberculosis is largely due to our inability to detect and treat all infectious cases of pulmonary tuberculosis in a timely manner, allowing continued M. tuberculosis transmission within communities. Diagnosis of tuberculosis can be made using indirect and direct methods. The indirect tests, such as interferon-gamma release assays, provide a new diagnostic method for M. tuberculosis infection, but do not discriminate between infection and active disease. The most common direct method for diagnosing TB worldwide is sputum smear microscopy (developed more than 100 years ago), where bacteria are observed in sputum samples examined under a microscope. In countries with more developed laboratory capacities, cases of tuberculosis may also be diagnosed using culture methods (the current gold standard) or, increasingly, using rapid molecular tests. In this review, we discuss the traditional methods for the diagnosis of tuberculosis. We also discuss other inexpensive assays that can be used to detect the presence of M. tuberculosis.
... However, available conventional tests such as MGIT and BACTEC are simply not feasible for developing nations because of their high costs and equipment requirements. The present study with a large sample size with different groups of patients from south India has demonstrated that MODS is a reliable method for detecting and determining drug susceptibility of MTB as reported in other regions.1011121718192021 The sensitivity of the MODS assay in detecting TB slightly varied between HIV-positive (89.2%) and -negative (93.9%) patients; the difference could have been due to the low shedding of MTB in the sputum of the HIV patients as reported, [10,22] alteration of the normal host immune response to MTB in persons with HIV, cavitation, and transfer of TB bacilli into respiratory secretions is markedly reduced, thereby hampering diagnosis by sputum microscopy and culture. ...
... The performance results for MODS in the detection of MDR-TB are similar to those obtained in other studies. [10,12,1718192021 The combined results for INH and RIF (in MDR-TB detection) had good agreement rates (84.2% sensitivity and Kappa value 0.85). In HIV-negative patients, excellent agreement rates (100% sensitivity and Kappa value 1) were observed. ...
Several rapid non-commercial culture-based methods and assays for drug susceptibility testing (DST) of Mycobacterium tuberculosis have emerged over the last decades. The aim of the current review was to summarise evidence on the performance of microscopic observation of drug susceptibility (MODS), thin-layer agar (TLA) and colorimetric redox-indicator (CRI) assays for detection of resistance to first- and second-line anti-tuberculosis (TB) drugs. Forty-three publications satisfying selection criteria were selected for data extraction. MODS and CRI assays demonstrated pooled sensitivity and specificity of > 93% for the detection of resistance to rifampicin and isoniazid and confirmed their utility for an accurate detection of multidrug-resistant TB (MDR-TB) in various settings. Sensitivity and specificity values for indirect DST for ethambutol (EMB) using CRI assays were 94.0% and 82.0%, respectively, suggesting that CRIs could be used to rule out resistance to EMB. Performance for other drugs varied more substantially across the reports. There was no sufficient evidence on the performance of the TLA assay for making any conclusion on its utility for DST. Our data suggests that non-commercial assays could be used for a rapid and accurate DST in settings where the use of commercial World Health Organization-endorsed assays could be limited due to a variety of reasons including limited resources, laboratory facilities or trained personnel. While inexpensive and easy-to-perform MODS and TLA assays can be used in low-income settings, using CRI assays for determination of minimal inhibitory concentrations may be implemented in middle- and high-income countries with high MDR-TB burden to guide clinical management of TB patients.
Performance of Microscopic Observation Drug Susceptibility for the Rapid Diagnosis of Tuberculosis and Detection of Drug Resistances in Bamako, Mali. Manuscript under review with the journal of clinical microbiology and Infection
Objectives:
In Mali early detection and treatment of multidrug resistance tuberculosis (MDR-TB) are still challenging due to cost, time and/or complexity associated with regular tests. Microscopic Observation Drug Susceptibility (MODS) is a low-cost assay validated by WHO in 2010. It is a liquid culture based assay to detect the "cording" characteristic of Mycobacterium tuberculosis complex (MTBc) and to assess susceptibility to both isoniazid and rifampicin defining MDR-TB. In this study we aimed to evaluate the performance of MODS as diagnostic tool compared to a validated method, the MGIT/AST/SIRE.
Methods and results:
Between January 2010 and October 2015, we included 98 suspected TB patients in an observational cohort study. The sensitivity and specificity of MODS assay for detecting TB were respectively 94.12% and 85.71% compared to the reference MGIT/7H11 culture, with a Cohen Kappa coefficient of 0.78 [95% CI: 0.517-1.043]. The median time to culture positivity for MODS assay and MGIT (plus interquartile range, IQR) was respectively eight days [IQR, 5-11] and six days [IQR, 5-6]. In detecting MDR-TB patients, the sensitivity and specificity of MODS assay were respectively 100% and 95.92%. The positive predictive value and negative predictive values were respectively 66.7% and 100%. The median turnaround time for obtaining MDR-TB results using MODS assay and MGIT/AST/SIRE was respectively nine days and 35 days. Thus, the MODS assay rapidly identifies MDR-TB in Mali than the MGIT/AST/SIRE.
Conclusion:
As an easy, simple, fast and affordable method, the MODS assay could significantly improve the management of tuberculosis.
Background: The lack of published information about children with multidrug-resistant tuberculosis (MDR-TB) is an obstacle to efforts to advocate for better diagnostics and treatment.
Objective: To describe the lack of recognition in the published literature of MDR-TB
and extensively drug-resistant TB (XDR-TB) in children.
Design: We conducted a systematic search of the literature published in countries that reported any MDR- or XDR-TB case by 2012 to identify MDR- or XDR-TB cases in adults and in children.
Results: Of 184 countries
and territories that reported any case of MDR-TB during 2005–2012, we identified adult MDR-TB cases in the published literature in 143 (78%) countries and pediatric MDR-TB cases in 78 (42%) countries. Of the 92 countries that reported any case of XDR-TB, we identified adult XDR-TB cases
in the published literature in 55 (60%) countries and pediatric XDR-TB cases for 9 (10%) countries.
Conclusion: The absence of publications documenting child MDR- and XDR-TB cases in settings where MDR- and XDR-TB in adults have been reported indicates both exclusion of childhood
disease from the public discourse on drug-resistant TB and likely underdetection of sick children. Our results highlight a large-scale lack of awareness about children with MDR- and XDR-TB.
Background:
The converging epidemics of HIV and tuberculosis (TB) pose one of the greatest public health challenges of our time. Rapid diagnosis of TB is essential in view of its infectious nature, high burden of cases, and emergence of drug resistance.
Objective:
The purpose of this present study was to evaluate the feasibility of implementing the microscopic observation drug susceptibility (MODS) assay, a novel assay for the diagnosis of TB and multi-drug-resistant tuberculosis (MDR-TB) directly from sputum specimens, in the Indian setting.
Materials and methods:
This study involved a cross-sectional, blinded assessment of the MODS assay on 1036 suspected cases of pulmonary TB in HIV-positive and HIV-negative patients against the radiometric method, BD-BACTEC TB 460 system.
Results:
Overall, the sensitivity, specificity, positive predictive value, and negative predictive value of the MODS assay in detecting MTB among TB suspected patients were 89.1%, 99.1%, 94.2%, 95.8%, respectively. In addition, in the diagnosis of drug-resistant TB, the MODS assay was 84.2% sensitive for those specimens reporting MDR, 87% sensitivity for those specimens reporting INH mono-resistance, and 100% sensitive for specimens reporting RIF mono-resistance. The median time to detection of TB in the MODS assay versus BACTEC was 9 versus 21 days (P<0.001).
Conclusion:
Costing 5 to 10 times lesser than the automated culture methods, the MODS assay has the potential clinical utility as a simple and rapid method. It could be effectively used as an alternative method for diagnosing TB and detection of MDR-TB in a timely and affordable way in resource-limited settings.
