Can metabolomics improve tuberculosis diagnostics?

With one third of the global human population suffering from tuberculosis (TB) in 2001, the disease was officially declared a worldwide emergency by the World Health Organization. Since then this disease has grown to epidemic proportions and the recent emergence of drug resistance, the rising incidence of HIV/TB co-infection, and the inability of the currently used vaccination, diagnostic and treatment protocols to control this pandemic, has made TB a research topic inviting urgent attention. The implementation of metabolomics, a relatively new research approach, which is defined as the study of all the small molecular weight compounds or metabolites in a system or sample, using highly sensitive and specific analytical techniques, shows promise in the quest to eradicate this disease. In this context, we describe here the advantages and limitations of the currently available TB diagnostic techniques, and the role that metabolomics has played in the identification of new biomarkers, not only leading to innovative approaches for TB diagnostics, but also to a better understanding of the intra-host changes induced by Mycobacterium tuberculosis infection and active disease.     

Social Stigma and Knowledge of Tuberculosis and HIV among Patients with Both Diseases in Thailand

Introduction

Disease-related stigma and knowledge are believed to be associated with patients'' willingness to seek treatment and adherence to treatment. HIV-associated tuberculosis (TB) presents unique challenges, because TB and HIV are both medically complex and stigmatizing diseases. In Thailand, we assessed knowledge and beliefs about these diseases among HIV-infected TB patients.

Methods

We prospectively interviewed and examined HIV-infected TB patients from three provinces and one national referral hospital in Thailand from 2005–2006. At the beginning of TB treatment, we asked patients standardized questions about TB stigma, TB knowledge, and HIV knowledge. Responses were grouped into scores; scores equal to or greater than the median score of study population were considered high. Multiple logistic regression analysis was used to identify factors associated with scores.

Results

Of 769 patients enrolled, 500 (65%) reported high TB stigma, 177 (23%) low TB knowledge, and 379 (49%) low HIV knowledge. Patients reporting high TB stigma were more likely to have taken antibiotics before TB treatment, to have first visited a traditional healer or private provider, to not know that monogamy can reduce the risk of acquiring HIV infection, and to have been hospitalized at enrollment. Patients with low TB knowledge were more likely to have severe TB disease, to be hospitalized at enrollment, to be treated at the national infectious diseases referral hospital, and to have low HIV knowledge. Patients with low HIV knowledge were more likely to know a TB patient and to have low TB knowledge.

Discussion

We found that stigma and low disease-specific knowledge were common among HIV-infected TB patients and associated with similar factors. Further research is needed to determine whether reducing stigma and increasing TB and HIV knowledge among the general community and patients reduces diagnostic delay and improves patient outcomes.     

Perceptions of Private Medical Practitioners on Tuberculosis Notification: A Study from Chennai,South India

Background

The Government of India declared TB as a notifiable disease in 2012. There is a paucity of information on the government''s mandatory TB notification order from the perspective of private medical practitioners (PPs).

Objective

To understand the awareness, perception and barriers on TB notification among PPs in Chennai, India.

Methods

Total of 190 PPs were approached in their clinics by trained field staff who collected data using a semi-structured and pre-coded questionnaire after getting informed consent. The data collected included PPs'' specialization, TB management practices, awareness about the TB notification order, barriers in its implementation and their suggestions to improve notification.

Results

Of 190 PPs from varied specializations, 138 (73%) had diagnosed TB cases in the prior three months, of whom 78% referred these patients to government facilities. Of 138 PPs, 73% were aware of the order on mandatory TB notification, of whom 46 (33%) had ever notified a TB case. Of 120 PPs, 63% reported reasons for not notifying TB cases. The main reasons reported for not notifying were lack of time (50%), concerns regarding patients'' confidentiality (24%) and fear of offending patients (11%). Of 145 PPs, 76% provided feedback about information they felt uncomfortable reporting during notification. PPs felt most uncomfortable reporting patient''s government-issued Aadhar number (77%), followed by patient''s phone number (37%) and residential address (26%). The preferred means of notification was through mobile phone communication (24%), SMS (18%) and e-mail (17%).

Conclusion

This study highlights that one-fourth of PPs were not aware of the TB notification order and not all those who were aware were notifying. While it is important to sensitize PPs on the importance of TB notification it is also important to understand the barriers faced by PPs and to make the process user-friendly in order to increase TB notification.     

Tuberculosis contact screening and isoniazid preventive therapy in a South Indian district: operational issues for programmatic consideration

Background

Under India''s Revised National Tuberculosis Control Programme (RNTCP), all household contacts of sputum smear positive Pulmonary Tuberculosis (PTB) patients are screened for TB. In the absence of active TB disease, household contacts aged <6 years are eligible for Isoniazid Preventive Therapy (IPT) (5 milligrams/kilogram body weight/day) for 6 months.

Objectives

To estimate the number of household contacts aged <6 years, of sputum smear positive PTB patients registered for treatment under RNTCP from April to June''2008 in Krishna District, to assess the extent to which they are screened for TB disease and in its absence initiated on IPT.

Methods

A cross sectional study was conducted. Households of all smear positive PTB cases (n = 848) registered for treatment from April to June''2008 were included. Data on the number of household contacts aged <6 years, the extent to which they were screened for TB disease, and the status of initiation of IPT, was collected.

Results

Households of 825 (97%) patients were visited, and 172 household contacts aged <6 years were identified. Of them, 116 (67%) were evaluated for TB disease; none were found to be TB diseased and 97 (84%) contacts were initiated on IPT and 19 (16%) contacts were not initiated on IPT due to shortage of INH tablets in peripheral health centers. The reasons for non-evaluation of the remaining eligible children (n = 56, 33%) include no home visit by the health staff in 25 contacts, home visit done but not evaluated in 31 contacts. House-hold contacts in rural areas were less likely to be evaluated and initiated on IPT [risk ratio 6.65 (95% CI; 3.06–14.42)].

Conclusion

Contact screening and IPT implementation under routine programmatic conditions is sub-optimal. There is an urgent need to sensitize all concerned programme staff on its importance and establishment of mechanisms for rigorous monitoring.     

The Past and Future of Tuberculosis Research

Renewed efforts in tuberculosis (TB) research have led to important new insights into the biology and epidemiology of this devastating disease. Yet, in the face of the modern epidemics of HIV/AIDS, diabetes, and multidrug resistance—all of which contribute to susceptibility to TB—global control of the disease will remain a formidable challenge for years to come. New high-throughput genomics technologies are already contributing to studies of TB''s epidemiology, comparative genomics, evolution, and host–pathogen interaction. We argue here, however, that new multidisciplinary approaches—especially the integration of epidemiology with systems biology in what we call “systems epidemiology”—will be required to eliminate TB.     

Defining Catastrophic Costs and Comparing Their Importance for Adverse Tuberculosis Outcome with Multi-Drug Resistance: A Prospective Cohort Study,Peru

Background

Even when tuberculosis (TB) treatment is free, hidden costs incurred by patients and their households (TB-affected households) may worsen poverty and health. Extreme TB-associated costs have been termed “catastrophic” but are poorly defined. We studied TB-affected households'' hidden costs and their association with adverse TB outcome to create a clinically relevant definition of catastrophic costs.

Methods and Findings

From 26 October 2002 to 30 November 2009, TB patients (n = 876, 11% with multi-drug-resistant [MDR] TB) and healthy controls (n = 487) were recruited to a prospective cohort study in shantytowns in Lima, Peru. Patients were interviewed prior to and every 2–4 wk throughout treatment, recording direct (household expenses) and indirect (lost income) TB-related costs. Costs were expressed as a proportion of the household''s annual income. In poorer households, costs were lower but constituted a higher proportion of the household''s annual income: 27% (95% CI = 20%–43%) in the least-poor houses versus 48% (95% CI = 36%–50%) in the poorest. Adverse TB outcome was defined as death, treatment abandonment or treatment failure during therapy, or recurrence within 2 y. 23% (166/725) of patients with a defined treatment outcome had an adverse outcome. Total costs ≥20% of household annual income was defined as catastrophic because this threshold was most strongly associated with adverse TB outcome. Catastrophic costs were incurred by 345 households (39%). Having MDR TB was associated with a higher likelihood of incurring catastrophic costs (54% [95% CI = 43%–61%] versus 38% [95% CI = 34%–41%], p<0.003). Adverse outcome was independently associated with MDR TB (odds ratio [OR] = 8.4 [95% CI = 4.7–15], p<0.001), previous TB (OR = 2.1 [95% CI = 1.3–3.5], p = 0.005), days too unwell to work pre-treatment (OR = 1.01 [95% CI = 1.00–1.01], p = 0.02), and catastrophic costs (OR = 1.7 [95% CI = 1.1–2.6], p = 0.01). The adjusted population attributable fraction of adverse outcomes explained by catastrophic costs was 18% (95% CI = 6.9%–28%), similar to that of MDR TB (20% [95% CI = 14%–25%]). Sensitivity analyses demonstrated that existing catastrophic costs thresholds (≥10% or ≥15% of household annual income) were not associated with adverse outcome in our setting. Study limitations included not measuring certain “dis-saving” variables (including selling household items) and gathering only 6 mo of costs-specific follow-up data for MDR TB patients.

Conclusions

Despite free TB care, having TB disease was expensive for impoverished TB patients in Peru. Incurring higher relative costs was associated with adverse TB outcome. The population attributable fraction indicated that catastrophic costs and MDR TB were associated with similar proportions of adverse outcomes. Thus TB is a socioeconomic as well as infectious problem, and TB control interventions should address both the economic and clinical aspects of this disease. Please see later in the article for the Editors'' Summary     

A Multi-Site Evaluation of Innovative Approaches to Increase Tuberculosis Case Notification: Summary Results

Background

Globally, TB notifications have stagnated since 2007, and sputum smear positive notifications have been declining despite policies to improve case detection. We evaluate results of 28 interventions focused on improving TB case detection.

Methods

We measured additional sputum smear positive cases treated, defined as the intervention area''s increase in case notification during the project compared to the previous year. Projects were encouraged to select control areas and collect historical notification data. We used time series negative binomial regression for over-dispersed cross-sectional data accounting for fixed and random effects to test the individual projects'' effects on TB notification while controlling for trend and control populations.

Results

Twenty-eight projects, 19 with control populations, completed at least four quarters of case finding activities, covering a population of 89.2 million. Among all projects sputum smear positive (SS+) TB notifications increased 24.9% and annualized notification rates increased from 69.1 to 86.2/100,000 (p = 0.0209) during interventions. Among the 19 projects with control populations, SS+TB case notifications increased 36.9% increase while in the control populations a 3.6% decrease was observed. Fourteen (74%) of the 19 projects'' SS+TB notification rates in intervention areas increased from the baseline to intervention period when controlling for historical trends and notifications in control areas.

Conclusions

Interventions were associated with large increases in TB notifications across many settings, using an array of interventions. Many people with TB are not reached using current approaches. Different methods and interventions tailored to local realities are urgently needed.     

Expression of GroES TB antigen in tobacco and potato

As the world races towards a plant-based bioeconomy, plants known to be ideal and economical bioreactors are being harnessed for the production of recombinant proteins. The major immunodominant 10 kDa GroES TB antigen (Chaperonin 10) gene from Mycobacterium tuberculosis was selected for expression in plants as a putative tuberculosis (TB) subunit vaccine candidate. Two crops, tobacco and potato, were engineered by stable plant transformation for expression of the 10 kDa GroES TB antigen using non-viral binary vectors. The integration of the GroES TB gene into the genomes of tobacco and potato was confirmed by PCR and Southern blotting. The expression of the GroES TB antigen in tobacco was 0.04–1.2 % of the total soluble protein (TSP). However, the expression of the same TB antigen in the Indian potato cv. Kufri bahar was comparatively low (0.033 % of TSP). The recombinant GroES plant derived protein was characterised and confirmed by MALDI-TOF–TOF and ELISA. This is the first report of the expression of the 10 kDa chaperonin in tobacco and potato.     

Accuracy of QuantiFERON-TB Gold Test for Tuberculosis Diagnosis in Children

ObjectivesTo evaluate the accuracy of the QuantiFERON-TB Gold assay (QFT-IT) in children with suspected active or latent TB infection (LTBI).MethodsA retrospective study was conducted on 621 children (0–14 years old) evaluated for TB infection or disease. Following clinical assessment, children were tested with the QFT-IT assay.ResultsAmong the 140 active TB suspects, we identified 19 cases of active disease. The overall sensitivity for active TB was 87.5%, ranging from 62.5% in children 25–36 months old to 100% in children older than 49 months. The overall specificity for active TB was 93.6%. Among the 481 children tested for LTBI screening, 38 scored positive and all but 2 had at least one risk factor for TB infection. Among the 26 children with indeterminate results, bacterial, viral or fungal pneumonia were later diagnosed in 11 (42.3%) cases and non-TB related extra-pulmonary infections in 12 (46.1%).ConclusionsOur results indicate that the children''s response to QFT-IT associates to active TB and risk factors for LTBI. Moreover, we show that mitogen response is also found in children of 1 year of age, providing support for QFT-IT use also in young children.     

Healthcare Workers' Challenges in the Implementation of Tuberculosis Infection Prevention and Control Measures in Mozambique

Objective

Healthcare Workers (HCWs) have a higher frequency of TB exposure than the general population and have therefore an occupational TB risk that infection prevention and control (IPC) measures aim to reduce. HCWs are crucial in the implementation of these measures. The objective of the study was to investigate Mozambican HCWs'' perceptions of their occupational TB risk and the measures they report using to reduce this risk. In addition, we explored the challenges HCWs encounter while using these TBIPC measures.

Methods

Focus group discussion. Analysis according content method.

Participants

Four categories of HCWs: auxiliary workers, medical (doctors and clinical officers), nurses and TB program staff.

Results

HCWs are aware of their occupational TB risk and use various measures to reduce their risk of infection. HCWs find it challenging to employ measures that minimize such risks and a lack of clear guidelines contributes to these challenges. HCWs'' and patient behavior further complicate the use of TBIPC measures.

Conclusion

HCWs in Mozambique perceive a high occupational risk of TB infection. They report several challenges using measures to reduce this risk such as shortage of material, lack of clear guidelines, insufficient motivation and inadequate training. Robust training with motivational approaches, alongside supervision and support for HCWs could improve implementation of TBIPC measures. Healthcare management should address the areas for improvement that are beyond the individual HCW''s control.     

Characterization of a novel antigen of Mycobacterium tuberculosis K strain and its use in immunodiagnosis of tuberculosis

Mycobacterium tuberculosis-specific antigens would be of great value in developing immunodiagnostic tests for tuberculosis (TB), but regional differences in molecular types of the organism may result in antigenic variation, which in turn affects the outcome of the tests. For example, the Beijing strains of M. tuberculosis are prevalent in East Asia, and in particular, the K strain and related strains of the Beijing family, are most frequently isolated during school outbreaks of TB in South Korea. From comparison of genome sequences between M. tuberculosis K strain and the H37Rv strain, a non-Beijing type, we identified a K strain-specific gene, InsB, which has substantial homology with the ESAT-6-like proteins. This study was, therefore, initiated to characterize the InsB protein for its immunogenicity in mice and to confirm its expression in TB patients by detecting antibodies to the protein. The InsB gene was cloned from M. tuberculosis K strain and expressed in Escherichia coli. The recombinant InsB protein was used for immunization of mice. All mice showed strong antibody responses to the InsB protein, and splenocytes stimulated with InsB showed strong IFN-γ and IL-17 responses and a weak IL-2 response, all of which have been implicated in disease expression and used for the immunodiagnosis of TB. Serum samples from TB patients also showed significant antibody responses to the InsB protein as compared to healthy control samples. These results indicate that the InsB protein is an M. tuberculosis K-strain-specific antigen that could further improve the current immunodiagnostic methods, especially for the South Korean population.     

Development of a standardized screening rule for tuberculosis in people living with HIV in resource-constrained settings: individual participant data meta-analysis of observational studies

Background

The World Health Organization recommends the screening of all people living with HIV for tuberculosis (TB) disease, followed by TB treatment, or isoniazid preventive therapy (IPT) when TB is excluded. However, the difficulty of reliably excluding TB disease has severely limited TB screening and IPT uptake in resource-limited settings. We conducted an individual participant data meta-analysis of primary studies, aiming to identify a sensitive TB screening rule.

Methods and Findings

We identified 12 studies that had systematically collected sputum specimens regardless of signs or symptoms, at least one mycobacterial culture, clinical symptoms, and HIV and TB disease status. Bivariate random-effects meta-analysis and the hierarchical summary relative operating characteristic curves were used to evaluate the screening performance of all combinations of variables of interest. TB disease was diagnosed in 557 (5.8%) of 9,626 people living with HIV. The primary analysis included 8,148 people living with HIV who could be evaluated on five symptoms from nine of the 12 studies. The median age was 34 years. The best performing rule was the presence of any one of: current cough (any duration), fever, night sweats, or weight loss. The overall sensitivity of this rule was 78.9% (95% confidence interval [CI] 58.3%–90.9%) and specificity was 49.6% (95% CI 29.2%–70.1%). Its sensitivity increased to 90.1% (95% CI 76.3%–96.2%) among participants selected from clinical settings and to 88.0% (95% CI 76.1%–94.4%) among those who were not previously screened for TB. Negative predictive value was 97.7% (95% CI 97.4%–98.0%) and 90.0% (95% CI 88.6%–91.3%) at 5% and 20% prevalence of TB among people living with HIV, respectively. Abnormal chest radiographic findings increased the sensitivity of the rule by 11.7% (90.6% versus 78.9%) with a reduction of specificity by 10.7% (49.6% versus 38.9%).

Conclusions

Absence of all of current cough, fever, night sweats, and weight loss can identify a subset of people living with HIV who have a very low probability of having TB disease. A simplified screening rule using any one of these symptoms can be used in resource-constrained settings to identify people living with HIV in need of further diagnostic assessment for TB. Use of this algorithm should result in earlier TB diagnosis and treatment, and should allow for substantial scale-up of IPT. Please see later in the article for the Editors'' Summary     

Resistome analysis of Mycobacterium tuberculosis: Identification of aminoglycoside 2'-Nacetyltransferase (AAC) as co-target for drug desigining

The emergence of multidrug resistant tuberculosis (MDRTB) highlights the urgent need to understand the mechanisms of resistance to the drugs and to develop a new arena of therapeutics to treat the disease. Ethambutol, isonazid, pyrazinamide, rifampicin are first line of drugs against TB, whereas aminoglycoside, polypeptides, fluoroquinolone, ethionamide are important second line of bactericidal drugs used to treat MDRTB, and resistance to one or both of these drugs are defining characteristic of extensively drug resistant TB. We retrieved 1,221 resistant genes from Antibiotic Resistance Gene Database (ARDB), which are responsible for resistance against first and second line antibiotics used in treatment of Mycobacterium tuberculosis infection. From network analysis of these resistance genes, 53 genes were found to be common. Phylogenetic analysis shows that more than 60% of these genes code for acetyltransferase. Acetyltransferases detoxify antibiotics by acetylation, this mechanism plays central role in antibiotic resistance. Seven acetyltransferase (AT-1 to AT-7) were selected from phylogenetic analysis. Structural alignment shows that these acetyltransferases share common ancestral core, which can be used as a template for structure based drug designing. From STRING analysis it is found that acetyltransferase interact with 10 different proteins and it shows that, all these interaction were specific to M. tuberculosis. These results have important implications in designing new therapeutic strategies with acetyltransferase as lead co-target to combat against MDR as well as Extreme drug resistant (XDR) tuberculosis.

Abbreviations

AA - amino acid, AT - Acetyltransferase, AAC - Aminoglycoside 2''-N-acetyltransferase, XDR - Extreme drug-resistant, MDR - Multidrug-resistant, Mtb - Mycobacterium tuberculosis, TB - Tuberculosis.     

Rib lesions in skeletons from early neolithic sites in Central Germany: On the trail of tuberculosis at the onset of agriculture

As an infectious disease, tuberculosis (TB) is one of the major causes of death worldwide. Paleopathological and paleomicrobiological studies indicate a long standing association of the causative agent Mycobacterium tuberculosis and its human host. Since the occurrence and the epidemic spread of this pathogen seem to be closely linked to social and biological factors, it is of particular interest to understand better the role of TB during periods of social and nutritional change such as the Neolithic. In this study, 118 individuals from three sites in Saxony‐Anhalt (Germany) dating to the Linear Pottery Culture (5400–4800 BC) were examined macroscopically to identify TB related bone lesions. In two individuals, Pott's disease was detected. In addition, periosteal reactions of varying degrees and frequency were observed mainly along the neck of the ribs in 6.5% (2/31) of subadults and 35.1% (20/57) of adults, with one site standing out markedly. Rib lesions, however, are not specific indicators of TB as they can also be caused by other diseases; so additional investigations were undertaken using histology and micro‐CT scans to say more about the disease process. Supplementary molecular analyses indicate the presence of pathogens belonging to the Mycobacterium tuberculosis complex in individuals of all sites. Furthermore, we discuss the occurrence and spread of TB during the Neolithic with regard to nutritional aspects and possible risks of infection. The data presented provide important insights into the health status of Early Neolithic populations in Central Germany. Am J Phys Anthropol, 2012. © 2012 Wiley Periodicals, Inc.     

A community survey of Parkinson's disease.

In a rural community of 80,000 people 69 patients were identified as having a diagnosis of Parkinson''s disease. After interview and examination we found that 55 met the generally accepted diagnostic criteria for Parkinson''s disease, 4 had possible Parkinson''s disease, 6 had essential tremor, 2 had dementia and 2 had other conditions. The patients with Parkinson''s disease had clinical and epidemiologic characteristics similar to those of patients in previous, mainly hospital-based, studies. These characteristics included mean age at onset (63 years), frequency rate of dementia (20%) and presence of postural tremor (11%). The pattern of treatment varied, some patients receiving more medication than is usual for the severity of their illness, and some patients receiving less than is usual. Parkinson''s disease can be difficult to diagnose and manage because of the clinical variation between patients in presentation and response to treatment.     

A controlled trial of the knowledge impact of tuberculosis information leaflets among staff supporting substance misusers: pilot study

Background

Information leaflets are widely used to increase awareness and knowledge of disease. Limited research has, to date, been undertaken to evaluate the efficacy of these information resources. This pilot study sought to determine whether information leaflets developed specifically for staff working with substance mis-users improved knowledge of tuberculosis (TB).

Method

Staffs working with individuals affected by substance mis-use were recruited between January and May 2008. All participants were subjectively allocated by their line manager either to receive the TB-specific leaflet or a control leaflet providing information on mental health. Level of knowledge of TB was assessed using questionnaires before and after the intervention and data analysed using McNemar''s exact test for matched pairs.

Results

The control group showed no evidence of a change in knowledge of TB, whereas the TB questionnaire group demonstrated a significant increase in knowledge including TB being curable (81% correct before to 100% correct after), length of treatment required (42% before to 73% after), need to support direct observation (18% to 62%) and persistent fever being a symptom (56% to 87%). Among key workers, who have a central role in implementing a care plan, 88% reported never receiving any TB awareness-raising intervention prior to this study, despite 11% of all respondents having TB diagnosed among their clients.

Conclusion

Further randomized controlled trials are required to confirm the observed increase in short-term gain in knowledge and to investigate whether knowledge gain leads to change in health status.     

Survival among Patients with HIV Infection and Smear-Negative Pulmonary Tuberculosis - United States, 1993–2006

Background

In patients with HIV and tuberculosis (TB) in resource-constrained settings, smear-negative disease has been associated with higher mortality than smear-positive disease. Higher reported mortality may be due to misdiagnosis, diagnostic delays, or because smear-negative disease indicates more advanced immune suppression.

Methods

We analyzed culture-confirmed, pulmonary TB among patients with TB and HIV in the United States from 1993–2008 to calculate prevalence ratios (PRs) for smear-negative disease by demographic and clinical characteristics. Allowing two years for treatment outcome to be reported, we determined hazard ratios (HRs) for survival by smear status, adjusted for significant covariates on patients before 2006.

Results

Among 16,710 cases with sputum smear results, 6,739 (39%) were sputum smear-negative and 9,971 (58%) were sputum smear-positive. The prevalence of smear-negative disease was lower in male patients (PR: 0.89, 95% confidence interval [CI]: 0.86–0.93) and in those who were homeless (PR: 0.92, CI: 0.87–0.97) or used alcohol excessively (PR: 0.91, CI: 0.87–0.95), and higher in persons diagnosed while incarcerated (PR: 1.20, CI: 1.13–1.27). Patients with smear-negative disease had better survival compared to patients with smear-positive disease, both before (HR: 0.82, CI: 0.75–0.90) and after (HR: 0.81, CI: 0.71–0.92) the introduction of combination anti-retroviral therapy.

Conclusions

In the United States, smear-negative pulmonary TB in patients with HIV was not associated with higher mortality, in contrast to what has been documented in high TB burden settings. Smear-negative TB can be routinely and definitively diagnosed in the United States, whereas high-burden countries often rely solely on AFB-smear microscopy. This difference could contribute to diagnostic and treatment delays in high-burden countries, possibly resulting in higher mortality.     

Classification and characterisation of extracellular vesicles-related tuberculosis subgroups and immune cell profiles

Around the world, tuberculosis (TB) remains one of the most common causes of morbidity and mortality. The molecular mechanism of Mycobacterium tuberculosis (Mtb) infection is still unclear. Extracellular vesicles (EVs) play a key role in the onset and progression of many disease states and can serve as effective biomarkers or therapeutic targets for the identification and treatment of TB patients. We analysed the expression profile to better clarify the EVs characteristics of TB and explored potential diagnostic markers to distinguish TB from healthy control (HC). Twenty EVs-related differentially expressed genes (DEGs) were identified, and 17 EVs-related DEGs were up-regulated and three DEGs were down-regulated in TB samples, which were related to immune cells. Using machine learning, a nine EVs-related gene signature was identified and two EVs-related subclusters were defined. The single-cell RNA sequence (scRNA-seq) analysis further confirmed that these hub genes might play important roles in TB pathogenesis. The nine EVs-related hub genes had excellent diagnostic values and accurately estimated TB progression. TB's high-risk group had significantly enriched immune-related pathways, and there were substantial variations in immunity across different groups. Furthermore, five potential drugs were predicted for TB using CMap database. Based on the EVs-related gene signature, the TB risk model was established through a comprehensive analysis of different EV patterns, which can accurately predict TB. These genes could be used as novel biomarkers to distinguish TB from HC. These findings lay the foundation for further research and design of new therapeutic interventions aimed at treating this deadly infectious disease.     

Rapid diagnosis of tuberculosis with the Xpert MTB/RIF assay in high burden countries: a cost-effectiveness analysis

Background

Xpert MTB/RIF (Xpert) is a promising new rapid diagnostic technology for tuberculosis (TB) that has characteristics that suggest large-scale roll-out. However, because the test is expensive, there are concerns among TB program managers and policy makers regarding its affordability for low- and middle-income settings.

Methods and Findings

We estimate the impact of the introduction of Xpert on the costs and cost-effectiveness of TB care using decision analytic modelling, comparing the introduction of Xpert to a base case of smear microscopy and clinical diagnosis in India, South Africa, and Uganda. The introduction of Xpert increases TB case finding in all three settings; from 72%–85% to 95%–99% of the cohort of individuals with suspected TB, compared to the base case. Diagnostic costs (including the costs of testing all individuals with suspected TB) also increase: from US$28–US$49 to US$133–US$146 and US$137–US$151 per TB case detected when Xpert is used “in addition to” and “as a replacement of” smear microscopy, respectively. The incremental cost effectiveness ratios (ICERs) for using Xpert “in addition to” smear microscopy, compared to the base case, range from US$41–$110 per disability adjusted life year (DALY) averted. Likewise the ICERS for using Xpert “as a replacement of” smear microscopy range from US$52–$138 per DALY averted. These ICERs are below the World Health Organization (WHO) willingness to pay threshold.

Conclusions

Our results suggest that Xpert is a cost-effective method of TB diagnosis, compared to a base case of smear microscopy and clinical diagnosis of smear-negative TB in low- and middle-income settings where, with its ability to substantially increase case finding, it has important potential for improving TB diagnosis and control. The extent of cost-effectiveness gain to TB programmes from deploying Xpert is primarily dependent on current TB diagnostic practices. Further work is required during scale-up to validate these findings. Please see later in the article for the Editors'' Summary