Advances in tuberculosis diagnostics: the Xpert MTB/RIF assay and future prospects for a point-of-care test

Tuberculosis in Infants and Children

One million children develop tuberculosis disease each year, and 210,000 die from complications of tuberculosis. Childhood tuberculosis is very different from adult tuberculosis in epidemiology, clinical and radiographic presentation, and treatment. This review highlights the many unique features of childhood tuberculosis, with special emphasis on very young children and adolescents, who are most likely to develop disease after infection has occurred.

Influence of Ebola on tuberculosis case finding and treatment outcomes in Liberia

Setting: National Leprosy and Tuberculosis (TB) Control Programme, Liberia. Objectives: To assess TB case finding, including human immunodeficiency virus (HIV) associated interventions and treatment outcomes, before (January 2013-March 2014), during (April 2014-June 2015) and after (July-December 2015) the Ebola virus disease outbreak. Design: A cross-sectional study and retrospective cohort analysis of outcomes. Results: The mean quarterly numbers of individuals with presumptive TB and the proportion diagnosed as smear-positive were: pre-Ebola (n = 7032, 12%), Ebola (n = 6147, 10%) and post-Ebola (n = 6795, 8%). For all forms of TB, stratified by category and age group, there was a non-significant decrease in the number of cases from the pre-Ebola to the Ebola and post-Ebola periods. There were significant decreases in numbers of cases with smear-positive pulmonary TB (PTB) from the pre-Ebola period (n = 855), to the Ebola (n = 640, P < 0.001) and post-Ebola (n = 568, P < 0.001) periods. The proportions of patients tested for HIV, found to be HIV-positive and started on antiretroviral therapy decreased as follows: pre-Ebola (respectively 72%, 15% and 34%), Ebola (69%, 14% and 30%) and post-Ebola (68%, 12% and 26%). Treatment success rates among TB patients were: 80% pre-Ebola, 69% Ebola (P < 0.001) and 73% post-Ebola (P < 0.001). Loss to follow-up was the main contributing adverse outcome. Conclusion: The principal negative effects of Ebola were the significant decreases in diagnoses of smear-positive PTB, the declines in HIV testing and antiretroviral therapy uptake and poor treatment success. Ways to prevent these adverse effects from recurring in the event of another Ebola outbreak need to be found.

The influence of the Ebola outbreak on presumptive and active tuberculosis in Bombali District, Sierra Leone

Setting: Bombali District, rural Sierra Leone. Objective: To compare the number of patients with presumptive tuberculosis (TB), the number of patients registered with TB (including testing for the human immunodeficiency virus [HIV] and initiation on antiretroviral therapy [ART]) and treatment outcomes during the pre-Ebola, Ebola and post-Ebola disease outbreak periods between 2013 and 2016. Design: This was a cross-sectional study and retrospective cohort analysis of treatment outcomes. Results: The mean monthly number of patients with presumptive TB before, during and post-Ebola was respectively 169, 145 and 210. The mean monthly number of registered TB cases was respectively 57, 57 and 96. Smear-positive TB was the most frequent type of TB, at 75%, 66% and 77%. The proportion of TB patients tested for HIV was 82% pre-Ebola, 74% Ebola and 99% post-Ebola. The proportion of HIV-positive patients with TB initiated on ART was respectively 46%, 85% and 100%. Treatment success among TB patients was 71% in the pre-Ebola period and 89% in the Ebola period (P < 0.001). Conclusion: During the Ebola outbreak, there were decreases in the number of presumptive TB patients and in the proportions of patients diagnosed with smear-positive TB and tested for HIV. The initiation of ART in HIV-infected TB patients and treatment outcomes remained acceptable. Pre-emptive actions are needed to maintain adequate control activities in future outbreaks.

Comparative Study of GeneXpert MTB/RIF Assay and Multiplex PCR Assay for Direct Detection of Mycobacterium tuberculosis in Suspected Pulmonary Tuberculosis Patients

Pulmonary tuberculosis (PTB) is one of the major infectious diseases in developing countries. The objective of this study was to compare rapid diagnostics technique, GeneXpert MTB/RIF (GeneXpert) and Multiplex PCR assay (MPCR) targeting IS6110 segment and mpb64 gene for direct detection of Mycobacterium tuberculosis (MTB) in suspected PTB patients. A cross sectional study was carried among 105 sputum samples from suspected PTB patients to evaluate GeneXpert and Multiplex PCR who visited National Tuberculosis Center, Nepal. The patient's sputum samples were used directly for the GeneXpert whereas DNA extraction by CTAB method was followed to process the sample for MPCR. The sensitivity and specificity of GeneXpert and MPCR in smear positive cases was 78.6, 33.3, and 100.0%, 66.7%, respectively (P = 0.125). However, in smear negative cases sensitivity and specificity of both methods exhibited 90.9, 95.2, and 100.0%, 100.0% respectively (P = 0.625). Finally, the sensitivity and specificity of GeneXpert and MPCR were 82.9, 95.3 and 100.0%, 98.5% respectively, (P = 0.549) in pulmonary cases. Comparatively, we observed higher sensitivity and specificity for MPCR than GeneXpert for both smear positive and negative samples. Thus, we recommend MPCR alongside GeneXpert for the better diagnostic accuracy of PTB in a resource-limited country where tuberculosis is endemic.

Mycobacteria-specific cytokine responses as correlates of treatment response in active and latent tuberculosis

OBJECTIVES

A biomarker indicating successful tuberculosis (TB) therapy would assist in determining appropriate length of treatment. This study aimed to determine changes in mycobacteria-specific antigen-induced cytokine biomarkers in patients receiving therapy for latent or active TB, to identify biomarkers potentially correlating with treatment success.

METHODS

A total of 33 adults with active TB and 36 with latent TB were followed longitudinally over therapy. Whole blood stimulation assays using mycobacteria-specific antigens (CFP-10, ESAT-6, PPD) were done on samples obtained at 0, 1, 3, 6 and 9 months. Cytokine responses (IFN-γ, IL-1ra, IL-2, IL-10, IL-13, IP-10, MIP-1β, and TNF-α) in supernatants were measured by Luminex xMAP immunoassay.

RESULTS

In active TB cases, median IL-1ra (with CFP-10 and with PPD stimulation), IP-10 (CFP-10, ESAT-6), MIP-1β (ESAT-6, PPD), and TNF-α (ESAT-6) responses declined significantly over the course of therapy. In latent TB cases, median IL-1ra (CFP-10, ESAT-6, PPD), IL-2 (CFP-10, ESAT-6), and IP-10 (CFP-10, ESAT-6) responses declined significantly.

CONCLUSIONS

Mycobacteria-specific cytokine responses change significantly over the course of therapy, and their kinetics in active TB differ from those observed in latent TB. In particular, mycobacteria-specific IL-1ra responses are potential correlates of successful therapy in both active and latent TB.

Multiplex detection of bacteria on an integrated centrifugal disk using bead-beating lysis and loop-mediated amplification

Although culture-based identification of bacteria is the gold-standard for the diagnosis of infectious diseases, it is time consuming. Recent advances in molecular diagnostics and microfluidic technologies have opened up new avenues for rapid detection of bacteria. Here, we describe a centrifugal-microfluidic chip for the detection of bacteria by integrating the cell lysis, clarification, and loop-mediated amplification (LAMP). The major advantages of this chip are as follows. Firstly, bacteria lysis was innovatively achieved by rotating a pair of magnets to generate bead-beating while the chip was kept stationary during lysis, which simplified the chip design because no additional valve was needed. Secondly, the on-chip assay time was short (within 70 min), which was competitive in emergency situations. Thirdly, results of the analysis can be interpreted by using a fluorescence detector or by the naked-eye, making it versatile in many areas, especially the resource-limited areas. The on-chip limits of detection of six types of bacteria were valued by gel electrophoresis, showing the similar results compared to the bench-top LAMP protocol. This chip can be used for rapid, sensitive, accurate and automated detection of bacteria, offering a promising alternative for simplifying the molecular diagnostics of infectious diseases.

Molecular diagnosis of central nervous system opportunistic infections and mortality in HIV-infected adults in Central China

BACKGROUND

CSF PCR is the standard diagnostic technique used in resource-rich settings to detect pathogens of the CNS infection. However, it is not currently used for routine CSF testing in China. Knowledge of CNS opportunistic infections among people living with HIV in China is limited.

METHODS

Intensive cerebrospiral fluid (CSF) testing was performed to evaluate for bacterial, viral and fungal etiologies. Pathogen-specific primers were used to detect DNA from cytomegalovirus (CMV), herpes simplex virus (HSV), varicella-zoster virus (VZV), Epstein-Barr virus (EBV), human herpesvirus 6 (HHV-6) and John Cunningham virus (JCV) via real-time polymerase chain reaction (PCR).

RESULTS

Cryptococcal meningitis accounted for 63.0% (34 of 54) of all causes of meningitis, 13.0% (7/54) for TB, 9.3% (5/54) for Toxoplasma gondii. Of 54 samples sent for viral PCR, 31.5% (17/54) were positive, 12 (22.2%) for CMV, 2 (3.7%) for VZV, 1 (1.9%) for EBV, 1 (1.9%) for HHV-6 and 1 (1.9%) for JCV. No patient was positive for HSV. Pathogen-based treatment and high GCS score tended to have a lower mortality rate, whereas patients with multiple pathogens infection, seizures or intracranial hypertension showed higher odds of death.

CONCLUSION

CNS OIs are frequent and multiple pathogens often coexist in CSF. Cryptococcal meningitis is the most prevalent CNS disorders among AIDS. The utility of molecular diagnostics for pathogen identification combined with the knowledge provided by the investigation may improve the diagnosis of AIDS related OIs in resource-limited developing countries, but the cost-efficacy remains to be further evaluated.

Diagnostic Performance of Tuberculosis-Specific IgG Antibody Profiles in Patients with Presumptive Tuberculosis from Two Continents

BACKGROUND

Development of rapid diagnostic tests for tuberculosis is a global priority. A whole proteome screen identified Mycobacterium tuberculosis antigens associated with serological responses in tuberculosis patients. We used World Health Organization (WHO) target product profile (TPP) criteria for a detection test and triage test to evaluate these antigens.

METHODS

Consecutive patients presenting to microscopy centers and district hospitals in Peru and to outpatient clinics at a tuberculosis reference center in Vietnam were recruited. We tested blood samples from 755 HIV-uninfected adults with presumptive pulmonary tuberculosis to measure IgG antibody responses to 57 M. tuberculosis antigens using a field-based multiplexed serological assay and a 132-antigen bead-based reference assay. We evaluated single antigen performance and models of all possible 3-antigen combinations and multiantigen combinations.

RESULTS

Three-antigen and multiantigen models performed similarly and were superior to single antigens. With specificity set at 90% for a detection test, the best sensitivity of a 3-antigen model was 35% (95% confidence interval [CI], 31-40). With sensitivity set at 85% for a triage test, the specificity of the best 3-antigen model was 34% (95% CI, 29-40). The reference assay also did not meet study targets. Antigen performance differed significantly between the study sites for 7/22 of the best-performing antigens.

CONCLUSIONS

Although M. tuberculosis antigens were recognized by the IgG response during tuberculosis, no single antigen or multiantigen set performance approached WHO TPP criteria for clinical utility among HIV-uninfected adults with presumed tuberculosis in high-volume, urban settings in tuberculosis-endemic countries.

Diagnostic system strengthening for drug resistant tuberculosis in Nigeria: impact and challenges

Background: The increasing prevalence of drug-resistant tuberculosis and the threat of extensively-drug-resistant tuberculosis in HIV hotspots have made the detection and treatment of drug-resistant tuberculosis in the sub-Saharan Africa setting a global public health priority.Objective: We sought to examine the impact and challenges of tuberculosis diagnostic capacity development for the detection of drug-resistant tuberculosis and bio-surveillance using a modular biosafety level 3 (BSL-3) laboratory in Nigeria.Method: In 2010, the United States President’s Emergency Plan for AIDS Relief (PEPFAR) programme, through the Institute of Human Virology at the University of Maryland in Baltimore, Maryland, United States, deployed a modular, BSL-3 laboratory to support the national tuberculosis programme in drug-resistant tuberculosis detection and bio-surveillance for effective tuberculosis prevention and control.Results: From 2010 until present, sputum samples from 11 606 suspected cases in 33 states were screened for drug-resistant tuberculosis. Of those, 1500 (12.9%) had mono-resistant tuberculosis strains, and 459 (4.0%) cases had multidrug-resistant tuberculosis. Over the lastfour years, 133 scientists were trained in a train-the-trainer programme on advanced tuberculosis culture, drug susceptibility testing, line-probe assays and Xpert® MTB/RIF, in addition to safety operations for biosafety facilities. Power instability, running cost and seasonal dust are notable challenges to optimal performance and scale up.Conclusion: Movable BSL-3 containment laboratories can be deployed to improve diagnostic capacity for drug-resistant tuberculosis and bio-surveillance in settings with limited resources.

Rolling Out Xpert® MTB/RIF for TB Detection in HIV-Infected Populations:An Opportunity for Systems Strengthening

Background

To eliminate preventable deaths, disease and suffering due to tuberculosis, improved diagnostic capacity is critical. The Cepheid Xpert MTB/RIF^® assay is recommended by the World Health Organization as the initial diagnostic test for people with suspected HIV-associated tuberculosis. However, despite high expectations, its scale-up in real-world settings has faced challenges, often due to the systems that support it.

Opportunities for System Strengthening

In this commentary, we discuss needs and opportunities for systems strengthening to support widespread scale-up of Xpert MTB/RIF as they relate to each step within the tuberculosis diagnostic cascade, from finding presumptive patients, to collecting, transporting and testing sputum specimens, to reporting and receiving results, to initiating and monitoring treatment and, ultimately, to ensuring successful and timely treatment and cure. Investments in evidence-based interventions at each step along the cascade and within the system as a whole will augment not only the utility of Xpert MTB/RIF, but also the successful implementation of future diagnostic tests.

Conclusion

Xpert MTB/RIF will only improve patient outcomes if optimally implemented within the context of strong tuberculosis programmes and systems. Roll-out of this technology to people living with HIV and others in resource-limited settings offers the opportunity to leverage current tuberculosis and HIV laboratory, diagnostic and programmatic investments, while also addressing challenges and strengthening coordination between laboratory systems, laboratory-programme interfaces, and tuberculosis-HIV programme interfaces. If successful, the benefits of this tool could extend beyond progress toward global End TB Strategy goals, to improve system-wide capacity for global disease detection and control.

The additional role of Xpert MTB/RIF in the diagnosis of intrathoracic tuberculous lymphadenitis

BACKGROUND

Diagnosis of intrathoracic tuberculosis (TB) lymphadenitis remains a challenge because of difficulties in obtaining adequate tissue and the lack of a sensitive test. Recently, Xpert MTB/RIF assay is being used for rapid diagnosis of pulmonary TB, but it has not yet been widely validated in intrathoracic TB lymphadenitis. The aim of this study was to assess the additional role of Xpert MTB/RIF in diagnosing intrathoracic TB lymphadenitis using endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) specimen.

METHODS

Consecutive patients who underwent Xpert MTB/RIF assay using EBUS-TBNA specimen from January 2012 and November 2013 at a tertiary referral hospital were recruited. Among them, the cases with malignant lymph nodes were excluded.

RESULTS

Among 73 patients, 13 (17.8%) cases were diagnosed with intrathoracic TB lymphadenitis. In detail, 10 patients were diagnosed using conventional methods only (histology or AFB culture) and 3 patients were additionally diagnosed when adding Xpert MTB/RIF assay. The median time to diagnosis using Xpert MTB/RIF (1 day) was shorter than conventional methods (3 days for histology, 14 days for AFB culture). Rifampin resistance was not detected in any patients.

CONCLUSION

In patients with enlarged intrathoracic lymph nodes and low suspicion of malignancy, combination of conventional diagnostic methods with Xpert MTB/RIF could lead to additional and rapid diagnosis of intrathoracic TB lymphadenitis.

Measuring mortality due to HIV-associated tuberculosis among adults in South Africa: Comparing verbal autopsy, minimally-invasive autopsy, and research data

BACKGROUND

The World Health Organization (WHO) aims to reduce tuberculosis (TB) deaths by 95% by 2035; tracking progress requires accurate measurement of TB mortality. International Classification of Diseases (ICD) codes do not differentiate between HIV-associated TB and HIV more generally. Verbal autopsy (VA) is used to estimate cause of death (CoD) patterns but has mostly been validated against a suboptimal gold standard for HIV and TB. This study, conducted among HIV-positive adults, aimed to estimate the accuracy of VA in ascertaining TB and HIV CoD when compared to a reference standard derived from a variety of clinical sources including, in some, minimally-invasive autopsy (MIA).

METHODS AND FINDINGS

Decedents were enrolled into a trial of empirical TB treatment or a cohort exploring diagnostic algorithms for TB in South Africa. The WHO 2012 instrument was used; VA CoD were assigned using physician-certified VA (PCVA), InterVA-4, and SmartVA-Analyze. Reference CoD were assigned using MIA, research, and health facility data, as available. 259 VAs were completed: 147 (57%) decedents were female; median age was 39 (interquartile range [IQR] 33-47) years and CD4 count 51 (IQR 22-102) cells/μL. Compared to reference CoD that included MIA (n = 34), VA underestimated mortality due to HIV/AIDS (94% reference, 74% PCVA, 47% InterVA-4, and 41% SmartVA-Analyze; chance-corrected concordance [CCC] 0.71, 0.42, and 0.31, respectively) and HIV-associated TB (41% reference, 32% PCVA; CCC 0.23). For individual decedents, all VA methods agreed poorly with reference CoD that did not include MIA (n = 259; overall CCC 0.14, 0.06, and 0.15 for PCVA, InterVA-4, and SmartVA-Analyze); agreement was better at population level (cause-specific mortality fraction accuracy 0.78, 0.61, and 0.57, for the three methods, respectively).

CONCLUSIONS

Current VA methods underestimate mortality due to HIV-associated TB. ICD and VA methods need modifications that allow for more specific evaluation of HIV-related deaths and direct estimation of mortality due to HIV-associated TB.

Clinical evaluation of the Abbott RealTime MTB Assay for direct detection of Mycobacterium tuberculosis-complex from respiratory and non-respiratory samples

Rapid and reliable diagnosis is crucial for correct management of tuberculosis. The Abbott RealTime MTB Assay represents a novel qualitative real-time PCR assay for direct detection of M. tuberculosis-complex (MTB) DNA from respiratory samples. The test targets two highly conserved sequences, the multi-copy insertion element IS6110 and the protein antigen B (PAB) gene of MTB, allowing even the detection of IS6610-deficient strains. We evaluated this commercial diagnostic test by analyzing 200 respiratory and, for the first time, 87 non-respiratory clinical specimens from our tertiary care institution and compared its results to our IS6110-based in-house real-time PCR for MTB as well as MTB culture. Overall sensitivity for Abbott RealTime MTB was 100% (19/19) in smear positive and 87.5% (7/8) in smear negative specimens, while the specificity of the assay was 100% (260/260). For both non-respiratory smear positive and smear negative specimens Abbott RealTime MTB tests showed 100% (8/8) sensitivity and 100% (8/8) specificity. Cycle threshold (Ct) value analysis of 16 MTB positive samples showed a slightly higher Ct value of the Abbott RealTime MTB test compared to our in-house MTB assay (mean delta Ct = 2.55). In conclusion, the performance of the new Abbott RealTime MTB Assay was highly similar to culture and in-house MTB PCR. We document successful analysis of 87 non-respiratory samples with the highly automated Abbott RealTime MTB test with no inhibition observed.

Clinical Impact and Cost-effectiveness of Xpert MTB/RIF Testing in Hospitalized Patients With Presumptive Pulmonary Tuberculosis in the United States

Background

Microscopic examination of acid-fast-stained sputum smears is the current standard of care in the United States to determine airborne infection isolation (AII) of inpatients with presumptive pulmonary tuberculosis (PTB). However, nucleic acid amplification testing (NAAT) with the Xpert MTB/RIF assay (Xpert) may be more efficient and less costly.

Methods

This prospective observational cohort study enrolled a consecutive sample of 318 AII-eligible inpatients from a public hospital in Seattle, Washington, from March 2012 to October 2013. Sputum samples were collected from each inpatient and analyzed using smear microscopy, culture, drug susceptibility testing, and NAAT. The performance, clinical utility (AII duration and survival), and cost-effectiveness from an institutional perspective were compared for 5 testing strategies.

Results

Among the 318 admissions with presumptive PTB, 20 (6.3%) were culture-positive for Mycobacterium tuberculosis. The sensitivity of 1 Xpert, 2 Xperts, 2 smears, or 3 smears compared to culture was 0.85 (95% confidence interval [CI], .61–.96), 0.95 (95% CI, .73–1.0), 0.70 (95% CI, .46–.88), and 0.80 (95% CI, .56–.93), respectively. A cost-effectiveness analysis of the study results demonstrated that an Xpert test on 1 unconcentrated sputum sample (assuming equivalent results for unconcentrated and concentrated sputum samples) is the most cost-effective strategy (99.9% preferred at willingness-to-pay of US$50000) and on average would save 51.5 patient-hours in AII and up to $11466 relative to microscopy without a compromise in sensitivity.

Conclusions

In hospitalized patients with presumptive PTB in a low-burden setting, NAAT can reduce AII and is comparably sensitive, more specific, and more cost-effective than smear microscopy.

Incremental Yield of Including Determine-TB LAM Assay in Diagnostic Algorithms for Hospitalized and Ambulatory HIV-Positive Patients in Kenya

Background

Determine-TB LAM assay is a urine point-of-care test useful for TB diagnosis in HIV-positive patients. We assessed the incremental diagnostic yield of adding LAM to algorithms based on clinical signs, sputum smear-microscopy, chest X-ray and Xpert MTB/RIF in HIV-positive patients with symptoms of pulmonary TB (PTB).

Methods

Prospective observational cohort of ambulatory (either severely ill or CD4<200cells/μl or with Body Mass Index<17Kg/m²) and hospitalized symptomatic HIV-positive adults in Kenya. Incremental diagnostic yield of adding LAM was the difference in the proportion of confirmed TB patients (positive Xpert or MTB culture) diagnosed by the algorithm with LAM compared to the algorithm without LAM. The multivariable mortality model was adjusted for age, sex, clinical severity, BMI, CD4, ART initiation, LAM result and TB confirmation.

Results

Among 474 patients included, 44.1% were severely ill, 69.6% had CD4<200cells/μl, 59.9% had initiated ART, 23.2% could not produce sputum. LAM, smear-microscopy, Xpert and culture in sputum were positive in 39.0% (185/474), 21.6% (76/352), 29.1% (102/350) and 39.7% (92/232) of the patients tested, respectively. Of 156 patients with confirmed TB, 65.4% were LAM positive. Of those classified as non-TB, 84.0% were LAM negative. Adding LAM increased the diagnostic yield of the algorithms by 36.6%, from 47.4% (95%CI:39.4–55.6) to 84.0% (95%CI:77.3–89.4%), when using clinical signs and X-ray; by 19.9%, from 62.2% (95%CI:54.1–69.8) to 82.1% (95%CI:75.1–87.7), when using clinical signs and microscopy; and by 13.4%, from 74.4% (95%CI:66.8–81.0) to 87.8% (95%CI:81.6–92.5), when using clinical signs and Xpert. LAM positive patients had an increased risk of 2-months mortality (aOR:2.7; 95%CI:1.5–4.9).

Conclusion

LAM should be included in TB diagnostic algorithms in parallel to microscopy or Xpert request for HIV-positive patients either ambulatory (severely ill or CD4<200cells/μl) or hospitalized. LAM allows same day treatment initiation in patients at higher risk of death and in those not able to produce sputum.

Diagnostic Accuracy of GeneXpert MTB/RIF Assay in Comparison to Conventional Drug Susceptibility Testing Method for the Diagnosis of Multidrug-Resistant Tuberculosis

Xpert MTB/RIF assay is regarded as a great achievement of modern medicine for the rapid diagnosis of multidrug-resistant tuberculosis (MDR-TB). The main purpose of this study was to determine the performance of Xpert MTB/RIF assay compared to conventional drug susceptibility testing (DST) method for the diagnosis of MDR-TB. A comparative cross sectional study was carried out at German-Nepal Tuberculosis Project, Kathmandu, Nepal, from April 2014 to September 2014. A total of 88 culture positive clinical samples (83 pulmonary and 5 extra-pulmonary) received during the study period were analyzed for detection of multidrug-resistant tuberculosis by both GeneXpert MTB/RIF assay and conventional DST method. McNemar chi square test was used to compare the performance of Xpert with that of DST method. A p-value of less than 0.05 was considered as statistically significant. Of total 88 culture positive samples, one was reported as invalid while 2 were found to contain nontuberculous Mycobacteria (NTM). Among remaining 85 Mycobacterium tuberculosis culture positive samples, 69 were found to be MDR-TB positive by both methods. The overall sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of GeneXpert MTB/RIF assay were found to be 98.6%, 100%, 100% and 93.8% respectively. Statistically, there was no significant difference between the diagnostic performance of Xpert and conventional DST method for detection of MDR-TB. GeneXpert MTB/RIF assay was found to be highly sensitive, specific and comparable to gold standard conventional DST method for the diagnosis of MDR-TB.

Comprehensiveness of HIV care provided at global HIV treatment sites in the IeDEA consortium: 2009 and 2014

INTRODUCTION

An important determinant of the effectiveness of HIV treatment programs is the capacity of sites to implement recommended services and identify systematic changes needed to ensure that invested resources translate into improved patient outcomes. We conducted a survey in 2014 of HIV care and treatment sites in the seven regions of the International epidemiologic Database to Evaluate AIDS (IeDEA) Consortium to evaluate facility characteristics, HIV prevention, care and treatment services provided, laboratory capacity, and trends in the comprehensiveness of care compared to data obtained in the 2009 baseline survey.

METHODS

Clinical staff from 262 treatment sites in 45 countries in IeDEA completed a site survey from September 2014 to January 2015, including Asia-Pacific with Australia (n = 50), Latin America and the Caribbean (n = 11), North America (n = 45), Central Africa (n = 17), East Africa (n = 36), Southern Africa (n = 87), and West Africa (n = 16). For the 55 sites with complete data from both the 2009 and 2014 survey, we evaluated change in comprehensiveness of care.

RESULTS

The majority of the 262 sites (61%) offered seven essential services (ART adherence, nutritional support, PMTCT, CD4+ cell count testing, tuberculosis screening, HIV prevention, and outreach). Sites that were publicly funded (64%), cared for adults and children (68%), low or middle Human Development Index (HDI) rank (68%, 68%), and received PEPFAR support (71%) were most often fully comprehensive. CD4+ cell count testing was universally available (98%) but only 62% of clinics offered it onsite. Approximately two-thirds (69%) of sites reported routine viral load testing (44-100%), with 39% having it onsite. Laboratory capacity to monitor antiretroviral-related toxicity and diagnose opportunistic infections varied widely by testing modality and region. In the subgroup of 55 sites with two surveys, comprehensiveness of services provided significantly increased across all regions from 2009 to 2014 (5.7 to 6.5, p < 0.001).

CONCLUSION

The availability of viral load monitoring remains suboptimal and should be a focus for site capacity, particularly in East and Southern Africa, where the majority of those initiating on ART reside. However, the comprehensiveness of care provided increased over the past 5 years and was related to type of funding received (publicly funded and PEPFAR supported).

Improving health-care delivery in low-resource settings with nanotechnology: Challenges in multiple dimensions

In the two decades after 1990, the rates of child and maternal mortality dropped by over 40% and 47%, respectively. Despite these improvements, which are in part due to increased access to medical technologies, profound health disparities exist. In 2015, a child born in a developing region is nearly eight times as likely to die before the age of 5 than one born in a developed region and developing regions accounted for nearly 99% of the maternal deaths. Recent developments in nanotechnology, however, have great potential to ameliorate these and other health disparities by providing new cost-effective solutions for diagnosis or treatment of a variety of medical conditions. Affordability is only one of the several challenges that will need to be met to translate new ideas into a medical product that addresses a global health need. This article aims to describe some of the other challenges that will be faced by nanotechnologists who seek to make an impact in low-resource settings across the globe.

Second line drug susceptibility testing to inform the treatment of rifampin-resistant tuberculosis: a quantitative perspective

Treatment failure and resistance amplification are common among patients with rifampin-resistant tuberculosis (TB). Drug susceptibility testing (DST) for second-line drugs is recommended for these patients, but logistical difficulties have impeded widespread implementation of second-line DST in many settings. To provide a quantitative perspective on the decision to scale up second-line DST, we synthesize literature on the prevalence of second-line drug resistance, the expected clinical and epidemiologic benefits of using second-line DST to ensure that patients with rifampin-resistant TB receive effective regimens, and the costs of implementing (or not implementing) second-line DST for all individuals diagnosed with rifampin-resistant TB. We conclude that, in most settings, second-line DST could substantially improve treatment outcomes for patients with rifampin-resistant TB, reduce transmission of drug-resistant TB, prevent amplification of drug resistance, and be affordable or even cost-saving. Given the large investment made in each patient treated for rifampin-resistant TB, these payoffs would come at relatively small incremental cost. These anticipated benefits likely justify addressing the real challenges faced in implementing second-line DST in most high-burden settings.

Can China achieve the WHO global targets for TB control by 2035?

To reach the ambitious WHO TB global targets by 2035, it is likely that China will need a comprehensive strategy that builds on its existing high-quality directly observed treatment, short-course program. This will require optimizing the use of existing tools within a changing health system landscape. In addition, new tools are needed to identify and treat TB in high-risk groups and in older people, who are a growing driver of disease incidence. Lastly, strategies are needed to address the proximate risk factors and social determinants that underlie trends in TB burden.

Parameter set for computer-assisted texture analysis of fetal brain

BACKGROUND

Magnetic resonance data were collected from a diverse population of gravid women to objectively compare the quality of 1.5-tesla (1.5 T) versus 3-T magnetic resonance imaging of the developing human brain. MaZda and B11 computational-visual cognition tools were used to process 2D images. We proposed a wavelet-based parameter and two novel histogram-based parameters for Fisher texture analysis in three-dimensional space.

RESULTS

Wavenhl, focus index, and dispersion index revealed better quality for 3 T. Though both 1.5 and 3 T images were 16-bit DICOM encoded, nearly 16 and 12 usable bits were measured in 3 and 1.5 T images, respectively. The four-bit padding observed in 1.5 T K-space encoding mimics noise by adding illusionistic details, which are not really part of the image. In contrast, zero-bit padding in 3 T provides space for storing more details and increases the likelihood of noise but as well as edges, which in turn are very crucial for differentiation of closely related anatomical structures.

CONCLUSIONS

Both encoding modes are possible with both units, but higher 3 T resolution is the main difference. It contributes to higher perceived and available dynamic range. Apart from surprisingly larger Fisher coefficient, no significant difference was observed when testing was conducted with down-converted 8-bit BMP images.

Analysis of discrepant results between the Genotype® MTBDRplus assay and an antimicrobial drug susceptibility test for isoniazid-resistant tuberculosis

BACKGROUND

We investigated discrepant results determined using the Genotype^®MTBDRplus assay and a conventional antimicrobial drug susceptibility test (ADST) for isoniazid (INH) resistance using sequencing analysis and analyzed the clinical course of patients with discrepant results.

METHODS

Among 1373 MTBDRplus assays performed at our tertiary referral center in South Korea between August 2009 and December 2015, the results for 46 (3.4%) differed from those for ADST. KatG and inhA gene sequencing analysis results were available for 23 patients. ADSTs were carried out using the absolute concentration method with Löwenstein-Jensen media.

RESULTS

Results from 11 patients indicated INH susceptibility by MTBDRplus assay and INH resistance by ADST. For 5 of these patients, sequencing revealed no evidence of mutations, whereas specific mutations were detected in the remaining 6 patients. These should have been detected using the MTBDRplus assay. The other 12 patients had isolates with the opposite discrepancy, that is INH resistance by MTBDRplus assay but INH susceptibility by ADST. For 7 of these cases, sequencing results were consistent with those of the MTBDRplus assay. However, sequencing analysis did not explain the discrepancies in the remaining 5 patients. All 23 patients with discrepant results received individualized treatment regimens determined by the attending physician according to their test results and susceptibility to other drugs, such as rifampin. Good outcomes were reported for the majority.

CONCLUSION

Discrepancies between test results for INH resistance on the MTBDRplus assay and ADST appear to be infrequent. Gene sequencing analysis is useful for identifying the cause of the discrepancy.

Implementation of a pragmatic, stepped-wedge cluster randomized trial to evaluate impact of Botswana's Xpert MTB/RIF diagnostic algorithm on TB diagnostic sensitivity and early antiretroviral therapy mortality

BACKGROUND

In 2012, as a pilot for Botswana's national Xpert MTB/RIF (Xpert) rollout plans, intensified tuberculosis (TB) case finding (ICF) activities were strengthened at 22 HIV treatment clinics prior to phased activation of 13 Xpert instruments. Together, the strengthened ICF intervention and Xpert activation are referred to as the "Xpert package".

METHODS

The evaluation, called the Xpert Package Rollout Evaluation using a Stepped-wedge design (XPRES), has two key objectives: (1) to compare sensitivity of microscopy-based and Xpert-based pulmonary TB diagnostic algorithms in diagnosing sputum culture-positive TB; and (2) to evaluate impact of the "Xpert package" on all-cause, 6-month, adult antiretroviral therapy (ART) mortality. A pragmatic, stepped-wedge cluster-randomized trial design was chosen. The design involves enrollment of three cohorts: (1) cohort R, a retrospective cohort of all study clinic ART enrollees in the 24 months before study initiation (July 31, 2012); (2) cohort A, a prospective cohort of all consenting patients presenting to study clinics after study initiation, who received the ICF intervention and the microscopy-based TB diagnostic algorithm; and (3) cohort B, a prospective cohort of all consenting patients presenting to study clinics after Xpert activation, who received the ICF intervention and the Xpert-based TB diagnostic algorithm. TB diagnostic sensitivity will be compared between TB culture-positive enrollees in cohorts A and B. All-cause, 6-month ART-mortality will be compared between cohorts R and B. With anticipated cohort R, A, and B sample sizes of about 10,131, 1,878, and 4,258, respectively, the study is estimated to have >80 % power to detect differences in pre-versus post-Xpert TB diagnostic sensitivity if pre-Xpert sensitivity is ≤52.5 % and post-Xpert sensitivity ≥82.5 %, and >80 % power to detect a 40 % reduction in all-cause, 6-month, ART mortality between cohorts R and B if cohort R mortality is ≥13/100 person-years.

DISCUSSION

Only one small previous trial (N = 424) among ART enrolees in Zimbabwe evaluated, in a secondary analysis, Xpert impact on all-cause 6-month ART mortality. No mortality impact was observed. This Botswana trial, with its larger sample size and powered specifically to detect differences in all-cause 6-month ART mortality, remains well-positioned to contribute understanding of Xpert impact.

TRIAL REGISTRATION

Retrospectively registered at ClinicalTrials.gov: NCT02538952 .

Xpert MTB/RIF - why the lack of morbidity and mortality impact in intervention trials?

Compared with smear microscopy, the Xpert MTB/RIF assay (Xpert), with superior accuracy and capacity to diagnose rifampicin resistance, has advanced TB diagnostic capability. However, recent trials of Xpert impact have not demonstrated reductions in patient morbidity and mortality. We conducted a narrative review of Xpert impact trials to summarize which patient-relevant outcomes Xpert has improved and explore reasons for no observed morbidity or mortality reductions. We searched PubMed, Google Scholar, Cochrane Library and Embase and identified eight trials meeting inclusion criteria: three individually randomized, three cluster-randomized, and two pre-post trials. In six trials Xpert increased diagnostic yield of bacteriologically-confirmed TB from sputa and in four trials Xpert shortened time to TB treatment. However, all-cause mortality was similar between arms in all six trials reporting this outcome, and the only trial to assess Xpert impact on morbidity reported no impact. Trial characteristics that might explain lack of observed impact on morbidity and mortality include: higher rates of empiric TB treatment in microscopy compared with Xpert arms, enrollment of study populations not comprised exclusively of populations most likely to benefit from Xpert, and health system weaknesses. So far as equipoise exists, future trials that address past limitations are needed to inform Xpert use in resource-limited settings.

Prevalence of drug resistant TB among outpatients at an HIV/TB clinic in Lilongwe, Malawi

BACKGROUND

We sought to determine the prevalence of drug resistant TB among outpatients initiating TB treatment in Lilongwe, Malawi.

METHODS

This was a prospective cohort study of patients 18 years and older initiating TB treatment at Martin Preuss Centre, the primary integrated HIV/TB clinic in Lilongwe, Malawi, from April 2011 to July 2012. Procedures included questionnaires, physical exam, chest x-ray, full blood count and sputum collection. Sputum samples underwent acid-fast bacilli (AFB) smear testing and culture by Lowenstein-Jensen (LJ) and liquid Mycobacteria Growth Indicator Tube (MGIT) methods. Drug sensitivity was investigated using the Hain GenoType MTBDRplus line probe assay.

RESULTS

Of the 702 patients, 219 (31.2%) were female and 653 (93.0%) were presenting for first-time TB treatment. HIV co-infection was present in 420 (59.8%) cases, with 137 (32.6%) of those patients receiving antiretroviral therapy at presentation. TB was culture-confirmed in 375 (53.4%) patients, 349 of which were first time treatment and 26 retreatment. Ten cases of isoniazid-resistant TB (2.9% of culture confirmed cases of newly treated TB), one of rifampin-resistant TB (0.3% culture confirmed cases of newly treated TB) and one of multi-drug resistant TB (MDR-TB) (3.8% of culture confirmed cases of retreatment TB) were detected.

CONCLUSIONS

MDR-TB prevalence is low among outpatients initiating TB treatment in Lilongwe.

Mycobacteria

The immunocompromised host is at increased risk of Mycobacterium tuberculosis complex and nontuberculous mycobacteria infection. Although Mycobacterium tuberculosis complex is a significant mycobacterial pathogen, nontuberculous mycobacteria causes substantial disease in those with suppressed immune responses. Mycobacterial infections can cause significant morbidity and mortality in this patient population, and rapid identification and susceptibility testing of the mycobacterial species is paramount to patient management and outcomes. Mycobacterial diagnostics has undergone some significant advances in the last two decades with immunodiagnostics (interferon gamma release assay), microscopy (light-emitting diode), culture (automated broth-based systems), identification (direct PCR, sequencing and matrix-assisted laser-desorption ionization–time of flight mass spectrometry) and susceptibility testing (molecular detection of drug resistance from direct specimens or positive cultures). Employing the most rapid and sensitive methods in the mycobacterial laboratory will have a tremendous impact on patient care and, in the case of Mycobacterium tuberculosis complex, in the control of tuberculosis.

Implementation and Operational Research: What Happens After a Negative Test for Tuberculosis? Evaluating Adherence to TB Diagnostic Algorithms in South African Primary Health Clinics

Introduction and Background:

Diagnostic tests for tuberculosis (TB) using sputum have suboptimal sensitivity among HIV-positive persons. We assessed health care worker adherence to TB diagnostic algorithms after negative sputum test results.

Methods:

The XTEND (Xpert for TB—Evaluating a New Diagnostic) trial compared outcomes among people tested for TB in primary care clinics using Xpert MTB/RIF vs. smear microscopy as the initial test. We analyzed data from XTEND participants who were HIV positive or HIV status unknown, whose initial sputum Xpert MTB/RIF or microscopy result was negative. If chest radiography, sputum culture, or hospital referral took place, the algorithm for TB diagnosis was considered followed. Analysis of intervention (Xpert MTB/RIF) effect on algorithm adherence used methods for cluster-randomized trials with small number of clusters.

Results:

Among 4037 XTEND participants with initial negative test results, 2155 (53%) reported being or testing HIV positive and 540 (14%) had unknown HIV status. Among 2155 HIV-positive participants [684 (32%) male, mean age 37 years (range, 18–79 years)], there was evidence of algorithm adherence among 515 (24%). Adherence was less likely among persons tested initially with Xpert MTB/RIF vs. smear [14% (142/1031) vs. 32% (364/1122), adjusted risk ratio 0.34 (95% CI: 0.17 to 0.65)] and for participants with unknown vs. positive HIV status [59/540 (11%) vs. 507/2155 (24%)].

Conclusions:

We observed poorer adherence to TB diagnostic algorithms among HIV-positive persons tested initially with Xpert MTB/RIF vs. microscopy. Poor adherence to TB diagnostic algorithms and incomplete coverage of HIV testing represents a missed opportunity to diagnose TB and HIV, and may contribute to TB mortality.

Implementation of HIV and Tuberculosis Diagnostics: The Importance of Context

BACKGROUND

Novel diagnostics have been widely applied across human immunodeficiency virus (HIV) and tuberculosis prevention and treatment programs. To achieve the greatest impact, HIV and tuberculosis diagnostic programs must carefully plan and implement within the context of a specific healthcare system and the laboratory capacity.

METHODS

A workshop was convened in Cape Town in September 2014. Participants included experts from laboratory and clinical practices, officials from ministries of health, and representatives from industry.

RESULTS

The article summarizes best practices, challenges, and lessons learned from implementation experiences across sub-Saharan Africa for (1) building laboratory programs within the context of a healthcare system; (2) utilizing experience of clinicians and healthcare partners in planning and implementing the right diagnostic; and (3) evaluating the effects of new diagnostics on the healthcare system and on patient health outcomes.

CONCLUSIONS

The successful implementation of HIV and tuberculosis diagnostics in resource-limited settings relies on careful consideration of each specific context.

The global tuberculosis situation and the inexorable rise of drug-resistant disease

The highly cost-effective DOTS strategy helped to bring the global tuberculosis (TB) epidemic under control in many parts of the world; however, the emergence and spread of drug-resistant strains pose a major threat to these gains. Molecular epidemiology studies, together with recent genomic evidence, provide proof that some drug-resistant strains are highly transmissible with documented epidemic spread. The potential for epidemic replacement of drug-susceptible with drug-resistant strains provides strong motivation for renewed emphasis on TB drug and vaccine development. It also reflects the need for enhanced infection control measures in health care and congregate settings, especially in TB endemic areas. The exploration of preventive therapy options for close contacts of patients with infectious drug-resistant TB also warrants further exploration, in an attempt to break the transmission cycle. Increased population mobility and large scale cross-border migration imply that the inexorable rise of drug-resistant TB is not geographically confined; it is a global concern that poses a very real threat to TB endemic and non-endemic settings. Failure to find new solutions will compromise traditional TB control efforts and derail momentum toward future TB elimination.

Use of Rapid, Point-of-Care Assays by Private Practitioners in Chennai, India: Priorities for Tuberculosis Diagnostic Testing

SETTING

Private practitioners are frequently the first point of healthcare contact for patients with tuberculosis (TB) in India. As new molecular tests are developed for point-of-care (POC) diagnosis of TB, it is imperative to understand these individuals' practices and preferences for POC testing.

OBJECTIVE

To evaluate rapid testing practices and identify priorities for novel POC TB tests among private practitioners in Chennai.

DESIGN

We conducted a cross-sectional survey of 228 practitioners practicing in the private sector from January 2014 to February 2015 who saw at least one TB patient in the previous year. Practitioners were randomly selected from both the general community and a list of practitioners who referred patients to a public-private mix program for TB treatment. We used standardized questionnaires to collect data on current practices related to point-of-care diagnosis and interest in hypothetical POC tests. We used multivariable Poisson regression with robust estimates of standard error to calculate measures of association.

RESULTS

Among 228 private practitioners, about half (48%) utilized any rapid testing in their current practice, most commonly for glucose (43%), pregnancy (21%), and malaria (5%). Providers using POC tests were more likely to work in hospitals (56% vs. 43%, P = 0.05) and less likely to be chest specialists (21% vs. 54%, P<0.001). Only half (51%) of providers would use a hypothetical POC test for TB that was accurate, equipment-free, and took 20 minutes to complete. Chest specialists were half as likely to express interest in performing the hypothetical POC TB test in-house as other practitioners (aPR 0.5, 95%CI: 0.2-0.9). Key challenges to performing POC testing for TB in this study included time constraints, easy access to local private labs and lack of an attached lab facility.

CONCLUSION

As novel POC tests for TB are developed and scaled up, attention must be paid to integrating these diagnostics into healthcare providers' routine practice and addressing barriers for POC testing.

Use of several immunological markers to model the probability of active tuberculosis

Blood-based biomarkers tests are attractive alternative for diagnosing tuberculosis to assays depending on mycobacteria detection. Given several immunological markers we used logistic regression to model the probability of active tuberculosis in a cohort of patients with active or latent tuberculosis, showing an increased accuracy in distinguishing active from latent tuberculosis.

Field evaluation of a novel preservation medium to transport sputum specimens for molecular detection of Mycobacterium tuberculosis in a rural African setting

OBJECTIVES

To assess the performance of an innovative method of transporting sputum to centralised facilities for molecular detection of Mycobacterium tuberculosis: using a swab to inoculate sputum in a transport medium, PrimeStore(®) Molecular Transport Medium (PS-MTM).

METHODS

Two sputum specimens were obtained from suspected patients with tuberculosis (TB) at rural healthcare facilities in South Africa. A swab was taken from each specimen and placed into PS-MTM, prior to it being processed by either liquid culture or Xpert MTB/RIF assay (Xpert).

RESULTS

A total of 141 patients (including 47 with laboratory-confirmed TB) were included in this analysis. M. tuberculosis was detected at 29% by culture and 29% by Xpert, whereas 31% tested positive by IS6110 real-time PCR of PS-MTM from the culture and 36% from the Xpert-paired specimen. Concordance between the method under evaluation with culture was 82% (McNemar, P = 0.55) and 84% (McNemar, P = 0.05) for Xpert. Stratified by culture result, the detection rate by IS6110 real-time PCR of PS-MTM was similar to Xpert for patients with positive culture (P = 0.32), but significantly higher if culture was negative (P = 0.008).

CONCLUSIONS

These results suggest that swab collection of sputum into PS-MTM for transport is a promising method for diagnosis of TB in rural healthcare settings, thereby potentially improving the options available for molecular diagnosis of TB in countries incapable of applying decentralised high-tech molecular testing.

Impact and cost-effectiveness of current and future tuberculosis diagnostics: the contribution of modelling

The landscape of diagnostic testing for tuberculosis (TB) is changing rapidly, and stakeholders need urgent guidance on how to develop, deploy and optimize TB diagnostics in a way that maximizes impact and makes best use of available resources. When decisions must be made with only incomplete or preliminary data available, modelling is a useful tool for providing such guidance. Following a meeting of modelers and other key stakeholders organized by the TB Modelling and Analysis Consortium, we propose a conceptual framework for positioning models of TB diagnostics. We use that framework to describe modelling priorities in four key areas: Xpert^® MTB/RIF scale-up, target product profiles for novel assays, drug susceptibility testing to support new drug regimens, and the improvement of future TB diagnostic models. If we are to maximize the impact and cost-effectiveness of TB diagnostics, these modelling priorities should figure prominently as targets for future research.

Digital PCR assay detection of circulating Mycobacterium tuberculosis DNA in pulmonary tuberculosis patient plasma

Nucleic acid amplification tests are a major diagnostic tool for pulmonary tuberculosis (PTB). Recently, digital PCR (dPCR) assay has improved sensitivity for the detection of small copy numbers of target molecules. The aim of this study is to explore the utility of dPCR for detecting Mycobacterium tuberculosis (MTB) DNA in PTB patient plasma. Total DNA was purified from plasma samples of newly diagnosed sputum smear-positive PTB patients. Copy numbers of MTB-specific genes in the samples were quantified with dPCR assays targeted for IS6110 or gyrB. A total of 33 PTB patients were enrolled. Significant differences between PTB patients and controls were observed in copy numbers of both targets: IS6110 mean ± SD, 144.8 ± 538.3 vs 0.44 ± 0.49 (copies/20 μL, p = 0.004; Mann-Whitney U test) and gyrB mean ± SD, 359.0 ± 2116 vs 0.07 ± 0.28 (copies/20 μL, p = 0.011; Mann-Whitney U test), respectively. This test had sensitivities of 65% or 29% and a specificity of 93% or 100% with the IS6110-targeted or gyrB-targeted assays, respectively. A dPCR assay successfully detected MTB DNA in PTB patient plasma. This minimally invasive and accurate method has potential to become an alternative diagnostic option.

Transcriptomics: the key to biomarker discovery during tuberculosis?

Tuberculosis is a global threat affecting millions of people and requires more efficient methods of diagnosis, monitoring treatment response and the development of more efficacious drug therapies and new vaccines. The use of transcriptomic approaches and gene expression techniques have contributed to the elucidation of these aspects concerning the study of tuberculosis, and more specifically, the utilization of transcriptional profiles to identify biomarkers. These markers are the key to developing tools required to improve diagnosis and treatment of tuberculosis. Several studies have led to the identification of markers able to distinguish between different infection states, as well as other pulmonary diseases. Utilizing a systems biology approach will assist in obtaining more reliable results, leading to the implementation of significant findings.

Prevalence of and risk factors for active tuberculosis in migrants screened before entry to the UK: a population-based cross-sectional study

BACKGROUND

An increasing number of countries with low incidence of tuberculosis have pre-entry screening programmes for migrants. We present the first estimates of the prevalence of and risk factors for tuberculosis in migrants from 15 high-incidence countries screened before entry to the UK.

METHODS

We did a population-based cross-sectional study of applicants for long-term visas who were screened for tuberculosis before entry to the UK in a pilot programme between Oct 1, 2005, and Dec 31, 2013. The primary outcome was prevalence of bacteriologically confirmed tuberculosis. We used Poisson regression to estimate crude prevalence and created a multivariable logistic regression model to identify risk factors for the primary outcome.

FINDINGS

476 455 visa applicants were screened, and the crude prevalence of bacteriologically confirmed tuberculosis was 92 (95% CI 84-101) per 100 000 individuals. After adjustment for age and sex, factors that were strongly associated with an increased risk of bacteriologically confirmed disease at pre-entry screening were self-report of close or household contact with an individual with tuberculosis (odds ratio 11·6, 95% CI 7·0-19·3; p<0·0001) and being an applicant for settlement and dependant visas (1·3, 1·0-1·6; p=0·0203).

INTERPRETATION

Migrants reporting contact with an individual with tuberculosis had the highest risk of tuberculosis at pre-entry screening. To tackle this disease burden in migrants, a comprehensive and collaborative approach is needed between countries with pre-entry screening programmes, health services in the countries of origin and migration, national tuberculosis control programmes, and international public health bodies.

FUNDING

Wellcome Trust, Medical Research Council, and UK National Institute for Health Research.

Accurate Detection of Rifampicin-Resistant Mycobacterium Tuberculosis Strains

In 2013 alone, the death rate among the 9.0 million people infected with Mycobacterium tuberculosis (TB) worldwide was around 14%, which is unacceptably high. An empiric treatment of patients infected with TB or drug-resistant Mycobacterium tuberculosis (MDR-TB) strain can also result in the spread of MDR-TB. The diagnostic tools which are rapid, reliable, and have simple experimental protocols can significantly help in decreasing the prevalence rate of MDR-TB strain. We report the evaluation of the 9G technology based 9G DNAChips that allow accurate detection and discrimination of TB and MDR-TB-RIF. One hundred and thirteen known cultured samples were used to evaluate the ability of 9G DNAChip in the detection and discrimination of TB and MDR-TB-RIF strains. Hybridization of immobilized probes with the PCR products of TB and MDR-TB-RIF strains allow their detection and discrimination. The accuracy of 9G DNAChip was determined by comparing its results with sequencing analysis and drug susceptibility testing. Sequencing analysis showed 100% agreement with the results of 9G DNAChip. The 9G DNAChip showed very high sensitivity (95.4%) and specificity (100%).

Tuberculosis-related mortality in people living with HIV in Europe and Latin America: an international cohort study

BACKGROUND

Management of tuberculosis in patients with HIV in eastern Europe is complicated by the high prevalence of multidrug-resistant tuberculosis, low rates of drug susceptibility testing, and poor access to antiretroviral therapy (ART). We report 1 year mortality estimates from a multiregional (eastern Europe, western Europe, and Latin America) prospective cohort study: the TB:HIV study.

METHODS

Consecutive HIV-positive patients aged 16 years or older with a diagnosis of tuberculosis between Jan 1, 2011, and Dec 31, 2013, were enrolled from 62 HIV and tuberculosis clinics in 19 countries in eastern Europe, western Europe, and Latin America. The primary endpoint was death within 12 months after starting tuberculosis treatment; all deaths were classified according to whether or not they were tuberculosis related. Follow-up was either until death, the final visit, or 12 months after baseline, whichever occurred first. Risk factors for all-cause and tuberculosis-related deaths were assessed using Kaplan-Meier estimates and Cox models.

FINDINGS

Of 1406 patients (834 in eastern Europe, 317 in western Europe, and 255 in Latin America), 264 (19%) died within 12 months. 188 (71%) of these deaths were tuberculosis related. The probability of all-cause death was 29% (95% CI 26-32) in eastern Europe, 4% (3-7) in western Europe, and 11% (8-16) in Latin America (p<0·0001) and the corresponding probabilities of tuberculosis-related death were 23% (20-26), 1% (0-3), and 4% (2-8), respectively (p<0·0001). Patients receiving care outside eastern Europe had a 77% decreased risk of death: adjusted hazard ratio (aHR) 0·23 (95% CI 0·16-0·31). In eastern Europe, compared with patients who started a regimen with at least three active antituberculosis drugs, those who started fewer than three active antituberculosis drugs were at a higher risk of tuberculosis-related death (aHR 3·17; 95% CI 1·83-5·49) as were those who did not have baseline drug-susceptibility tests (2·24; 1·31-3·83). Other prognostic factors for increased tuberculosis-related mortality were disseminated tuberculosis and a low CD4 cell count. 18% of patients were receiving ART at tuberculosis diagnosis in eastern Europe compared with 44% in western Europe and 39% in Latin America (p<0·0001); 12 months later the proportions were 67% in eastern Europe, 92% in western Europe, and 85% in Latin America (p<0·0001).

INTERPRETATION

Patients with HIV and tuberculosis in eastern Europe have a risk of death nearly four-times higher than that in patients from western Europe and Latin America. This increased mortality rate is associated with modifiable risk factors such as lack of drug susceptibility testing and suboptimal initial antituberculosis treatment in settings with a high prevalence of drug resistance. Urgent action is needed to improve tuberculosis care for patients living with HIV in eastern Europe.

FUNDING

EU Seventh Framework Programme.

Tackling the tuberculosis epidemic in sub-Saharan Africa--unique opportunities arising from the second European Developing Countries Clinical Trials Partnership (EDCTP) programme 2015-2024

Tuberculosis (TB) today remains a global emergency affecting 9.0 million people globally. The African Region bears the highest global TB/HIV burden and over 50% of TB cases in SSA are co-infected with HIV. An estimated 1.5 million died from the TB globally in 2013. A large majority of the 360,000 HIV-positive TB cases who died were from sub-Saharan Africa. Research and development is an important pillar of the WHO post-2015 global TB strategy. Advances in development of diagnostics, drugs, host-directed therapies, and vaccines will require evaluation under field conditions through multi-centre clinical trials at different geographical locations. Thus it is critically important that these evaluations are fully supported by all African governments and the capacity, trained staff and infrastructure required to perform the research and evaluations is built and made available. This viewpoint article reviews the opportunities provided by recently launched second programme (2015-2024) of the European & Developing Countries Clinical Trials Partnership (EDCTP2) for tackling the TB epidemic in Africa through its magnanimous portfolio. The unique opportunities provided by EDCTP2 for leadership of scientific research in TB and other diseases fully devolving to Africa are also covered.

Tuberculosis and mass gatherings-opportunities for defining burden, transmission risk, and the optimal surveillance, prevention, and control measures at the annual Hajj pilgrimage

Tuberculosis (TB) is now the most common infectious cause of death worldwide. In 2014, an estimated 9.6 million people developed active TB. There were an estimated three million people with active TB including 360000 with multidrug-resistant TB (MDR-TB) who were not diagnosed, and such people continue to fuel TB transmission in the community. Accurate data on the actual burden of TB and the transmission risk associated with mass gatherings are scarce and unreliable due to the small numbers studied and methodological issues. Every year, an estimated 10 million pilgrims from 184 countries travel to the Kingdom of Saudi Arabia (KSA) to perform the Hajj and Umrah pilgrimages. A large majority of pilgrims come from high TB burden and MDR-TB endemic areas and thus many may have undiagnosed active TB, sub-clinical TB, and latent TB infection. The Hajj pilgrimage provides unique opportunities for the KSA and the 184 countries from which pilgrims originate, to conduct high quality priority research studies on TB under the remit of the Global Centre for Mass Gatherings Medicine. Research opportunities are discussed, including those related to the definition of the TB burden, transmission risk, and the optimal surveillance, prevention, and control measures at the annual Hajj pilgrimage. The associated data are required to develop international recommendations and guidelines for TB management and control at mass gathering events.

[Tuberculosis and immigration]

The incidence of tuberculosis worldwide is declining. However, in Western countries this decline is slower due to the impact of immigration. Tuberculosis in the immigrant population is related to health status in the country of origin and with overcrowding and poverty conditions in the host country. Immigrants with tuberculosis are younger, have a higher prevalence of extrapulmonary forms, greater proportion of drug resistance and higher treatment default rates than those of natives. New molecular techniques not only reduce diagnostic delay time but also allow the rapid identification of resistances and improve knowledge of transmission patterns. It is necessary to implement measures to improve treatment compliance in this population group like facilitating access to health card, the use of fixed-dose combination drugs, the participation of cultural mediators and community health workers and gratuity of drugs.

CD-Based Microfluidics for Primary Care in Extreme Point-of-Care Settings

We review the utility of centrifugal microfluidic technologies applied to point-of-care diagnosis in extremely under-resourced environments. The various challenges faced in these settings are showcased, using areas in India and Africa as examples. Measures for the ability of integrated devices to effectively address point-of-care challenges are highlighted, and centrifugal, often termed CD-based microfluidic technologies, technologies are presented as a promising platform to address these challenges. We describe the advantages of centrifugal liquid handling, as well as the ability of a standard CD player to perform a number of common laboratory tests, fulfilling the role of an integrated lab-on-a-CD. Innovative centrifugal approaches for point-of-care in extremely resource-poor settings are highlighted, including sensing and detection strategies, smart power sources and biomimetic inspiration for environmental control. The evolution of centrifugal microfluidics, along with examples of commercial and advanced prototype centrifugal microfluidic systems, is presented, illustrating the success of deployment at the point-of-care. A close fit of emerging centrifugal systems to address a critical panel of tests for under-resourced clinic settings, formulated by medical experts, is demonstrated. This emphasizes the potential of centrifugal microfluidic technologies to be applied effectively to extremely challenging point-of-care scenarios and in playing a role in improving primary care in resource-limited settings across the developing world.

Pilot study of a rapid and minimally instrumented sputum sample preparation method for molecular diagnosis of tuberculosis

Nucleic acid amplification testing (NAAT) enables rapid and sensitive diagnosis of tuberculosis (TB), which facilitates treatment and mitigates transmission. Nucleic acid extraction from sputum constitutes the greatest technical challenge in TB NAAT for near-patient settings. This report presents preliminary data for a semi-automated sample processing method, wherein sputum is disinfected and liquefied, followed by PureLyse^® mechanical lysis and solid-phase nucleic acid extraction in a miniaturized, battery-operated bead blender. Sputum liquefaction and disinfection enabled a >10⁴ fold reduction in viable load of cultured Mycobacterium tuberculosis (M.tb) spiked into human sputum, which mitigates biohazard concerns. Sample preparation via the PureLyse^® method and a clinically validated manual method enabled positive PCR-based detection for sputum spiked with 10⁴ and 10⁵ colony forming units (cfu)/mL M.tb. At 10³ cfu/mL sputum, four of six and two of six samples amplified using the comparator and PureLyse^® method, respectively. For clinical specimens from TB cases and controls, the two methods provided 100% concordant results for samples with 1 mL input volume (N = 41). The semi-automated PureLyse^® method therefore performed similarly to a validated manual comparator method, but is faster, minimally instrumented, and can be integrated into TB molecular diagnostic platforms designed for near-patient low-resource settings.