Quantitative IFN-γ Release Assay and Tuberculin Skin Test Results to Predict Incident Tuberculosis. A Prospective Cohort Study

Quantitative interferon-gamma releasing assay in predicting tuberculosis in South Korean military: a retrospective cohort study

OBJECTIVE

The interferon-gamma releasing assay (IGRA) has been widely used to diagnose latent tuberculosis infection (TBI). However, there are limited data on the association between performance in the IGRA and risk of tuberculosis disease (TBD), as well as on the appropriate IGRA threshold for initiating TBI treatment.

METHODS

The analysis was performed using the IGRA results in the Korean Military Manpower Administration database (January 2017 to December 2021), and TBD cases reported to the Korean Military Medical Command (January 2017 to June 2023). All Korean candidates for 18-month military service underwent the IGRA in the pre-enlistment examination, and enlistees who tested positive (≥0.35 IU/mL) were advised to receive TBI treatment before enlistment.

RESULTS

From 2017 to 2021, 1 647 941 individuals were screened, with 29 574 testing positive for IGRA. Excluding nonenlistees namely individuals with TBD before enlistment, 19 387 individuals were IGRA positive and 1 356 324 IGRA negative. Of the positives, 4351 were excluded due to discontinued or ongoing TBI treatment at or after enlistment. During follow-up of 9219 untreated and 5818 treated positive individuals and 1 356 324 negatives, TBD occurred in 22 of the IGRA-positive individuals (97.5/100 000 person-years [95% CI, 61.1-147.7]), predominantly in the untreated group (18 cases, 130.1/100 000 person-years [95% CI, 77.1-205.7]) compared to the treated group (4 cases, 45.9/100 000 person-years [95% CI 12.5 - 117.4]), whereas 57 cases occurred in the IGRA-negative group (2.8/100 000 person-years [95% CI, 2.2-3.6]). Elevating the cutoff of IGRA from 0.35 IU/mL to 1.33 IU/mL increased positive predictive value (0.2% vs. 0.4%, p 0.03), with insignificant loss of sensitivity (24% vs. 20%, p 0.69) and decreased numbers needing treatment from 790.5 to 415.3.

DISCUSSION

Elevated IGRA levels before enlistment are associated with risk of TBD during military service. It is worth considering raising the IGRA threshold for treatment of TBI in cohorts of healthy, young military individuals.

Tuberculosis prevention: current strategies and future directions

BACKGROUND

An estimated one fourth of the world's population is infected with Mycobacterium tuberculosis, and 5-10% of those infected develop tuberculosis in their lifetime. Preventing tuberculosis is one of the most underutilized but essential components of curtailing the tuberculosis epidemic. Moreover, current evidence illustrates that tuberculosis manifestations occur along a dynamic spectrum from infection to disease rather than a binary state as historically conceptualized. Elucidating determinants of transition between these states is crucial to decreasing the tuberculosis burden and reaching the END-TB Strategy goals as defined by the WHO. Vaccination, detection of infection, and provision of preventive treatment are key elements of tuberculosis prevention.

OBJECTIVES

This review provides a comprehensive summary of recent evidence and state-of-the-art updates on advancements to prevent tuberculosis in various settings and high-risk populations.

SOURCES

We identified relevant studies in the literature and synthesized the findings to provide an overview of the current state of tuberculosis prevention strategies and latest research developments.

CONTENT

We present the current knowledge and recommendations regarding tuberculosis prevention, with a focus on M. bovis Bacille-Calmette-Guérin vaccination and novel vaccine candidates, tests for latent infection with M. tuberculosis, regimens available for tuberculosis preventive treatment and recommendations in low- and high-burden settings.

IMPLICATIONS

Effective tuberculosis prevention worldwide requires a multipronged approach that addresses social determinants, and improves access to tuberculosis detection and to new short tuberculosis preventive treatment regimens. Robust collaboration and innovative research are needed to reduce the global burden of tuberculosis and develop new detection tools, vaccines, and preventive treatments that serve all populations and ages.

Update on the diagnosis of tuberculosis

BACKGROUND

Tuberculosis (TB) remains a global public health threat, and the development of rapid and precise diagnostic tools is the key to enabling the early start of treatment, monitoring response to treatment, and preventing the spread of the disease.

OBJECTIVES

An overview of recent progress in host- and pathogen-based TB diagnostics.

SOURCES

We conducted a PubMed search of recent relevant articles and guidelines on TB screening and diagnosis.

CONTENT

An overview of currently used methods and perspectives in the following areas of TB diagnostics is provided: immune-based diagnostics, X-ray, clinical symptoms and scores, cough detection, culture of Mycobacterium tuberculosis and identifying its resistance profile using phenotypic and genotypic methods, including next-generation sequencing, sputum- and non-sputum-based molecular diagnosis of TB and monitoring of response to treatment.

IMPLICATIONS

A brief overview of the most relevant advances and changes in international guidelines regarding screening and diagnosing TB is provided in this review. It aims at reviewing all relevant areas of diagnostics, including both pathogen- and host-based methods.

Interferon-gamma release assay conversion after Mycobacterium tuberculosis exposure specifically associates with greater risk of progression to tuberculosis: A prospective cohort study in Leicester, UK

OBJECTIVES

We investigated whether quantifying the serial QuantiFERON-TB Gold (QFT) response improves tuberculosis (TB) risk stratification in pulmonary TB (PTB) contacts.

METHODS

A total of 297 untreated adult household PTB contacts, QFT tested at baseline and 3 months after index notification, were prospectively observed (median 1460 days). Normal variance of serial QFT responses was established in 46 extrapulmonary TB contacts. This informed categorisation of the response in QFT-positive PTB contacts as converters, persistently QFT-positive with significant increase (PPincrease), and without significant increase (PPno-increase).

RESULTS

In total, eight co-prevalent TB (disease ≤3 months after index notification) and 12 incident TB (>3 months after index notification) cases were diagnosed. Genetic linkage to the index strain was confirmed in all culture-positive progressors. The cumulative 2-year incident TB risk in QFT-positive contacts was 8.4% (95% confidence interval, 3.0-13.6%); stratifying by serial QFT response, significantly higher risk was observed in QFT converters (28%), compared with PPno-increase (4.8%) and PPincrease (3.7%). Converters were characterised by exposure to index cases with a shorter interval from symptom onset to diagnosis (median reduction 50.0 days, P = 0.013).

CONCLUSIONS

QFT conversion, rather than quantitative changes of a persistently positive serial QFT response, is associated with greater TB risk and exposure to rapidly progressive TB.

Detection of Mycobacterium tuberculosis DNA in CD34+ peripheral blood mononuclear cells of adults with tuberculosis infection and disease

OBJECTIVES

To investigate whether Mycobacterium tuberculosis (Mtb) DNA is detected in peripheral blood mononuclear cells (PBMC) of subjects with tuberculosis (TB) or TB infection (TBI) living in a low-burden country.

METHODS

We prospectively enrolled 57 patients with TB, 41 subjects with TBI, and 39 controls in Rome, Italy. PBMC were isolated, cluster of differentiation (CD)34+ and CD34- cells were immunomagnetic separated, DNA was extracted, and digital polymerase chain reaction for IS6110 and rpoB sequences was used to detect Mtb DNA in PBMC subsets and unfractionated PBMC.

RESULTS

We detected Mtb DNA at a low copy number in CD34+ cells in 4o f 30 (13%) patients with TB, 2 of 24 (8%) subjects with TBI, and 1 of 24 (4%) controls. Mtb DNA was detected in unfractionated PBMC in 3 of 51 (6%) patients with TB, 2 of 38 (5%) subjects with TBI, and 2 of 36 (6%) controls. In CD34- cells, only 1 of 31 (3%) subjects with TBI tested positive for Mtb DNA.

CONCLUSIONS

Mtb DNA was detected at low frequencies and levels in the PBMC of subjects with TBI and donors with TB living in a low-burden country. In particular, Mtb DNA was detected more frequently in CD34+ cells, supporting the hypothesis that these cells may represent a Mtb niche. This finding informs biological understanding of Mtb pathogenesis and may support the development of a microbial blood biomarker for Mtb infection.

Important role of DNA methylation hints at significant potential in tuberculosis

Tuberculosis (TB), an infectious disease caused by Mycobacterium tuberculosis (Mtb) infection, has persisted as a major global public health threat for millennia. Until now, TB continues to challenge efforts aimed at controlling it, with drug resistance and latent infections being the two main factors hindering treatment efficacy. The scientific community is still striving to understand the underlying mechanisms behind Mtb's drug resistance and latent infection. DNA methylation, a critical epigenetic modification occurring throughout an individual's growth and development, has gained attention following advances in high-throughput sequencing technologies. Researchers have observed abnormal DNA methylation patterns in the host genome during Mtb infection. Given the escalating issue of drug-resistant Mtb, delving into the role of DNA methylation in TB's development is crucial. This review article explores DNA methylation's significance in human growth, development and disease, and its role in regulating Mtb's evolution and infection processes. Additionally, it discusses potential applications of DNA methylation research in tuberculosis.

Tuberculosis infection and hypertension: prevalence estimates from the US National Health and Nutrition Examination Survey

OBJECTIVES

Tuberculosis infection (TBI) is marked by dynamic host-pathogen interactions with persistent low-grade inflammation and is associated with increased risk of cardiovascular diseases (CVD) including acute coronary syndrome, myocardial infarction and stroke. However, few studies assess the relationship between TBI and hypertension, an intermediate of CVD. We sought to determine the association between TBI and hypertension using data representative of the adult US population.

METHODS

We performed cross-sectional analyses using data from the 2011-2012 US National Health and Nutrition Examination Survey (NHANES). Eligible participants included adults with valid QuantiFERON-TB Gold In-Tube (QFT-GIT) test results who also had blood pressure measures and no history of TB disease. TBI was defined by a positive QFT-GIT. We defined hypertension by either elevated measured blood pressure levels (ie, systolic ≥130 mm Hg or diastolic ≥80 mm Hg) or known hypertension indications (ie, self-reported previous diagnosis or use of antihypertensive medications). Analyses were performed using robust quasi-Poisson regressions and accounted for the stratified probability sampling design of NHANES.

RESULTS

The overall prevalence of TBI was 5.7% (95% CI 4.7% to 6.7%) and hypertension was present among 48.9% (95% CI 45.2% to 52.7%) of participants. The prevalence of hypertension was higher among those with TBI (58.5%, 95% CI 52.4% to 64.5%) than those without TBI (48.3%, 95% CI 44.5% to 52.1%) (prevalence ratio (PR) 1.2, 95% CI 1.1 to 1.3). However, after adjusting for confounders, the prevalence of hypertension was similar for those with and without TBI (adjusted PR 1.0, 95% CI 1.0 to 1.1). The unadjusted prevalence of hypertension was higher among those with TBI versus no TBI, especially among individuals without CVD risk factors including those with normal body mass index (PR 1.6, 95% CI 1.2 to 2.0), euglycaemia (PR 1.3, 95% CI 1.1 to 1.5) or non-smokers (PR 1.2, 95% CI 1.1 to 1.4).

CONCLUSIONS

More than half of adults with TBI in the USA had hypertension. Importantly, we observed a relationship between TBI and hypertension among those without established CVD risk factors.

SUMMARY

The prevalence of hypertension was high (59%) among adults with TBI in the USA. In addition, we found that the prevalence of hypertension was significantly higher among adults with positive QFT without established hypertension risk factors.

[Recommendations for Contact Tracing for Tuberculosis - Update 2023]

The aim of contact tracing for tuberculosis is in addition to active case finding the detection of chains of infection and the prevention of the further spread of the disease. In this context, a careful selection of contact persons is necessary, depending on the type and duration of contact, to identify persons who are recently infected and therefore to increase the benefit of a preventive therapy and to avoid unnecessary testing of persons who are not at risk of infection. Since the last update of the recommendations on contact tracing, data on the use of interferon-y release assays (IGRAs) in children has been improved markedly. These are the preferred test in contact tracing of adults. For children, both IGRAs and the tuberculin skin test can be used equivalently. Rifampicin for 4 months, rifampicin and isoniazid for 3 months, or isoniazid for 9 months are recommended as preventive therapy in cases of confirmed infection.The implementation of the contact tracing in different age groups as well as legal framework conditions and socio-medical aspects and challenges are dealt with in detail. In addition, special cases, such as environmental screening in day-care centers, schools, or other community facilities, are discussed separately.

Predicting stringent QuantiFERON-TB Gold Plus conversions in contacts of tuberculosis patients

OBJECTIVES

To assess associations between disease severity in index TB patients and QuantiFERON-TB Gold Plus (QFT-Plus) results in contacts, and predictors for QFT-Plus conversion in contacts over 6-12 months.

METHODS

TB patients (n = 295) and the contacts (n = 1051) were enrolled during 2018-2021 with QFT-Plus performed at baseline and months 6 and 12. A strong CD8 response was defined as TB2 interferon gamma (IFN-γ) response minus TB1 >0.6 IU/ml and stringent conversion as change from QFT-plus negative to high-positive QFT-Plus (TB1 or TB2 IFN-γ responses >0.7 IU/ml).

RESULTS

Contacts with index TB patients with sputum smear >1+ was associated with positive QFT-Plus compared to those without (p < 0.001). Contacts with index TB patients with bilateral lung disease were more likely to have strong CD8 responses than those without (p = 0.038). QFT-Plus stringent conversion occurred in 9.7% of contacts over 6-12 months. A TB1 IFN-γ response ≥0.03 IU/ml combined with a TB2 ≥0.06 IU/ml was predictive of a 19-fold increased risk for QFT-Plus stringent conversion in contacts (odd ratio 19.565 [8.484-45.116], p < 0.001).

CONCLUSION

Bacterial burden and bilateral lung disease of index TB patients were associated with positive QFT-Plus and strong CD8 responses in contacts. TB1 and TB2 IFN-γ responses were synergistically predictive of stringent conversion in contacts.

Examining Test Cutoffs to Optimize Diagnosis of Latent Tuberculosis Infection in People Born Outside the United States

Rationale: Detection of latent tuberculosis infection (LTBI) in persons born in high tuberculosis (TB) incidence countries living in low TB incidence countries is key to TB elimination in low-incidence countries. Optimizing LTBI tests is critical to targeting treatment. Objectives: To compare the sensitivity and specificity of tuberculin skin test (TST) and two interferon-γ release assays at different cutoffs and of a single test versus dual testing. Methods: We examined a subset (N = 14,167) of a prospective cohort of people in the United States tested for LTBI. We included non-U.S.-born, human immunodeficiency virus-seronegative people ages 5 years and older with valid TST, QuantiFERON-TB Gold-in-Tube (QFT), and T-SPOT.TB (TSPOT) results. The sensitivity/specificity of different test cutoffs and test combinations, obtained from a Bayesian latent class model, were used to construct receiver operating characteristic (ROC) curves and assess the area under the curve (AUC) for each test. The sensitivity/specificity of dual testing was calculated. Results: The AUC of the TST ROC curve was 0.81 (95% credible interval (CrI), 0.78-0.86), with sensitivity/specificity at cutoffs of 5, 10, and 15 mm of 86.5%/61.6%, 81.7%/71.3%, and 55.6%/88.0%, respectively. The AUC of the QFT ROC curve was 0.89 (95% CrI, 0.86-0.93), with sensitivity/specificity at cutoffs of 0.35, 0.7, and 1.0 IU/mL of 77.7%/98.3%, 66.9%/99.1%, and 61.5%/99.4%. The AUC of the TSPOT ROC curve was 0.92 (95% CrI, 0.88-0.96) with sensitivity/specificity for five, six, seven, and eight spots of 79.2%/96.7%, 76.8%/97.7%, 74.0%/98.6%, and 71.8%/99.5%. Sensitivity/specificity of TST-QFT, TST-TSPOT, and QFT-TSPOT at standard cutoffs were 73.1%/99.4%, 64.8%/99.8%, and 65.3%/100%. Conclusion: Interferon-γ release assays have a better predictive ability than TST in people at high risk of LTBI.

[Recommendations for contact tracing for tuberculosis - update 2023]

The aim of contact tracing for tuberculosis is in addition to active case finding the detection of chains of infection and the prevention of the further spread of the disease. In this context, a careful selection of contact persons is necessary, depending on the type and duration of contact, to identify persons who are recently infected and therefore to increase the benefit of a preventive therapy and to avoid unnecessary testing of persons who are not at risk of infection. Since the last update of the recommendations on contact tracing, data on the use of interferon-y release assays (IGRAs) in children has been improved markedly. These are the preferred test in contact tracing of adults. For children, both IGRAs and the tuberculin skin test can be used equivalently. Rifampicin for 4 months, rifampicin and isoniazid for 3 months, or isoniazid for 9 months are recommended as preventive therapy in cases of confirmed infection.The implementation of the contact tracing in different age groups as well as legal framework conditions and socio-medical aspects and challenges are dealt with in detail. In addition, special cases, such as environmental screening in day-care centers, schools, or other community facilities, are discussed separately.

Research tests for the diagnosis of tuberculosis infection

INTRODUCTION

Despite huge efforts, tuberculosis (TB) is still a major public health threat worldwide, it is estimated that a quarter of the global population is infected by Mycobacterium tuberculosis (Mtb). For controlling TB and reducing Mtb transmission it is fundamental to diagnose TB infection (TBI) as well as the progressors from TBI to disease to identify those requiring preventive therapy. At present, there is no gold standard test for TBI diagnosis although several new methodologies have been attempted.

AREAS COVERED

This review provides an update on the most recent approaches to develop reliable tests to diagnose TBI and progressors from infection to disease. Experimental tests are based on either the direct identification of Mtb (i.e., Mtb DNA upon host cells isolation; Mtb proteins or peptides) or host response (i.e., levels and quality of specific anti-Mtb antibodies; host blood transcriptome signatures).

EXPERT OPINION

The experimental tests described are very interesting. However, further investigation and randomized clinical trials are needed to improve the sensitivity and specificity of these new research-based tests. More reliable proofs-of-concept and simplification of technical procedures are necessary to develop new diagnostic tools for identifying TBI patients and those that will progress from infection to TB disease.

Tuberculosis infection and hypertension: Prevalence estimates from the US National Health and Nutrition Examination Survey

Objectives

Latent Tuberculosis infection (LTBI) is marked by dynamic host-pathogen interactions with persistent low-grade inflammation and is associated with increased risk of cardiovascular diseases (CVD) including acute coronary syndrome, myocardial infarction, and stroke. However, few studies assess the relationship between LTBI and hypertension, an intermediate of CVD. We sought to determine the association between LTBI and hypertension using data representative of the adult US population.

Methods

We performed cross-sectional analyses using data from the 2011-2012 US National Health and Nutrition Examination Survey (NHANES). Eligible participants included adults with valid QuantiFERON-TB Gold In-Tube (QFT-GIT) test results who also had blood pressure measures and no history of TB disease. LTBI was defined by a positive QFT-GIT. We defined hypertension by either elevated measured blood pressure levels (i.e., systolic ≥130mmHg or diastolic ≥80mmHg) or known hypertension indications (i.e., self-reported previous diagnosis or use of antihypertensive medications). Analyses were performed using robust quasi-Poisson regressions and accounted for the stratified probability sampling design of NHANES.

Results

The overall prevalence of LTBI was 5.7% (95%CI 4.7-6.7) and hypertension was present among 48.9% (95%CI 45.2-52.7) of participants. The prevalence of hypertension was higher among those with LTBI (58.5%, 95%CI 52.4-64.5) than those without LTBI (48.3%, 95%CI 44.5-52.1) (prevalence ratio [PR]=1.2, 95%CI 1.1-1.3). However, after adjusting for confounders, the prevalence of hypertension was similar for those with and without LTBI (adjusted PR=1.0, 95%CI 0.9 -1.1). Among individuals without CVD risk factors of elevated BMI (PRnormal BMI=1.6, 95%CI 1.2-2.0), hyperglycemia (PReuglycemia=1.3, 95%CI 1.1-1.5), or cigarette smoking (PRnon-smokers=1.2, 95%CI 1.1-1.4), the unadjusted prevalence of hypertension was higher among those with LTBI vs. no LTBI.

Conclusions

More than half of adults with LTBI in the US had hypertension. Importantly, we observed a relationship between LTBI and hypertension among those without established CVD risk factors.

End-point definition and trial design to advance tuberculosis vaccine development

Tuberculosis (TB) remains a leading infectious cause of death worldwide and the coronavirus disease 2019 pandemic has negatively impacted the global TB burden of disease indicators. If the targets of TB mortality and incidence reduction set by the international community are to be met, new more effective adult and adolescent TB vaccines are urgently needed. There are several new vaccine candidates at different stages of clinical development. Given the limited funding for vaccine development, it is crucial that trial designs are as efficient as possible. Prevention of infection (POI) approaches offer an attractive opportunity to accelerate new candidate vaccines to advance into large and expensive prevention of disease (POD) efficacy trials. However, POI approaches are limited by imperfect current tools to measure Mycobacterium tuberculosis infection end-points. POD trials need to carefully consider the type and number of microbiological tests that define TB disease and, if efficacy against subclinical (asymptomatic) TB disease is to be tested, POD trials need to explore how best to define and measure this form of TB. Prevention of recurrence trials are an alternative approach to generate proof of concept for efficacy, but optimal timing of vaccination relative to treatment must still be explored. Novel and efficient approaches to efficacy trial design, in addition to an increasing number of candidates entering phase 2-3 trials, would accelerate the long-standing quest for a new TB vaccine.

Evaluation of Host Protein Biomarkers by ELISA From Whole Lysed Peripheral Blood for Development of Diagnostic Tests for Active Tuberculosis

Tuberculosis (TB) remains a significant global health crisis and the number one cause of death for an infectious disease. The health consequences in high-burden countries are significant. Barriers to TB control and eradication are in part caused by difficulties in diagnosis. Improvements in diagnosis are required for organisations like the World Health Organisation (WHO) to meet their ambitious target of reducing the incidence of TB by 50% by the year 2025, which has become hard to reach due to the COVID-19 pandemic. Development of new tests for TB are key priorities of the WHO, as defined in their 2014 report for target product profiles (TPPs). Rapid triage and biomarker-based confirmatory tests would greatly enhance the diagnostic capability for identifying and diagnosing TB-infected individuals. Protein-based test methods e.g. lateral flow devices (LFDs) have a significant advantage over other technologies with regard to assay turnaround time (minutes as opposed to hours) field-ability, ease of use by relatively untrained staff and without the need for supporting laboratory infrastructure. Here we evaluate the diagnostic performance of nine biomarkers from our previously published biomarker qPCR validation study; CALCOCO2, CD274, CD52, GBP1, IFIT3, IFITM3, SAMD9L, SNX10 and TMEM49, as protein targets assayed by ELISA. This preliminary evaluation study was conducted to quantify the level of biomarker protein expression across latent, extra-pulmonary or pulmonary TB groups and negative controls, collected across the UK and India, in whole lysed blood samples (WLB). We also investigated associative correlations between the biomarkers and assessed their suitability for ongoing diagnostic test development, using receiver operating characteristic/area under the curve (ROC) analyses, singly and in panel combinations. The top performing single biomarkers for pulmonary TB versus controls were CALCOCO2, SAMD9L, GBP1, IFITM3, IFIT3 and SNX10. TMEM49 was also significantly differentially expressed but downregulated in TB groups. CD52 expression was not highly differentially expressed across most of the groups but may provide additional patient stratification information and some limited use for incipient latent TB infection. These show therefore great potential for diagnostic test development either in minimal configuration panels for rapid triage or more complex formulations to capture the diversity of disease presentations.

Evaluation of a transcriptomic signature of tuberculosis risk in combination with an interferon gamma release assay: A diagnostic test accuracy study

BACKGROUND

We evaluated the diagnostic and prognostic performance of a transcriptomic signature of tuberculosis (TB) risk (RISK11) and QuantiFERON-TB Gold-plus (QFTPlus) as combination biomarkers of TB risk.

METHODS

Healthy South Africans who were HIV-negative aged 18-60 years with baseline RISK11 and QFTPlus results were evaluated in a prospective cohort study conducted between Sept 20, 2016 and Dec 20, 2019. Prevalence and incidence-rate ratios were used to evaluate risk of TB. Positive (LR+) and negative (LR-) likelihood ratios were used to compare individual tests versus Both-Positive (RISK11+/QFTPlus+) and Either-Positive (RISK11+ or QFTPlus+) combinations.

FINDINGS

Among 2912 participants, prevalent TB in RISK11+/QFTPlus+ participants was 13·3-fold (95% CI 4·2-42·7) higher than RISK11-/QFTPlus-; 2·4-fold (95% CI 1·2-4·8) higher than RISK11+/QFTPlus-; and 4·5-fold (95% CI 2·5-8·0) higher than RISK11-/QFTPlus+ participants. Risk of incident TB in RISK11+/QFTPlus+ participants was 8·3-fold (95% CI 2·5-27·0) higher than RISK11-/QFTPlus-; 2·5-fold (95% CI 1·0-6·6) higher than RISK11+/QFTPlus-; and 2·1-fold (95% CI 1·2-3·4) higher than RISK11-/QFTPlus+ participants, respectively. Compared to QFTPlus, the Both-Positive test combination increased diagnostic LR+ from 1·3 (95% CI 1·2-1·5) to 4·7 (95% CI 3·2-7·0), and prognostic LR+ from 1·4 (95% CI 1·2-1·5) to 2·8 (95% CI 1·5-5·1), but did not improve upon RISK11 alone. Compared with RISK11, the Either-Positive test combination decreased diagnostic LR- from 0·7 (95% CI 0·6-0·9) to 0·3 (95% CI 0·2-0·6), and prognostic LR- from 0·9 (95% CI 0·8-1·0) to 0·3 (0·1-0·7), but did not improve upon QFTPlus alone.

INTERPRETATION

Combining two tests such as RISK11 and QFTPlus, with discordant individual performance characteristics does not improve overall discriminatory performance, relative to the individual tests.

FUNDING

Bill and Melinda Gates Foundation, South African Medical Research Council.

The burden and predictors of latent tuberculosis infection among immigrants in South Korea: a retrospective cross-sectional study

BACKGROUND

Approximately one-fourth of the global population is latently infected with Mycobacterium tuberculosis. An understanding of the burden of latent tuberculosis infection (LTBI) among immigrants compared with the general Korean population should be the first step in identifying priority groups for LTBI diagnosis and treatment. The study aimed to compute the age-standardized LTBI prevalence and predictors among immigrants with LTBI in South Korea.

METHODS

In 2018, the Korea Disease Control and Prevention Agency implemented a pilot LTBI screening project for immigrants using a chest radiography and the QuantiFERON Gold In-Tube assay. A standardized prevalence ratio (SPR) was computed to compare the LTBI burden in immigrants and the general Korean population.

RESULTS

During the duration of the project, a total of 8108 immigrants (5134 males and 2974 females) underwent LTBI screening. The SPR of 1.547 (95% confidence interval [CI] 1.468-1.629) in males and 1.261 (95% CI 1.177-1.349) in females were both higher than the Korean reference population. Furthermore, among the immigrants, those aged < 40 years and Korean diaspora visa holders had a higher SPR.

CONCLUSION

This study found a higher LTBI prevalence among immigrant population in South Korea compared to that in the general Korean population, and the SPR was higher among those aged < 40 years and the Korean diaspora. The findings can be used as baseline evidence for including immigrants in South Korea in the at-risk group with a priority need for LTBI screening and treatment.

The diagnostic performance of novel skin-based in-vivo tests for tuberculosis infection compared with purified protein derivative tuberculin skin tests and blood-based in vitro interferon-γ release assays: a systematic review and meta-analysis

BACKGROUND

Novel skin-based tests for tuberculosis infection might present suitable alternatives to current tests; however, diagnostic performance of new tests compared with the purified protein derivative-tuberculin skin test (TST) or interferon-γ release assays (IGRA) needs systematic assessment.

METHODS

In this systematic review and meta-analysis, we searched English (Medline OVID), Chinese (Chinese Biomedical Literature Database and the China National Knowledge Infrastructure), and Russian (e-library) databases from the inception of each database to May 15, 2019, (with updated search of the Russian and English databases on Oct, 20 2020) using terms "ESAT6" OR "CFP10" AND "skin test" AND "Tuberculosis" OR "C-Tb" OR "Diaskintest". We included studies reporting on the performance of index tests alone or compared with a comparator. Inclusion criteria varied according to review objectives and performance outcome, but reporting of test cut-offs for positivity applied to study population was required from all studies. We used a hierarchy of reference standards for tuberculosis infection consistent with the 2020 WHO framework to evaluate diagnostic performance. Two authors independently reviewed the titles and abstracts for English and Chinese (LF and MK) and Russian studies (MK and VN). Study quality was assessed with QUADAS-2. Pooled random-effects estimates are presented when appropriate for total agreement proportion, sensitivity in microbiologically confirmed tuberculosis and specificity in cohorts with low risk of tuberculosis infection. This study is registered with PROSPERO, CRD42019135572.

FINDINGS

We identified 1466 original articles, of which 37 (2·5%) studies, including 10 915 individuals (7111 Diaskintest, 2744 C-Tb, 887 EC, 173 DPPD), were included in the qualitative analysis (29 [78%] studies of Diaskintest, five [15%] studies of C-Tb, two [5%] studies of EC-skintest, and one [3%] study of DPPD). 22 (1·5%) studies including 5810 individuals (3143 Diaskintest, 2129 C-Tb, 538 EC-skintest) were included in the quantitative analysis: 15 (68%) of Diaskintest, five (23%) of C-Tb, and two (9%) of EC-skintest. Tested sub-populations included individuals with HIV, children (0-18 years), and individuals exposed to tuberculosis. Studies were heterogeneous with moderate to high risk of bias. Nine head-to-head studies of index test versus TST and IGRA permitted direct comparisons and pooling. In a mixed cohort of people with and without tuberculosis, Diaskintest pooled agreement with IGRA was 87·16% (95% CI 79·47-92·24) and 55·45% (46·08-64·45) with TST-5 mm cut-off (TST^{5 mm}). Diaskintest sensitivity was 91·18% (95% CI 81·72-95·98) compared with 88·24% (78·20-94·01) for TST^{5 mm}, 89·66 (78·83-95·28) for IGRA QuantiFERON, and 90·91% (79·95-96·16) for TSPOT.TB. C-Tb agreement with IGRA in individuals with active tuberculosis was 79·80% (95% CI 76·10-83·07) compared with 78·92% (74·65-82·63) for TST5 mm/15 mm cut-off (TST^{5 mm/15 mm}). TST^5/15mm reflects threshold in cohorts that applied stratified cutoffs: 5 mm for HIV-infected, immunocompromised, or BCG-naive individuals, and 15mm for BCG-vaccinated immunocompetent individuals. C-Tb sensitivity was 74·52% (95% CI 70·39-78·25) compared with a sensitivity of 78·18% (67·75-85·94) for TST^{5 mm/15 mm}, and 71·67% (63·44-78·68) for IGRA. Specificity was 97·85% (95% CI 93·96-99·25) for C-Tb versus 93·31% (90·22-95·48) for TST 15 mm cut-off and 99·15% (79·66-99·97) for IGRA. EC-skintest sensitivity was 86·06% (95% CI 82·39-89·07).

INTERPRETATION

Novel skin-based tests for tuberculosis infection appear to perform similarly to IGRA or TST; however, study quality varied. Evaluation of test performance, patient-important outcomes, and diagnostic use in current clinical algorithms will inform implementation in key populations.

FUNDING

StopTB (New Diagnostics Working Group) and FIND.

TRANSLATIONS

For the Chinese and Russian translations of the abstract see Supplementary Materials section.

Latent Tuberculosis Infection Screening and Treatment in Congregate Settings (TB FREE COREA): Demographic Profiles of Interferon-Gamma Release Assay Cohort

In 2017, the Korean government launched an unprecedentedly large-scaled latent tuberculosis infection (LTBI) screening project which covered more than a million individuals in congregate settings. A total of 1,047,689 participants of source population (n = 2,336,157) underwent LTBI testing from 2017 to 2018. The overall LTBI test uptake rate during this project was 44.8%. Workers in daycare centers (83.5%) and kindergartens (78.9%) showed high participation rate. A total of 1,012,206 individuals with valid results of interferon-gamma release assay (IGRA) were selected to constitute the IGRA cohort. Most of the enrolled participants in the IGRA cohort were in their working age. Approximately, three-quarters of total enrolled population were female. Investigating the LTBI prevalence, stages of LTBI care cascade, natural history of LTBI, efficacy of LTBI treatment and cost-effectiveness of LTBI screening are feasible within this IGRA cohort.

The knowns and unknowns of latent Mycobacterium tuberculosis infection

Humans have been infected with Mycobacterium tuberculosis (Mtb) for thousands of years. While tuberculosis (TB), one of the deadliest infectious diseases, is caused by uncontrolled Mtb infection, over 90% of presumed infected individuals remain asymptomatic and contain Mtb in a latent TB infection (LTBI) without ever developing disease, and some may clear the infection. A small number of heavily Mtb-exposed individuals appear to resist developing traditional LTBI. Because Mtb has mechanisms for intracellular survival and immune evasion, successful control involves all of the arms of the immune system. Here, we focus on immune responses to Mtb in humans and nonhuman primates and discuss new concepts and outline major knowledge gaps in our understanding of LTBI, ranging from the earliest events of exposure and infection to success or failure of Mtb control.

Evaluation of CD8+ response in QuantiFERON-TB Gold Plus as a marker of recent infection

BACKGROUND

Diagnosis and treatment of latent tuberculosis (TB) infection (LTBI) is essential for the elimination of TB. Preventive therapy could be limited to those with recent TB contact. QuantiFERON-TB Gold Plus (QFT-Plus), a new Interferon-γ release assay, includes a new antigen tube (TB2), which elicits CD4⁺ and CD8⁺ T-cell responses.

OBJECTIVE

The aim of the study was to evaluate CD8⁺ T-cell response as a marker of recent TB infection.

DESIGN

We retrospectively studied 1165 patients who were screened for LTBI. Patients were divided according to history of recent exposure to TB (contact with a confirmed index case in the previous year). CD8⁺ T-cell activity was measured as the difference between QFT-Plus tubes (TB2-TB1) using two cut-offs (>0.35 IU/mL and >0.60 IU/mL).

RESULTS

CD8⁺ T-cell activity was significantly higher in the exposed group for both cut-offs (96 - 13% vs 36 - 5% patients - OR 1.68, 95% CI 1.13-2.52 for >0.35 IU/mL and 77 vs 28 patients - OR 1.72 95% CI 1.10-2.70 for >0.60 IU/mL). CD8⁺ T-cell activity also showed an association with positive sputum smear of the index case and higher exposure time.

CONCLUSION

CD8⁺ T-cell activity as measured with TB2-TB1 shows a significant association with recent exposure to TB, especially in patients with higher exposure and may prove to be a useful tool in identifying patients with recent LTBI.

Incidence of tuberculosis in advanced lung cancer patients treated with immune checkpoint inhibitors - A nationwide population-based cohort study

OBJECTIVES

The aim of this study was to investigate the risk of TB in advanced non-small cell lung cancer (NSCLC) patients treated with Immune checkpoint inhibitors (ICI) after a platinum-based chemotherapy.

MATERIALS AND METHODS

A nationwide population-based retrospective cohort study using National health insurance dataset was designed. Patients who were diagnosed as lung cancer between September 1st, 2017 and August 31st, 2018 in South Korea were selected. Among them, those with NSCLC who initiated a platinum-based chemotherapy within 3 months were finally included and followed up until December 31st, 2018. Patients who received nivolumab, pembrolizumab, and atezolizumab within study period were classified as the ICI group. Cox proportional hazard model with time-varying covariates was used to determine effects of the duration of conventional chemotherapy, ICI, and consecutive use of systemic steroid on TB.

RESULTS

A total of 6335 patients were enrolled with 3568.7 years of total follow-up period. Among them, 899 patients underwent ICI treatment. Within the follow-up period, 15 TB cases were identified in the ICI group (incidence: 2582.5 per 100,000 person-years) and 63 TB cases were found in the conventional chemotherapy group (incidence: 2108.5 per 100,000 person-years). In a multivariable Cox proportional hazard model, treatment with ICI was not a significant risk factor for TB development (hazard ratio (HR): 1.21, 95 % confidence interval (CI): 0.45-3.26,p =  0.700). Instead, prolonged use of steroid was associated with an increased TB risk (HR: 1.91, 95 %CI: 0.89-4.08, p =  0.095), although its statistical significance was dependent on the operational definition of the effect duration. Previous TB history and older age were independent risk factors for TB disease.

CONCLUSION

In this real-world study, additional treatment with ICI did not increase the risk of TB in advanced NSCLC patients who underwent a cytotoxic chemotherapy. However, TB incidence in these patients was high regardless of ICI treatment.

CLASSIFICATIONS

Systemic Treatments.

Interferon-gamma release assay levels and risk of progression to active tuberculosis: a systematic review and dose-response meta-regression analysis

Background

Identifying and treating individuals with high risk of progression from latent tuberculosis infection to active tuberculosis (TB) disease is critical for eliminating the disease. We aimed to conduct a systematic review and meta-regression analysis to quantify the dose-response relationship between interferon-gamma release assay (IGRA) levels and the risk of progression to active TB.

Methods

We searched PubMed and Embase from 1 January 2001 to 10 May 2020 for longitudinal studies that reported the risk of progression from latent to active TB as a function of baseline IGRA values. We used a novel Bayesian meta-regression method to pool effect sizes from included studies and generate a continuous dose-response risk curve. Our modeling framework enabled us to incorporate random effects across studies, and include data with different IGRA ranges across studies. The quality of included studies were assessed using the Newcastle-Ottawa scale (NOS).

Results

We included 34 studies representing 581,956 person-years of follow-up with a total of 788 incident cases of TB in the meta-regression analysis. Higher levels of interferon-gamma were associated with increased risk of progression to active tuberculosis. In the dose-response curve, the risk increased sharply between interferon-gamma levels 0 and 5 IU/ml, after which the risk continued to increase moderately but at a slower pace until reaching about 15 IU/ml where the risk levels off. Compared to 0 IU/ml, the relative risk of progression to active TB among those with interferon-gamma levels of 0.35, 1, 5, 10, 15, and 20 IU/ml were: 1.64 (1.28–2.08), 2.90 (2.02–3.88), 11.38 (6.64–16.38), 19.00 (13.08–26.90), 21.82 (14.65–32.57), and 22.31 (15.43–33.00), respectively. The dose-response relationship remains consistent when limiting the analysis to studies that scored highest in the NOS.

Conclusion

The current practice of dichotomizing IGRA test results simplifies the TB infection disease continuum. Evaluating IGRA test results over a continuous scale could enable the identification of individuals at greatest risk of progression to active TB.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06141-4.

Discovery and validation of a personalized risk predictor for incident tuberculosis in low transmission settings

The risk of tuberculosis (TB) is variable among individuals with latent Mycobacterium tuberculosis infection (LTBI), but validated estimates of personalized risk are lacking. In pooled data from 18 systematically identified cohort studies from 20 countries, including 80,468 individuals tested for LTBI, 5-year cumulative incident TB risk among people with untreated LTBI was 15.6% (95% confidence interval (CI), 8.0-29.2%) among child contacts, 4.8% (95% CI, 3.0-7.7%) among adult contacts, 5.0% (95% CI, 1.6-14.5%) among migrants and 4.8% (95% CI, 1.5-14.3%) among immunocompromised groups. We confirmed highly variable estimates within risk groups, necessitating an individualized approach to risk stratification. Therefore, we developed a personalized risk predictor for incident TB (PERISKOPE-TB) that combines a quantitative measure of T cell sensitization and clinical covariates. Internal-external cross-validation of the model demonstrated a random effects meta-analysis C-statistic of 0.88 (95% CI, 0.82-0.93) for incident TB. In decision curve analysis, the model demonstrated clinical utility for targeting preventative treatment, compared to treating all, or no, people with LTBI. We challenge the current crude approach to TB risk estimation among people with LTBI in favor of our evidence-based and patient-centered method, in settings aiming for pre-elimination worldwide.

Primary Prophylaxis to Prevent Tuberculosis Infection in Prison Inmates: A Randomized, Double-Blind, Placebo-Controlled Trial

In many low- and middle-income countries, tuberculosis (TB) incidence in prisons is high, exposing incarcerated populations to an elevated risk of TB infection. We conducted a randomized, double-blind, placebo-controlled trial among HIV-negative male inmates of a high TB burden prison to determine whether isoniazid given twice weekly (900 mg) for 12 months prevents TB infection. The primary outcome was QuantiFERON-TB Gold in Plus (QFT) conversion to ≥ 0.35 international units per milliliter (IU/mL) at 6 months; secondary outcomes included alternative QFT thresholds (≥ 0.7, ≥ 2.0, and ≥ 4.0 IU/mL). In total, 467 participants were randomly assigned to intervention (N = 258) or control (N = 209). In an interim analysis of participants who had completed 6 months of follow-up (N = 170), QFT conversion occurred in 20.8% (19/91) and 21.5% (17/79) of participants in intervention and control arms (efficacy: 2.9%, P = 0.91), respectively. The trial was then stopped according to the trial protocol, and the remaining participants prematurely discontinued. In an analysis of secondary outcomes, the intervention arm had significantly lower rates of conversion at a cutoff of ≥ 2.0 IU/mL (efficacy: 82.6%, P < 0.01). In conclusion, 900 mg of isoniazid, administered twice a week, did not effectively prevent QFT conversion at a cutoff point ≥ 0.35 IU/mL in a trial of QFT-negative inmates. Higher QFT cutoffs are associated with sustained conversion and greater protection. Future clinical trials that evaluate protection for latent infection should use the highest cutoff than that recommended by the manufacturer.