Combining SARS-CoV-2 interferon-gamma release assay with humoral response assessment to define immune memory profiles.

OBJECTIVES: In the post-SARS-CoV-2 pandemic era, "breakthrough infections" are still documented, due to variants of concerns (VoCs) emergence and waning humoral immunity. Despite widespread utilization, the definition of the anti-Spike (S) immunoglobulin-G (IgG) threshold to define protection has unveiled several limitations. Here, we explore the advantages of incorporating T-cell response assessment to enhance the definition of immune memory profile. METHODS: SARS-CoV-2 interferon-gamma release assay test (IGRA) was performed on samples collected longitudinally from immunocompetent healthcare workers throughout their immunization by infection and/or vaccination, anti-receptor-binding domain IgG levels were assessed in parallel. The risk of symptomatic infection according to cellular/humoral immune capacities during Omicron BA.1 wave was then estimated. RESULTS: Close to 40% of our samples were exclusively IGRA-positive, largely due to time elapsed since their last immunization. This suggests that individuals have sustained long-lasting cellular immunity, while they would have been classified as lacking protective immunity based solely on IgG threshold. Moreover, the Cox regression model highlighted that Omicron BA.1 circulation raises the risk of symptomatic infection while increased anti-receptor-binding domain IgG and IGRA levels tended to reduce it. CONCLUSION: The discrepancy between humoral and cellular responses highlights the significance of assessing the overall adaptive immune response. This integrated approach allows the identification of vulnerable subjects and can be of interest to guide antiviral prophylaxis at an individual level.

Cost-effectiveness of latent tuberculosis infection testing and treatment with 6-week regimen among key population in rural communities in China: a decision analysis study.

PURPOSE: Several model studies suggested the implementation of latent tuberculosis infection (LTBI) testing and treatment could greatly reduce the incidence of tuberculosis (TB) and achieve the 2035 target of the "End TB" Strategy in China. The present study aimed to evaluate the cost-effectiveness of LTBI testing and TB preventive treatment among key population (≥ 50 years old) susceptible to TB at community level in China. METHODS: A Markov model was developed to investigate the cost-effectiveness of LTBI testing using interferon gamma release assay (IGRA) and subsequent treatment with 6-month daily isoniazid regimen (6H) (as a standard regimen for comparison) or 6-week twice-weekly rifapentine and isoniazid regimen (6-week H2P2) in a cohort of 10,000 adults with an average initial age of 50 years. RESULTS: In the base-case analysis, LTBI testing and treatment with 6H was dominated (i.e., more expensive with a lower quality-adjusted life year (QALY)) by LTBI testing and treatment with 6-week H2P2. LTBI testing and treatment with 6-week H2P2 was more effective than no intervention at a cost of $20,943.81 per QALY gained, which was below the willingness-to-pay (WTP) threshold of $24,211.84 per QALY gained in China. The one-way sensitivity analysis showed the change of LTBI prevalence was the parameter that most influenced the results of the incremental cost-effectiveness ratios (ICERs). CONCLUSION: As estimated by a Markov model, LTBI testing and treatment with 6-week H2P2 was cost-saving compared with LTBI testing and treatment with 6H, and it was considered to be a cost-effective option for TB control in rural China.

Cost-Effectiveness Analysis Comparing QuantiFERON-TB Gold Plus Test and Tuberculin Skin Test for the Diagnosis of Latent Tuberculosis Infection in Immunocompetent Subjects in Colombia.

OBJECTIVES: To determine the cost-effectiveness of the QuantiFERON-TB Gold Plus (QFT-Plus) test versus the tuberculin skin test in diagnosing latent tuberculosis infection in immunocompetent subjects in the context of the Colombian healthcare system. METHODS: A hypothetical cohort of 2000 immunocompetent adults vaccinated with Bacillus Calmette-Guérin at birth who are asymptomatic for tuberculosis disease was simulated and included in a decision tree over a horizon of <1 year. The direct healthcare costs related to tests, antituberculosis treatment, and medical care were considered, and diagnostic performance was used as a measure of effectiveness. The incremental cost-effectiveness ratio (ICER) was estimated, and univariate deterministic and probabilistic sensitivity analyses were carried out using 5000 simulations. The currency was the US dollar for the year 2022, with a cost-effectiveness threshold of $6666 USD (1 gross domestic product per capita for 2022). RESULTS: QFT-Plus was cost-effective with an ICER of $5687 USD for each correctly diagnosed case relative to a threshold of $6666 USD. In the deterministic analysis, QFT-Plus was cost-effective in half of the proposed scenarios. The variable that most affected the ICER was the prevalence of latent tuberculosis and test sensitivities. In the probabilistic analysis, QFT-Plus was cost-effective in 54.74% of the simulated scenarios, and tuberculin skin test was dominant in 13.84%. CONCLUSIONS: The study provides evidence of the cost-effectiveness of QFT-Plus compared with the tuberculin skin test in diagnosing latent tuberculosis infection in immunocompetent adults in the Colombian context.

Cost-effectiveness of interferon-γ release assay for screening of latent tuberculosis infection in individuals with schizophrenia.

Schizophrenia is recognized as a significant risk factor for tuberculosis (TB). This study aimed to evaluate the effectiveness and cost-effectiveness of interferon-γ release assay (IGRA) with preventive treatment for screening of latent tuberculosis infection (LTBI) in individuals with schizophrenia. A state transition model was developed from a healthcare payer perspective on a lifetime horizon. Ten strategies were compared by combining two different tests for LTBI, i.e. IGRA and tuberculin skin test (TST), and five different preventive treatments, i.e. 9-month isoniazid (9H), 3-month isoniazid and rifapentine (3HP) by directly observed therapy, 3HP by self-administered therapy, 3-month isoniazid and rifampin (3RH), and 4-month rifampin (4R). The main outcomes were costs, quality-adjusted life-years (QALYs), life expectancy life-years (LYs), incremental cost-effectiveness ratios, drug-sensitive tuberculosis (DS-TB) cases, and TB-related deaths. For both bacillus Calmette-Guérin (BCG)-vaccinated and non-BCG-vaccinated individuals, IGRA with 4R was the most cost-effective and TST with 3RH was the least effective. Among schizophrenic individuals in Japan, IGRA with 4R saved US$17.8 million, increased 58,981 QALYs and 935 LYs, and prevented 222 DS-TB cases and 75 TB-related deaths compared with TST with 3RH. In individuals with schizophrenia, IGRA with 4R is recommended for LTBI screening with preventive treatment to reduce costs, morbidity, and mortality from TB.

A costing framework to compare tuberculosis infection tests.

OBJECTIVE: To develop a framework to estimate the practical costs incurred from, and programmatic impact related to, tuberculosis (TB) infection testing-tuberculin skin tests (TST) versus interferon gamma release assay (IGRA)-in a densely populated high-burden TB area. METHODS: We developed a seven-step framework that can be tailored to individual TB programmes seeking to compare TB infection (TBI) diagnostics to inform decision-making. We present methodology to estimate (1) the prevalence of TBI, (2) true and false positives and negatives for each test, (3) the cost of test administration, (4) the cost of false negatives, (5) the cost of treating all that test positive, (6) the per-test cost incurred due to treatment and misdiagnosis and (7) the threshold at which laboratory infrastructure investments for IGRA are outweighed by system-wide savings incurred due to IGRA utilisation. We then applied this framework in a densely populated, peri-urban district in Lima, Peru with high rates of Bacillus Calmette-Guérin (BCG) vaccination. FINDINGS: The lower sensitivity of TST compared with IGRA is a major cost driver, leading to health system and societal costs due to misdiagnosis. Additionally, patient and staff productivity costs were greater for TST because it requires two patient visits compared with only one for IGRA testing. When the framework was applied to the Lima setting, we estimate that IGRA-associated benefits outweigh infrastructural costs after performing 672 tests. CONCLUSIONS: Given global shortages of TST and concerns about costs of IGRA testing and laboratory capacity building, this costing framework can provide public health officials and TB programmes guidance for decision-making about TBI testing locally. This framework was designed to be adaptable for use in different settings with available data. Diagnostics that increase accuracy or mitigate time to treatment should be thought of as an investment instead of an expenditure.

Comparative analysis between STANDARD-E Covi-FERON ELISA with pre-existing IFN-γ release assays and determination of the optimum cutoff value for assessment of T-Cell response to SARS-CoV-2.

BACKGROUND: Interferon-gamma (IFN-γ) release assays (IGRAs) are useful for the assessment of the T-cell response to severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2). We aimed to assess the performance of the newly developed IGRA ELISA test compared to the pre-existing assays and to validate the cutoff value in real-world conditions. METHODS: We enrolled 219 participants and assessed agreement between STANDARD-E Covi-FERON ELISA with Quanti-FERON SARS-CoV-2 (QFN SARS-CoV-2), as well as with T SPOT Discovery SARS-CoV-2 based on Cohen's kappa-index. We further determined the optimal cutoff value for the Covi-FERON ELISA according to the immune response to vaccinations or infections. RESULTS: We found a moderate agreement between Covi-FERON ELISA and QFN SARS-CoV-2 before vaccination (kappa-index = 0.71), whereas a weak agreement after the first (kappa-index = 0.40) and second vaccinations (kappa-index = 0.46). However, the analysis between Covi-FERON ELISA and T SPOT assay demonstrated a strong agreement (kappa-index >0.7). The cut-off value of the OS (original spike) marker was 0.759 IU/mL with a sensitivity of 96.3% and specificity of 78.7%, and that of the variant spike (VS) marker was 0.663 IU/mL with a sensitivity and specificity of 77.8% and 80.6%, respectively. CONCLUSION: The newly determined cut-off value may provide an optimum value to minimize and prevent the occurrence of false-negative or false-positive during the assessment of T-cell immune response using Covi-FERON ELISA under real-world conditions.

A cost-effectiveness evaluation of latent tuberculosis infection screening of a migrant population in Malaysia.

To estimate the costs and benefits of screening for latent tuberculosis infection (LTBI) in a migrant population in Malaysia. An economic model was developed from a Malaysian healthcare perspective to compare QuantiFERON-TB Gold Plus (QuantiFERON) with the tuberculin skin test (TST). A decision tree was used to capture outcomes relating to LTBI screening followed by a Markov model that simulated the lifetime costs and benefits of the patient cohort. The Markov model did not capture the impact of secondary infections. The model included an R shiny interactive interface to allow adaptation to other scenarios and settings. QuantiFERON is both more effective and less costly than TST (dominant). Compared with QuantiFERON, the lifetime risk of developing active TB increases by approximately 40% for TST due to missed LTBI cases during screening (i.e. a higher number of false negative cases for TST). For a migrant population in Malaysia, QuantiFERON is cost-effective when compared with TST. Further research should consider targeted LTBI screening for migrants in Malaysia based on common risk factors.

Prevalence and management of tuberculosis infection in Apulian rheumatologic patients treated with biologics: An observational cohort 10-year study from the BIOPURE registry.

INTRODUCTION: The objective of this study was to assess the 10-year prevalence of latent tuberculosis infection (LTBI) among Apulian patients with rheumatic diseases (RDs). Secondary endpoint was to record new cases of active TB disease and LTBI among patients treated with biologic disease-modifying antirheumatic drugs (bDMARDs). METHODS: We analysed the results from the patients included in the BIOPURE registry from 2009 to 2018, who underwent QuantiFERON-TB Gold In-tube (QFT-GIT) test as screening before bDMARDs treatment. Demographic and clinical data were recorded at the time of the first QFT-GIT test. Administration of preventive therapy and bDMARD treatments were recorded for patients with positive QFT-GIT test. All new tuberculosis infections were recorded during the follow-up. RESULTS: The final study population included 3028 patients (855 rheumatoid arthritis, 1001 psoriatic arthritis, 833 spondyloarthritis, 130 connective tissue diseases, 33 systemic vasculitis and 176 other inflammatory rheumatic conditions), more frequently female (67.2%), with a mean age of 52 ± 18 years. Patients with QFT-GIT-positive test were elderly people, predominantly male with higher prevalence of diabetes as comorbidity. The 10-year prevalence of LTBI was 10.8%. Of note, no cases of TB reactivation were recorded in patients who completed preventive therapy treatment. Three thousand and sixteen patients were followed over time (42.6 ± 30 months), and five (.2%) developed active TB, which corresponds to .47 cases per 1000 person-years. CONCLUSIONS: In the 10-year observation, the use of bDMARDs seems to be safe in rheumatologic patients with positive QFT-GIT test treated according to current recommendations. Nevertheless, cases of primary TB disease did occur during treatment with biologicals.

Teste de Liberação de Interferon-gama (IGRA) para detecção de infecção latente pelo Mycobacterium tuberculosis em pacientes com doenças inflamatórias imunomediadas ou receptores de transplante de órgãos sólidos / Interferon Gamma Release Test (IGRA) for detection of latent infection by Mycobacterium tuberculosis in patients with immune-mediated inflammatory diseases or solid organ transplant recipients

A ILTB é um estado de resposta imune persistente aos antígenos do Mycobacterium tuberculosis, porém, sem sintomas clínicos ou achados radiológicos compatíveis com doença ativa. Estima-se que esta condição possa estar presente em um terço da população mundial. Assim, é importante diagnosticar a ILTB nas populações que requerem terapias imunossupressoras devido ao potencial risco de ativação da doença para sua forma transmissível. O diagnóstico precoce da ILTB permite o tratamento preconizado que impede sua ativação, sendo fundamental esta estratégia sanitária para reduzir e controlar a carga global da tuberculose (TB). O Centre for Disease Control and Prevention (CDC) americano informa que é recomendável o uso do IGRA ou PT para diagnóstico da ILTB na prática de saúde pública, enfatizando as limitações de ambos os testes, e recomenda que a TB deve ser excluída antes de iniciar o tratamento para ILTB. A World Health Organization (WHO) informa que tanto a PT quanto o IGRA podem ser usados para testar a ILTB, embora não haja fortes evidências de que um teste deva ser preferido em relação ao outro em termos de predizer a progressão da infecção para a doença de TB ativa. A WHO ainda recomenda que não sejam usados nem a PT nem os IGRAs em pessoas com baixo risco de infecção e com TB ativa, sendo necessário excluir a possibilidade de a doença estar ativa por meio de avaliação clínica, radiografia de tórax e exame de escarro. PERGUNTA DE PESQUISA: O teste de liberação de interferon-gama (IGRA), quando comparado a prova tuberculínica (PT), é acurado para detecção de infecção latente pelo Mycobacterium tuberculosis (ILTB) e capaz de prever ativação da tuberculose (TB) em pacientes com doença inflamatória imunomediada (DIIM) ou receptores de órgão sólidos candidatos ou em uso de terapia imunossupressora? AVALIAÇÃO ECONÔMICA: Foi realizada análise de custo-efetividade da ampliação de uso do IGRA para o diagnóstico da ILTB, tendo como comparador a PT, sob a perspectiva do SUS. Para tanto, um modelo de árvore de decisão foi elaborado, considerando como desfecho o número de casos de TB ativa evitados. A razão de custo-efetividade incremental (RCEI) para utilização do IGRA foi igual a R$ 8.340,68 por caso adicional de TB evitado em pacientes portadores de DIIM. Para pacientes candidatos a transplante de órgãos sólidos, a RCEI foi igual a R$ 48.905,19 por caso adicional de TB ativa evitado. De acordo com a análise de sensibilidade determinística, a variável mais sensível do modelo, no caso de pacientes portadores de DIIM, foi a especificidade do IGRA. Por outro lado, a sensibilidade do IGRA foi a variável mais sensível no caso de pacientes candidatos a transplantes de órgãos sólidos. Das 1.000 simulações realizadas na análise de sensibilidade probabilística, para a população portadora de DIIM, em 98% o IGRA mostrou ser a alternativa mais efetiva e de maior custo, enquanto este percentual foi cerca de 89% para pacientes candidatos a transplantes de órgão sólidos. ANÁLISE DE IMPACTO ORÇAMENTÁRIO: O impacto orçamentário incremental total em cinco anos da incorporação do IGRA para diagnóstico da ILTB em pacientes portadores de DIIM foi igual a R$ 40.527.273,25. No caso dos pacientes candidatos a transplante de órgãos sólidos, o impacto orçamentário incremental em cinco anos foi igual a R$ 1.131.654,58. Considerando a incorporação do IGRA para ambas as populações, o impacto orçamentário incremental total em cinco anos seria de R$ 41.658.927,83. Em um cenário alternativo, em que o IGRA alcançaria um market share de 90% após cinco anos de sua incorporação, o impacto orçamentário incremental total seria de R$ 103.202.100,74 para ambas as populações. MONITORAMENTO DO HORIZONTE TECNOLÓGICO: Foram encontradas quatro novas tecnologias, sendo uma de produção nacional (Eco F TB Feron ­ IFN-Gamma), dois testes com registros Anvisa, mas sem aprovação FDA (Vidas TB-IGRA, da empresa Biomerieux SA e QIAreach Quantiferon-TB Test, da empresa Qiagen GmbH) e um dispositivo com registro Anvisa e FDA (Família Liaison Quantiferon TB Gold Plus, da empresa Diasorin Ltda). Em relação aos depósitos e patentes concedidas, foi possível evidenciar quatro documentos patentários, sendo um, em fase nacional, com pedido brasileiro. CONSIDERAÇÕES FINAIS: Por não existir padrão ouro para o diagnóstico da ILTB, a implantação da estratégia da identificação dos casos antes do início de uma terapia imunossupressora é um desafio. Foram avaliados desfechos relevantes para o desempenho dos testes com populações heterogêneas com alto risco para o desenvolvimento da tuberculose ativa: pacientes com DIIM e pacientes candidatos a transplante de órgãos sólidos. As evidências incluídas foram provenientes de países com realidades diversas quanto à situação vacinal com BCG e taxas endêmicas de TB. Além disso, os estudos apresentaram grande fragilidade metodológica com variabilidade na métrica e nos resultados de acurácia, como também, heterogeneidade dos tipos de teste IGRA avaliados e no ponto de corte de positividade da PT, impossibilitando a metaanálise dos resultados na maioria dos estudos de síntese. De modo geral, os estudos não foram capazes de aferir o teste mais acurado ou mesmo a taxa de concordância entre eles, assim como não foram esclarecedores quanto ao teste com maior desempenho estratégico para identificar ILTB e evitar progressão da TB ativa. Contudo, os diferentes tipos de teste IGRA demonstraram resultados semelhantes com a PT, com certo direcionamento favorável ao IGRA para prever progressão de TB ativa quando se trata de pacientes com DIIM. Embora na perspectiva econômica os resultados tenham apontado para o IGRA como uma tecnologia com maior custo e maior efetividade, comparado à PT nas duas populações avaliadas, a incorporação do teste IGRA como uma alternativa de teste diagnóstico da ILTB pode se tornar uma decisão estratégica no que se refere a previsão e a provisão da rede quando na análise de possível desabastecimento do teste diagnóstico já disponível no SUS. RECOMENDAÇÃO PRELIMINAR DA CONITEC: Os membros presentes na 110ª Reunião Ordinária, em 06 de julho de 2022, deliberaram, por unanimidade, sem nenhuma declaração de conflito de interesses, encaminhar o tema para consulta pública com recomendação preliminar favorável a ampliação de uso do teste de liberação de interferon-gama (IGRA) para detecção de infecção latente pelo Mycobacterium tuberculosis em pacientes com doenças inflamatórias imunomediadas ou receptores de transplante de órgãos sólidos. Considerou-se a importância do IGRA como alternativa diagnóstica para o controle epidemiológico da tuberculose e para o auxílio na identificação e no prognóstico dos pacientes com maior risco de desenvolver a tuberculose ativa, além das questões organizacionais e logísticas que sugerem a necessidade de mais um teste diagnóstico para ILTB. CONSULTA PÚBLICA: A Consulta Pública nº 64/2022 foi realizada no período de 20/09/2022 a 10/10/2022 recebendo 135 contribuições de experiência ou opinião. A maioria destes respondentes apresentou-se favorável à recomendação inicial da Conitec. Dois profissionais de saúde manifestaram-se desfavoráveis à incorporação do procedimento. Em geral, os participantes que se posicionaram de forma favorável mencionaram a precisão do teste IGRA na detecção de ILTB, a garantia de um tratamento adequado para determinados grupos de pacientes, a garantia do uso com segurança de imunobiológicos e imunossupressores, a necessidade de acesso ao teste pelo SUS, as vantagens do procedimento em relação à prova tuberculínica e a alta prevalência da tuberculose no Brasil. Entre os participantes que possuíram experiência com a tecnologia avaliada, foram mencionados como aspectos positivos o rastreio mais específico e sensível do teste, a comodidade na realização, maior segurança e resultado rápido. Em contraponto, o alto custo do procedimento foi apontado como uma dificuldade de acesso. As contribuições técnico-científicas totalizaram 37, sendo quatro oriundas de pessoa jurídica e 33 de pessoa física, e todas concordaram com a recomendação inicial da Conitec. RECOMENDAÇÃO FINAL DA CONITEC: Os membros presentes na 114ª Reunião Ordinária, em 09 de novembro de 2022, deliberaram, por unanimidade, sem nenhuma declaração de conflito de interesses, recomendar a ampliação de uso do teste de liberação de interferon-gama (IGRA) para detecção de infecção latente pelo Mycobacterium tuberculosis em pacientes com doenças inflamatórias imunomediadas ou receptores de transplante de órgãos sólidos. Considerou-se a importância do IGRA como alternativa diagnóstica e nas questões organizacionais e logísticas no SUS. Foi assinado o Registro de Deliberação nº 778/2022. DECISÃO: : Ampliar o uso, no âmbito do Sistema Único de Saúde - SUS, do Teste de Liberação de Interferon-gama (IGRA) para detecção de infecção latente pelo Mycobacterium tuberculosis em pacientes com doenças inflamatórias imunomediadas ou receptores de transplante de órgãos sólidos, conforme protocolo estabelecido pelo Ministério da Saúde, conforme a Portaria nº 171, publicada no Diário Oficial da União nº 230, seção 1, página 295, em 8 de dezembro de 2022.

A systematic review of cost-utility analyses of screening methods in latent tuberculosis infection in high-risk populations.

BACKGROUND: The World Health Organisation (WHO) recommends that testing and treatment for latent tuberculosis infection (LTBI) should be undertaken in high-risk groups using either interferon gamma release assays (IGRAs) or a tuberculin skin test (TST). As IGRAs are more expensive than TST, an assessment of the cost-effectiveness of IGRAs can guide decision makers on the most appropriate choice of test for different high-risk populations. This current review aimed to provide the most up to date evidence on the cost-effectiveness evidence on LTBI testing in high-risk groups-specifically evidence reporting the costs per QALY of different testing strategies. METHODS: A comprehensive search of databases including MEDLINE, EMBASE and NHS-EED was undertaken from 2011 up to March 2021. Studies were screened and extracted by two independent reviewers. The study quality was assessed using the Bias in Economic Evaluation Checklist (ECOBIAS). A narrative synthesis of the included studies was undertaken. RESULTS: Thirty-two studies reported in thirty-three documents were included in this review. Quality of included studies was generally high, although there was a weakness across all studies referencing sources correctly and/or justifying choices of parameter values chosen or assumptions where parameter values were not available. Inclusions of IGRAs in testing strategies was consistently found across studies to be cost-effective but this result was sensitive to underlying LTBI prevalence rates. CONCLUSION: While some concerns remain about uncertainty in parameter values used across included studies, the evidence base since 2010 has grown with modelling approaches addressing the weakness pointed out in previous reviews but still reaching the same conclusion that IGRAs are likely to be cost-effective in high-income countries for high-risk populations. Evidence is also required on the cost-effectiveness of different strategies in low to middle income countries and countries with high TB burden.

GeneXpert or chest-X-ray or tuberculin skin testing for household contact assessment (GXT): protocol for a cluster-randomized trial.

BACKGROUND: The World Health Organization recommends tuberculosis (TB) preventive treatment (TPT) for all people living with HIV (PLH) and household contacts (HHC) of index TB patients. Tests for TB infection (TBI) or to rule out TB disease (TBD) are preferred, but if not available, this should not be a barrier if access to these tests is limited for high-risk people, such as PLH and HHC under 5 years old. There is equipoise on the need for these tests in different risk populations, especially HHC aged over 5. METHODS: This superiority cluster-randomized multicenter trial with three arms of equal size compares, in Benin and Brazil, three strategies for HHC investigation aged 0-50: (i) tuberculin skin testing (TST) or interferon gamma release assay (IGRA) for TBI and if positive, chest X-Ray (CXR) to rule out TBD in persons with positive TST or IGRA; (ii) same as (i) but GeneXpert (GX) replaces CXR; and (iii) no TBI testing. CXR for all; if CXR is normal, TPT is recommended. All strategies start with symptom screening. Clusters are defined as HHC members of the same index patients with newly diagnosed pulmonary TBD. The main outcome is the proportion of HHC that are TPT eligible who start TPT within 3 months of the index TB patient starting TBD treatment. Societal costs, incidence of severe adverse events, and prevalence of TBD are among secondary outcomes. Stratified analyses by age (under versus over 5) and by index patient microbiological status will be conducted. All participants provide signed informed consent. The study was approved by the Research Ethic Board of the Research Institute of the McGill University Health Centre, the Brazilian National Ethical Board CONEP, and the "Comité Local d'Éthique Pour la Recherche Biomédicale (CLERB) de l'Université de Parakou," Benin. Findings will be submitted for publication in major medical journals and presented in conferences, to WHO and National and municipal TB programs of the involved countries. DISCUSSION: This randomized trial is meant to provide high-quality evidence to inform WHO recommendations on investigation of household contacts, as currently these are based on very low-quality evidence. TRIAL REGISTRATION: ClinicalTrials.gov NCT04528823.

Predicting Airborne Infection Risk: Association Between Personal Ambient Carbon Dioxide Level Monitoring and Incidence of Tuberculosis Infection in South African Health Workers.

BACKGROUND: High rates of tuberculosis (TB) transmission occur in hospitals in high-incidence countries, yet there is no validated way to evaluate the impact of hospital design and function on airborne infection risk. We hypothesized that personal ambient carbon dioxide (CO2) monitoring could serve as a surrogate measure of rebreathed air exposure associated with TB infection risk in health workers (HWs). METHODS: We analyzed baseline and repeat (12-month) interferon-γ release assay (IGRA) results in 138 HWs in Cape Town, South Africa. A random subset of HWs with a baseline negative QuantiFERON Plus (QFT-Plus) underwent personal ambient CO2 monitoring. RESULTS: Annual incidence of TB infection (IGRA conversion) was high (34%). Junior doctors were less likely to have a positive baseline IGRA than other HWs (OR, 0.26; P = .005) but had similar IGRA conversion risk. IGRA converters experienced higher median CO2 levels compared to IGRA nonconverters using quantitative QFT-Plus thresholds of ≥0.35 IU/mL (P < .02) or ≥1 IU/mL (P < .01). Median CO2 levels were predictive of IGRA conversion (odds ratio [OR], 2.04; P = .04, ≥1 IU/mL threshold). Ordinal logistic regression demonstrated that the odds of a higher repeat quantitative IGRA result increased by almost 2-fold (OR, 1.81; P = .01) per 100 ppm unit increase in median CO2 levels, suggesting a dose-dependent response. CONCLUSIONS: HWs face high occupational TB risk. Increasing median CO2 levels (indicative of poor ventilation and/or high occupancy) were associated with higher likelihood of HW TB infection. Personal ambient CO2 monitoring may help target interventions to decrease TB transmission in healthcare facilities and help HWs self-monitor occupational risk, with implications for other airborne infections including coronavirus disease 2019.

Accuracy of interferon gamma release assays for the COVID-19 immunity assessment.

Emerging evidence suggests that T-cells play a significant role in COVID-19 immunity both in the context of natural infection and vaccination. Easy to use IGRA assays including QFN SARS are considered attractive alternatives to more "traditional" but laborious methods for detection of SARS-CoV-2-specific T-cell responses. In our Letter we are proposing explanations to an apparently lower than expected T-cell responses (44 % reactive individuals) reported by Krüttgen et al in a small cohort of healthy double vaccinated individuals. These results could have been affected by reporting raw optical density values instead of calculated Interferon-É£ concentrations which is supported by unexpectedly low mitogen responses in healthy individuals. This study highlights an importance of adhering to good laboratory practice principles as well as overall importance of accurate T-cell immunity assessment using IGRA assays.

Prevalence of Latent Tuberculosis Infection Among Healthy Young Children and Adolescents and a Two-step Approach for the Diagnosis of Tuberculosis Infection in Chengdu, China.

BACKGROUND: China has a high burden of tuberculosis and latent tuberculosis infection (LTBI). The aim of this study was to estimate the prevalence of LTBI among healthy young children and adolescents and test a 2-step approach to explore the threshold for the diagnosis of tuberculosis infection in Chengdu, China. METHODS: Healthy preschool children and school-going children in Chengdu, Sichuan Province, were screened for LTBI using the tuberculin skin test (TST). Preschool children with TST ≥ 5 mm also underwent interferon-γ release assay (IGRA) to explore the threshold of this 2-step approach. RESULTS: In total, 5667 healthy young children and adolescents completed TST test between July 2020 and January 2021 and were included in the present analysis. The age of the participants ranged from 2.4 to 18 years (median 7.25 ± 4.514 years), of which 2093 (36.9%) were younger than 5 years. The overall prevalence of LTBI was 6.37% and 6.64% in children younger than 5 years old. Fourteen of the 341 preschool children with TST ≥5 mm were interferon-γ release assay positive, of which 4 showed a TST result of 5-10 mm, and 6 preschool children received preventive treatment for LTBI. CONCLUSIONS: Healthy young children and adolescents should also be considered as important target populations for LTBI screening. TST can be recommended for first-line screening as part of a 2-step approach for LTBI screening using a positive threshold of 5 mm.

The Health and Economic Benefits of Tests That Predict Future Progression to Tuberculosis Disease.

BACKGROUND: Effective targeting of latent tuberculosis infection (LTBI) treatment requires identifying those most likely to progress to tuberculosis (TB). We estimated the potential health and economic benefits of diagnostics with improved discrimination for LTBI that will progress to TB. METHODS: A base case scenario represented current LTBI testing and treatment services in the United States in 2020, with diagnosis via. interferon-gamma release assay (IGRA). Alternative scenarios represented tests with higher positive predictive value (PPV) for future TB but similar price to IGRA, and scenarios that additionally assumed higher treatment initiation and completion. We predicted outcomes using multiple transmission-dynamic models calibrated to different geographic areas and estimated costs from a societal perspective. RESULTS: In 2020, 2.1% (range across model results: 1.1%-3.4%) of individuals with LTBI were predicted to develop TB in their remaining lifetime. For IGRA, we estimated the PPV for future TB as 1.3% (0.6%-1.8%). Relative to IGRA, we estimated a test with 10% PPV would reduce treatment volume by 87% (82%-94%), reduce incremental costs by 30% (15%-52%), and increase quality-adjusted life years by 3% (2%-6%). Cost reductions and health improvements were substantially larger for scenarios in which higher PPV for future TB was associated with greater initiation and completion of treatment. CONCLUSIONS: We estimated that tests with better predictive performance would substantially reduce the number of individuals treated to prevent TB but would have a modest impact on incremental costs and health impact of TB prevention services, unless accompanied by greater treatment acceptance and completion.

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.

Assessment of Interferon Gamma-Induced Protein 10 mRNA Release Assay for Detection of Latent Tuberculosis Infection in Egyptian Pediatric Household Contacts.

OBJECTIVES: Current diagnostic tests for tuberculosis (TB) in children living in low-endemic countries are limited by low specificity and the inability of the current tests to differentiate between active TB and latent TB infection (LTBI). This study aimed to evaluate the blood IP-10 mRNA expression level to detect LTBI in Egyptian pediatric household contacts (PHC). METHODS: TB-specific IP-10 and IFN-γ mRNA levels were assessed by real-time quantitative PCR (RT-qPCR) in 72 Egyptian PHC of active pulmonary TB cases. All study participants were also assessed by Tuberculin Skin Test (TST) and Quantiferon gold in tube (QFN-GIT) assay. RESULTS: IP-10 and IFN-γ mRNA expression levels were significantly higher in PHC with active TB or LTBI than TB negative (p < 0.0001). The level of IP-10 mRNA expression was significantly higher in PHC with active TB than LTBI (p = 0.0008). In contrast, there was no significant differences in the IFN-γ mRNA expression between PHC with active TB compared to LTBI (p = 0.49). The sensitivity and specificity of the IP-10 RT-qPCR were 94.2% and 95.2%, respectively, in PHC with active TB compared to 85.7% and 81.8% in PHC with LTBI. The negative and positive predictive values and accuracy of IP-10 RT-qPCR for distinguishing active TB from LTBI were 85.2%, 58.3%, and 72.6% respectively. CONCLUSION: Blood IP-10 mRNA expression level may be a potential diagnostic marker to help distinguish active TB from LTBI in PHC.

Broad T Cell Targeting of Structural Proteins After SARS-CoV-2 Infection: High Throughput Assessment of T Cell Reactivity Using an Automated Interferon Gamma Release Assay.

Background: Adaptive immune responses to structural proteins of the virion play a crucial role in protection against coronavirus disease 2019 (COVID-19). We therefore studied T cell responses against multiple SARS-CoV-2 structural proteins in a large cohort using a simple, fast, and high-throughput approach. Methods: An automated interferon gamma release assay (IGRA) for the Nucleocapsid (NC)-, Membrane (M)-, Spike-C-terminus (SCT)-, and N-terminus-protein (SNT)-specific T cell responses was performed using fresh whole blood from study subjects with convalescent, confirmed COVID-19 (n = 177, more than 200 days post infection), exposed household members (n = 145), and unexposed controls (n = 85). SARS-CoV-2-specific antibodies were assessed using Elecsys® Anti-SARS-CoV-2 (Ro-N-Ig) and Anti-SARS-CoV-2-ELISA (IgG) (EI-S1-IgG). Results: 156 of 177 (88%) previously PCR confirmed cases were still positive by Ro-N-Ig more than 200 days after infection. In T cells, most frequently the M-protein was targeted by 88% seropositive, PCR confirmed cases, followed by SCT (85%), NC (82%), and SNT (73%), whereas each of these antigens was recognized by less than 14% of non-exposed control subjects. Broad targeting of these structural virion proteins was characteristic of convalescent SARS-CoV-2 infection; 68% of all seropositive individuals targeted all four tested antigens. Indeed, anti-NC antibody titer correlated loosely, but significantly with the magnitude and breadth of the SARS-CoV-2-specific T cell response. Age, sex, and body mass index were comparable between the different groups. Conclusion: SARS-CoV-2 seropositivity correlates with broad T cell reactivity of the structural virus proteins at 200 days after infection and beyond. The SARS-CoV-2-IGRA can facilitate large scale determination of SARS-CoV-2-specific T cell responses with high accuracy against multiple targets.

Comparing the cost-effectiveness of two screening strategies for latent tuberculosis infection in Portugal.

INTRODUCTION AND OBJECTIVES: Screening for latent tuberculosis infection (LTBI) in close contacts of infectious TB cases might include Tuberculin Skin Test (TST) and Interferon-Gamma Release Assays (IGRA), in combination or as single-tests. In Portugal, the screening strategy changed from TST followed by IGRA to IGRA-only testing in 2016. Our objective was to compare the cost-effectiveness of two-step TST/IGRA with the current IGRA-only screening strategy in immunocompetent individuals exposed to individuals with respiratory TB. MATERIALS AND METHODS: We reviewed clinical records of individuals exposed to infectious TB cases diagnosed in 2015 and 2016, in two TB outpatient centers in the district of Porto. We estimated medical, non-medical and indirect costs for each screening strategy, taking into account costs of tests and health care personnel, travel distance from place of residence to screening site and employment status. We calculated the incremental cost-effectiveness ratio (ICER) as the cost difference between the two screening strategies with the difference number of LTBI diagnosis as a measure of cost-effectiveness, assuming that treating LTBI is a cost-effective intervention. We also calculated adjusted odds-ratios to test the association between diagnosis of LTBI and screening strategy and estimated the total cost for averting a potential TB case. RESULTS: We compared 499 contacts TST/IGRA screened with 547 IGRA-only. IGRA-only strategy yielded a higher screening effectiveness for diagnosing latent tuberculosis infection (aOR 2.12, 95%CI: 1.53 - 2.94). ICER was €106 per LTBI diagnosis, representing increased effectiveness with a slightly increased cost of IGRA-only screening strategy. CONCLUSIONS: Our data suggests that in Portugal LTBI screening with IGRA-only is more cost-effective than the two-step TST/IGRA testing strategy, preventing a higher number of cases of TB cases.

A cross-sectional study of latent tuberculosis infection, insurance coverage, and usual sources of health care among non-US-born persons in the United States.

ABSTRACT: More than 70% of tuberculosis (TB) cases diagnosed in the United States (US) occur in non-US-born persons, and this population has experienced less than half the recent incidence rate declines of US-born persons (1.5% vs 4.2%, respectively). The great majority of TB cases in non-US-born persons are attributable to reactivation of latent tuberculosis infection (LTBI). Strategies to expand LTBI-focused TB prevention may depend on LTBI positive non-US-born persons' access to, and ability to pay for, health care.To examine patterns of health insurance coverage and usual sources of health care among non-US-born persons with LTBI, and to estimate LTBI prevalence by insurance status and usual sources of health care.Self-reported health insurance and usual sources of care for non-US-born persons were analyzed in combination with markers for LTBI using 2011-2012 National Health and Nutrition Examination Survey (NHANES) data for 1793 sampled persons. A positive result on an interferon gamma release assay (IGRA), a blood test which measures immunological reactivity to Mycobacterium tuberculosis infection, was used as a proxy for LTBI. We calculated demographic category percentages by IGRA status, IGRA percentages by demographic category, and 95% confidence intervals for each percentage.Overall, 15.9% [95% confidence interval (CI) = 13.5, 18.7] of non-US-born persons were IGRA-positive. Of IGRA-positive non-US-born persons, 63.0% (95% CI = 55.4, 69.9) had insurance and 74.1% (95% CI = 69.2, 78.5) had a usual source of care. IGRA positivity was highest in persons with Medicare (29.1%; 95% CI: 20.9, 38.9).Our results suggest that targeted LTBI testing and treatment within the US private healthcare sector could reach a large majority of non-US-born individuals with LTBI. With non-US-born Medicare beneficiaries' high prevalence of LTBI and the high proportion of LTBI-positive non-US-born persons with private insurance, future TB prevention initiatives focused on these payer types are warranted.