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Urgent improvements in the diagnosis and management of Mycobacterium tuberculosis infection are required to reach End TB goals. Conventional interferon-gamma release assays (IGRAs), such as QuantiFERON-TB Gold Plus (QFT-Plus), require substantial laboratory infrastructure and large blood volumes, limiting use in high-burden settings. The QIAreach QuantiFERON-TB (QIAreach QFT) was developed to overcome these challenges but has not previously been evaluated in field conditions in a low-income, high-burden country, or at scale in children. We performed a diagnostic evaluation of QIAreach QFT against QFT-Plus, in a cross-sectional IGRA survey in Blantyre, Malawi. We recruited a population-representative sample of children aged 1-4 years and adolescents and adults aged 10-40 years, from households and primary care. We calculated sensitivity, specificity, and Cohen's kappa for QIAreach QFT against QFT-Plus, and constructed Bayesian hurdle-categorical models to compare quantitative test results. A total of 1,049 participants were recruited (64%: 1-4 years; 13%: 10-19 years; and 23%: 20-40 years). More participants had a positive QIAreach QFT result (32%) compared to QFT-Plus (15%). Over half of positive QIAreach QFT results had time-to-positivity of exactly 20 min, the assay cutoff. There was minimal agreement between QFT-Plus and QIAreach QFT results ( κ = 0.26), which was lowest in children aged 1-4 years ( κ = 0.13). Sensitivity and specificity of QIAreach QFT relative to QFT-Plus were 62% and 74%, respectively, with poor correlation between quantitative results. The suboptimal performance of QIAreach QFT, particularly in young children, suggests that it cannot currently be recommended for wider use and that the urgent need for an accessible test of Mtb infection remains unmet., Importance: Almost a quarter of the world's population has evidence of Mycobacterium tuberculosis (Mtb) infection. Monitoring and addressing this substantial burden of so-called "latent" tuberculosis (TB) infection will be critical to reach End TB targets. However, current interferon-gamma release assays (IGRAs) for Mtb infection are costly, and require a large volume of venous blood and significant laboratory processing, which are major barriers to their wider use in low-income countries. The novel QIAreach QuantiFERON-TB (QIAreach) assay has been designed as a more accessible alternative. We sought to evaluate it against a reference standard of QuantiFERON-TB Gold Plus, in a large cross-sectional survey in Blantyre, Malawi. To our knowledge, this is the first diagnostic evaluation of QIAreach QFT to be performed in a population-based survey in a low-income high-incidence setting, and to specifically focus on young children (a priority group for interventions targeting Mtb infection). In contrast to previous studies in other settings, we observed poor performance of QIAreach QFT, particularly in young children where there was little correlation between the novel test and the reference standard. This leads us to conclude that this test cannot be widely recommended for use in its current form; indeed manufacture is currently suspended. We believe our findings are of urgent importance to policymakers, clinicians, and researchers and underscore the importance of careful evaluation of new diagnostics in the contexts where they are intended to be used., Competing Interests: The manufacturers of QFT-Plus and QIAreach QFT (QIAGEN) provided tests at reduced or no cost for the purposes of research and technical support for quality control but played no role in study design, collection, analysis, or dissemination of findings.

The aim of this study was to evaluate the diagnostic accuracy of the IGRA, TST, and TBST by combining diagnostic test accuracy (DTA) analysis and network meta-analysis (NMA) to increase the reliability and accuracy of diagnostic methods and promote the eradication of TB. An electronic search of the PubMed, Embase, and Cochrane databases was conducted, from the date of establishment to September 30, 2024. Data were synthesized with frequentist random-effects network meta-analyses, a single-group rate meta-analysis algorithm, and a bivariate mixed-effects logistic regression model. Summarized receiver operating characteristic curves and Fagan nomograms were used to assess diagnostic accuracy and clinical utility. Deeks' funnel plots and the Quality Assessment of Diagnostic Accuracy Studies 2 tools were used to assess publication bias and risk of bias. Sources of heterogeneity were investigated using subgroup analyses. Forty-nine studies were identified. The diagnostic performance of the three diagnostic methods for TB infection is summarized as follows: the pooled sensitivity was 77.9% (95% confidence interval [CI], 0.69-0.856), and the pooled specificity was 80.3% (95% CI, 0.75-0.86). The sensitivity and specificity of the IGRA were 82.1% (95% CI, 0.78-0.86) and 81.1% (95% CI, 0.75-0.86), respectively, both higher than the TST. However, the TBST exhibited the highest specificity, at 98.5% (95% CI, 0.96-1.00), with a sensitivity of 78.7% (95% CI, 0.68-0.88), which was between that of the IGRA and TST. Subgroup analysis found that population categories and reference standards, among other factors, may be attributed to heterogeneity. In addition, the TST and IGRA add-on TBST can significantly improve diagnostic accuracy. In our study, the IGRA showed higher sensitivity, whereas the TBST showed higher specificity. Interestingly, under certain conditions, TST add-on TBST and IGRA add-on TBST showed better accuracy than TST and IGRA alone and could provide more effective guidance for clinical practice (PROSPERO CRD42023420136).

Purpose: Comparing the performance of commercially available SARS-CoV-2 T-cell immunoassay responses may provide useful information for future observational or intervention studies as well as to their potential customers., Method: Whole blood was collected from a total of 183 subjects fully vaccinated against COVID-19: 55 healthy controls (Group 1), 50 hematological patients (Group 2), 50 chronic kidney disease patients (Group 3), and 28 elderly nursing home residents (Group 4). Samples were tested with the Roche Elecsys® IGRA (Interferon-gamma release assay) SARS-CoV-2 test (Roche Diagnostics, Rotkreuz, Switzerland), the Euroimmun SARS-CoV-2 test (Euroimmun, Lubeck, Germany), the SARS-CoV-2 T Cell Analysis Kit (Miltenyi Biotec, Bergisch Gladbach, Germany), and a flow-cytometry for intracellular cytokine (IFN-γ) staining-based immunoassay (FC-ICS)., Results: Overall, the Roche Elecsys® assay returned the highest number of positive results (151/179; 84.3%), followed by the Euroimmun test (127/183; 69%), and the FC-ICS (135/179; 75%). The Kappa coefficient of agreement was best between IGRAs (0.64). Most discordant results across assays involved patients from Group 2. Overall, IFN-γ concentrations measured by both IGRAs correlated strongly (rho = 0.78; 95% CI 0.71-0.84; P < 0.001) irrespective of the study group. The frequencies of SARS-CoV-2-reactive IFN-γ T cells and IFN-γ concentrations measured by the IGRAs correlated moderately for CD4 + T cells, however, weakly for CD8 + T cells. SARS-CoV-2-experienced participants displayed stronger responses than SARS-CoV-2-naïve when IGRAs, rather than FC-ICS, were used., Conclusion: The SARS-CoV-2 immunoassays evaluated in the present study did not return interchangeable qualitative or quantitative results either in seemingly healthy individuals or in immunosuppressed patients., (© 2024. The Author(s).)

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., Competing Interests: Author Disclosures Author disclosure forms can be accessed in the Supplemental Material section., (Copyright © 2023 International Society for Health Economics and Outcomes Research. Published by Elsevier Inc. All rights reserved.)

Background: Treatment of latent tuberculosis infection is an important strategy to prevent tuberculosis disease. In the USA, three tests are used to identify latent tuberculosis infection: the tuberculin skin test (TST) and two IFN-γ release assays (T-SPOT.TB and QuantiFERON). To our knowledge, few large studies have compared all three tests among people at high risk of latent tuberculosis infection or progression to tuberculosis disease. We aimed to assess test agreement between IFN-γ release assays and TST to provide guidance on their use in important risk groups., Methods: In this observational cohort study, we enrolled participants at high risk of latent tuberculosis infection or progression to tuberculosis disease at ten US sites with 18 affiliated clinics, including close contacts of infectious tuberculosis cases, people born in countries whose populations in the USA have high (≥100 cases per 100 000 people) or moderate (10-99 cases per 100 000 people) tuberculosis incidence, and people with HIV. Participants were interviewed about demographics and medical risk factors, and all three tests were administered to each participant. The primary endpoints for this study were the proportions of positive test results by test type stratified by risk group and test concordance by risk group for participants with valid results for all three test types. The study is registered at ClinicalTrials.gov, NCT01622140., Findings: Between July 12, 2012, and May 5, 2017, 26 292 people were approached and 22 131 (84·2%) were enrolled in the study. Data from 21 846 (98·7%) participants were available for analysis, including 3790 (17·3%) born in the USA and 18 023 (82·5%) born outside the USA. Among non-US-born participants overall, the RR comparing the proportions of TST-positive results (7476 [43·2%] of 17 306 participants) to QuantiFERON-positive results (4732 [26·5%] of 17 882 participants) was 1·6 (95% CI 1·6-1·7). The risk ratio (RR) for the comparison with the proportion of T-SPOT.TB-positive results (3693 [21·6%] of 17 118 participants) was 2·0 (95% CI 1·9-2·1). US-born participants had less variation in the proportions of positive results across all tests. The RRs for the proportion of TST-positive results (391 [10·9%] of 3575 participants) compared with the proportion of QuantiFERON-positive results (445 [12·0%] of 3693 participants) and T-SPOT.TB-positive results (295 [8·1%] of 3638 participants) were 0·9 (95% CI 0·8-1·0) and 1·3 (1·2-1·6), respectively. 20 149 (91·0%) of 21 846 participants had results for all three tests, including 16 712 (76%) non-US-born participants. Discordance between TST and IFN-γ release assay results varied by age among non-US-born participants and was greatest among the 848 non-US-born children younger than 5 years. 204 (87·2%) of 234 non-US-born children younger than 5 years with at least one positive test were TST-positive and IFN-γ release assay-negative. The proportion of non-US-born participants who were TST-negative but IFN-γ release assay-positive ranged from one (0·5%) of 199 children younger than 2 years to 86 (14·5%) of 594 participants aged 65 years and older (p trend <0·0001). Test agreement was higher between the two IFN-γ release assays than between TST and either IFN-γ release assay, regardless of birthplace. κ agreement was particularly low between TST and IFN-γ release assays in non-US-born children younger than 5 years., Interpretation: Our findings support the preferential use of IFN-γ release assays for the diagnosis of latent tuberculosis in high-risk populations, especially in very young and older people born outside the USA., Funding: US Centers for Disease Control and Prevention., Competing Interests: Declaration of interests We declare no competing interests., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

In this cross-sectional study of 284 children and adolescents with clinically or radiologically suspected tuberculosis in a low-endemic country, the QuantiFERON-TB Gold Plus assay specificity, sensitivity, positive predictive value and negative predictive value were 91.5%, 87.3%, 86.4%, and 91.2%, respectively. The specificity was higher than that observed in tuberculin skin tests performed simultaneously, but similar to previous-generation interferon-gamma release assays., Competing Interests: M.T. has received QuantiFERON assays at reduced pricing or free of charge for TB diagnostics projects from the manufacturer (Cellestis/Qiagen) in the past and has received support for conference attendance from Cepheid. The manufacturers had no influence on the study design, data collection, analysis or interpretation, writing of the manuscript, or decision to submit the data for publication. The remaining authors have no other conflicts of interest to disclose., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Immunocompromised status can result in indeterminate QuantiFERON-TB Gold In-Tube (QFT-GIT) results, but the association of indeterminate results with immunocompetent status in children is unknown. Therefore, we aimed to identify factors associated with indeterminate QFT-GIT results for immunocompetent children. We conducted a retrospective chart review of children (aged ≤ 18 years) who underwent QFT-GIT between September 2006 and July 2017 at the Severance Hospital, Seoul, South Korea. Of the 2037 QFT-GIT assays included in the present study, 7.7% yielded indeterminate QFT-GIT results. Multivariable logistic regression analysis identified younger age (OR 0.88; 95% CI 0.836-0.927; P < 0.001), elevated white blood cell (WBC) count (OR 1.066; 95% CI 1.020-1.115; P = 0.005), decreased albumin levels (OR 0.505; 95% CI 0.316-0.807; P = 0.004), and low-dose steroid therapy (< 1 mg/kg per day of prednisone or equivalent for < 2 weeks) (OR 76.146; 95% CI 8.940-648.569; P < 0.001) as significant factors influencing indeterminate results. Younger age, high WBC count, low albumin levels, and low-dose steroid therapy were associated with indeterminate QFT-GIT results. Low-dose steroid therapy had the highest OR for the indeterminate results compared to other significant risk factors. Our study suggests that screening for steroid doses is important prior to performing interferon-gamma release assays for immunocompetent children.

Tuberculosis (TB) remains a worldwide problem. Despite the high disease rate, not all who are infected with Mycobacterium Tuberculosis ( Mtb ) develop disease. Interferon-γ (IFN-γ) specific T cell immune assays such as Quantiferon and Elispot, as well as a skin hypersensitivity test, known as a tuberculin skin test, are widely used to infer infection. These assays measure immune conversion in response to Mtb . Some individuals measure persistently negative to immune conversion, despite high and prolonged exposure to Mtb . Increasing interest into this phenotype has led to multiple publications describing various aspects of these responses. However, there is a lack of a unified "resister" definition. A universal definition will improve cross study data comparisons and assist with future study design and planning. We review the current literature describing this phenotype and make recommendations for future studies., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Gutierrez, Kroon, Möller and Stein.)

Tuberculosis (TB) is one of the leading infectious causes of death worldwide and despite the progress recently made in TB control at a global level, the decline in its incidence is still slow. It is therefore crucial to evaluate the performance of new tools for monitoring of TB treatment. The aim of this study was to evaluate the response to tuberculosis treatment using the QuantiFERON-TB Gold Plus (QFT-Plus) kit. Blood samples of 100 patients with active TB were taken before treatment and after three months, if treatment was successful and sputum culture was negative. Whole blood was incubated in the presence or absence of the TB antigens, TB1 and TB2-specific antigens, and the production of IFN-γ was determined using the QuantiFERON-TB Gold Plus (QFT-Plus) test. The data were analyzed using SPSS 16 software and statistical significance was assessed at a two-tailed P value of 0.05. The median values of IFN-γ released following stimulation with TB1 peptides decreased slightly after treatment (2.5 IU/mL (IQR: 0.9-5.3), compared to the baseline (3.4 IU/mL (IQR: 0.5-6.6)). Also, with respect to the TB1 antigen, 38 out of 45 patients were positive for the QFT test before treatment (84.4%) and 37 cases after treatment (82.2%). On the other hand, the median values of IFN-γ determined with the TB2 test declined marginally after treatment (2.7 IU/mL; IQR: 0.95-5.8), as compared to pretreatment (3.0 IU/mL; IQR: 0.7-8.9). Thirty-nine out of 45 patients (86.7%) before initiation of treatment and 37 cases following a 3-month treatment (82.2%) were had positive values. Moreover, the median values of IFN-γ of TB2 minus TB1 before and after treatment were 0.17 (IQR: 0-1.0) and 0.03 (IQR: 0.0.48), respectively; however, these differences were not significant (p value=0.29). Conclusion: The results of this study show no significant differences between the IFN-γ release in TB patients prior to and after treatment. However, more extensive studies are needed in different populations with higher sample sizes to validate these results.

Introduction: The interferon-γ release assays as potent adjunct tools for the quick detection of TB in high burden countries is feasible. In this retrospective study, we aimed to identify the risk factors for negative T-SPOT results in confirmed active tuberculosis., Methodology: We consecutively enrolled 1,021 patients who were positive for acid-fast bacilli smear staining or culture-confirmed mycobacterial infection and simultaneously tested with the T-SPOT.TB assay. All of the included specimens were used to discriminate the Mycobacterium species using the biochip assay. We collected basic clinical characteristics and laboratory results for further analysis., Results: Of the 1,021 patients enrolled in the study, 89 patients were identified as having nontuberculous mycobacteria (NTM). Ninety-nine patients were excluded from the analysis because of indeterminate T-SPOT.TB results, while the remaining 833 patients were identified as having Mycobacterium tuberculosis infection. In total, 159 patients had false-negative T-SPOT.TB results (19.1% of 833). The concordance rate between the T-SPOT.TB results and final diagnoses in females was always lower than that in males. Multivariate logistic regression analysis showed that female sex (OR 1.81; 95% CI 1.19, 2.7; p = 0.006), age (OR 1.02; 95% CI 1.01, 1.03; p = 0.003), acid-fast bacilli (AFB) smear-negative (OR 5.45; 95% CI 3.62, 8.19; p < 0.001), HIV coinfection (OR 6.83; 95% CI 2.73, 17.10; p < 0.001) were associated with negative T-SPOT.TB result., Conclusions: Female is another independent risk factor of negative T-SPOT.TB results, besides to elder, HIV co-infection, acid-fast bacilli (AFB) smear-negative who are suspected of having active TB infection., Competing Interests: No Conflict of Interest is declared, (Copyright (c) 2020 Yanwan Shangguan, Hong Fang, Shuting Wang, Zhongkang Ji, Pei Shi, Xuewen Feng, Kaijin Xu.)

Background: Use of interferon-gamma releasing assays (IGRAs) in children <2 years old may derive many of the same advantages, which have led to preference over tuberculin skin test (TST) in older children, but data are limited. Since 2011, we have tested children <2 years old with Quantiferon-TB Gold/Gold Plus (QFT)) in select clinical scenarios at Denver Health, a health system encompassing a TB clinic, refugee and immigrant screening and primary care., Methods: We identified patients <2 years old tested with QFT between February, 2011 and August, 2019. The primary outcome measure was incident cases of TB among tested patients. Test results and in vitro characteristics were analyzed, as were demographic, epidemiologic and clinical outcomes., Results: We analyzed 116 QFTs ordered in children age 7-23 months. Two were positive, 3 indeterminate, 3 failed/refused phlebotomy and the remainder (93%) were negative. Mitogen tube results were robust. Thirteen patients were TST-positive: 11 were QFT-negative, 1 QFT-positive and 1 failed phlebotomy. Eight patients received some form of TB medication, including 4 QFT-negative patients who were treated for active TB or latent TB infection based on positive TST or clinical findings. Among QFT-negative patients, including 6 TST-positive, not treated for active TB or latent TB infection, no TB disease has been identified over a median follow-up time of 2.96 years., Conclusions: IGRA use was not limited by barriers of phlebotomy, indeterminate result or gamma-interferon production. The risk of missing an infected but IGRA-negative patient can be reduced by treatment of select patients at higher risk. Current recommendations against IGRA use in children <2 years old could be amended to allow careful introduction, particularly among well-appearing BCG-vaccinated patients.

We present a pediatric case series describing false-positive QuantiFERON-TB Gold In-tube (QFT-GIT) assay (QIAGEN, Germany) results observed in a tertiary hospital in Spain (2013-2018). During the study period, 7 of 737 test results were considered false-positives: 4 children with chronic medical conditions, 1 Mycobacterium lentiflavum lymphadenitis, 1 infant born to a mother with pulmonary tuberculosis, and 1 child exposed to a noninfectious tuberculosis patient. Data regarding interferon-gamma release assays false-positive results in children are scarce, and more studies are necessary to determine the rates of false-positive results in low-prevalence settings.

Background: Currently, tuberculin skin test (TST) and interferon gamma release assay (IGRA) are used to find the latent tuberculosis infection (LTBI) cases in the candidates of heart transplantation. Therefore, this study aimed to compare TST and IGRA to diagnose LTBI in pediatric heart transplant candidates., Methods: This cross-sectional study was performed on 50 children, who were candidates for heart transplantation, of whom 42 cases underwent heart transplantation in Shahid Rajaie Cardiovascular, Medical, and Research center, Tehran, Iran, from 2016 to 2017., Results: Participants of the study included 24 male patients (%48) (p-value = 0.67). The mean age of the patients was 8.18 ± 4.27 years (1-16 years). According to the results, IGRA was negative in all patients, and no indeterminate result was reported, while the purified derivative test (PPD) was positive in three (6%) cases. In comparison with QFT, an accuracy of 94% was achieved for TST to diagnose Mycobacterium tuberculosis infection., Conclusions: It seems that TST can still be used as an accurate test for screening LTBI in pediatric candidates for heart transplantation., (© 2020 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

The QuantiFERON TB Gold Plus (QFT-Plus) test is a newly approved interferon-gamma releasing assay test for detecting latent tuberculosis. Although blood samples for QFT test can be refrigerated for 48 h in lithium-heparin tubes according to package inserts, no published data are available on the effects of sample refrigeration on the test results. We conducted a clinical study that aimed to elucidate whether sample refrigeration for 48 h affects QFT-Plus test results. We collected 2 blood samples each from 40 participants for QFT-Plus; one sample was refrigerated before incubation for QFT-Plus assay, while the other sample was incubated soon after collection and treated as control. After comparing QFT-Plus test results of refrigerated samples and control samples, the concordance rate and kappa coefficient between them were 95% and 0.90, respectively. Thus, blood samples for QFT-Plus test can be refrigerated for 48 h in lithium-heparin tubes without influencing the test results., Competing Interests: Declarations of Competing Interest The funder of this study is a QFT-Plus distributor in Japan., (Copyright © 2019 Japanese Society of Chemotherapy and The Japanese Association for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.)

Objectives: The interferon-gamma release assay (IGRA) is useful for diagnosing Mycobacterium tuberculosis infections, especially in countries where Bacille Calmette-Guérin vaccinations are performed. However, reproducibility of the IGRA is unclear, as recent data suggest high IGRA conversion and reversion rates in serial tests among healthcare workers. This longitudinal study aimed to evaluate reproducibility of T-SPOT.TB for screening M. tuberculosis infections in Japan., Methods: Results of T-SPOT.TB tests performed between April 2014 and March 2016 at two hospitals in Yokohama, Japan, where the incidence of tuberculosis was 18.0 per 100,000 population in 2014, were analyzed., Results: In total, 3890 T-SPOT.TB tests were included. Overall, positive and negative test rates were 8.4% and 87.6%, respectively. Among 373 serial tests within two years, conversion and reversion rates were only 1.1% and 12.5%, respectively. Almost all patients who were initially negative (98.9%) remained so. There was no statistically significant difference between the outcomes observed at the two hospitals., Conclusions: The conversion rate of T-SPOT.TB in Japan is as low as that recently reported in other countries where the incidence of tuberculosis is low. These data indicate that T-SPOT.TB is a reproducible tuberculosis screening tool at local hospitals in areas with a moderate incidence of tuberculosis., (Copyright © 2019 Japanese Society of Chemotherapy and The Japanese Association for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.)

A negative interferon-γ release assay (IGRA) result might inappropriately lower the clinical suspicion for childhood tuberculosis (TB) and result in delayed treatment initiation. However, the risk factors associated with false-negative IGRA results in children remain unclear. Between May 2012 and January 2018, 156 culture-confirmed childhood TB patients who had received T-SPOT.TB test were included. Data, including demographic information and clinicopathological variables, were collected via questionnaires. Univariate and multivariate logistic regression analyses were performed to estimate the odds ratio (OR) and corresponding 95% CI of risk factors associated with false-negative T-SPOT.TB results. The positive rate of T-SPOT.TB test was 85.9% in childhood TB patients. Multivariate analysis revealed that younger age (≤ 9 years; OR = 4.782; 95% CI: 1.689, 13.539), weight for age ( z -score > 0.37; OR = 4.256; 95% CI: 1.458, 12.428), and hypoproteinemia (total protein ≤ 68.4 g/L; OR = 7.131; 95% CI: 1.864, 27.271) were risk factors for false-negative T-SPOT.TB results in childhood TB. Younger age, overweight, and hypoproteinemia were found to be associated with false-negative T-SPOT.TB results in childhood TB. Health care professionals should consider these risk factors when evaluating suspected childhood TB with negative T-SPOT.TB results.

The cytokine interferon gamma-inducible protein 10 (IP-10) is a sensitive biomarker of Mycobacterium bovis (M. bovis) infection in African buffaloes (Syncerus caffer). However, elevated levels of IP-10 in QuantiFERON®-TB Gold (QFT) unstimulated whole blood compromises the utility of this biomarker. In this study, IP-10 and interferon gamma (IFN-γ) concentrations in whole blood samples from M. bovis culture-confirmed buffaloes with varying degrees of pathological changes (n = 72) and uninfected controls (n = 70) were measured in the IP-10 release assay (IPRA) and IFN-γ release assay (IGRA), respectively. Findings suggest that concentrations of both cytokines in QFT Nil tubes were higher in infected buffaloes with macroscopic pathological changes consistent with bovine tuberculosis compared to uninfected controls, and IGRA values increased with more severe pathological changes in infected buffaloes (p < 0.05). Finally, in culture-confirmed buffaloes with IPRA-negative and IGRA-positive test results, most animals were also those with the most advanced pathology. We conclude that IP-10 and IFN-γ concentrations measured in QFT Nil tubes may provide insight into the presence of M. bovis pathology in infected buffaloes. Furthermore, this study highlights the value in evaluating cytokine production in both antigen-stimulated and unstimulated samples when interpreting cytokine release assay results., (Copyright © 2019 Elsevier B.V. All rights reserved.)

We systematically retested children with borderline-positive quantiferon (0.35-0.99 IU/mL) during the period 2015-2019. Among 647 tests, 27 (4%) were positive (>0.35 IU/mL). Borderline-positive quantiferon accounted for 10 of 27 (37%) positive tests. When retested, 9 of 10 (90%) were negative. Children younger than 5 years had negative tuberculin skin tests. Thus, we found high test variability in the borderline range and, in some children, high suspicion of false positive tests.

Tuberculosis (TB) is the most common opportunistic infection in human immunodeficiency virus (HIV)-infected patients. Diagnosis and treatment of latent tuberculosis infection (LTBI) is the most important step in preventing the development of active TB. In our country where TB is moderately endemic, HIV-infected patients should be investigated for LTBI. Tuberculin skin test (TST) and interferongamma release assays (IGRA) are used in the diagnosis of LTBI but there isn't a standard practice. The aim of this study is to compare the TST and T-SPOT.TB test efficiency in the diagnosis of LTBI in HIVinfected patients. Patients who had no previous active TB infection, who were not treated for LTBI and who had no active tuberculosis infection at the time of admission were included in the study. A total of 100 HIV-infected patients who were admitted to the Infectious Diseases and Clinical Microbiology outpatient clinic between June 2015 and March 2016 were evaluated cross-sectionally. CD4+ T lymphocyte counts in the last one month were detected. All patients underwent chest radiography at the time of admission. Patients who are not considered as active TB infection with clinical and laboratory findings and who had no TST within the last one month were included in the study. TST was performed after the blood samples were taken for T-SPOT.TB test. In our study, 87% of the patients were male and the mean age was 40.2. The mean CD4+ T lymphocyte count was 605 cells/mm³ (26-1313). 16% of the patients had a history of encountring a person with tuberculosis and 81% had BCG vaccination scar. TST positivity and T-SPOT.TB positivity were 22.9% and 22%, respectively. The concordance between the two tests was found to be moderate (Kappa= 0.491). It was determined that BCG vaccination and the presence of a contact with a patient with TB did not affect TST and T-SPOT.TB test positivity (p> 0.05). There was a positive correlation between CD4+ T lymphocyte count and TST measurement values (r= 0.3, p= 0.003). Accordingly, as the number of CD4+ T lymphocytes increased, TST positivity increased (p= 0.007). T-SPOT.TB test was not affected by CD4+ T lymphocyte count (p= 0.289). Our study showed that TST was affected by CD4+ T lymphocyte count and patients' compliance with this test was also low. On the contrary T-SPOT.TB test was not affected by CD4+ T lymphocyte count. There was no statistically significant difference between T-SPOT.TB test positivity and CD4+ T lymphocyte count (p= 0.289). The concordance between the two tests was found to be moderate. It is thought that the main reason for the discordance between the tests is due to false negative or false positive results of TST. In conclusion, T-SPOT.TB was found more reliable in the diagnosis of LTBI in HIV-infected individuals. In the light of these findings, especially in HIV-infected patients with low CD4+ T lymphocyte counts, T-SPOT.TB test can be considered for LTBI diagnosis.

Immunological tests, including the QuantiFERON-TB Gold In-Tube (QFT-IT) assay, represent an important aid for diagnosing active tuberculosis (TB) and latent TB infections in children, but concerns about their use in children <5 years of age persist. This is a multicenter retrospective study comparing a population of 226 children to 521 adults with pulmonary or extrapulmonary TB. The aim was to evaluate the QFT-IT performance, analyzing both qualitative and quantitative results, according to age, birthplace, and disease localization. Compared to culture, QFT-IT sensitivity was 93.9%, 100%, and 94.4% in children ≤2, 2 to 5, and 5 to 16 years of age, respectively, and was significantly higher than that in adults (81.0%) ( P  < 0.0001). The rate of indeterminate test results for children (2.2%) was significantly lower than that for adults (5.2%) ( P  < 0.0001). In children, QFT-IT sensitivity was not affected by disease localization or birthplace (Italy born versus foreign born). Interferon gamma (IFN-γ) values in response to TB antigen and mitogen were significantly higher in children than in adults (TB antigen, median of 10 versus 1.66 IU IFN-γ/ml; mitogen, median of 10 versus 6.70 IU IFN-γ/ml; P  < 0.0001). In summary, this study supports the use of QFT-IT as a complementary test for the diagnosis of pediatric TB even under 2 years of age. Our observations could be applicable to the new version of the test, QuantiFERON-TB Gold Plus, which has recently been shown to have similar sensitivity in active TB, although data in children are still lacking., (Copyright © 2019 American Society for Microbiology.)

In the United States, high concern for iatrogenic reactivation to tuberculosis (TB) disease secondary to prescribed immunosuppression has resulted in increased use of the QuantiFERON-TB Gold In-Tube test (QFT-GIT) to screen for Mycobacterium tuberculosis (Mtb) infection. The aim of our study was to determine indications for QFT-GIT testing and risk factors for indeterminate QFT-GIT results. We retrospectively identified patients with QFT-GIT testing over a six-month period in a tertiary care academic health care system and performed a record review. Inpatients were 11 times more likely to have an indeterminate QFT-GIT result than outpatients (95% CI 7.6-16.2). 61.5% inpatient QFT-GITs were ordered during workup of active TB. Providers treating exogenously or endogenously immunosuppressed patients ordered the most QFT-GITs. We highlight the significant limitations of TB screening tests in the inpatient setting and the need to test earlier in those requiring immunosuppressive therapy to avoid indeterminate results.

Competing Interests: POTENTIAL CONFLICT OF INTEREST: The authors have indicated they have no potential conflicts of interest to disclose.

Background: Frequent reversion has been commonly observed in serial QuantiFERON-TB Gold In-Tube (QFT) tests, which limited its accuracy in defining the status of Mycobacterium tuberculosis (MTB) infection. Serum cytokine profiles might provide additional information to clarify the infection status., Method: Based on a population-based cohort study aiming to track MTB infection acquisition and disease development, serum profiles of 12 cytokines were determined by bead-based multiplex assays in parallel with QFT and tuberculin skin tests (TST) to explore potential relation between serum cytokines and MTB infection status., Results: Totally, 309 subjects got QFT conversion in one year (2013-2014) and 46.92% (145/309) of them got reversion in 2015. The study subjects were classified into three groups according to their QFT and TST results in 2015 (QFT persistence positive, QFT-/TST + and QFT-/TST-). The serum levels of MCP-1 and IL-8 were significantly different among the three groups. Furthermore, level of IL-8 was dramatically lower in QFT-/TST- group as compared to the other two groups, and no significant difference was observed for QFT-/TST + group as comparing with persistent positive group., Conclusion: Our results suggested that the decreased serum level of IL-8 might be potential biomarker to identify QFT reversion caused by infection clearance., (Copyright © 2018. Published by Elsevier Ltd.)

Background: Most of internationally adopted children (IAC) come from countries in which tuberculosis (TB) is endemic. Interpretation of discordant Tuberculin Skin Test (TST) and Quantiferon-Gold In Tube (QFT) results is under debate., Methods: Children consecutively referred to our IAC Center between 2009-2017 were prospectively evaluated and screened with protocol recommended by the America Academy of Pediatrics, including TST and QFT. TB infection prevalence was evaluated and possible risk factors associated with discordant TST/QFT results were investigated., Results: 1775 IAC were enrolled (median age: 5.8; IQR:3.3-8.2; 1065 [60.0%] males). Most of the children came from a European country (715; 40.3%) and, among them, 428 (59.9%) from Russia. Active pulmonary TB was diagnosed in 7 (0.4%) children while LTBI was diagnosed in 255 (14.4%) children. Concordant TST-/QFT-result was observed in 1520 (85.6%) children, concordant TST+/QFT + result in 63 children (3.5%), while 169 children (9.5%) displayed TST+/QFT-result and the remaining 23 children (1.3%) TST-/QFT+. Factor significantly associated with discordant TST+/QFT-result was BCG vaccination (aOR:2.62; 95%CI. 1.12-6.12; P = 0.026) and age <5 years (aOR: 5.59; 95%CI:2.27-12.18; P < 0001). . No significant association was evidenced with, continent of origin, eosinophilia or gender., Conclusions: Our data suggest that QFT might be used as unique screening assay in IAC, but further studies are needed at this regard., (Copyright © 2018. Published by Elsevier Ltd.)

Background: The clinical utility of interferon-γ release assays (IGRAs) for diagnosis of active tuberculosis is unclear, although they are commonly used in countries with a low incidence of tuberculosis. We aimed to resolve this clinical uncertainty by determining the accuracy and utility of commercially available and second-generation IGRAs in the diagnostic assessment of suspected tuberculosis in a low-incidence setting., Methods: We did a prospective cohort study of adults with suspected tuberculosis in routine secondary care in England. Patients were tested for Mycobacterium tuberculosis infection at baseline with commercially available (T-SPOT.TB and QuantiFERON-TB Gold In-Tube [QFT-GIT]) and second-generation (incorporating novel M tuberculosis antigens) IGRAs and followed up for 6-12 months to establish definitive diagnoses. Sensitivity, specificity, positive and negative likelihood ratios, and predictive values of the tests were determined., Findings: Of the 1060 adults enrolled in the study, 845 were included in the analyses and 363 were diagnosed with tuberculosis. Sensitivity of T-SPOT.TB for all tuberculosis diagnosis, including culture-confirmed and highly probable cases, was 81·4% (95% CI 76·6-85·3), which was higher than QFT-GIT (67·3% [62·0-72·1]). Second-generation IGRAs had a sensitivity of 94·0% (90·0-96·4) for culture-confirmed tuberculosis and 89·2% (85·2-92·2) when including highly probable tuberculosis, giving a negative likelihood ratio for all tuberculosis cases of 0·13 (95% CI 0·10-0·19). Specificity ranged from 86·2% (95% CI 82·3-89·4) for T-SPOT.TB to 80·0% (75·6-83·8) for second-generation IGRAs., Interpretation: Commercially available IGRAs do not have sufficient accuracy for diagnostic evaluation of suspected tuberculosis. Second-generation tests, however, might have sufficiently high sensitivity, low negative likelihood ratio, and correspondingly high negative predictive value in low-incidence settings to facilitate prompt rule-out of tuberculosis., Funding: National Institute for Health Research., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Background: Female genital tuberculosis (FGTB) is one of the major causes of infertility. However, nonspecific manifestations and the lack of easy access to gold-standard diagnostic test render a diagnostic difficult for FGTB. The objective of this study was to determine T-SPOT.TB (an interferon-γ release assay, IGRA) performance in patients with FGTB., Methods: A total of 213 female patients with validated T-SPOT.TB results were recruited in this retrospective study. Among which, 103 were confirmed FGTB, and 110 were excluded from tuberculosis (control). Of the confirmed FGTB patients, 52 were confirmed by microbiologically/histopathologically examination, while the remaining 51 were clinically confirmed (successfully responsive to anti-tuberculosis treatment). T-SPOT.TB test was performed in both FGTB and control group during the diagnostic procedure., Results: The overall sensitivity and specificity of T-SPOT.TB were 86.41% and 75.45% respectively. Sensitivity of T-SPOT.TB was significantly higher when compared with conventional tuberculosis diagnostic tests. Moreover, T-SPOT.TB test using pelvic effusion (PE) showed higher sensitivity than using corresponding peripheral blood (PB) (94.44% vs 72.22%, P < 0.001). Mean value of spot forming cells (SFCs) of T-SPOT.TB using PE was significantly higher than that of PB in FGTB group (193 (IQR 105-280) SFCs/2.5 × 10 5 PEMCs vs 71 (IQR 36-107) SFCs/2.5 × 10 5 PBMCs, P = 0.01), while this was not detected in control group (11 (IQR 0-22) SFCs/2.5 × 10 5 PEMCs vs 9 (IQR 0-18) SFCs/2.5 × 10 5 PBMCs, P = 0.77)., Conclusion: These results demonstrated that T-SPOT.TB, especially PE T-SPOT.TB, is an useful adjunct in FGTB diagnosis., (© 2018 Wiley Periodicals, Inc.)

Background: Mycobacterium tuberculosis remains as a vital threat to global health and its diagnosis is still complicated. Since there is no gold standard for the diagnosis of latent tuberculosis infection (LTBI), its diagnosis routinely relies on measurement of host immune responses to M. tuberculosis antigens using the Tuberculin Skin Test (TST) and Interferon-Y Release Assays (IGRAs)., Objective: The aim of this study was to evaluate LTBI among hospitalized children and their parents/ guardians as general populations., Methods: A cross-sectional study comparing TST and IGRA for the diagnosis of suspected LTBI was performed in children and their guardians (as general population) in Children Medical Center, an Iranian referral hospital., Results: In this study, 81 patients hospitalized in CMC and 102 patient's guardians were included. A total of 57 patients (70.4%) had performed a TST and were interpreted during the study. Among them, 32 (56%) had a positive test result when a cut-off of 10 mm induration. There were fewer positive IGRA test results than positive TST results (33% versus 56%) in children. Among guardians, TST and IGRA were positive in 41% and 40% respectively. The agreement between the IGRA test and the TST among them was 0.7, while this was as slightly lower in children (0.63)., Conclusion: The results of our study indicate that the IGRA test has a higher specificity than TST, especially in children, while the frequency of positive results with both tests in adults was similar. Considering the false positive results reported with the TST, replacement of the IGRA test with TST in children is recommended., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

Interferon gamma release assays (IGRAs) are important tools in identifying prior tuberculosis exposure. The new-generation QuantiFERON-TB Gold Plus (QFT-Plus) assay, recently approved for use in the United States, differs from the current-generation QFT Gold-In-Tube (QFT-GIT) assay with the addition of a second antigen tube that also contains novel CD8 + T-cell-stimulating peptides. The QFT-Plus assay has increased sensitivity in immunocompromised populations, and we sought to assess the specificity of QFT-Plus compared to that of QFT-GIT in low-risk individuals. We enrolled adults without tuberculosis risk factors, including a subgroup with pulmonary nontuberculous mycobacterial (NTM) disease due to Mycobacterium avium complex (MAC) or Mycobacterium abscessu s. The primary outcome measures included specificity, interassay concordance, and agreement between the QFT-Plus and QFT-GIT assays. Of 262 participants enrolled, 51 had pulmonary NTM. The median age was 39 years (age range, 18 to 78 years); 73% were female. Among the 262 individuals who were enrolled, 5 (1.9%) individuals had positive QFT-Plus results, and 3 of these individuals also had positive QFT-GIT results. The two individuals with discordant results (QFT-Plus positive/QFT-GIT negative) had only one tube positive in the QFT-Plus assay. The overall specificity of QFT-Plus and QFT-GIT was 98.1% (95% confidence interval [CI], 95.6, 99.4%) and 98.9% (95% CI, 96.7, 99.8%), respectively. The QFT-Plus specificity was similar in both the NTM (98.0% [95% CI, 89.4, 99.9%]) and non-NTM (98.1% [95% CI, 95.2, 99.5%]) groups. QFT-Plus has a high specificity, similar to that of the QFT-GIT assay, including in patients with pulmonary MAC or M. abscessus disease., (Copyright © 2018 American Society for Microbiology.)

QuantiFERON-TB Gold Plus (QFT-Plus) is a new-generation QuantiFERON-TB Gold In-Tube (QFT-GIT) assay which has two antigen-coated tubes called TB1, which contains long peptides derived from ESAT-6 and CFP-10, and TB2, which contains the same components as TB1 and additional short peptides which potentially stimulate CD8 + T cells through the presentation of major histocompatibility complex class I. This is the first study to compare QFT-Plus and QFT-GIT for use in the diagnosis of latent tuberculosis infection (LTBI) among immunocompromised patients in the Republic of Korea. Among 317 consecutive patients who underwent screening for LTBI before solid organ or hematopoietic stem cell transplantation and tumor necrosis factor alpha inhibitor treatment, LTBI was identified in 92 (29.0%) and 88 (27.8%) patients by QFT-GIT and QFT-Plus, respectively. The rate of concordance between QFT-GIT and QFT-Plus was 93.7% (κ value, 0.860), and the indeterminate rate (3.2%) was similar between QFT-GIT and QFT-Plus. Of 20 (6.3%) samples with discordant results, 11 (55.0%) and 7 (35.0%) were positive by QFT-GIT alone and QFT-Plus alone, respectively, and 2 (15.0%) were indeterminate by each assay. The interferon gamma level in samples with discordant results ranged from 0.39 to 1.10 IU/ml, except for one sample, in which the gamma interferon level was 2.97 IU/ml only in TB2. Conclusively, there was a high degree of agreement between the results of QFT-GIT and QFT-Plus for the screening of immunocompromised patients for LTBI. The reactivity in TB2 contributed substantially to the difference between QFT-GIT and QFT-Plus, particularly in solid organ transplant candidates. The significance of the discrete responses in TB1 and TB2 of QFT-Plus needs to be explored further by means of an immunological and clinical approach in different patient groups and clinical settings., (Copyright © 2018 American Society for Microbiology.)

Objectives: Reversion of tuberculosis (TB) infection testing has been suggested to be associated with prophylactic treatment efficacy. However, evidences based on randomized controlled study were sparse., Methods: Studies on serial QuantiFERON-TB Gold In-Tube (QFT) test, among individuals with and without prophylactic treatment were identified in the databases of PubMed, MEDLINE and EMBASE up to 28 February 2018. The reversion rates were quantitatively summarized by means of meta-analysis using the random-effect model., Results: A total of 52 eligible studies were included in the meta-analysis on QFT test reversion rate among participants with (20 studies) and without (32 studies) prophylactic treatment. Summarized reversion rate was found to be 24.9% (95% confidence interval [CI]: 18.4-32.9%) and 25.3% (95% CI: 19.6-32.0%) for those completed or without treatment, respectively. When the analysis was restricted to the participants completed treatment, higher summarized rate of QFT reversion was found among those with longer course therapy (9INH vs. the other regimens), studies from Asia (vs. Europe and America), and individuals with immunosuppression disorders (vs. general populations)., Conclusions: Our results suggested that QFT reversion was frequently observed regardless of with or without prophylactic treatment. Serial QFT testing might be inappropriate for evaluating preventive treatment efficacy., (Copyright © 2018 The British Infection Association. Published by Elsevier Ltd. All rights reserved.)

We investigated the prevalence of latent tuberculosis infection (LTBI) among the residents in seven long-term care facilities (LTCFs) located in different regions of Taiwan and compared the performance of two interferon gamma release assays, i.e., QuantiFERON-TB Gold In-Tube (QFT-GIT) and QuantiFERON-TB Gold Plus (QFT-Plus) for screening LTBI. We also assessed the diagnostic performance against a composite reference standard (subjects with persistent-positive, transient-positive, and negative results from QFTs during reproducibility analysis were classified as definite, possible, and not LTBI, respectively). Two hundred forty-four residents were enrolled, and 229 subjects were included in the analysis. The median age was 80 years (range, 60 to 102 years old), and 117 (51.1%) were male. Among them, 66 (28.8%) and 74 (32.3%) subjects had positive results from QFT-GIT and QFT-Plus, respectively, and the results for 215 (93.9%) subjects showed agreement. Using the composite reference standard, 66 (28.8%), 11 (4.8%), and 152 (66.4%) were classified as definite, possible, and not LTBI, respectively. For definite LTBI, the sensitivity, specificity, positive predictive value, and negative predictive value of QFT-GIT were 89.4%, 95.7%, 89.4%, and 95.7%, respectively, and those for QFT-Plus were 100.0%, 95.1%, 89.2%, and 100.0%, respectively. The sensitivity of QFT-GIT decreased gradually with patient age. Compared to QFT-GIT, QFT-Plus displayed significantly higher sensitivity (100.0% versus 89.4%, P = 0.013) and similar specificity (95.1% versus 95.7%). In conclusion, a high prevalence of LTBI was found among elders in LTCFs in Taiwan. The new QFT-Plus test demonstrated a higher sensitivity than QFT-GIT in the older adults in LTCFs., (Copyright © 2018 American Society for Microbiology.)

The QuantiFERON-TB Gold Plus (QFT-Plus; Qiagen, Germantown, MD) interferon gamma release assay (IGRA) received FDA clearance in 2017 and will replace the prior version of the assay, the QFT-Gold In-Tube (QFT-GIT). Here, we compared performances of the QFT-Plus assay and the QFT-GIT version in a diverse patient population, including patients undergoing evaluation for or follow-up of latent tuberculosis infection (LTBI; n = 39) or active TB infection ( n = 3), and in health care workers (HCWs; n = 119) at Mayo Clinic (Rochester, MN). Compared to the QFT-GIT, the QFT-Plus assay showed 91.2% (31/34) positive, 98.4% (124/126) negative, and 96.6% (156/161) overall qualitative agreement among the 161 enrolled subjects, with a Cohen's kappa value of 0.91 (excellent interrater agreement). Among the 28 patients diagnosed with LTBI at the time of enrollment, the QFT-GIT and QFT-Plus assays agreed in 24 (85.7%) patients; in all four discordant patients, the positivity of the QFT-GIT or QFT-Plus IGRA was associated with low-level interferon gamma (IFN-γ) reactivity, ranging from 0.36 IU/ml to 0.66 IU/ml. Additionally, we document a high degree of correlation between IFN-γ levels in the QFT-GIT TB antigen tube and each of the two QFT-Plus TB antigen tubes, as well as between the QFT-Plus TB1 and TB2 tubes (Pearson's correlation coefficients [ R ] > 0.95). Overall, we show comparable results between the QFT-GIT and QFT-Plus assays in our study population composed of subjects presenting with a diverse spectrum of TB infections. Our findings suggest that the necessary transition to the QFT-Plus assay will be associated with a minimal difference in assay performance characteristics., (Copyright © 2018 American Society for Microbiology.)

Objective: To determine the performance of QuantiFERON-TB IN-Gold for the diagnosis active tuberculosis and latent tuberculosis., Results: A total of 213 participants (136 tuberculosis suspects, 66 latently infected) were enrolled. Of 213, 21 (15.4%) of the tuberculosis suspects and 3 (4.5%) of the latent tuberculosis groups were human immunodeficiency virus infected. The sensitivity, specificity, positive and negative predictive value of QuantiFERON-TB IN-Gold for the diagnosis of active tuberculosis was 70.3% (26/37), 49.5% (49/99), 34.7% (26/75) and 83.1% (49/59) respectively. A kappa value of 0.316 (p = 0.001, 95% CI 1.605-1.609) between QuantiFERON-TB IN-Gold and tuberculin skin test were found.

This study aimed to determine whether there are seasonal changes in the performance of QuantiFERON-TB Gold In-Tube (QFT-GIT) assays, an interferon-gamma release assay widely used for the diagnosis of tuberculosis infection. Results of 31,932 QFT-GIT assays performed at a large independent, accredited diagnostic service provider in London, UK over a 4.5-year-period were analysed. The proportion of positive results was significantly lower in autumn (14.8%) than in spring (16.0%; p = 0.0366) and summer (17.5%; p < 0.0001), but similar to winter (15.2%; p = 0.4711). The proportion of indeterminate results was significantly higher in autumn (8.2%) than in spring (6.2%; p < 0.0001), summer (4.8%; p < 0.0001), and winter (6.2%; p < 0.0001). The highest proportions of indeterminate results were observed in October (8.4%) and November (8.8%), the lowest in June (4.5%). Our data show that significant seasonal variation occurs in the performance of QFT-GIT assays in a temperate climate setting. Potential underlying mechanisms, including host and environmental factors, are discussed., (Copyright © 2018 Elsevier Ltd. All rights reserved.)