Incidence, risk factors for active tuberculosis infection and changes of IGRA in patients with Takayasu arteritis: a prospective cohort study

There is limited evidence to support the association between tuberculosis (TB) and the occurrence of Takayasu arteritis (TAK). To investigate the incidence of active TB (ATB) in TAK and explore the impact of anti-rheumatic therapy on the occurrence of ATB or reactivation of Latent TB infection (LTBI) and their effect on interferon-γ release assay (IGRA) results, we conducted a prospective study based on the Chinese Registry for Systemic Vasculitis cohort. The standard incidence ratio (SIR) was calculated and stratified by age. Kaplan-Meier analysis was used to determine the effect of variables on ATB or LTBI reactivation in patients with TAK. Data from 825 patients with TAK in the registry were analysed. During a median follow-up of 5 years, 5 patients developed ATB with a crude incidence of 154 (95%CI:57-381) person-years/100,000. The SIR was 5.59 (95%CI:1.81-13.04). Glucocorticoids and conventional disease-modifying anti-rheumatic drugs (cDMARDs) did not increase the risk of ATB or LTBI reactivation (P > 0.05). However, the use of tumour necrosis factor inhibitor (TNFi) increased the risk of ATB in patients with LTBI (P < 0.001). Furthermore, the value of the IGRA assay decreased after treatment (P < 0.05). In conclusion, the incidence of TB infection is markedly increased in patients with TAK and patients with TAK are at high risk of developing ATB. Treatment with glucocorticoids and cDMARDs does not significantly increase the risk for ATB in patients with TAK. Moreover, IGRA may have limited effectiveness in monitoring ATB infection or LTBI reactivation in patients with TAK.

Utility of interferon-gamma releasing assay for the diagnosis of active tuberculosis in children: A systematic review and meta-analysis

INTRODUCTION

The accurate diagnosis of tuberculosis (TB) in children is essential for its effective management and control. Reliable diagnostic tools that are currently available for identifying TB infection include the in vivo tuberculosis skin test (TST) and ex vivo interferon-gamma release assays (IGRAs). This systematic review and meta-analysis aimed to evaluate the diagnostic accuracy of IGRAs in children.

METHODS

Of the 768 screened studies, 47 met the eligibility criteria. Data from 9065 patients, including 1086 (12.0 %) with confirmed TB, were included in the analysis. The overall quality of the included studies, assessed using the Quality Assessment of Diagnostic Accuracy Studies-2 tool, was unclear.

RESULTS

The calculated pooled sensitivity and specificity of IGRAs in children were 0.85 (95 % confidence interval [CI]: 0.79-0.89) and 0.94 (95 % CI: 0.88-0.97), respectively. Subpopulation analysis revealed that the sensitivities and specificities were as follows: QuantiFERON tests: 0.83 (95 % CI: 0.74-0.89) and 0.93 (95 % CI: 0.87-0.96), T-SPOT: 0.87 (95 % CI: 0.79-0.91) and 0.99 (95 % CI: 0.85-1.00), IGRAs in children under 15 years: 0.77 (95 % CI: 0.43-0.94) and 0.96 (95 % CI: 0.84-0.97), and IGRAs in children under 5 years: 0.85 (95 % CI: 0.52-0.97) and 0.94 (95 % CI: 0.90-0.99), respectively.

CONCLUSIONS

This study demonstrated that the sensitivity and specificity of the IGRAs in children were moderate and high, respectively. Therefore, the IGRAs may be useful for detecting TB infection in children.

CLINICAL TRIAL REGISTRATION

The review protocol was prospectively registered with the University Hospital Medical Information Network Clinical Trials Registry (UMIN000046737).

An early and trustable indicator suggestive of non-tuberculosis mycobacteria isolation in a high tuberculosis burden setting

BACKGROUND

Distinguishing between nontuberculous mycobacterial (NTM) lung infections and pulmonary tuberculosis becomes challenging due to their similar clinical manifestations and radiological images. Consequently, instances of delayed diagnosis or misdiagnosis are highly frequent. A feasible and reliable indicator of the existence of NTM in the early stages of the disease would help to solve this dilemma.

METHODS

In this study, we evaluated the potential of smear-positive and Xpert assay (Cepheid, USA) negative outcomes as an early indicator of possible NTM infection in a high TB-burden setting retrospectively and prospectively.

RESULTS

During the study period, 12·77% (138/1081) of the smear-positive cases yielded negative outcomes with the simultaneous Xpert assay. From the 110 patients who yielded smear-positive/Xpert-negative outcomes and cultivated strain as well, 105 (95·45%) were proved to have NTM isolated. By incorporating an additional criterion of a negative result from the Interferon-gamma release assay, the accuracy of the screening method reached 100%. Regarding the NTM presence prediction value, smear-positive/Xpert-negative has a sensitivity of 24·86% (45/181) in all NTM isolated cases but 93·75-96·55% accuracy in retrospective study or 93·75% accuracy in prospective study in smear-positive NTM isolated cases. In addition, the specificity was ∼99·47% (943/948) in smear-positive tuberculosis cases.

CONCLUSION

The clue of the presence of NTM could be obtained on the first day of the hospital visit due to the point of care (POC) feature of smear testing and Xpert assay. About one-fourth of the NTM-isolated patients would benefit from this rapid, convenient, and reliable screening strategy in the given circumstance. Smear-positive/Xpert-negative outcome is an early, trustable indicator that is indicative of NTM isolation.

Determination of latent tuberculosis infection from plasma samples via label-free SERS sensors and machine learning

Effective diagnostic tools for screening of latent tuberculosis infection (LTBI) are lacking. We aim to investigate the performance of LTBI diagnostic approaches using label-free surface-enhanced Raman spectroscopy (SERS). We used 1000 plasma samples from Northeast Thailand. Fifty percent of the samples had tested positive in the interferon-gamma release assay (IGRA) and 50 % negative. The SERS investigations were performed on individually prepared protein specimens using the Raman-mapping technique over a 7 × 7 grid area under measurement conditions that took under 10 min to complete. The machine-learning analysis approaches were optimized for the best diagnostic performance. We found that the SERS sensors provide 81 % accuracy according to train-test split analysis and 75 % for LOOCV analysis from all samples, regardless of the batch-to-batch variation of the sample sets and SERS chip. The accuracy increased to 93 % when the logistic regression model was used to analyze the last three batches of samples, following optimization of the sample collection, SERS chips, and database. We demonstrated that SERS analysis with machine learning is a potential diagnostic tool for LTBI screening.

Screening for latent tuberculosis in migrants-status quo and future challenges

OBJECTIVES

To review the evidence that migrants from tuberculosis (TB) high-incidence countries migrating to TB low-incidence countries significantly contribute to active TB cases in the counties of destination, primarily through reactivation of latent TB.

METHODS

This is a narrative review. The different screening programs in the countries of destination are reviewed either based on screening and preventive treatment of latent TB pre or more commonly - post arrival.

RESULTS

Screening can be performed using interferon-gamma release assays (IGRA) or tuberculin skin tests (TST). Preventive treatment of latent TB is using either monotherapy with isoniazid, or in combination with rifampicin or rifapentine. We discuss the ethical issues of preventive treatment in asymptomatic individuals and how these are addressed in different screening programs.

CONCLUSION

Screening migrants from TB high endemic countries to TB low endemic countries is beneficial. There is a lack of standardization and agreement on screening protocols, follow up and treatment.

QuantiFERON-CMV assay by chemiluminescence immunoassay: Is it more suitable for real-live monitoring of transplant patients?

BACKGROUND

The QuantiFERONCMV (QF-CMV) assay is an interferon-gamma release assay (IGRA) used to monitor CMV-specific cell-mediated immunity (CMV-CMI) by ELISA in transplant patients. However, a chemiluminescent immunoassay (CLIA) has been developed to quantify IFNG in the QuantiFERON-Tuberculosis (TB) to detect latent TB infection.

OBJECTIVES

The aim of this work is to compare the results of QF-CMV by ELISA with those obtained by CLIA in an automated Liaison XL analyzer using the QuantiFERON-TB Gold Plus reagents.

STUDY DESIGN

The QF-CMV assay had been performed by ELISA in kidney and lung transplant patients between July 2019-April 2023 at the IMIBIC/Reina Sofía Hospital (Cordoba, Spain). The remaining QF-CMV supernatants had been preserved at -80 ºC from then. Now, the IFNG levels in the same samples were determined by CLIA.

RESULTS

One hundred and three QF-CMV supernatants from kidney (n = 50) and lung (n = 53) transplant patients were selected. An agreement of 87.4 % (kappa coefficient 0.788) between CLIA and ELISA was observed. Thirteen (12.6 %) discrepant results were detected. Some Indeterminate results by ELISA converted to Non-reactive by CLIA (0.53-0.92 IU/mL for Mitogen-Nil values). Likewise, borderline Non-reactive results by ELISA were above the 0.2 IU/mL cut-off by CLIA and then were Reactive (0.21-0.31 for CMV-Nil values).

CONCLUSION

CLIA shows substantial concordance with ELISA and acceptable discrepancies. The possible higher sensitivity of CLIA returns a higher number of Reactive results, which entails potential clinical consequences. Therefore, a new threshold to confer protection against CMV infection after transplantation needs to be defined.

Is the new tuberculous antigen-based skin test ready for use as an alternative to tuberculin skin test/interferon-gamma release assay for tuberculous diagnosis? A narrative review

In recent years, novel specific Mycobacteria tuberculous (TB) antigen-based skin test (TBST) has become available for clinical use. The mechanism of TBST is similar to the interferon-gamma release assay (IGRA), making it a potential alternative for identifying latent tuberculous infection (LTBI), especially in subjects with history of bacille Calmette-Guérin vaccination. Three different commercial brands have been developed in Denmark, Russia, and China. Clinical studies in the respective countries have shown promising sensitivity, specificity, and safety profile. Some studies attempted to address the applicability of TBST in specific subject groups but the discrepancy in defining LTBI and problematic methodologies undermine the generalisation of the results to other communities across the world. Limited cost-effectiveness studies for TBST have been conducted without exploring the health economics for preventing development of LTBI into active TB. Unlike IGRA, no clinical studies have addressed the correlation of TBST results (magnitude of induration) with the likelihood of development of active TB. Moreover, the different TBSTs are not widely available for clinical use. While TBST is a promising test to overcome the shortcomings of tuberculin skin tests, more clinical data are needed to support its general application globally for the diagnosis of LTBI.

Prevalence estimates of tuberculosis infection in adults in Denmark: a retrospective nationwide register-based cross-sectional study, 2010 to 2018

BackgroundTuberculosis (TB) elimination requires identifying and treating persons with TB infection (TBI).AimWe estimate the prevalence of positive interferon gamma release assay (IGRA) tests (including TB) and TBI (excluding TB) in Denmark based on TBI screening data from patients with inflammatory bowel disease (IBD) or inflammatory rheumatic disease (IRD).MethodsUsing nationwide Danish registries, we included all patients with IBD or IRD with an IGRA test performed between 2010 and 2018. We estimated the prevalence of TBI and positive IGRA with 95% confidence intervals (CI) in adolescents and adults aged 15-64 years after sample weighting adjusting for distortions in the sample from the background population of Denmark for sex, age group and TB incidence rates (IR) in country of birth.ResultsIn 13,574 patients with IBD or IRD, 12,892 IGRA tests (95.0%) were negative, 461 (3.4%) were positive and 221 (1.6%) were indeterminate, resulting in a weighted TBI prevalence of 3.2% (95% CI: 2.9-3.5) and weighted positive IGRA prevalence of 3.8% (95% CI: 3.5-4.2) among adults aged 15-64 years in the background population of Denmark. Unweighted TBI prevalence increased with age and birthplace in countries with a TB IR higher than 10/100,000 population.ConclusionEstimated TBI prevalence is low in Denmark. We estimate that 200,000 persons have TBI and thus are at risk of developing TB. Screening for TBI and preventive treatment, especially in persons born in high TB incidence countries or immunosuppressed, are crucial to reduce the risk of and eliminate TB.

Development and Evaluation of an NTM-IGRA to Guide Pediatric Lymphadenitis Diagnosis

BACKGROUND

Diagnosis of nontuberculous mycobacteria (NTM) infections remains a challenge. In this study, we describe the evaluation of an immunological NTM-interferon (IFN)-γ release assay (IGRA) that we developed using glycopeptidolipids (GPLs) as NTM-specific antigens.

METHODS

We tested the NTM-IGRA in 99 samples from pediatric patients. Seventy-five were patients with lymphadenitis: 25 were NTM confirmed, 45 were of unknown etiology but compatible with mycobacterial infection and 5 had lymphadenitis caused by an etiologic agent other than NTM. The remaining 24 samples were from control individuals without lymphadenitis (latently infected with M. tuberculosis , uninfected controls and active tuberculosis patients). Peripheral blood mononuclear cells were stimulated overnight with GPLs. Detection of IFN-γ producing cells was evaluated by enzyme-linked immunospot assay.

RESULTS

NTM culture-confirmed lymphadenitis patient samples had a significantly higher response to GPLs than the patients with lymphadenitis of unknown etiology but compatible with mycobacterial infection ( P < 0.001) and lymphadenitis not caused by NTM ( P < 0.01). We analyzed the response against GPLs in samples from unknown etiology lymphadenitis but compatible with mycobacterial infection cases according to the tuberculin skin test (TST) response, and although not statistically significant, those with a TST ≥5 mm had a higher response to GPLs when compared with the TST <5 mm group.

CONCLUSIONS

Stimulation with GPLs yielded promising results in detecting NTM infection in pediatric patients with lymphadenitis. Our results indicate that the test could be useful to guide the diagnosis of pediatric lymphadenitis. This new NTM-IGRA could improve the clinical handling of NTM-infected patients and avoid unnecessary misdiagnosis and treatments.

Increased rates of indeterminate results in QuantiFERON-TB gold in-tube during the COVID-19 epidemic in Hunan province, China

Increased rates of indeterminate QuantiFERON-TB Gold In-Tube (QFT-GIT) results have been reported since the COVID-19 epidemic in Hunan Province, China. The indeterminate result (ITR) rate of QFT increased from an average of 5.2% to 12.4%, paralleling the first COVID-19 pandemic wave in the region. QFT-GIT results of 243 hospitalized patients with COVID-19 from January 2022 to April 2023 at Xiangya Hospital of Central South University were analyzed. Of the 243 patients, 71 (29.2%) had ITRs due to reduced interferon-gamma production in the positive control. Multiple factors are associated with ITRs, such as disease severity, respiratory failure incidence, immunosuppressant use, and prognosis. Additionally, interferon-gamma (Mitogen-Nil) levels differed significantly depending upon disease severity, prognosis, immunosuppressant use, sepsis symptoms, respiratory failure, or hyperlipidemia. An abnormal increase in the ITR rate in the QFT was observed after the COVID-19 pandemic, and an optimal machine learning predictive model for indeterminate QFT results was established.

Interferon-Gamma-Release assay and absolute CD8 lymphocyte count for acquired immunosuppression monitoring in critically ill patients

Guided biomarker-personalized immunotherapy is advancing rapidly as a means to rejuvenate immune function in injured patients who are the most immunosuppressed. A recent study introduced a fully automated interferon-γ release assay (IGRA) for monitoring the functionality of T lymphocytes in patients with septic shock. While a significant decrease in IFN-γ release capacity was observed, a significant correlation with CD8 lymphocyte absolute count was also reported, raising the question of whether ex-vivo IFN-γ production would be only a surrogate marker for lymphocyte count or if these two parameters conveyed distinct and complementary information. In a large cohort of more than 353 critically ill patients following various injuries (sepsis, trauma, major surgery), the primary objective of the present study was to simultaneously evaluate the association between ex vivo IFN-γ release and CD8 cell count with regard to adverse outcome. Our findings provide a clear-cut result, as they distinctly demonstrate that IGRA offers higher-quality information than CD8 count in terms of an independent association with the occurrence of an adverse outcome. These results strengthen the case for incorporating IGRA into the array of biomarkers of interest for defining endotypes in sepsis. This holds especially true given that fully automated tests are now readily available and could be used in routine clinical practice.

Multiple cytokine analysis based on QuantiFERON-TB gold plus in different tuberculosis infection status: an exploratory study

BACKGROUND

More efficient and convenient diagnostic method is a desperate need to reduce the burden of tuberculosis (TB). This study explores the multiple cytokines secretion based on QuantiFERON-TB Gold Plus (QFT-Plus), and screens for optimal cytokines with diagnostic potential to differentiate TB infection status.

METHODS

Twenty active tuberculosis (ATB) patients, fifteen patients with latent TB infection (LTBI), ten patients with previous TB and ten healthy controls (HC) were enrolled. Whole blood samples were collected and stimulated by QFT-Plus TB1 and TB2 antigens. The levels of IFN-γ, TNF-α, IL-2, IL-6, IL-5, IL-10, IP-10, IL-1Ra, CXCL-1 and MCP-1 in supernatant were measured by Luminex bead-based multiplex assays. The receiver operating characteristic curve was used to evaluate the diagnostic accuracy of cytokine for distinguishing different TB infection status.

RESULTS

After stimulation with QFT-Plus TB1 and TB2 antigens, the levels of all cytokines, except IL-5 in TB2 tube, in ATB group were significantly higher than that in HC group. The levels of IL-1Ra concurrently showed the equally highest AUC for distinguishing TB infection from HC, followed by the levels of IP-10 in both TB1 tube and TB2 tube. Moreover, IP-10 levels displayed the largest AUC for distinguishing ATB patients from non-ATB patients. Meanwhile, the levels of IP-10 also demonstrated the largest AUC in both TB1 tube and TB2 tube for distinguishing ATB patients from LTBI.

CONCLUSIONS

In addition to conventional detection of IFN-γ, measuring IP-10 and IL-1Ra based on QFT-Plus may have the more tremendous potential to discriminate different TB infection status.

QuantiFERON Gold-In-Tube for the diagnosis of mycobacterial tuberculosis infection in children under 5 years of age: A systematic review and meta-analysis

BACKGROUND

Previous meta-analysis regarding the performance of QuantiFERON Gold-In-Tube in children have yielded contrasting results. Emerging data in children younger than 5 years of age necessitates a new analysis.

METHODS

Systematic searches were conducted of MedLINE, EMBASE and Cochrane databases between 1998-2023. Pooled estimates of sensitivities and specificities of QFT-GIT compared to tuberculin skin test (TST) were calculated. The Kappa (k) coefficient was calculated for each study to determine the degree of congruence between TST and QFT-GIT results. Studies including patients co-infected with HIV or other immune compromising conditions or those treated with anti-tubercular treatment were excluded.

RESULTS

Seventeen studies (4335 patients) were included in quantitative analysis. All studies were conducted in middle to high income countries. They were conducted across 14 countries and 4 studies in countries with high TB incidence. The pooled sensitivity, specificity and DOR were 0.45 (0.42-0.48), 0.96 (0.96-0.97) and 18.84 (7.33-48.41) respectively. The ability of QFT-GIT to discriminate with disease and no disease was "good" as demonstrated by a summary receiver operating characteristic curve with area under curve of 0.7812. The average Kappa (k) co-efficient was 0.501 with a wide variety of values between studies (0.167 to 0.800).

CONCLUSION

The findings of this meta-analysis support the judicious use of QFT-GIT in children 5 years and under, with caution as a sole test to exclude Tuberculosis in this age group. The heterogeneity and methodological quality of diagnostic studies limits the generalisability of results.

Interferon-gamma release assay for screening of tuberculosis infection in children

BACKGROUND

Interferon-gamma release assay (IGRA) is the main tool for the diagnosis of latent tuberculosis (TB) infection (LTBI). However, the indeterminate results were more frequent in children, and the underlying reasons were largely speculative. We aimed to compare QuantiFERON-TB Gold In-Tube (QFT-GIT) with X.DOT-TB (XDOT) for diagnosing LTBI, and to identify the risk factors associated with indeterminate results in children.

METHODS

A retrospective study for children<18 years old, at risk for LTBI or progression to TB disease, received either QFT-GIT or X.DOT-TB tests was performed at Beijing Children's Hospital from August 2019 to August 2022.

RESULTS

A total of 33,662 children were recruited, including 15,129 (44.9%) tested with X.DOT-TB and 18,533 (55.1%) with QFT-GIT. Proportion of positive and indeterminate results in children with respiratory disease was significantly higher than did that with other diseases, respectively (P < 0.001). The indeterminate rate of X.DOT-TB and QFT-GIT results decreased with increasing age (P < 0.001). Proportion of QFT-GIT indeterminate results was higher than that of X.DOT-TB across age groups. Male, age and disease classification all presented a statistically significant association with indeterminate IGRA results.

CONCLUSIONS

The positive rates of X.DOT-TB and QFT-GIT in children were 3.1% and 1.8%, respectively. The X.DOT-TB assay performed better than QFT-GIT in children, and male, age and underlying diseases were associated with an increased risk of indeterminate IGRA results.

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.

A five-year analysis of latent tuberculosis infection in Queensland, 2016-2020

Background Australia is aiming to reach tuberculosis pre-elimination targets by 2035. As a low-incidence setting, control efforts will increasingly rely on the management of latent tuberculosis infection (LTBI). We undertook this descriptive analysis to assess the recent trends of LTBI testing in Queensland. Methods Our objective was to describe the features of LTBI testing in Queensland, and to estimate the range of possible annual notifications were it to be made a notifiable condition. We collated both state-wide and region-specific data on tuberculin skin testing (TST) and interferon gamma release assays (IGRA) conducted in Queensland during the five-year period 1 January 2016 - 31 December 2020. We used reports on Medicare-funded TST and IGRA testing in Queensland, as well as tuberculosis notification data, to understand the representativeness of our data and to derive state-wide estimates. Results We analysed 3,899 public TST, 5,463 private TST, 37,802 public pathology IGRA, and 31,656 private pathology IGRA results. The median age of people tested was 31 years; 57% of those tested were female. From our data sources, an annual average of 1,067 positive IGRA and 354 positive TST results occurred in Queensland. Building on this minimum value, we estimate possible latent tuberculosis notifications in Queensland could range from 2,901 to 6,995 per annum. Private laboratory TSTs are estimated to contribute the lowest number of potential notifications (range: 170-340), followed by private laboratory IGRA testing (range: 354-922), public laboratory IGRA testing (range: 706-1,138), and public setting TSTs (range: 1,671-4,595). Conclusion If LTBI were to be made notifiable, these estimates would place it among the ten most notified conditions in Queensland. This has implications for potential surveillance methods and goals, and their associated system and resource requirements.

Impact of Reversion of Mycobacterium tuberculosis Immunoreactivity Tests on the Estimated Annual Risk of Tuberculosis Infection

A key metric in tuberculosis epidemiology is the annual risk of infection (ARI), which is usually derived from tuberculin skin test (TST) and interferon-γ release assay (IGRA) prevalence surveys carried out in children. Derivation of the ARI assumes that immunoreactivity is persistent over time; however, reversion of immunoreactivity has long been documented. We used a deterministic, compartmental model of Mycobacterium tuberculosis (Mtb) infection to explore the impact of reversion on ARI estimation using age-specific reversion probabilities for the TST and IGRA. Using empirical data on TST reversion (22.2%/year for persons aged ≤19 years), the true ARI was 2-5 times higher than that estimated from immunoreactivity studies in children aged 8-12 years. Applying empirical reversion probabilities for the IGRA (9.9%/year for youths aged 12-18 years) showed a 1.5- to 2-fold underestimation. ARIs are increasingly underestimated in older populations, due to the cumulative impact of reversion on population reactivity over time. Declines in annual risk did not largely affect the results. Ignoring reversion leads to a stark underestimation of the true ARI in populations and our interpretation of Mtb transmission intensity. In future surveys, researchers should adjust for the reversion probability and its cumulative effect with increasing age to obtain a more accurate reflection of the burden and dynamics of Mtb infection.

Community treatment of latent tuberculosis in child and adult refugee populations: outcomes and successes

Background

Tuberculosis (TB) is the world's leading infectious cause of death, killing millions every year. In Canada, considered a low-incidence country for TB, the burden of the disease is unequally distributed, with most cases of latent tuberculosis infection (LTBI) experienced by newcomers from endemic regions. The purpose of this study was to measure LTBI treatment acceptance and completion outcomes of LTBI treatment at the REACH clinic in Saskatoon, a local refugee clinic providing primary care-based LTBI management.

Methods

A retrospective case series by sampling methodology was applied to review patients who visited the REACH clinic between January 2017 and June 2021 and who had an interferon-gamma release assay (IGRA) or tuberculin skin test (TST) done for LTBI screening. Those with positive results were retained for analysis. The LTBI treatment acceptance and completion groups were compared according to demographic variables, WHO regions of origin, year of arrival to Canada, and LTBI treatment regimen.

Results

A total of 523 patients were screened for LTBI, of whom 125 tested positive, leading to a test positivity of 23.9%. The treatment acceptance rate was 84.8%, and the treatment completion rate was 93.3%. All of those who declined treatment were more than 18 years of age (p = 0.02). Otherwise, treatment acceptance and completion rates did not vary significantly in association with gender, categories of refugees, WHO region of origin, year of arrival to Canada, or LTBI treatment regimen used.

Discussion

The refugee clinic acceptance and completion rates in this study are high and meet Canadian TB standards of care. The multidisciplinary clinic model and community support are important facilitators, which, in combination with shorter treatment regimens, offer a path forward for LTBI management among refugees resettling in low-incidence countries.

Comparison of the Standard E TB-Feron ELISA and QuantiFERON-TB Gold PLUS assays: the advantageous use of whole recombinant protein antigens for latent tuberculosis diagnosis

The laboratory diagnosis of latent tuberculosis is often performed using interferon-gamma release assays. Here, we compared two enzyme-linked immunosorbent assay-based interferon-gamma release assays, namely, the newly developed Standard E TB-Feron enzyme-linked immunosorbent assay (STFE) and the QuantiFERON-TB Gold PLUS assay (QFT-GP), using samples from 155 participants. The STFE is based on using whole EAST6 and CFP10 recombinant antigens for latent tuberculosis diagnosis. The participants were classified into four groups and screened using both assays per the manufacturers' instructions. Thereafter, two statistical analyses were conducted to compare the obtained results. First, the STFE results were compared with the QTF-GP results (used as the gold standard) to calculate the total concordance, sensitivity, and specificity of STFE. Second, positivity and negativity concordances were calculated to differentiate healthy participants from participants with tuberculosis. The STFE showed 97% and 94% sensitivity and specificity, respectively. Furthermore, its positivity and negativity concordances were 91% and 98%, respectively. These results indicate the coordinated clinical performance of STFE in detecting latent tuberculosis and its improved performance in targeting tuberculosis-infected participants. Based on the comparison of the latent tuberculosis diagnostic abilities of STFE and QFT-GP, we establish the suitability and superior performance of STFE as a diagnostic tool.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSION

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

Evaluation of a New Chemiluminescent Immunoassay-Based Interferon-Gamma Release Assay for Detection of Latent Tuberculosis Infection

Background and Objectives: This study aimed to evaluate the performance of a new chemiluminescent immunoassay-based tuberculosis (TB) interferon-gamma release assay (IGRA), AdvanSureI3 TB-IGRA (LG Chem Ltd., Seoul, Republic of Korea), for detecting latent tuberculosis infection in comparison with T-SPOT.TB (Oxford Immunotec, Oxford, UK). Materials and Methods: Between June 2021 and December 2021, 125 non-duplicate blood specimens were collected from adult volunteers; each subject received both tests concurrently. Total agreement and Cohen's kappa coefficient (κ) were used to calculate concordance. The Jonckheere-Terpstra test was used to examine the correlation between interferon-gamma (IFN-γ) levels in AdvanSureI3 TB-IGRA and spot counts in T-SPOT.TB. Results: The IGRA findings of the two assays revealed 90.8% (95% confidence interval [CI] = 84.2-94.8) total agreement with κ of 0.740 (95% CI = 0.595-0.885), showing substantial agreement between the two tests. Additionally, the amount of IFN-γ in AdvanSureI3 TB-IGRA increased with the spot counts in T-SPOT.TB (p < 0.001). Conclusions: Our research revealed that the results of the AdvanSureI3 TB-IGRA were comparable to those of T-SPOT.TB.

Tuberculosis and childhood cancer - A review of literature

Tuberculosis and malignancy are major public health problems in developing countries like India and causes significant morbidity and mortality. Mycobacterium tuberculosis is an aerobic acid-fast bacilli which is an important pathogen especially complicating clinical status of paediatric oncology patients and treatment of infection with this bacilli is challenging in this subpopulation of patients because of ongoing immunosuppression and relative lack of published guidelines. Atypical presentations of tuberculosis in children also complicate the diagnosis and management. All the more, in tuberculosis endemic area lung cancer may be mistakenly diagnosed as tuberculosis or vice versa and this wrong diagnosis increases the burden on country's health status. It is noted that tuberculosis prevalence is high in children with haematological malignancy and head and neck tumours compared to other solid organ tumours. Moreover, it is found that morbidity and mortality from tuberculosis is more in children from WHO listed high TB burden countries who undergo hematopoietic stem cell and solid organ transplantation. Use of immune checkpoint inhibitors as novel therapy in treatment of childhood malignancies has led to modification of the body's immunological response and has resulted in increased latent tuberculosis infection reactivation as one immune-related infectious consequence. Latent TB infection screening is important concept in management of paediatric oncology patients. Currently, the tests employed as screening diagnostics for LTBI are interferon-gamma release assay (IGRA) blood test and the tuberculin skin test (TST). Various regimens have been suggested for the treatment of LTBI. But, after a positive IGRA or TST and prior to latent TB treatment, active tuberculosis should be ruled out by detailed history taking, examination and appropriate investigations so as to minimize the risk of drug resistance with anti-tuberculosis monotherapy used in LTBI treatment. To add on to literature, Non tuberculous mycobacteria are universally present environmental organisms. However, in immunocompromised children especially in subpopulation of malignancy, NTM is known to cause infections which needs protocol based management. Also importance has to given to implementation of adequate preventive and corrective measures to prevent such opportunistic infection in paediatric oncology subpopulation. In this review, we provide an overview of tuberculosis in paediatric oncology patients and summarize the expansive body of literature on the tuberculosis mimicking carcinoma, tuberculosis burden in transplantation patients and those receiving immune check point inhibitors, latent TB infection screening and management, and NTM infection in children with malignancy.

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

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

Evaluation of the fully automated LIAISON®XL chemiluminescence analyzer for QuantiFERON®-CMV testing in transplant recipients

BACKGROUND

Monitoring CMV-specific cell-mediated immunity by the QuantiFERON®-CMV (QF-CMV) may be useful in predicting the risk of CMV infection in transplant recipients (TR).

OBJECTIVES

As the QuantiFERON-Tuberculosis (QFT®-Plus) became available on the fully automated LIAISON®XL chemiluminescence (CLIA) analyzer, we evaluated the performance of the QF-CMV on the LIAISON®XL analyzer using the QuantiFERON®-TB Gold Plus reagent.

STUDY DESIGN

Between 2018 and 2022, 81 samples from TR were collected at the Department of Virology of Limoges Hospital, France. Whole blood was collected into each of the three QF-CMV collection tubes: a CMV-antigen tube (QF-Ag), a mitogen tube (QF-Mg) (positive control), and a nil tube (negative control). The QF-CMV was performed on the LIAISON®XL analyzer, and results were compared with those obtained by conventional microplate ELISA.

RESULTS

Intra- and inter-assay coefficients of variation were inferior to 20%. No inter-sample contamination was found (p=0.366). The level of concordance between CLIA and the commonly used ELISA method was 88.9%. Positive and negative percent agreements were 92.3% and 85.7%, respectively, with a very good agreement between assays (κ=0.818). Most discordances were due to indeterminate- or negative-ELISA/positive-CLIA results (most of ELISA results were borderline). Linear regression analyses demonstrated a strong correlation between both assays (QF-Ag Pearson's r=0.978, QF-Mg Pearson's r=0.963). No significant difference was observed in median QF-CMV values between both assays (QF-Ag p=0.776; QF-Mg p=0.853; Mann-Whitney U test). The Bland-Altman plots showed a minor difference in IFN-γ release (QF-Ag -0.069 IU/ml, 95% limits of agreement (LoA): -1.589; 1.451; QF-Mg 0.190 IU/ml, 95% LoA: -2.070; 2.450).

CONCLUSION

Automated QF-CMV with CLIA is comparable to QF-CMV performed by ELISA with a presumably higher sensitivity for IFN-γ detection that may result in the conversion of samples close to the ELISA cut-off into positive results. Moreover, the use of a random-access analyzer allows to optimize the follow-up of TR.

Interferon-gamma release assay for the diagnosis of latent tuberculosis infection in the prison population with a positive tuberculin test: a descriptive study in a prison (Burgos, Spain)

OBJECTIVES

A high prevalence of prison inmates have a positive tuberculin skin test (TST) and sometimes unnecessary treatment for latent tuberculosis infection (LTBI) is prescribed. The prison tuberculosis prevention and control program has not generalized the use of QuantiFERON (QFT) in prisons. We set out to describe the implementation and usefulness of QFT in a population of inmates with positive TST, and to detect false positives and avoid unnecessary treatments. We also analysed the sociodemographic variables of the inmate population.

MATERIAL AND METHODS

All the positive TST tests between December 2020 and December 2021 from an average population of 300 inmates in Burgos prison were analysed. The QFT value was measured in all the positive cases. Sociodemographic variables were analysed and finally the number of inmates with positive TST, but with a negative QFT result and therefore not requiring LTBI treatment, was evaluated.

RESULTS

A total of 41 inmates were included in the study, with a mean age of 44 years. The proportion between Spanish inmates and foreigners was similar. Of all the positive TST, 48.8% were QFT negative.

DISCUSSION

It was observed that QFT is a safe method for the diagnosis of LTBI in prisons and that its use would contribute to a more specific selection of inmates who actually need chemoprophylactic treatment for LTBI.

Use of Interferon-Gamma Release Assays in Children <2 Years Old

While interferon-gamma release assays (IGRAs) are widely used for detecting tuberculosis (TB) infection, tuberculin skin tests (TSTs) remain preferred for children under the age of 2 years. The preference for TST stems from concern over IGRA sensitivity in young children. However, TSTs are susceptible to false-positive results following Bacille Calmette-Guérin (BCG) vaccination, which is common in infancy, and exposure to nontuberculous mycobacteria. We reviewed available data for IGRA performance in children under age 2 years. Across four cohorts of high-risk children under age 2 (mostly case contacts or those born in tuberculosis endemic regions), 0 of 575 untreated children with negative IGRA test results progressed to tuberculosis disease-including 0 of 70 who were TST positive but IGRA negative. While neither TSTs nor IGRAs are perfectly sensitive for the diagnosis of tuberculosis infection, IGRAs are an acceptable alternative to TST in children <2 years of age.

Inflated Gamma Interferon Response with QuantiFERON-TB Gold Plus Using the Automated Liaison XL Analyzer: a Testing Algorithm To Mitigate False-Positive Results in Low-Incidence Settings

The Liaison XL chemiluminescence immunoassay (CLIA) analyzer allows total automation of gamma interferon (IFN-γ) measurement for the QuantiFERON-TB Gold Plus assay (QFT-Plus) that is used to diagnose Mycobacterium tuberculosis infection. To evaluate CLIA accuracy, plasma samples from 278 patients undergoing QFT-Plus testing were first tested with an enzyme-linked immunosorbent assay (ELISA; 150 negatives and 128 positives) and subsequently with the CLIA. Three strategies to mitigate false-positive CLIA results were investigated in 220 samples with borderline-negative ELISA results (TB1 and/or TB2, 0.1 to 0.34 IU/mL). The Bland-Altman plot of difference versus average of the two IFN-γ measurements in the Nil and antigen (TB1 and TB2) tubes showed higher IFN-γ measurements across the range of values with the CLIA than with the ELISA. Bias was 0.21 IU/mL (standard deviation, 0.61; 95% confidence interval [CI], -1.0 to 1.41). Linear regression of difference versus average had a slope of 0.08 (95% CI, 0.05 to 0.10), which was significantly nonzero (P < 0.0001). The CLIA had positive and negative percent agreement levels with the ELISA of 91.7% (121/132) and 95.2% (139/146), respectively. In borderline-negative samples tested with ELISA, CLIA was positive in 42.7% (94/220). CLIA with a standard curve resulted in 36.4% (80/220) positivity. Retesting CLIA false positives (TB1 or TB2 range, 0 to ≤1.3 IU/mL) with ELISA reduced false positives by 84.3% (59/70). Retesting with CLIA reduced the false-positive rate by 10.4% (8/77). Implementing the Liaison CLIA for QFT-Plus in low-incidence settings risks falsely elevating conversion rates and overburdening clinics and overtreating patients. Confirming borderline positives with ELISA is a viable strategy to mitigate false-positive CLIA results.

QuantiFERON-TB Gold Plus Performance in Children: A Narrative Review

This review summarizes studies evaluating the performance of the QuantiFERON-TB Gold Plus (QFT-Plus) interferon-gamma release assay (IGRA) test for Mycobacterium tuberculosis ( Mtb ) infection in children. Literature searching was conducted using PubMed, MEDLINE and Embase (January 2017 to December 2021) and the terms "children" or "pediatric" and "IGRAs" or "QuantiFERON-TB Gold Plus." Selected studies (N = 14; 4646 subjects) enrolled children with Mtb infection, tuberculosis (TB) disease or healthy children with household TB contacts. Agreement between QFT-Plus and tuberculin skin test (TST) (kappa values) ranged from -0.201 (no agreement) to 0.83 (almost perfect agreement). Assay sensitivity of QFT-Plus (against reference standard of microbiologically confirmed TB disease) was 54.5%-87.3%, with no reported difference in children less than 5 versus greater than or equal to 5 years of age. In individuals less than or equal to 18 years of age, the rate of indeterminate results was 0%-33.3% (2.6% in children <2 years). IGRAs may overcome the limitations of TST in young, Bacillus Calmette-Guérin-vaccinated children.

Differentially expressed transcript isoforms associate with resistance to tuberculin skin test and interferon gamma release assay conversion

BACKGROUND

A mechanistic understanding of uncommon immune outcomes such as resistance to infection has led to the development of novel therapies. Using gene level analytic methods, we previously found distinct monocyte transcriptional responses associated with resistance to Mycobacterium tuberculosis (Mtb) infection defined as persistently negative tuberculin skin test (TST) and interferon gamma release assay (IGRA) reactivity among highly exposed contacts (RSTR phenotype).

OBJECTIVE

Using transcript isoform analyses, we aimed to identify novel RSTR-associated genes hypothesizing that previous gene-level differential expression analysis obscures isoform-specific differences that contribute to phenotype.

MATERIALS AND METHODS

Monocytes from 49 RSTR versus 52 subjects with latent Mtb infection (LTBI) were infected with M. tuberculosis (H37Rv) or left unstimulated (media) prior to RNA isolation and sequencing. RSTR-associated gene expression was then identified using differential transcript isoform analysis.

RESULTS

We identified 81 differentially expressed transcripts (DETs) in 70 genes (FDR <0.05) comparing RSTR and LTBI phenotypes with the majority (n = 79 DETs) identified under Mtb-stimulated conditions. Seventeen of these genes were previously identified with gene-level bulk RNAseq analyses including genes in the IFNγ response that had increased expression among LTBI subjects, findings consistent with a clinical phenotype based on IGRA reactivity. Among the subset of 23 genes with positive differential expression among Mtb-infected RSTR monocytes, 13 were not previously identified. These novel DET genes included PDE4A and ZEB2, which each had multiple DETs with higher expression among RSTR subjects, and ACSL4 and GAPDH that each had a single transcript isoform associated with RSTR.

CONCLUSION AND LIMITATIONS

Transcript isoform-specific analyses identify transcriptional associations, such as those associated with resistance to TST/IGRA conversion, that are obscured when using gene-level approaches. These findings should be validated with additional RSTR cohorts and whether the newly identified candidate resistance genes directly influence the monocyte Mtb response requires functional study.

VIDAS3® TB-IGRA assay: evaluation of performance characteristics in a predominantly low risk, low incidence population

OBJECTIVES

To evaluate the analytical performance of the TB-IGRA® assay on the VIDAS3 platform (bioMérieux) when testing a predominantly low risk population in a low incidence area.

RESULTS

Eighty-eight percent of the results were concordant between QuantiFERON®-TB Gold-Plus (QFT®-Plus, QIAGEN) and TB-IGRA®. All 12 of 99 (12.1%) discordant results were determined positive only with the TB-IGRA® assay. In 11 of 12 of these discordant cases, no explanation could be found in the medical record. Five of these discrepant results were probably caused by the use of contaminated stimulation reagents. The remaining 6 discrepant samples were also part of the reproducibility experiment and only 2 results were reproducible positive. Overall, in the reproducibility experiment 5 of 25 (20.0 %) results were not repeatable.

CONCLUSIONS

the TB-IGRA® assay seems prone to contamination. Besides, we documented a reproducibility of only 80.0% with the TB-IGRA® assay.

Efficacy and Risk Factors of Interferon-Gamma Release Assays among HIV-Positive Individuals

Latent tuberculosis is prevalent in HIV-infected people and has an impact on the progression of AIDS. The aim of this study is to match a more accurate IGRA method for the better detection of latent tuberculosis infection in HIV patients. All 2394 patients enrolled were tested using three IGRA methods. The positive rate consistency of pairwise comparison and risk factors were analyzed. Receiver operator characteristic (ROC) curve analysis was applied to evaluate the diagnostic value of T-SPOTTB. The positive rates of the three methods were statistically different (p < 0.001). The CD4⁺ T cell number statistically impacted the QuantiFERON and Wan Tai tests after the analysis with univariate logistic regression, while no statistical difference was observed in T-SPOT.TB. Additionally, there was a better sensitivity and specificity of T-SPOT.TB if the positive cut-off value of ESAT-6 and CFP-10 was 4.5 and 5.5, respectively. This study provides an insight into the IGRA methods and demonstrated that the positive response detected via QuantiFERON declined with decreased CD4⁺ T cells in the HIV-infected population; T-SPOT.TB functions independently of the CD4⁺ T cell level and Wan Tai was affected in some cases. This will be useful in the diagnosis of LTBI in the HIV-infected population, which will be a key step toward TB elimination in China.

Interferon Gamma Release Assay Results and Testing Trends Among Patients Younger Than 2 Years Old at Two US Health Centers

BACKGROUND

Interferon-gamma release assays (IGRAs) are approved for children ≥2 years old to aid in diagnosis of Mycobacterium tuberculosis (TB) infection and disease. Tuberculin skin tests (TSTs) continue to be the recommended method for diagnosis of TB infection in children <2 years, in part due to limited data and concern for high rates of uninterpretable results.

METHODS

We performed a retrospective cohort study of IGRA use in patients <2 years old in 2 large Boston healthcare systems. The primary outcome was the proportion of valid versus invalid/indeterminate IGRA results. Secondary outcomes included concordance of IGRAs with paired TSTs and trends in IGRA usage over time.

RESULTS

A total of 321 IGRA results were analyzed; 308 tests (96%) were valid and 13 (4%) were invalid/indeterminate. Thirty-seven IGRAs were obtained in immunocompromised patients; the proportion of invalid/indeterminate results was significantly higher among immunocompromised (27%) compared with immunocompetent (1%) patients ( P < 0.001). Paired IGRAs and TSTs had a concordance rate of 64%, with most discordant results in bacille Calmette-Guérin-vaccinated patients. The proportion of total TB tests that were IGRAs increased over the study period (Pearson correlation coefficient 0.85, P < 0.001).

CONCLUSIONS

The high proportion of valid IGRA test results in patients <2 years of age in a low TB prevalence setting in combination with the known logistical and interpretation challenges associated with TSTs support the adoption of IGRAs for this age group in certain clinical scenarios. Interpretation of IGRAs, particularly in immunocompromised patients, should involve consideration of the broader clinical context.

Active and latent TB screening in recently arrived persons from Afghanistan: feasibility and lessons learned

We describe an active and latent tuberculosis (TB) screening programme undertaken in Manchester, UK in response to the arrival of a cohort of refugees from Afghanistan. In total, 217 adults and 347 children were offered screening, which involved a symptom questionnaire, Mantoux test or interferon gamma release assay, blood-borne virus screening and a chest X-ray in participants over the age of 11. We found a latent TB infection (LTBI) rate of 15% in adults and 1.5% in children, which is lower than global LTBI estimates. One case of active TB was detected. Screening was undertaken in the hotels where participants were temporarily housed, leading to high participant engagement levels. Attendance rates were almost doubled compared with a previous hospital-based screening programme. Hotel-based screening for TB presented several challenges, including transfer of information and results to secondary care. Understanding these challenges and learning from the programme has helped us refine our screening protocol to optimise migrant TB screening in Manchester in the future.

Serial interferon-gamma release assay in lung cancer patients receiving immune checkpoint inhibitors: a prospective cohort study

Recent advancements in cancer immunotherapy using immune checkpoint inhibitors (ICIs) have received considerable attention. Although advantageous, ICI therapies cause unique immune-related adverse events (irAEs) in some patients. Moreover, infectious diseases, such as tuberculosis, have been recognized as emerging concerns during immunotherapy. We aimed to evaluate the interferon-gamma release assay (IGRA) conversion rate and active tuberculosis incidence during immunotherapy to elucidate the incidence of tuberculosis reactivation after ICI therapy induction.We prospectively assessed IGRA results in lung cancer patients who received ICI monotherapy before ICI treatment and at 6 and 12 months after ICI treatment. We also assessed computed tomography findings to determine the presence of active tuberculosis when positive IGRA results were obtained. The ICIs used were nivolumab, pembrolizumab, atezolizumab, and durvalumab.In all, 178 patients were prospectively recruited between March 2017 and March 2020. Of these, 123 completed serial IGRAs, of whom 18, 101, and 4, respectively, had positive, negative, and indeterminate IGRAs at baseline. Three and four patients, respectively, showed IGRA reversion and conversion during immunotherapy. One patient with a sustained, stable positive IGRA and one with IGRA conversion developed active pulmonary tuberculosis during immunotherapy.We found that 3.3% and 1.6% of the patients developed IGRA conversion and active tuberculosis, respectively. Of the four patients who developed IGRA conversion, one developed active pulmonary tuberculosis during immunotherapy. Another patient with sustained, stable positive IGRA developed active tuberculosis. Physicians should be alert to tuberculosis development during ICI therapy, and IGRA testing is a useful tool to assess the risk of developing active tuberculosis.

Are interferon-gamma release assays reliable to detect tuberculosis infection in patients with rheumatoid arthritis treated with Janus kinase inhibitors?

Background

Screening for latent tuberculosis infection is recommended in patients with rheumatoid arthritis (RA) starting Janus kinase inhibitors (Jaki). Interferon (IFN)-gamma release assays (IGRAs) are increasingly used for this purpose. Jaki tend to decrease the levels of IFNs, questioning the reliability of IGRAs during treatment with these drugs.

Objectives

To compare the performance of QuantiFERON-TB Gold Plus (QFT-P) and QFT Gold In-tube (QFT-GIT) in RA patients treated with Jaki.

Methods

RA patients underwent QFT-P and QFT-GIT at baseline (T0), and after 3 (T3) and 12 months (T12) of treatment with Jaki. The agreement between the two tests was calculated. The agreement between IGRAs and tuberculin skin test (TST) or chest radiography at baseline was also determined. The variability of QTF-P results was longitudinally assessed.

Results

Twenty-nine RA patients (F/M 23/6; median age/IQR 63/15.5 years; median disease duration/IQR 174/216 months) were enrolled. A perfect agreement was found between QFT-P and QFT-GIT at all times (κ = 1). At T0, no agreement was recorded between IGRAs and TST (κ = -0.08) and between TST and chest radiography (κ = -0.07), a low agreement was found between QFT-P and chest radiography (κ = 0.17). A variation of 33.3% in the results of QFT-P was recorded at T3 vs T0, of 29.4% at T12 vs T0, and of 11.8% at T12 vs T3. The median levels of IFN-γ produced by lymphocytes in response to the mitogen of QFT-P decreased after 3 months followed by an increase after 12 months (not significant). No change in the median number of circulating lymphocytes was documented. Glucocorticoids intake was associated with a higher probability of negative or indeterminate IGRA results at T0 (p<0.0001).

Conclusion

A response to IGRAs is detectable during treatment with Jaki. However, fluctuations in the results of IGRAs have been observed in the absence of correlation with clinical outcomes, thus challenging their interpretation.

Detecting Mycobacterium tuberculosis Infection in Children Migrating to Australia

In 2015, Australia updated premigration screening for tuberculosis (TB) disease in children 2-10 years of age to include testing for infection with Mycobacterium tuberculosis and enable detection of latent TB infection (LTBI). We analyzed TB screening results in children <15 years of age during November 2015-June 2017. We found 45,060 child applicants were tested with interferon-gamma release assay (IGRA) (57.7% of tests) or tuberculin skin test (TST) (42.3% of tests). A total of 21 cases of TB were diagnosed: 4 without IGRA or TST, 10 with positive IGRA or TST, and 7 with negative results. LTBI was detected in 3.3% (1,473/44,709) of children, for 30 applicants screened per LTBI case detected. LTBI-associated factors included increasing age, TB contact, origin from a higher TB prevalence region, and testing by TST. Detection of TB and LTBI benefit children, but the updated screening program's effect on TB in Australia is likely to be limited.

Significant difference in Th1/Th2 paradigm induced by tuberculosis-specific antigens between IGRA-positive and IGRA-negative patients

False negative interferon-γ release assay (IGRA) results constitute the major dilemma for the diagnosis of tuberculosis (TB) infections. Herein, we conducted a cohort study to compare the host immunological response to TB-specific antigens between active TB patients with positive and negative IGRA results and control groups. A total of 274 laboratory-confirmed TB patients were included in our analysis, consisting of 221 were IGRA positive and 53 were IGRA negative. Patients with the elderly were identified as an independent risk factor for negative IGRA results. In addition, the elevated level of IL-4 and the decreased levels of IFN-γ, IL-2, IL-6, IL-1β, and IL-12 in IGRA negative TB relative to IGRA positive TB group, demonstrating a significant difference in Th1/Th2 paradigm between two groups. The IFN-γ&IL-2 based assay could correctly identify 247 out of 307 MTB-infected individuals [271 TB patients and 36 individuals with latent TB infection (LTBI)], demonstrating a sensitivity of 80.5%. Then the IFN-γ and IL-4 were applied to distinguish healthy control and IGRA-negative group. When using the stepwise algorithm, the sensitivity for detecting Mycobacterium tuberculosis (MTB) infections was significantly increased from 80.5% to 89.6%. Additionally, patients with negative IGRA results had a conversion to culture-negative status longer than those with positive IGRA results. In conclusion, a stepwise algorithm outperforms IGRA assays to accurately identify MTB infections by the combination IFN-γ, IL-2, and IL-4. Further study is needed to evaluate the accuracy of our diagnostic algorithm in the LTBI population.

Latent Tuberculosis Infection in Haematopoietic Stem Cell Transplant Recipients: A Retrospective Italian Cohort Study in Tor Vergata University Hospital, Rome

The results of tuberculosis (TB) screening and reactivation in a cohort of 323 adult patients undergoing haematopoietic stem cell transplantation (HSCT) from 2015 to 2019 at the University Hospital of Tor Vergata, Rome, Italy, were reported. A total of 260 patients, 59 (18.3%) autologous and 264 (81.7%) allogeneic transplants, underwent Interferon Release (IFN)-γ (IGRA) test screening: 228 (87.7%) were negative, 11 (4.2%) indeterminate and 21 (8.1%) positive. Most of the IGRA-positive patients were of Italian origin (95.2%) and significantly older than the IGRA-negative (p < 0.001); 22 (8.5%) patients underwent a second IGRA during the first year after transplantation, and 1 tested positive for IGRA. Significantly lower monocyte (p = 0.044) and lymphocyte counts (p = 0.009) were detected in IGRA negative and IGRA indeterminate patients, respectively. All latent TB patients underwent isoniazid prophylaxis, and none of them progressed to active TB over a median follow-up period of 63.4 months. A significant decline in TB screening practices was shown from 2015 to 2019, and approximately 19% of patients were not screened. In conclusion, 8.1% of our HSCT population had LTBI, all received INH treatment, and no reactivation of TB was observed during the follow-up period. In addition, 19% escaped screening and 8% of these came from countries with a medium TB burden, therefore at higher risk of possible development of TB.

Biomarkers to identify Mycobacterium tuberculosis infection among borderline QuantiFERON results

BACKGROUND

Screening for tuberculosis (TB) infection often includes QuantiFERON-TB Gold Plus (QFT) testing. Previous studies showed that two-thirds of patients with negative QFT results just below the cut-off, so-called borderline test results, nevertheless had other evidence of TB infection. This study aimed to identify a biomarker profile by which borderline QFT results due to TB infection can be distinguished from random test variation.

METHODS

QFT supernatants of patients with a borderline (≥0.15 and <0.35 IU·mL-1), low-negative (<0.15 IU·mL-1) or positive (≥0.35 IU·mL-1) QFT result were collected in three hospitals. Bead-based multiplex assays were used to analyse 48 different cytokines, chemokines and growth factors. A prediction model was derived using LASSO regression and applied further to discriminate QFT-positive Mycobacterium tuberculosis-infected patients from borderline QFT patients and QFT-negative patients RESULTS: QFT samples of 195 patients were collected and analysed. Global testing revealed that the levels of 10 kDa interferon (IFN)-γ-induced protein (IP-10/CXCL10), monokine induced by IFN-γ (MIG/CXCL9) and interleukin-1 receptor antagonist in the antigen-stimulated tubes were each significantly higher in patients with a positive QFT result compared with low-negative QFT individuals (p<0.001). A prediction model based on IP-10 and MIG proved highly accurate in discriminating patients with a positive QFT (TB infection) from uninfected individuals with a low-negative QFT (sensitivity 1.00 (95% CI 0.79-1.00) and specificity 0.95 (95% CI 0.74-1.00)). This same model predicted TB infection in 68% of 87 patients with a borderline QFT result.

CONCLUSIONS

This study was able to classify borderline QFT results as likely infection-related or random. These findings support additional laboratory testing for either IP-10 or MIG following a borderline QFT result for individuals at increased risk of reactivation TB.

CLINICAL APPLICATION OF RT-PCR IN TUBERCULOSIS DNA DETECTION COMBINED WITH TB-IGRA IN THE DIAGNOSIS OF SPUTUM SMEAR-NEGATIVE PULMONARY TUBERCULOSIS

The aim was to investigate detection of pulmonary alveolar lavage fluid tuberculosis DNA by real-time fluorescent polymerase chain reaction (RT-PCR) combined with clinical application of the sputum smear-negative pulmonary tuberculosis diagnosis with TB interferon-γ release assay (TB-IGRA). From October 2014 to October 2015, 632 outpatients and inpatients treated in our hospital were randomly selected, of which 459 patients as the research group managed with RT-PCR detection combined with TB-IGRA and 173 patients as the control group undergoing electronic bronchoscopy alveolar lavage fluid detection, with detection results statistically evaluated. The positive rate in the research group was 96.51%, i.e. significantly higher than that in the control group (66.47%), yielding a statistically significant difference (χ²=109.68, p=0.00). The true positive rate was 97.7% in the research group and 67.92% in the control group; the true positive rate was significantly higher in the research group patients as compared with the control group, yielding a statistically significant difference (χ²=112.04, p=0.00). The sensitivity and specificity, as well as Youden index were significantly higher in the research group as compared with the control group. In conclusion, TB DNA detection by RT-PCR combined with TB-IGRA is a very good method of diagnosing tuberculosis, and it can be implemented in clinical diagnosis of pulmonary tuberculosis.

Correlation between tuberculosis-specific interferon-γ release assay and intrathoracic calcification: A cross-sectional study

Background

Although persistent tuberculosis (TB) infection is known to cause calcification in the lungs, the relationship between intrathoracic calcification and the results of the interferon-γ release assay (IGRA) has not been fully elucidated. This study aimed to assess the association between intrathoracic calcification and IGRA results.

Methods

We retrospectively included consecutive patients who concurrently underwent chest X-ray, chest computed tomography (CT), and an IGRA. Patients with a current diagnosis of active TB or treatment history of active TB or latent tuberculosis infection (LTBI) were excluded. The association between calcification according to the chest X-ray or CT and IGRA results were analyzed using binomial logistic regression.

Results

This study included 574 patients, and 38 (7%) patients had a positive IGRA result. Patients with a positive result were significantly older and had a higher proportion of comorbidities, and history of tuberculosis exposure compared to those with a negative result. Calcification of the lung field and mediastinal lymph nodes according to chest CT was more frequently observed in patients with a positive IGRA result, whereas no significant difference was observed concerning the proportion of lung field calcification on chest X-ray between patients with positive and negative IGRA results. In multivariate analysis, calcification of mediastinal lymph nodes alone (adjusted odds ratio [OR] = 3.82, 95% confidence interval [CI] = 1.76–8.26) and the combination of lung field and mediastinal lymph node calcification (adjusted OR = 4.12, 95% CI = 1.51–11.76) on chest CT was independently associated with positive IGRA results.

Conclusions

The finding of mediastinal lymph node calcification, with or without lung field calcification, on chest CT was associated with positive IGRA results independent of TB exposure history. Previous TB infection including eliminated TB infection and LTBI can be suspected when calcified lymph nodes in are observed the mediastinum on chest CT.

Variability of interferon-γ release assays in people at high risk of tuberculosis infection or progression to tuberculosis disease living in the United States

OBJECTIVES

Interferon-γ release assays, including T-SPOT.TB (TSPOT) and QuantiFERON Gold In-Tube (QFT), are important diagnostic tools for tuberculosis infection, but little work has been done to study the performance of these tests in populations prioritized for tuberculosis testing in the United States, especially those other than health care personnel.

METHODS

Participants were enrolled as part of a large, prospective cohort of people at high risk of tuberculosis infection or progression to tuberculosis disease. All participants were administered a tuberculin skin test, TSPOT, and QFT test. A subset of participants had their QFT (n = 919) and TSPOT (n = 885) tests repeated when they returned to get their tuberculin skin test read 2 to 3 days later (repeat study). A total of 531 participants had a TSPOT performed twice on the same sample taken at the same time (split study).

RESULTS

The QFT repeat test interpretations were discordant (one test positive and the other negative) for 6.4% of participants (59 of 919), and the TSPOT tests were discordant for 60 of 885 participants in the repeat study (6.8%) and 41 of 531 participants in the split study (7.7%). There was a high degree of variability in the quantitative test results for both QFT and TSPOT, and discordance was not associated with both test results being near the established cut-offs. Furthermore, the proportion of discordance was similar when comparing participants in both the TSPOT repeat and TSPOT split studies.

DISCUSSION

Both QFT and TSPOT were 6% to 8% discordant. The results should be interpreted with caution, particularly when seeing a conversion or reversion in serial testing.

Interferon gamma release assays for diagnosis of osteoarticular tuberculosis: A systematic review and meta-analysis

Background

Although the Interferon Gamma Release Assays (IGRA) is often used to identify latent tuberculosis, it also plays a crucial role in diagnosing active extrapulmonary tuberculosis. Some studies have assessed the use of IGRA as a biomarker for osteoarticular tuberculosis (OATB), which is elevated following TB infection. Still, conclusive results about its effectiveness have not been reported.

Method

We searched PubMed, Embase, and Cochran databases. We obtained literature related to the diagnosis of OATB by IGRA, and the retrieval period was from the establishment of the database to June 2021. The bivariate random effect model was used to summarize the sensitivity, specificity, and accuracy of other indicators in diagnosing OATB by IGRA, and the forest plot and receiver operating characteristic (ROC) curve were used for testing.

Results

We included seven studies involving 643 subjects in diagnosing OATB by IGRA. The comprehensive sensitivity and specificity were 0.84 (95% CI, 0.70–0.92) and 0.78 (95% CI, 0.66–0.87), respectively. The area under the curve (AUC) was 0.87.

Conclusion

In blood samples, the diagnostic accuracy of IGRAS is poor in patients with suspected OAT. We conclude that IGRA may not be appropriate for patients with OATB.

Comparison of diagnostic accuracy of QuantiFERON-TB Gold Plus and T-SPOT.TB in the diagnosis of active tuberculosis in febrile patients

OBJECTIVE

This study aimed to compare the accuracy of QuantiFERON-TB Gold Plus (QFT-Plus) and T-SPOT.TB for diagnosing active tuberculosis (ATB) in febrile patients, to explore influencing factors of positive results and to verify the potential value of QFT-Plus in the identification of ATB and latent tuberculosis infection (LTBI).

METHODS

A total of 240 febrile patients with ATB (n = 80) and non-ATB (n = 160) were recruited to assess the accuracy of QFT-Plus and T-SPOT.TB for diagnosing ATB. Multivariable logistic regression was used to analyze the influencing factors of positive results.

RESULTS

The proportion of indeterminate results (ITRS) in QFT-Plus and T-SPOT.TB were 3.3% and 0%, respectively. The consistency between the results of the QFT-Plus and T-SPOT.TB was substantial. The area under the receiver operating characteristic curve (AUROC) of the QFT-Plus and T-SPOT.TB for diagnosing ATB was 0.792 and 0.849 (p = 0.070), respectively. The sensitivity of differentiating ATB from non-ATB was 92.2% in QFT-Plus versus 95.0% in T-SPOT.TB. The influencing factors of T-SPOT.TB positive result were male (odds ratio (OR) = 2.33, 95% confidence interval (CI) 1.27-4.26, p = 0.006), evidence of previous TB (OR 11.36, 95% CI 4.62-27.94, p < 0.001), while male (OR = 3.17, 95% CI 1.73-5.84, p < 0.001), evidence of previous TB (OR = 7.58, 95% CI 3.60-15.98, p <0.001), and use of immunosuppressant (OR = 0.49, 95% CI 0.260.94, p = 0.030) were influencing factors for QFT-Plus positive result. There was no significant difference in QFT-Plus in differentiating ATB from LTBI in febrile patients.

CONCLUSION

There was no significant difference between QFT-Plus and T-SPOT.TB for diagnosing ATB in febrile patients. QFT-Plus is prone to ITRS. The influencing factors including males, evidence of the previous TB, and use of immunosuppressant should be considered when interpreting positive results.

[Comparison of QuantiFERON-TB Gold Plus and QuantiFERON-TB Gold In Tube in the diagnosis of pulmonary tuberculosis]

Objective: To compare the screening value of QuantiFERON-TB Gold Plus (QFT-Plus) and QuantiFERON®-TB Gold in tube (QFT-GIT) in the auxiliary diagnosis of pulmonary tuberculosis (TB). Methods: A screening test was performed. Patients who were hospitalized in Guangzhou Chest Hospital and underwent QFT-GIT testing from October to December 2020 were prospectively included as research subjects, QFT-Plus testing was added. And the basic information, clinical manifestations, laboratory test results, imaging examinations and other data of these patients were collected. A total of 207 patients were included and divided into tuberculosis group and non-tuberculosis group according to these data. There were 124 cases in the tuberculosis group (94 confirmed patients and 30 clinically diagnosed patients), including 90 males and 34 females, aged 18-93 years, with a median age of 57 (38, 67) years. The non-tuberculosis group included 83 patients (16 patients with non-tuberculous Mycobacteria and 67 patients with other lung diseases), including 49 males and 34 females, with a median age of 60 (51, 68) years. The confirmed patients were subdivided into three grades of low, medium and high Mycobacteriam tuberculosis (MTB) bacterial load, and three grades of mild, moderate and severe pulmonary tuberculosis. The results of QFT-Plus and QFT-GIT were compared, and the levels of IFN-γ in different antigen tubes were compared. Differences between different groups were compared using Mann-Whitney U test and Kruskal-Wallis H test. Results: The QFT-Plus showed a high degree of agreement with the QFT-GIT (κ=0.786, 95%CI: 0.740-0.832), while the main discordant result was QFT-GIT negative/QFT-Plus positive, accounting for 15/17. The sensitivity of QFT-GIT was 80.7%(95%CI: 0.706-0.880), the specificity was 76.3%(95%CI: 0.649-0.850), the positive predictive value was 79.8%(95%CI: 0.697-0.873), and the negative predictive value was 77.3%(95%CI: 0.659-0.859), repectively. QFT-Plus showed a sensitivity of 84.3%(95%CI: 0.743-0.910), a specificity of 78.8% (95%CI: 0.679-0.868), and a positive predictive value of 80.5%(95%CI: 0.703-0.879), the negative predictive value being 82.9%(95%CI: 0.721-0.902), slightly improved to that of the QFT-GIT. Also, this study found that there were significant differences in IFN-γ values between different MTB load or disease severity (P<0.05). Conclusions: There is a good consistency between the QFT-Plus test and the QFT-GIT test, both of which show good application value in the auxiliary diagnosis of pulmonary tuberculosis. Moreover, because of the addition of tuberculosis-specific CD8 cell antigen, the QFT-Plus test has higher sensitivity, lower uncertainty and more application value. This study also found that the bacterial load and disease severity of patients with pulmonary tuberculosis may have a certain correlation with the measured value of IFN-γ.

Diagnostic Accuracy of Interferon-Gamma Release Assays for Tuberculous Meningitis: A Systematic Review and Meta-Analysis

Background

In this study, we evaluated and compared the accuracy of blood and cerebrospinal fluid (CSF) interferon release tests [interferon-gamma release assays (IGRAs)] in the diagnosis of tuberculous meningitis (TBM) by a meta-analysis of the relevant literature.

Methods

We searched for studies published before 2021 in Medline, Embase, the Cochrane database, and Chinese databases. All studies used the QuantiFERON-TB Gold In-Tube and/or T-SPOT.TB method. Blood and/or CSF tests that met the guidelines for the quality assessment of studies with diagnostic accuracy were included. We used the revised diagnostic accuracy study quality assessment to assess the quality of the included studies. Begg’s funnel plots were used to assess publication bias in the meta-analysis of the diagnostic studies, and statistical analyses were performed by using Stata (Version 12) software.

Results

A total of 12 blood and/or CSF IGRA studies were included in this meta-analysis, with 376 patients and 493 controls. The sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, diagnostic odds ratio, and area under the summary receiver operating characteristic curve (SROC) of the blood IGRAs in the pooled data from 12 studies were 74% (95% CI: 0.65-0.82), 78% (95% CI: 0.68-0.86), 3.38 (95% CI 2.26-5.06), 0.33 (95% CI: 0.23-0.46), 10.25 (95% CI: 5.46-19.25), and 0.83 (95% CI: 0.79-0.86), respectively. For CSF IGRAs, these values for the pooled data from the 10 studies included were 79% (95% CI: 0.71-0.85), 95% (95% CI: 0.88-0.98), 16.30 (95% CI 6.5-40.83), 0.22 (95% CI: 0.16-0.31), 57.93 (95% CI: 22.56-148.78), and 0.91 (95% CI: 0.88-0.93), respectively.

Conclusion

CSF IGRAs exhibited a better diagnostic accuracy than blood IGRAs in diagnosing TBM.

Increased Risk of Incident Diabetes Among Individuals With Latent Tuberculosis Infection

OBJECTIVE

In cross-sectional U.S. studies, patients with diabetes had twice the prevalence of latent tuberculosis infection (LTBI) compared with those without diabetes. However, whether LTBI contributes to diabetes risk is unknown. We used longitudinal data to determine if LTBI is associated with increased diabetes incidence.

RESEARCH DESIGN AND METHODS

We conducted a retrospective cohort study among U.S. Veterans receiving care in the Veterans Health Administration from 2000 to 2015. Eligibility included all patients without preexisting diabetes who received a tuberculin skin test (TST) or interferon-γ release assay (IGRA). We excluded patients with a history of active TB and those diagnosed with diabetes before or within 2 years after LTBI testing. Patients were followed until diabetes diagnosis, death, or 2015. LTBI was defined as TST or IGRA positive. Incident diabetes was defined by use of ICD-9 codes in combination with a diabetes drug prescription.

RESULTS

Among 574,113 eligible patients, 5.3% received both TST/IGRA, 79.1% received TST only, and 15.6% received IGRA only. Overall, 6.6% had LTBI, and there were 2,535,149 person-years (PY) of follow-up after LTBI testing (median 3.2 years). The diabetes incidence rate (per 100,000 PY) was greater in patients with LTBI compared with those without (1,012 vs. 744; hazard ratio [HR] 1.4 [95% CI 1.3-1.4]). Increased diabetes incidence persisted after adjustment for covariates (adjusted HR [aHR] 1.2 [95% CI 1.2-1.3]) compared with those without LTBI. Among patients with LTBI, diabetes incidence was similar in those treated for LTBI compared with those who were not treated (aHR 1.0 [95% CI 0.9-1.1]).

CONCLUSIONS

Comprehensive longitudinal data indicate that LTBI is associated with increased diabetes incidence. These results have implications for people with LTBI, ∼25% of the global population.

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.

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.