Management implications of latent TB among under-five children at risk: Insights from a community study in Mumbai, India.

BACKGROUND: Latent tuberculosis infection (LTBI) management is crucial to WHO's End TB Strategy. Indian guidelines recommend treating under-five children with household TB contacts after ruling out active TB, regardless of TBI testing. However, the precise LTBI burden among children in high TB burden settings like India is unknown. A community-based study in Mumbai's urban slums screened and managed under-five children at LTBI risk to understand its epidemiology and inform TB control interventions. METHODS: Total 369 eligible under-five children were enrolled for the study. LTBI screening was done using Tuberculin skin test and Interferon gamma release assay. Active TB was ruled out before initiation of TB preventive therapy among LTBI positives. Statistical tests like chi-square, logistic regression analysis and Hosmer-Lemeshow test were used. RESULTS: Overall, LTBI prevalence among under-five children was 12.4% by IGRA and 21.4% by TST. Undernourished children had significantly lower LTBI positivity by IGRA (p = 0.027), while those with household contacts, longer contact duration and drug-resistant tuberculosis (DR-TB) exhibited proportionally greater IGRA positivity (p = <0.001). CONCLUSION: The study found a lower LTBI prevalence among under-five children compared to adults, with key risk factors being HHC, DR-TB contact, and prolonged exposure. These findings suggest the need to revise or revisit the TPT framework for this age group in India, particularly by implementing a test-and-treat approach.

Comparative Evaluation of Diagnostic Performance: Standard E TB Feron ELISA vs QuantiFERON-TB Gold Plus for Latent Tuberculosis Infection Detection in Diverse Risk Groups in Bangladesh.

Background: Around one-quarter of the global population has latent tuberculosis infection (LTBI). If left untreated, LTBI has 5-10% lifetime risk of developing into TB. Interferon-gamma release Assays (IGRAs) are more sensitive than the tuberculin skin test for LTBI detection. However, the high cost and complexity of IGRAs are barriers to adoption in resource-constrained settings. This study evaluated the diagnostic performance of a more affordable IGRA, Standard E TB-Feron (TBE), among different risk groups in Bangladesh. Methods: 532 participants of all age groups were enrolled from the TB Screening and Treatment Centers and Dhaka Hospital of icddr,b between June and September 2023. The participants were categorized into four risk groups: healthy people, healthcare workers/ attendants of TB patients, patients with microbiologically confirmed TB, and people with a history of TB. The diagnostic performance of TBE was compared to QuantiFERON-TB Gold Plus (QFT-Plus) for all groups. GeneXpert, culture, and microscopy were used to confirm TB microbiologically. Results: TBE had an overall agreement of 85.9% (95% CI, 82.5% to 88.7%), positive percent agreement of 86.1% (95% CI, 80.6% to 90.5%), and negative percent agreement of 85.7% (95% CI, 81.3% -89.4%) with QFT-Plus. Among 81 culture-positive patients, TBE and QFT-Plus were positive for 60 (74.1%) and 62 (76.5%) respectively. Among healthy people, TBE and QFT results were positive for 49 (24.5%) and 59 (29.5%) respectively. Among health workers and contacts, TBE and QFT-Plus were positive for 79 (39.5%) and 73 (35.5%) respectively. Conclusion: We found a substantial agreement (Cohen's kappa of 0.71) between TBE and QFT-Plus in detecting LTBI across different groups, suggesting its potential as a cost-effective diagnostic tool. Implementation of TBE in routine clinical practice could increase accessibility to LTBI diagnosis, facilitating the timely initiation of preventative therapy, and leading to a reduction of active TB incidence.

Diagnostic accuracy of QuantiFERON-TB Gold Plus with Chemiluminescence Immunoassay: a systematic review and meta-analysis.

INTRODUCTION: Tuberculosis (TB) remains a global health challenge, underscoring the need for accurate diagnosis, particularly for Latent TB Infection. This meta-analysis assesses the diagnostic performance of QuantiFERON-TB Gold Plus (QFT) using Enzyme-Linked Immunosorbent Assay (ELISA) with Chemiluminescence Immunoassay (CLIA). AREAS COVERED: We systematically reviewed studies comparing QFT-CLIA with QFT-ELISA for TB detection. The literature search was carried out on PubMed, Scopus, and Web of Science, covering publications up to September 15, 2023. We included studies that assessed sensitivity, specificity, positive and negative likelihood ratios (PLR and NLR), Diagnostic Odds Ratio (DOR), and concordance. EXPERT OPINION: QFT-CLIA demonstrated high sensitivity of 0.97 (95% CI: 0.95-0.99) and specificity of 0.99 (95% CI: 0.92-1.0), with PLR of 72.19 (95% CI: 11.25-463.17), NLR of 0.03 (95% CI: 0.02-0.05), and DOR of 2494.55 (95% CI: 301.67-20627.87). The overall agreement between QFT-CLIA and QFT-ELISA was strong (0.92, 95% CI: 0.88-0.97), although the agreement for indeterminate results was slightly lower (0.83, 95% CI: 0.70-0.96). The high diagnostic accuracy and broader quantitative range of QFT-CLIA compared to ELISA may lead to more positive results and better classification of borderline cases. However, further research is needed to validate its diagnostic capabilities.

Prevalence, Risk Factors, and Result Features in the Detection of Latent Tuberculosis Infection in Thai Healthcare Workers Using QuantiFERON-TB Gold Plus.

Introduction Latent tuberculosis infection (LTBI) is an enormous reservoir for tuberculosis (TB), and healthcare workers (HCWs) are at high risk for TB infection. QuantiFERON-TB Gold Plus (QFT-Plus) is an alternative to the tuberculin skin test for LTBI detection, but data on its application and LTBI detected by QFT-Plus in high TB burden countries are limited. This study aimed to determine the prevalence of LTBI and its risk factors, and to investigate the QFT-Plus results in Thai HCWs. Methods A cross-sectional analytical study was conducted among HCWs at a secondary care hospital in Health Region 5, Thailand. Eligible HCWs were enrolled and underwent QFT-Plus testing. Interferon-gamma (IFN-γ) values in tubes were analysed. The prevalence and associated risk factors for LTBI were assessed based on laboratory and sociodemographic data. Logistic regression analyses were applied to calculate odds ratios (OR, aOR) reported with 95% confidence intervals (CI). Results Of the 269 participants enrolled, their median age was 42 years and 93.31% (n = 251/269) were female. The majority (n = 178/269, 66.17%) were nurses or nurse assistants and 42.75% (n = 115/269) worked in the inpatient medical wards. Overall, the QFT-Plus results showed 110 (40.89%) positive with good agreement (93.68%; κ 0.87) and high correlation (Spearman's ρ 0.91) of IFN-γ concentrations in the two antigen tubes. A true difference in IFN-γ values for predicting a recent infection was found about 7.81% (n = 21/269). By univariate and multivariate analyses, the participants' age > 40 years (OR = 3.21, 95% CI: 1.84-5.64%; aOR = 2.05, 95% CI: 1.07-3.96%), and employment duration > 10 years (OR = 3.19, 95% CI: 1.66-6.37%; aOR = 2.34, 95% CI: 1.05-5.21%) were significantly associated with the increased risk of LTBI (p-value < 0.05). Conclusions The prevalence of LTBI among these HCWs was high, and the increased risk factors for LTBI according to QFT-Plus positivity were age over 40 years and working time in the hospital for more than 10 years. It is important to screen HCWs in this setting for LTBI, particularly those with long employment durations and older ages. The high prevalence of LTBI suggests that LTBI management, such as regular screening and treatment, should be considered together with strengthening preventive measures, especially in high-risk groups.

Evaluating the diagnostic accuracy of QIAreach QuantiFERON-TB compared to QuantiFERON-TB Gold Plus for tuberculosis: a systematic review and meta-analysis.

Accurate tuberculosis (TB) diagnosis remains challenging, especially in resource-limited settings. This study aims to assess the diagnostic performance of the QIAreach QuantiFERON-TB (QFT) assay, with a specific focus on comparing its diagnostic performance with the QuantiFERON-TB Gold Plus (QFT-Plus). We systematically reviewed relevant individual studies on PubMed, Scopus, and Web of Science up to January 20, 2024. The focus was on evaluating the diagnostic parameters of the QIAreach QFT assay for TB infection, which included sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (PLR), negative likelihood ratio (NLR), and concordance with the QFT-Plus assay. QIAreach QFT demonstrated strong diagnostic performance with a pooled sensitivity of 99% (95% CI 95-100%) and specificity of 94% (95% CI 85-97%). Additionally, it showed a PLR of 15.6 (95% CI 6.5-37.5) and NLR of 0.01 (95% CI 0-0.03). The pooled PPV and NPV were 88% (95% CI 70-98%) and 100% (95% CI 99-100%), respectively. Concordance analysis with QFT-Plus revealed a pooled positive percent agreement of 98% (95% CI 88-100%) and pooled negative percent agreement of 91% (95% CI 81-97%), with a pooled overall percent agreement of 92% (95% CI 83-98). In conclusion, QIAreach QFT has shown promising diagnostic performance, with a strong concordance with QFT-Plus. However, further studies are needed to comprehensively evaluate its diagnostic performance in the context of TB infection.

Tuberculin test using Indian indigenous purified-protein derivative (PPD) shows only moderate agreement with international standard PPD.

Background: In India, the prevalence of Latent TB infection (LTBI) is estimated to be around 40%. Various formulations of PPD(Purified protein derivative) are available, for diagnosis of LTBI, which may give variable responses. The commercially available PPD in India is by Arkray Healthcare (TST-Arkray). It is unclear if this product may have a similar sensitivity compared to other internationally accepted tuberculins (TST-Tubersol). Objectives: To assess the performance of the two TSTs compared to Quantiferon-Gold Plus (QFT-Plus). Methodology: A blood sample was collected for the QFT-Plus test. Both the TSTs were placed in the right and the left volar aspect of the forearms and 48 hrs later, the subjects came back to the study site for reading. Results: Among the 512 participants who were recruited, 326 subjects were healthcare professionals and 186 subjects were household contacts of patients with tuberculosis. They were tested with both TST-Tubersol and TST-Arkray, 139(27 %) participants tested positive for TST-Tubersol (≥10 mm), whereas 203 participants (40.1 %)tested positive for TST-Arkray. There was moderate agreement between the two tests with k = 0.58. Also, there was only poor agreement between both the TSTs with QFT Plus(kappa = 0.19 for Tubersol and 0.17 for Arkray). With QFT-Plus as gold standard, the sensitivity, specificity, PPV and NPV of TST-Tubersol, ast an induration cut-off of 10 mm was 46.8 %,76.3 %,31.8 % and 85.8 %. respectively and TST- Arkray; 60.6 %, 64 %, 28.5 % and 87.2 % respectively. Conclusion: The Indian TST (Arkray Diagnostics) has shown moderate agreement with the internationally accepted Tubersol. Additionally, there was poor agreement between the TSTs and QFT plus test.

Apical fibrobullous lung disease in spondyloarthritis patients with biologic DMARDs indication.

OBJECTIVE: The rate of pleuroparenchymal involvement in patients with SpA varies widely, from 0% to 85%. The most common form is apical fibrobullous disease (AFLD). The aim of this study was to determine the incidence of AFLD and associated factors in SpA patients under and/or planned to start biologic DMARDs (bDMARDs) therapy. METHODS: The records of 3021 SPA patients registered with HUR-BIO who had indication of bDMARDs between 2010 and 2021 were scanned. The study included 2489 patients with at least one chest radiograph (X-ray). Patient demographics, comorbidities, laboratory data, bDMARDs used, baseline DASs, and purified protein derivative and/or QuantiFERON test results before initiation of bDMARDs were recorded. RESULTS: Of the 2489 patients, 36 (1.4%) were found to have AFLD by X-ray and/or CT. The mean disease duration was 11.7 (7.1) years. Patients with AFLD were more likely to be male [28 (77.8%) vs 1321 (53.9%), P = 0.004], older [56.3 (10.5) years vs 44.8 (11.4) years, P < 0.001], heavy smokers [27 (79.4%) vs 1468 (60.9%), P = 0.028] and have had longer disease duration [17. 7 (9.7) years vs 11.6 (7) years, P = 0.001]. QuantiFERON positivity was higher in the AFLD group [9 (36%) vs 309 (16.1%), P = 0.013]. While treatment with adalimumab was less preferred in those with AFLD, treatment with etanercept was more frequently preferred. CONCLUSION: As the radiological findings of AFLD can be confused with those of tuberculosis, special attention should be paid to differentiating between tuberculosis and the disease in males and in patients who have had long disease duration.

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.

Comparison of interferon-gamma production between TB1 and TB2 tubes of QuantiFERON-TB Gold Plus: a meta-analysis.

OBJECTIVES: CD8 T-cells play an important role in interferon-gamma (IFN-γ) production as a host defense against tuberculosis (TB) infection. Therefore, QuantiFERON-TB Gold Plus (QFT-Plus) was developed by adding a TB2 tube beside the TB1 tube. This study aimed to compare and analyze the difference in IFN-γ production between the two tubes in general and specific populations. CONTENT: PubMed, Web of Science, and EBSCO were searched for studies reporting IFN-γ production levels in the TB1 and TB2 tubes. Statistical analysis was performed using RevMan 5.3. SUMMARY: A total of 17 studies met the inclusion criteria. The IFN-γ production in the TB2 tube was statistically higher than that in the TB1 tube (mean difference (MD)=0.02, 95 % confidence interval (95 % CI): 0.01-0.03). Further subgroup analysis in specific populations revealed that the MD of IFN-γ production between the TB2 and TB1 tubes was significantly higher in active TB subjects than in latent TB infection (LTBI) subjects (MD=1.13, 95 % CI: 0.49-1.77, and MD=0.30, 95 % CI: 0.00-0.60, respectively). A similar finding was found in immune-mediated inflammatory disease subjects, but not statistically significant. Interestingly, IFN-γ production capacity was lower in active TB subjects than in LTBI subjects in each of the TB1 and TB2 tubes. OUTLOOK: This study is the first to systematically compare IFN-γ production between the TB1 and TB2 tubes. The IFN-γ production was higher in the TB2 tube than in the TB1 tube, representing the host's CD8 T-cell response magnitude to TB infection.

Do the drug doses of conventional synthetic DMARDs used for the treatment of biologic/targeted-synthetic DMARDs naive rheumatoid arthritis patients affect QuantiFERON-TB Gold Plus test results?

We aimed to obtain the effects of immunosuppressive doses on the QuantiFERON-TB Gold Plus (QFT-Plus) test results in Rheumatoid Arthritis (RA) patients. Besides this, the impact of the TB2 tube in QFT-Plus test was also investigated. This study included RA patients registered to HURBIO and were screened via QFT-Plus test for latent tuberculosis between January 2018 and March 2021, before the initiation of treatment of biologic/targeted-synthetic disease modifying anti-rheumatismal drugs (b/ts-DMARDs). Patients using methotrexate ≥ 10 mg or leflunomide (any dose) or steroids (≥ 7.5 mg prednisolone) at the time of QFT-Plus test were classified as the "high dose" group and the rest of the patients constituted the "low dose" group. The study included 534 RA patients; 353 [66.1%] in the high-dose group and 181 [33.9%] in the low-dose group. While QFT-Plus test was positive in 10.5% (37/353) patients in the high-dose group, it was positive in 20.4% (37/181) patients in the low-dose group (p < 0.001). The percentage of QFT-Plus indeterminate results were similar (around 2%) in both groups. The contribution of the TB2 tube to QFT-Plus test positivity was 6.89%. During a median (inter-quartile range) follow-up period of 23 (7-38) months under treatment of b/ts-DMARDs, latent TB reactivation was not observed. Primer active tuberculosis disease developed in two patients. Positive test results of Interferon-Gamma Release Assays (IGRAs) could decrease as immunosuppressive treatment doses increase in patients with RA and addition of the TB2 tube could increase test sensitivity.

Prevalence of Latent Tuberculosis Infection among Patients Undergoing Regular Hemodialysis in Disenfranchised Communities: A Multicenter Study during COVID-19 Pandemic.

Background and Objectives: Due to their weakened immune response, hemodialysis (HD) patients with latent tuberculosis infection (LTBI) are at higher risk for active tuberculosis (TB) disease and are more subject to patient-to-patient transmission within dialysis units. Consequently, current guidelines advocate screening these patients for LTBI. To our knowledge, the epidemiology of LTBI in HD patients has never been examined before in Lebanon. In this context, this study aimed to determine LTBI prevalence among patients undergoing regular HD in Northern Lebanon and to identify potential factors associated with this infection. Notably, the study was conducted during the COVID-19 pandemic, which is likely to have catastrophic effects on TB and increase the risk of mortality and hospitalization in HD patients. Materials and Methods: A multicenter cross-sectional study was carried out in three hospital dialysis units in Tripoli, North Lebanon. Blood samples and sociodemographic and clinical data were collected from 93 HD patients. To screen for LTBI, all patient samples underwent the fourth-generation QuantiFERON-TB Gold Plus assay (QFT-Plus). Multivariable logistic regression analysis was used to identify the predictors of LTBI status in HD patients. Results: Overall, 51 men and 42 women were enrolled. The mean age of the study population was 58.3 ± 12.4 years. Nine HD patients had indeterminate QFT-Plus results and were therefore excluded from subsequent statistical analysis. Among the remaining 84 participants with valid results, QFT-Plus was positive in 16 patients, showing a positivity prevalence of 19% (95% interval for p: 11.3%, 29.1%). Multivariable logistic regression analysis showed that LTBI was significantly associated with age [OR = 1.06; 95% CI = 1.01 to 1.13; p = 0.03] and a low-income level [OR = 9.29; 95% CI = 1.62 to 178; p = 0.04]. Conclusion: LTBI was found to be prevalent in one in five HD patients examined in our study. Therefore, effective TB control measures need to be implemented in this vulnerable population, with special attention to elderly patients with low socioeconomic status.

Performance of T-Track® TB, a Novel Dual Marker RT-qPCR-Based Whole-Blood Test for Improved Detection of Active Tuberculosis.

Tuberculosis (TB) is one of the leading causes of death by an infectious disease. It remains a major health burden worldwide, in part due to misdiagnosis. Therefore, improved diagnostic tests allowing the faster and more reliable diagnosis of patients with active TB are urgently needed. This prospective study examined the performance of the new molecular whole-blood test T-Track® TB, which relies on the combined evaluation of IFNG and CXCL10 mRNA levels, and compared it to that of the QuantiFERON®-TB Gold Plus (QFT-Plus) enzyme-linked immunosorbent assay (ELISA). Diagnostic accuracy and agreement analyses were conducted on the whole blood of 181 active TB patients and 163 non-TB controls. T-Track® TB presented sensitivity of 94.9% and specificity of 93.8% for the detection of active TB vs. non-TB controls. In comparison, the QFT-Plus ELISA showed sensitivity of 84.3%. The sensitivity of T-Track® TB was significantly higher (p < 0.001) than that of QFT-Plus. The overall agreement of T-Track® TB with QFT-Plus to diagnose active TB was 87.9%. Out of 21 samples with discordant results, 19 were correctly classified by T-Track® TB while misclassified by QFT-Plus (T-Track® TB-positive/QFT-Plus-negative), and two samples were misclassified by T-Track® TB while correctly classified by QFT-Plus (T-Track® TB-negative/QFT-Plus-positive). Our results demonstrate the excellent performance of the T-Track® TB molecular assay and its suitability to accurately detect TB infection and discriminate active TB patients from non-infected controls.

Comparing the diagnostic performance of QuantiFERON-TB Gold Plus with QFT-GIT, T-SPOT.TB and TST: a systematic review and meta-analysis.

BACKGROUND: QuantiFERON-TB Gold Plus (QFT-Plus) is an important test that has emerged in recent years for detecting TB infection. We conducted a review to compare the sensitivity, specificity and positive rate of QFT-Plus with that of QuantiFERON-TB Gold In-Tube (QFT-GIT), T-cell spot of tuberculosis assay (T-SPOT.TB) and Tuberculin test (TST). METHODS: PubMed and Embase were searched, without language restrictions, from 1 January 2015 to 31 March 2022 using "Mycobacterium tuberculosis Infections" and "QuantiFERON-TB-Plus" as search phrases. We estimated the sensitivity from studies of patients with active tuberculosis, specificity from studies of populations with very low risk of TB exposure, and positive rate from studies of high-risk populations. The methodological quality of the eligible studies was assessed, and a random-effects model meta-analysis was used to determine the risk difference (RD). We assessed the pooled rate by using a random-effects model. This study was registered in PROSPERO (CRD 42021267432). RESULTS: Of 3996 studies, 83 were eligible for full-text screening and 41 were included in the meta-analysis. In patients with active TB, the sensitivity of QFT-Plus was compared to that of QFT-GIT and T-SPOT.TB, respectively, and no statistically differences were found. In populations with a very low risk of TB exposure, the specificity of QFT-Plus was compared with that of QFT-GTI and T-SPOT.TB, respectively, and no statistically differences were found. Two studies were eligible to compare the specificity of the QFT-Plus test with that of the TST test, and the pooled RD was 0.12 (95% CI 0.02 to 0.22). In high-risk populations, 18 studies were eligible to compare the positive rate of the QFT-Plus test with that of the QFT-GIT test, and the pooled RD was 0.02 (95% CI 0.01 to 0.03). The positive rate of QFT-Plus was compared with that of T-SPOT.TB and TST groups, and no statistically differences were found. CONCLUSIONS: The diagnostic performance of QFT-Plus was similar to that of QFT-GIT and T-SPOT.TB, but was slightly more specific than TST.

Reduced capability of refrigerated white rhinoceros whole blood to produce interferon-gamma upon mitogen stimulation.

Ante-mortem surveillance for Mycobacterium bovis (M. bovis) infection in the Kruger National Park (KNP) rhinoceros population currently relies on results from the QuantiFERON-TB Gold (In-Tube) Plus (QFT)-interferon gamma (IFN-γ) release assay (IGRA). However, same-day processing of rhinoceros blood samples for this test is a logistical challenge. Therefore, a pilot study was performed to compare mitogen-stimulated and unstimulated IFN-γ concentrations in plasma from rhinoceros whole blood processed within 6 h of collection or stored at 4°C for 24 and 48 h prior to incubation in QFT tubes. Replicate samples of heparinized whole blood from seven subadult male white rhinoceros were used. Results showed no change in IFN-γ levels in unstimulated samples, however the relative concentrations of IFN-γ (based on optical density values) in mitogen plasma decreased significantly with increased time blood was stored post-collection and prior to QFT stimulation. These findings support a need for same-day processing of rhinoceros blood samples for QFT-IGRA testing as per the current practice. Further investigation using TB-antigen stimulated samples is warranted to properly assess the impact of blood storage on TB test results in rhinoceros.

Evaluation of tuberculosis diagnostic biomarkers in immunocompromised hosts based on cytokine levels in QuantiFERON-TB Gold Plus.

Tuberculosis (TB) remains a serious health concern globally. QuantiFERON-TB (QFT) is a diagnostic tool for TB detection, and its sensitivity is reduced in immunocompromised hosts with low T lymphocyte counts or abnormal T cell function. This study aimed to evaluate the correlation between T cell and cytokine levels in patients with active TB using QFT-Plus. Forty-five patients with active TB were enrolled, and the cytokines in QFT-Plus tube supernatants were quantified using the MAGPIX System. CD4+ T cell count negatively correlated with patient age (p < 0.001, r = -0.51). The levels of TB1-responsive interleukin-1 receptor antagonist (IL-1Ra) and IL-2 correlated with CD4+ T cell count, whereas the levels of TB2-responsive IL-1Ra and IFN-γ-induced protein 10 correlated with both CD4+ and CD8+ T cell counts. Cytokines that correlated with CD4+ and CD8+ T cell counts might not be suitable TB diagnostic biomarkers in immunocompromised hosts. Notably, cytokines that did not correlate with the T cell counts, such as monocyte chemoattractant protein-1, might be candidate biomarkers for TB in immunocompromised hosts. Our findings might help improve TB diagnosis, which could enable prompt treatment and minimize poor disease outcomes.

The Pitfalls of Mining for QuantiFERON Gold in Severely Ill Patients With COVID-19.

Objective: To assess the proportion of indeterminate QuantiFERON-TB Gold Plus (QFT-Plus) results in patients admitted for severe coronavirus disease 2019 (COVID-19) pneumonia and evaluate the factors associated with indeterminate QFT-Plus results. Patients and Methods: Data on COVID-19 admissions at Mayo Clinic in Florida were extracted between October 13, 2020, and September 20, 2021, and data from a prepandemic cohort were extracted between October 13, 2018, and September 20, 2019. A secondary analysis of the COVID-19 cohort was performed using gradient boosting modeling to generate variable importance and SHapley Additive exPlanations plots. Results: Our findings demonstrated more indeterminate QFT-Plus test results in patients hospitalized for severe COVID-19 infection than in patients without COVID-19 (139 of 495, 28.1%). The factors associated with indeterminate QFT-Plus test results included elevated levels of C-reactive protein, ferritin, lactate dehydrogenase and interleukin-6 and included lower levels of leukocyte, lymphocyte, and platelet counts. Conclusion: The patients with severe COVID-19 had a higher likelihood of indeterminate QFT-Plus results, which were associated with elevated levels of inflammatory markers consistent with severe infection. Interferon-gamma release assay screening tests are likely confounded by COVID-19 infection itself, limiting the screening ability for latent tuberculosis infection reactivation. Indeterminate QFT-Plus results may also require follow-up QFT-Plus testing after patient recovery from COVID-19, increasing the cost and complexity of medical decision making and management. Additional risk assessments may be needed in this patient population for screening for latent tuberculosis infection in patients with severe COVID-19.

QuantiFERON-TB Gold Plus Assay in Patients With Latent vs. Active Tuberculosis in a Low Incidence Setting: Level of IFN-γ, CD4/CD8 Responses, and Release of IL-2, IP-10, and MIG.

Objectives: We analyzed the results of the QuantiFERON Glod Plus assay (QFT) and cytokine patterns associated with active tuberculosis (ATB) among patients with positive QFT. Methods: A total of 195 patients are QFT-positive, among which 24 had an ATB and 171 had a latent tuberculosis infection (LTBI). Interferon-gamma (IFN-γ) secretion was analyzed relative to interleukin-2 (IL-2), IFN-γ inducible protein or CXCL-10 (IP-10), and monokine induced by IFN-γ or CXCL-9 (MIG) secretion, and then compared between two sets of peptide antigens [tube 1 - cluster of differentiation 4 (CD4+) T cell stimulation; tube 2 - CD4+/CD8+ T cell response]. Results: Higher IFN-γ responses were measured in the ATB group (p = 0.0089). The results showed that there was a lower ratio of tube 1/tube 2 IFN-γ concentrations in the ATB group (p = 0.0009), and a median [interquartile ranges (IQR)] difference between the two sets at -0.82 IU/ml (-1.67 to 0.18) vs. -0.07 IU/ml (-0.035 to 0.11, p < 0.0001) in the ATB group compared to the LTBI group, respectively. In addition, patients with low ratios of IL-2/IFN-γ, IP-10/IFN-γ, and MIG/IFN-γ were much more likely to have ATB. Conclusion: High levels of IFN-γ secretion, preferential IFN-γ response in tube 2, and lower secretion of IL-2, IP-10, and MIG release relative to IFN-γ secretion were more likely observed in subjects with ATB. These features of T cell response may be helpful in low prevalence settings to suspect ATB in patients tested positive for IFN-γ release assays (IGRA).

Prevalence of latent tuberculosis infection among pre-clinical and clinical medical students using QuantiFERON-TB gold plus and tuberculin skin test at a teaching hospital in Thailand: A cross-sectional study.

BACKGROUND: Healthcare workers are considered to be at a higher risk of acquiring tuberculosis (TB) infection than the general population. Clinical medical students are part of the healthcare team and clinical practice are done during their clinical rotation. They could be exposed to similar occupational risks as the healthcare workers. Most students who become infected have latent tuberculosis infection (LTBI) and may not exhibit any clinical symptoms. Some students with LTBI can progress to TB disease during clinical rotations in the hospitals. Therefore, screening for LTBI in this population represents hospital aspect of public health strategy and infection control in medical school in high TB burden countries. OBJECTIVE: We aimed to determine the prevalence of LTBI among fourth-year medical students and sixth-year medical students by using QuantiFERON-TB Gold Plus (QFT-Plus) and Tuberculin Skin Test (TST). METHODS: A cross-sectional study of fourth-year medical students (n = 73) and sixth-year medical students (n = 85) was conducted at the School of Medicine, Chulalongkorn University, Bangkok, Thailand. The medical students (n = 158) who met the eligibility criteria were recruited into the study. LTBI was detected by using QFT-Plus and some of the participants had a tuberculin skin test (TST). The TST was interpreted after 48-72 h. The participants who tested positive by QFT-Plus were considered to have LTBI. Demographic information and data on occupational TB exposure were collected via a questionnaire. A multivariate logistic regression was used to test for associations between independent variables and results of the QFT-Plus. RESULTS: A total of 158 participants were included in this study. The overall prevalence of LTBI was 6.3% (n = 10) as determined by QFT-Plus. The LTBI prevalence was higher in the sixth-year medical students (9.4%) compared to the fourth-year medical students (2.7%). Higher risk of LTBI was associated with sixth-year medical students (odds ratio, 3.69 [95%CI, 0.75-17.96]), but this was not significant. Moreover, history of occupational TB exposure without PPE yielded an odds ratio of 2.98 [95%CI, 0.68-13.12] but it was not statistically significant due to the small sample size. One hundred thirty-nine (88%) participants were BCG vaccinated as per the national vaccination requirements. No abnormal chest X-rays were found for any of the positive participants. Of the 158 participants, 41 (25.9%) of them had TST. Of the 41 participants, 6 (14.6%) tested positive at a cut-off of ≥ 10 mm for TST, which was concordant with QFT-Plus results. The agreement between the two tests was 0.57 using kappa coefficients. CONCLUSION: The screening of TB infection in new healthcare workers (HCWs), especially medical students, is essential to reduce future nosocomial TB incidences in the hospitals. This study showed that there was a high prevalence of LTBI among sixth-year medical students compared to fourth-year medical students. Our results suggest that tendency of higher LTBI prevalence might be associated with advanced clinical years, thus tailored public health education strategy and infection control in tertiary care hospitals for new healthcare workers in TB endemic countries may prevent nosocomial TB disease from developing in the future. Therefore, active surveillance should be done for all new HCWs, and TB preventive therapy should be administered to recent converters.

In-hospital blood collection increases the rate of indeterminate results in interferon-gamma release assays.

BACKGROUND: The interferon (IFN)-γ release assay (IGRA) has recently been established as a method to evaluate the infection status of tuberculosis instead of the tuberculin skin test. However, indeterminate results can create challenges to interpretation. The IGRA has been available in Japan since 2005, including the recently launched QuantiFERON-TB Gold Plus (QFT-plus) assay. OBJECTIVES: The aim of this study was to investigate the clinical features and predictors of indeterminate results by the QFT-plus test in routine practice. METHODS: This was a cross-sectional study of 1258 patients. Multivariate logistic regression models were employed to investigate the clinical factors related to indeterminate results by the QFT-plus. RESULTS: Overall, 91.8% of results were found to be conclusive and 8.2% were indeterminate. The QFT-plus indeterminate results were predominantly due to a low level of IFN-γ production by mitogens. Multivariate analysis indicated that an indeterminate result was significantly associated with age, sex, corticosteroid use, autoimmune disease, and inpatient setting. CONCLUSION: Certain types of individuals are at higher risk of an indeterminate IGRA result. The QFT-plus test for hospitalized patients should be avoided as much as possible, and it is better to perform the test for those patients in outpatient settings.