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

Objectives: To determine the cost-effectiveness of the QuantiFERON-TB Gold Plus (QFT-Plus) test versus the tuberculin skin test in diagnosing latent tuberculosis infection in immunocompetent subjects in the context of the Colombian healthcare system., Methods: A hypothetical cohort of 2000 immunocompetent adults vaccinated with Bacillus Calmette-Guérin at birth who are asymptomatic for tuberculosis disease was simulated and included in a decision tree over a horizon of <1 year. The direct healthcare costs related to tests, antituberculosis treatment, and medical care were considered, and diagnostic performance was used as a measure of effectiveness. The incremental cost-effectiveness ratio (ICER) was estimated, and univariate deterministic and probabilistic sensitivity analyses were carried out using 5000 simulations. The currency was the US dollar for the year 2022, with a cost-effectiveness threshold of $6666 USD (1 gross domestic product per capita for 2022)., Results: QFT-Plus was cost-effective with an ICER of $5687 USD for each correctly diagnosed case relative to a threshold of $6666 USD. In the deterministic analysis, QFT-Plus was cost-effective in half of the proposed scenarios. The variable that most affected the ICER was the prevalence of latent tuberculosis and test sensitivities. In the probabilistic analysis, QFT-Plus was cost-effective in 54.74% of the simulated scenarios, and tuberculin skin test was dominant in 13.84%., Conclusions: The study provides evidence of the cost-effectiveness of QFT-Plus compared with the tuberculin skin test in diagnosing latent tuberculosis infection in immunocompetent adults in the Colombian context., Competing Interests: Author Disclosures Author disclosure forms can be accessed in the Supplemental Material section., (Copyright © 2023 International Society for Health Economics and Outcomes Research. Published by Elsevier Inc. All rights reserved.)

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

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

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

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

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

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

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

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

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

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

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

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

Rationale: To identify infected contacts of tuberculosis (TB) cases, the UK National Institute for Health and Care Excellence (NICE) recommended the addition of IFN-γ release assays (IGRA) to the tuberculin skin test (TST) in its 2006 TB guidelines. Treatment for TB infection was no longer recommended for children who screened TST-positive but IGRA-negative., Objectives: We performed a cohort study to evaluate the risk of TB disease in this group., Methods: Children exposed to an infectious case of TB in their household were recruited from 11 pediatric TB clinics. TST and IGRA were performed at baseline, with IGRA repeated at 8 weeks and TST repeated if initially negative. Children were treated according to 2006 NICE guidelines and followed for 24 months., Measurements and Main Results: Of 431 recruited children, 392 completed the study. We diagnosed 48 (12.2%) cases of prevalent TB disease, 105 (26.8%) with TB infection, and 239 (60.9%) without TB infection or disease. Eighteen children aged 2 years and above had a positive TST but persistently negative IGRA. None received TB infection treatment and none developed TB disease. Ninety (26.1%) children qualified for TB infection treatment according to 2006 NICE guidelines. In contrast, 147 (42.7%) children would have qualified under revised NICE guidance, issued in 2016., Conclusions: In this low-prevalence setting we saw no incident cases of TB disease in children who were TST-positive but IGRA-negative and did not receive treatment for TB infection. Following the latest NICE guidance, significantly more children will require medication.

Background: T-cell Xtend (TCX) was introduced to extend the blood storage time for T-SPOT.TB test, a widely used commercial interferon gamma release assay (IGRA) for rapid in vitro tuberculosis., Methods: A total of 99 Uyghur suspected tuberculosis patients were recruited in this study. T-SPOT.TB test was performed with fresh blood (controls), 36 hours delayed blood and delayed and TCX-treated (at 36 hours) blood from each patient, respectively., Results: White blood cells and lymphocytes proportion in peripheral blood mononuclear cells s and spot-forming cells in positive control wells decreased significantly in delayed blood samples when compared with controls, while this decrease was not detected in TCX-treated group. In the 58 patients with paired T-SPOT.TB results of three groups of samples, a higher positive rate was observed in TCX-treated group than both in controls and untreated group (41.4% vs 37.9% and 25.9%). The concordance of T-SPOT.TB results between the treated group and controls was 0.856, whereas the agreement between controls and untreated group was unsatisfactory (0.649). In the 23 elderly patients (>70 years old) with paired T-SPOT.TB results of controls and TCX group, treated group showed a non-significant trend toward higher positive rate than controls (43.5% vs 26.1%, P=.22). Meanwhile, TCX treatment reduced the risk of false negative T-SPOT.TB results in the elderly population., Conclusion: Deterioration of blood sample caused by long storage time can be neutralized by TCX treatment. The results provide data for the utility of TCX in a novel population and in Asian region, and reveal the potential of TCX to improve the accuracy of T-SPOT.TB test in elderly population., (© 2017 Wiley Periodicals, Inc.)

Background: Clinical accuracy of IGRAs remains unclear on patients with immune-mediated inflammatory diseases (IMIDs). Here, we assess the impact of immunosuppressants and IMIDs on QuantiFERON-TB Gold In-Tube (QFN-G-IT) and T-SPOT.TB accuracy., Methods: Patients with IMIDs who required latent tuberculosis infection (LTBI) screening were enrolled and classified into: (i) 50 patients with inflammatory rheumatic diseases, (ii) 50 patients with psoriasis and (iii) 30 patients with Crohn's disease. A total of 44 healthy individuals without immunosuppression were also included as controls. Tuberculin skin test (TST), T-SPOT.TB and QFN-G-IT assays were performed. IGRAs were performed following manufacturer's instructions., Results: Immunosuppressant's intake was more frequent on patients with Crohn's disease and psoriasis. Positive IGRAs and TST results were reduced in Crohn's disease patients, whereas rate of indeterminate T-SPOT.TB results was increased in this group with respect to the other IMIDs analysed and controls. When IFN-γ response was studied, the levels of this cytokine after mitogen stimulation were significantly lower in Crohn's and inflammatory rheumatic diseases than in psoriasis. Interestingly, psoriatic patients were the only ones not receiving corticosteroids. Furthermore, a negative correlation was observed between the IFN-γ secreted after mitogen stimulation and corticosteroids dose., Conclusions: IMIDs seem to negatively affect the clinical accuracy of IGRAs, being Crohn's disease patients the most affected individuals due to their concomitant drug-profile and impaired immune response.

T-SPOT.TB didn't perform a perfect diagnosis for active tuberculosis (ATB), and some factors may influence the results. We did this study to evaluate possible factors associated with the sensitivity and specificity of T-SPOT.TB, and the diagnostic parameters under varied conditions. Patients with suspected ATB were enrolled prospectively. Influencing factors of the sensitivity and specificity of T-SPOT.TB were evaluated using logistic regression models. Sensitivity, specificity, predictive values (PV), and likelihood ratios (LR) were calculated with consideration of relevant factors. Of the 865 participants, 205 (23.7%) had ATB, including 58 (28.3%) microbiologically confirmed TB and 147 (71.7%) clinically diagnosed TB. 615 (71.7%) were non-TB. 45 (5.2%) cases were clinically indeterminate and excluded from the final analysis. In multivariate analysis, serous effusion was the only independent risk factor related to lower sensitivity (OR = 0.39, 95% CI: 0.18-0.81) among patients with ATB. Among non-TB patients, age, TB history, immunosuppressive agents/glucocorticoid treatment and lymphocyte count were the independent risk factors related to specificity of T-SPOT.TB. Sensitivity, specificity, PV+, PV-, LR+ and LR- of T-SPOT.TB for diagnosis of ATB were 78.5%, 74.1%, 50.3%, 91.2%, 3.0 and 0.3, respectively. This study suggests that influencing factors of sensitivity and specificity of T-SPOT.TB should be considered for interpretation of T-SPOT.TB results.

Paratuberculosis vaccination in cattle has been restricted due to its possible interference with the official diagnostic methods used in tuberculosis eradication programs. To overcome this drawback, new possibilities to detect Mycobacterium bovis infected cattle in paratuberculosis vaccinated animals were studied under experimental conditions. Three groups of 5 calves each were included in the experiment: one paratuberculosis vaccinated group, one paratuberculosis vaccinated and M. bovis infected group and one M. bovis infected group. The performance of the IFN-gamma release assay (IGRA) and the skin test using conventional avian and bovine tuberculins (A- and B-PPD) but also other more specific antigens (ESAT-6/CFP10 and Rv3615c) was studied under official and new diagnostic criteria. Regarding the IGRA of vaccinated groups, when A- and B-PPD were used the sensitivity reached 100% at the first post-challenge sampling, dropping down to 40-80% in subsequent samplings. The sensitivity for the specific antigens was 80-100% and the specificity was also improved. After adapting the diagnostic criteria for the conventional antigens in the skin test, the ability to differentiate between M. bovis infected and non-infected animals included in paratuberculosis vaccinated groups was enhanced. Taking for positive a relative skin thickness increase of at least 100%, the single intradermal test specificity and sensitivity yielded 100%. The comparative intradermal test was equally accurate considering a B-PPD relative skin increase of at least 100% and greater than or equal to that produced by A-PPD. Using the specific antigens as a proteic cocktail, the specificity and sensitivity reached 100% considering the new relative and absolute cut-offs in all experimental groups (Δ≥30% and Δmm ≥ 2, respectively). Results suggest that the interference caused by paratuberculosis vaccination in cattle could be completely overcome by applying new approaches to the official tuberculosis diagnostic tests., Competing Interests: The authors have declared that no competing interests exist.

QuantiFERON-TB Gold IT analyses interferon-γ release from CD4(+) T cells after stimulation with specific tuberculosis (TB) antigens. Its sensitivity is approximately 80% for active TB. A new test generation (QFTGplus) also analyses the response of CD8(+) T cells. We investigated both test generations in a direct head-to-head comparison in a German pulmonary hospital. Sensitivity rates for active TB were identical, no matter whether diagnosis was bacteriologically confirmed or not., (Copyright © 2016 European Society of Clinical Microbiology and Infectious Diseases. Published by Elsevier Ltd. All rights reserved.)

Intestinal tuberculosis (ITB) remains prevalent in Asia. An interferon-γ assay (QuantiFERON-TB gold test [QFT]) is considered to be an effective supplementary tool for diagnosing ITB. We retrospectively analyzed the clinical features of ITB patients based on the initial results of QFT. A total of 109 patients with ITB were enrolled, and 82 patients (75.2%) showed positive QFT results. In the QFT-positive group, the mean age (44.1±12.0 years) was significantly higher than that in the QFT-negative group (37.0±14.8, p=0.0096). Abdominal pain (p=0.006) and diarrhea (p=0.030) were more frequent in the QFT-negative group. Further, C-reactive protein (CRP) levels were significantly higher in the QFTnegative group (6.4±9.9 mg/dL) than in the QFT-positive group (1.3±2.3, p<0.001). Multivariate analysis confirmed that younger age (p=0.016), diarrhea (p=0.042), and high levels of CRP (p=0.029) were independent predictors of QFTnegative results in patients with ITB. These results suggest that prior exposure to TB, reflected by QFT positivity, may cause mild inflammation in patients with ITB.

Currently, there are two types of interferon-gamma release assays (IGRAs) in use for the detection of tuberculosis (TB) infection, the QuantiFERON-TB Gold In-Tube test (GFT-GIT) and T-SPOT.TB. Owing to contradictory reports regarding whether the results of these IGRAs are affected by the age of the patient, we aimed to determine if these two tests have age-related differences in sensitivity. We retrospectively reviewed the medical records of diagnosed TB patients who were tested using either QFT-GIT or T-SPOT.TB from February 2008 to December 2013. The positivity of the two tests was analyzed and compared with true TB infection, which was defined as active TB based on either a positive Mycobacterium culture or a positive TB polymerase chain reaction. The QFT-GIT group included 192 TB patients, and the T-SPOT.TB group included 212 TB patients. Of the patients with pulmonary TB, 76 (39.6%) were in the QFT-GIT group and 143 (67.5%) in the T-SPOT.TB group. The overall sensitivity was 80.2% for QFT-GIT and 91.0% for T.SPOT.TB. The sensitivities of QFT-GIT and T-SPOT.TB according to age group were as follows: <29 years, 93.3% and 96.7%; 30-49 years, 86.5% and 94.7%; 50-69 years, 76.8% and 87.5%; and >70 years, 68.3% and 85.7%, respectively. The trend of age-related changes in sensitivity was significant for both QFT-GIT (p = 0.004) and T.SPOT.TB (p = 0.039). However, only QFT-GIT was significantly related to age in the multivariate analysis. QFT-GIT, but not T-SPOT.TB, was significantly affected by patient age.

Background: Tuberculosis (TB), caused by Mycobacterium tuberculosis (MTB) [(Zopf 1883) Lehmann and Neumann 1896], is a major cause of morbidity and mortality. Nearly one-third of the world's population is infected with MTB; TB has an annual incidence of 9 million new cases and each year causes 2 million deaths worldwide., Objectives: To investigate the clinical effectiveness and cost-effectiveness of screening tests [interferon-gamma release assays (IGRAs) and tuberculin skin tests (TSTs)] in latent tuberculosis infection (LTBI) diagnosis to support National Institute for Health and Care Excellence (NICE) guideline development for three population groups: children, immunocompromised people and those who have recently arrived in the UK from high-incidence countries. All of these groups are at higher risk of progression from LTBI to active TB., Data Sources: Electronic databases including MEDLINE, EMBASE, The Cochrane Library and Current Controlled Trials were searched from December 2009 up to December 2014., Review Methods: English-language studies evaluating the comparative effectiveness of commercially available tests used for identifying LTBI in children, immunocompromised people and recent arrivals to the UK were eligible. Interventions were IGRAs [QuantiFERON(®)-TB Gold (QFT-G), QuantiFERON(®)-TB Gold-In-Tube (QFT-GIT) (Cellestis/Qiagen, Carnegie, VA, Australia) and T-SPOT.TB (Oxford Immunotec, Abingdon, UK)]. The comparator was TST 5 mm or 10 mm alone or with an IGRA. Two independent reviewers screened all identified records and undertook a quality assessment and data synthesis. A de novo model, structured in two stages, was developed to compare the cost-effectiveness of diagnostic strategies., Results: In total, 6687 records were screened, of which 53 unique studies were included (a further 37 studies were identified from a previous NICE guideline). The majority of the included studies compared the strength of association for the QFT-GIT/G IGRA with the TST (5 mm or 10 mm) in relation to the incidence of active TB or previous TB exposure. Ten studies reported evidence on decision-analytic models to determine the cost-effectiveness of IGRAs compared with the TST for LTBI diagnosis. In children, TST (≥ 5 mm) negative followed by QFT-GIT was the most cost-effective strategy, with an incremental cost-effectiveness ratio (ICER) of £18,900 per quality-adjusted life-year (QALY) gained. In immunocompromised people, QFT-GIT negative followed by the TST (≥ 5 mm) was the most cost-effective strategy, with an ICER of approximately £18,700 per QALY gained. In those recently arrived from high TB incidence countries, the TST (≥ 5 mm) alone was less costly and more effective than TST (≥ 5 mm) positive followed by QFT-GIT or T-SPOT.TB or QFT-GIT alone., Limitations: The limitations and scarcity of the evidence, variation in the exposure-based definitions of LTBI and heterogeneity in IGRA performance relative to TST limit the applicability of the review findings., Conclusions: Given the current evidence, TST (≥ 5 mm) negative followed by QFT-GIT for children, QFT-GIT negative followed by TST (≥ 5 mm) for the immunocompromised population and TST (≥ 5 mm) for recent arrivals were the most cost-effective strategies for diagnosing LTBI that progresses to active TB. These results should be interpreted with caution given the limitations identified. The evidence available is limited and more high-quality research in this area is needed including studies on the inconsistent performance of tests in high-compared with low-incidence TB settings; the prospective assessment of progression to active TB for those at high risk; the relative benefits of two-compared with one-step testing with different tests; and improved classification of people at high and low risk for LTBI., Study Registration: This study is registered as PROSPERO CRD42014009033., Funding: The National Institute for Health Research Health Technology Assessment programme.

Interferon-gamma (IFN-γ) release assays (IGRAs) are used to detect cellular immune recognition of Mycobacterium tuberculosis The chemokine IFN-γ-inducible protein 10 (IP-10) is an alternative diagnostic biomarker to IFN-γ. Several conditions interfere with IGRA test performance. We aimed to assess the possible influence of Plasmodium falciparum infection on the IGRA test QuantiFERON-TB GOLD® In-Tube (QFT) test and an in-house IP-10 release assay. In total, 241 Tanzanian adults were included; 184 patients with uncomplicated malaria (88 human immunodeficiency virus [HIV] coinfected) and 57 HIV-infected patients without malaria infection. Malaria was treated with artemether-lumefantrine (Coartem®). QFT testing was performed before initiation of malaria treatment and at days 7 and 42. In total, 172 patients completed follow-up. IFN-γ and IP-10 was measured in QFT supernatants. We found that during malaria infection IFN-γ and IP-10 levels in the unstimulated samples were elevated, mitogen responsiveness was impaired, and CD4 cell counts were decreased. These alterations reverted after malaria treatment. Concurrent malaria infection did not affect QFT test results, whereas there were more indeterminate IP-10 results during acute malaria infection. We suggest that IGRA and IP-10 release assay results of malaria patients should be interpreted with caution and that testing preferably should be postponed until after malaria treatment., (© The American Society of Tropical Medicine and Hygiene.)

Background: Tuberculosis (TB) is a global public health problem, causing morbidity and mortality in adults and children. The most reliable diagnostic tools currently available are the in vivo Tuberculin Skin Test (TST) and the ex vivo Interferon-γ release assays (IGRAs). Several clinical, radiological, and bacteriological features make the detection of active (overt disease) TB in children difficult. Although recently developed immunological assays such as QuantiFERON-TB Gold In-Tube (QFT-IT) and T-SPOT®.TB are commonly used to identify active TB in adults, different evidence is required for diagnosis in children. The purpose of this study was to reassess the sensitivity and specificity of IGRAs in detecting microbiologically confirmed active TB in immunocompetent children., Methods: A systematic review and meta-analysis of studies reporting on the diagnostic accuracy of tests for TB in immunocompetent children aged 0-18 years, with confirmation by positive M. tuberculosis cultures, were undertaken. Electronic databases were searched up to September 2015 and study quality assessment was performed using QUADAS-2., Results: Fifteen studies were included in our meta-analysis. Results showed that there were no significant differences in sensitivity between TST (88.2%, 95% confidence interval [CI] 79.4-94.2%), QFT-IT (89.6%, 95% CI 79.7-95.7%) and T SPOT (88.5%, 95% CI 80.4-94.1%). However, both QFT-IT (95.4%, 95% CI 93.8-96.6%) and T-SPOT (96.8%, 95% CI 94.2-98.5%) have significantly higher specificity than TST (86.3%, 95% CI 83.9-88.6%)., Conclusions: QFT-IT and T-SPOT have higher specificity than TST for detecting active TB cases in immunocompetent children.

Background: Tuberculosis (TB) is one of the most serious infectious diseases globally and has high mortality rates. A variety of diagnostic tests are available, yet none are wholly reliable. Serum cytokines, although significantly and frequently induced by different diseases and thus good biomarkers for disease diagnosis and prognosis, are not sufficiently disease-specific. TB-specific antibody detection, on the other hand, has been reported to be highly specific but not sufficiently sensitive. In this study, our aim was to improve the sensitivity and specificity of TB diagnosis by combining detection of TB-related cytokines and TB-specific antibodies in peripheral blood samples., Methods: TB-related serum cytokines were screened using a human cytokine array. TB-related cytokines and TB-specific antibodies were detected in parallel with microarray technology. The diagnostic performance of the new protocol for active TB was systematically compared with other traditional methods., Results: Here, we show that cytokines I-309, IL-8 and MIG are capable of distinguishing patients with active TB from healthy controls, patients with latent TB infection, and those with a range of other pulmonary diseases, and that these cytokines, and their presence alongside antibodies for TB-specific antigens Ag14-16kDa, Ag32kDa, Ag38kDa and Ag85B, are specific markers for active TB. The diagnostic protocol for active TB developed here, which combines the detection of three TB-related cytokines and TB-specific antibodies, is highly sensitive (91.03%), specific (90.77%) and accurate (90.87%)., Conclusions: Our results show that combining detection of TB-related cytokines and TB-specific antibodies significantly enhances diagnostic accuracy for active TB, providing greater accuracy than conventional diagnostic methods such as interferon gamma release assays (IGRAs), TB antibody Colloidal Gold Assays and microbiological culture, and suggest that this diagnostic protocol has potential for clinical application.

Background: Interferon-γ release assays such as the QuantiFERON-TB Gold In-Tube Test (QFT-GIT) are designed to detect Mycobacterium tuberculosis infections, whether latent or manifesting as disease. However, a substantial number of persons with culture-confirmed tuberculosis (TB) have negative QFT-GITs. Information on host factors contributing to false-negative and indeterminate results are limited., Methods: A multicenter retrospective cohort study was performed with 1,264 culture-confirmed TB patients older than 18 years who were subjected to the QFT-GIT at one of the six hospitals between May 2007 and February 2014. Patients with human immunodeficiency virus infection were excluded. Clinical and laboratory data were collected in South Korea., Results: Of all patients, 87.6% (1,107/1,264) were diagnosed with pulmonary TB and 12.4% (157/1,264) with extrapulmonary TB. The rate of negative results was 14.4% (182/1,264). The following factors were highly correlated with false-negative results in the QFT-GIT: advanced age (age ≥ 65 years, odds ratio [OR] 1.57, 95% confidence interval [CI] 1.03-2.39), bilateral disease as determined by chest radiography (OR 1.75, 95% CI 1.13-2.72), malignancy (OR 2.42, 95% CI 1.30-4.49), and lymphocytopenia (total lymphocyte count < 1.0 × 109/L, OR 1.86, 95% CI 1.21-2.87)., Conclusions: Consequently, QFT-GIT results need to be interpreted with caution in patients with these host risk factors such as the elderly, bilateral disease on chest radiography, or malignancy, or lymphocytopenia.

Background: Few data relate interferon-γ-release-assay results in children to source case sputum status, the best predictor of infectiousness of tuberculosis (TB) patients. We evaluated the QuantiFERON-Gold-in-tube assay (QFT) and tuberculin skin test (TST) in children with different types of TB exposure., Methods: The TST and QFT were performed in referred TB-exposed children and adolescents who had not undergone prior TST screening (tested in parallel), and the QFT was performed in referred TST-positive individuals. Source case characteristics were obtained from referring public health units. We excluded children with known immunocompromising conditions and those known to have TB disease at the time of evaluation., Results: For 103 patients tested in parallel, overall test agreement was very good in the Bacillus Calmette-Guerein (BCG) unimmunized contacts (κ = 0.83) and contacts of household smear-positive (HS+) cases (κ = 0.67), but test agreement was poor in those with lower-risk contact (κ = 0.34). Only 3 of 59 HS+ patients were QFT-positive and TST-negative. On multivariate analysis, a positive QFT was strongly associated with HS+ exposure (odds ratio [OR], 6.6; 95% confidence interval [CI], 2.2-20]) but not BCG; and a positive TST was associated with BCG alone. For 92 referred TST-positive individuals, the QFT was negative in 21% of HS+ contacts, 65% of lower-risk contacts (OR, 6.8; 95% CI, 1.9-25), and 82% of the patients with unknown contact history (OR, 15.5; 95% CI, 5-54). Application of the Canadian 2010 guidelines would exclude from treatment 43 (72%) of the 73 TST+, QFT- patients., Conclusions: For close contacts of HS+ individuals, the QFT added little sensitivity to the TST for detection of TB infection. The QFT correlated much better with exposure than the TST, especially in BCG-immunized children, and it has the greatest potential benefit for evaluation of those at lower risk of latent TB infection., (© The Author 2014. Published by Oxford University Press on behalf of the Pediatric Infectious Diseases Society. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.)

Background/aim: HIV infection is a risk factor for re-activation of latent tubercolosis infection (LTBI). In recent years new blood tests for the detection of TB infection have been developed: Quantiferon TB Gold in Tube and TSPOT TB, which are interferon-γ releasing assays (IGRAs), have improved the identification of LTBI. In our study we have compared IGRAs and TST in HIV-positive patients with different settings of immunodeficiency., Patients and Methods: 98 consecutive HIV patients were recruited. They underwent a blood draw, a chest radiography and a tuberculin skin test. The HIV infection setting was detected and IGRAs were carried-out. Five patients showed a complete correspondence of TST, TSPOT-TB and QFT-IT. Discordant results were observed in patients testing positive to IGRAs but negative to TST. Only 2 patients showed positive TST and negative IGRAs., Conclusion: Our study showed a poor concordance between tuberculin skin test and IGRAs, mainly in patients with a low CD4 cell count., (Copyright © 2015 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved.)

Interferon-gamma (IFN-γ) release assays (IGRAs) such as the Quantiferon Gold In-tube test are in vitro assays that measure IFN-γ release from T cells in response to M. tuberculosis (Mtb)-specific antigens. Unlike the tuberculin skin test (TST), IGRA is specific and able to distinguish Mtb-infection from BCG vaccination. In this study we evaluated the concordance between TST and IGRA and the efficacy of IGRA in diagnosing new Mtb infection in household contacts (HHC) of pulmonary tuberculosis (PTB) cases. A total of 357 HHC of TB cases in Vitória, Brazil were studied. A TST was performed within 2 weeks following enrollment of the HHC and if negative a second TST was performed at 8-12 weeks. HHC were categorized as initially TST positive (TST+), persistently TST negative (TST-), or TST converters (TSTc), the latter representative of new infection. IGRA was performed at 8-12 weeks following enrollment and the test results were positive in 82% of TST+, 48% of TSTc, and 12% of TST-, indicating poor concordance between the two test results among HHC in each category. Evaluating CXCL10 levels in a subset of IGRA supernatants or lowering the IGRA cutoff value to define a positive test increased agreement between TST and IGRA test results. However, ROC curves demonstrated that this resulted in a trade-off between sensitivity and specificity of IGRA with respect to TST. Together, the findings suggest that until the basis for the discordance between TST and IGRA is fully understood, it may be necessary to utilize both tests to diagnose new Mtb infection in recently exposed HHC. Operationally, in IGRA negative HHC, it may be useful to employ a lower cutoff value for IGRA to allow closer monitoring for potential conversion.

Background: Identifying latent tuberculosis infection (LTBI) in people migrating from TB endemic regions to low incidence countries is an important control measure. However, no prospective longitudinal comparisons between diagnostic tests used in such migrant populations are available., Objectives: To compare commercial interferon (IFN)-gamma release assays (IGRAs) and the tuberculin skin test (TST) for diagnosing LTBI in a migrant population, and the influence of antecedent TST and LTBI treatment on IGRA performance., Materials and Methods: This cohort study, performed from February to September 2012, assessed longitudinal IGRA and TST responses in Nepalese military recruits recently arrived in the UK. Concomitant T-SPOT.TB, QFT-GIT and TST were performed on day 0, with IGRAs repeated 7 and 200 days later, following treatment for LTBI if necessary., Results: 166 Nepalese recruits were prospectively assessed. At entry, 21 individuals were positive by T-SPOT.TB and 8 individuals by QFT-GIT. There was substantial agreement between TST and T-SPOT.TB positives at baseline (71.4% agreement; κ = 0.62; 95% CI:0.44-0.79), but only moderate concordance between positive IGRAs (38.1% agreement; κ = 0.46; 95% CI:0.25-0.67). When reassessed 7 days following TST, numbers of IGRA-positive individuals changed from 8 to 23 for QFT-GIT (p = 0.0074) and from 21 to 23 for T-SPOT.TB (p = 0.87). This resulted in an increase in IGRA concordance to substantial (64.3% agreement; κ = 0.73; 95% CI:0.58-0.88). Thus, in total on day 0 and day 7 after testing, 29 out of 166 participants (17.5%) provided a positive IGRA and of these 13 were TST negative. Two hundred days after the study commenced and three months after treatment for LTBI was completed by those who were given chemoprophylaxis, 23 and 21 participants were positive by T-SPOT.TB or QFT-GIT respectively. When individual responses were examined longitudinally within this population 35% of the day 7 QFT-GIT-positive, and 19% T-SPOT.TB-positive individuals, were negative by IGRA. When the change in the levels of secreted IFN-γ was examined after chemoprophylaxis the median levels were found to have fallen dramatically by 77.3% from a pre-treatment median concentration of IFN-γ 2.73 IU/ml to a post-treatment median concentration IFN-γ 0.62 (p = 0.0002)., Conclusions: This study suggests differences in the capacity of commercially available IGRAs to identify LTBI in the absence of antecedent TST and that IGRAs, in the time periods examined, may not be the optimal tests to determine the success of chemoprophylaxis for LTBI.

Background: Most people exposed to M. tuberculosis show no evidence of clinical disease. Five to 10% of individuals with latent infection progress to develop overt disease during their life time. Identification of people with latent TB infection will increase case detection rates and may dictate new treatment policies to control tuberculosis. This study aimed to determine LTBI point prevalence in a population from Sudan using two different diagnostic methods: the tuberculin skin test (TST) and the IFN-γ release assay (IGRA)., Methods: This was a prospective, community-based and case-controlled study. Following informed consent, household contacts (HHCs; n = 98) of smear-positive index cases and Community controls (CCs; 186), were enrolled. Tuberculin skin test (TST), whole blood stimulation with ESAT-6/CFP-10 ± TB7.7 antigens or purified protein derivative (PPD) and IFN-γ levels determination with ELISA were performed. The levels of IFN-γ and TST induration between the CCs and the HHCs were compared using student t-test, Chi-square and Kappa coefficient. Pearson correlation test was used to compare TST and IFN-γ. P levels of <0.05 were considered significant., Results: TST induration of ≥ 10 mm gave an LTBI point prevalence of 327 cases/1000 individuals among HHCs compared to 126 cases/1000 individuals among CCs (p = 0.000). PPD-induced IFN-γ release assay gave an LTBI point prevalence of 418 cases/1000 individuals among HHCs compared to 301 cases/1000 individuals among CCs (p =0.06). On the other hand ESAT-6/CFP-10 ± TB7.7-induced IFN-γ gave an LTBI point prevalence of 429 cases/1000 individuals among HHCs compared to 268 cases/1000 individuals among CCs (p = 0.01). IFN-γ productions levels induced by ESAT-6/CPF-10 ± TB7.7 antigens in HHCS and CCs were not significantly different from those induced by PPD (p = 0.7)., Conclusion: IFN-γ release assay (IGRA) gave higher LTBI point prevalence compared to TST in HHCs and CCs. PPD gave comparable results to ESAT-6/CFP-10 ± TB7.7 antigens in whole blood IFN-γ release, making it a cheap alternative to the recombinant antigens.

Background: Improved tests to diagnose latent TB infection (LTBI) are needed. We sought to evaluate the performance of two commercially available interferon-gamma release assays (IGRAs) compared to the tuberculin skin test (TST) for the diagnosis of LTBI and to identify risk factors for LTBI among HIV-infected individuals in Georgia, a country with high rates of TB., Methods: HIV-patients were enrolled from the National AIDS Center in Tbilisi, Georgia. After providing informed consent, each participant completed a questionnaire, had blood drawn for QuantiFERON-TB Gold in-Tube (QFT-GIT) and T-SPOT.TB testing and had a TST placed. The TST was read at 48-72 hrs with ≥ 5 mm induration considered positive., Results: Between 2009-2011, 240 HIV-infected persons (66% male) with a median age of 38 years and a median CD4 count of 255 cells/μl (IQR: 124-412) had diagnostic testing for LTBI performed. 94% had visible evidence of a BCG scar. The TST was positive in 41 (17%) patients; QFT-GIT in 70 (29%); and T-SPOT.TB in 56 (24%). At least one diagnostic test was positive in 109 (45%) patients and only among 13 (5%) patients were all three tests positive. Three (1%) QFT-GIT and 19 (8%) T-SPOT.TB test results were indeterminate. The agreement among all pairs of tests was poor: QFT-GIT vs. T-SPOT.TB (κ = 0.18, 95% CI .07-.30), QFT-GIT vs. TST (κ = 0.29, 95% CI .16-.42), and TST vs. T-SPOT.TB (κ = 0.22, 95% CI .07-.29). Risk factors for LTBI varied by diagnostic test and none showed associations between positive test results and well-known risk factors for TB, such as imprisonment, drug abuse and immunological status., Conclusions: A high proportion of HIV patients had at least one positive diagnostic test for LTBI; however, there was very poor agreement among all tests. This lack of agreement makes it difficult to know which test is superior and most appropriate for LTBI testing among HIV-infected patients. While further follow-up studies will help determine the predictive ability of different LTBI tests, improved modalities are needed for accurate detection of LTBI and assessment of risk of developing active TB among HIV-infected patients.

Gamma interferon (IFN-γ) release assays (IGRAs) are functional assays used serially to measure the efficacy of novel tuberculosis (TB) vaccines and to screen health care workers for latent tuberculosis infection (LTBI). However, studies have shown nonreproducible IGRA results. In this study, we investigated the effects of blood volume (0.8, 1.0, and 1.2 ml), tube shaking (gentle versus vigorous), and incubation duration (16, 20, and 24 h) on the reproducibility of QuantiFERON-TB Gold In-Tube (QFT-GIT) results for 50 subjects (33 uninfected and 17 infected). The median IFN-γ TB response (TB antigen [Ag] minus nil value) was significantly higher with 0.8 ml blood (1.04 IU/ml) than with 1.0 ml (0.85 IU/ml; P = 0.002) or 1.2 ml (0.49 IU/ml; P < 0.001) for subjects with LTBI. Compared with 0.8 ml (11.8%), there were larger proportions of false-negative results with 1.0 ml (29.4%; P = 0.2) and 1.2 ml (41.2%; P = 0.05) of blood for infected subjects. Blood volume did not significantly change the proportions of positive results in uninfected controls. Compared with gentle shaking, vigorous shaking increased the median IFN-γ response in nil (0.04 versus 0.06 IU/ml; P < 0.001) and TB Ag (0.12 versus 0.24 IU/ml; P = 0.004) tubes and increased TB responses (TB Agvigorous minus nilgentle) (0.02 versus 0.08 IU/ml; P = 0.004). The duration of incubation did not have a significant impact on the proportion of positive results in uninfected or infected subjects. This study identified blood volume and tube shaking as novel preanalytical sources of variability which require further standardization in order to improve the quality and reproducibility of QFT-GIT results.

Background: Active tuberculosis infection represents a very common and significant threat to HIV-infected patients. But measures to accurately detect it are limited., Objective: To compare and analyze the diagnostic efficacy of T-SPOT.TB alone and in combination with TST in HIV-infected patients in China., Method: TST (tuberculin skin test) and T-SPOT.TB were performed on 131 HIV-infected patients admitted in Beijing You'an Hospital and Beijing Ditan Hospital between Oct, 2010 and Jul, 2012, who were initially diagnosed as suspected ATB (active TB). The patients were further categorized into ATB and Not ATB based on clinical and cultural evidences. The performance of TST and T-SPOT.TB were analyzed and compared., Results: The sensitivity and specificity of T-SPOT.TB were 41.3% and 94.6%, respectively, both higher than TST (12.9% and 91.8%). By combining T-SPOT.TB and TST, the sensitivity did not increase, but specificity was elevated to 100%. TST, T-SPOT.TB and their combinations all performed better in patients with extra-pulmonary diseases than with pulmonary disorders. False-positive T-SPOT.TB results were found to be associated with history of prior TB. In addition, concomitant bacterial infections and low CD4 counts were associated with increased ATB risk., Conclusions: T-SPOT.TB is superior in screening ATB in HIV-infected patients in China over traditional TST. Additional TST would help to confirm a positive T-SPOT.TB result. Both tests work better for patients with extra-pulmonary conditions.

Interferon (IFN)-γ release assays (IGRAs) are probably the most accurate tests for the detection of latent Mycobacterium tuberculosis infection, but IGRAs are labour intensive and the transport of samples over longer distances is difficult. IFN-γ-induced protein (IP)-10 is expressed at 100-fold higher levels than IFN-γ, and IP-10 release assays have comparable performance to IGRAs. The aim of this study was to explore the diagnostic potential of a novel IP-10 release assay based on dried plasma spots (DPS). The presence of IP-10 and IFN-γ was determined in plasma and in DPS by ELISA. Diagnostic algorithms for plasma and DPS tests for IP-10 were developed on a training cohort comprising 60 tuberculosis (TB) patients and 59 healthy controls. Diagnostic accuracy was assessed in a validation cohort comprising 78 TB patients and 98 healthy controls. Plasma was measured in Spain and DPS samples were sent to Denmark using the conventional postal service for analysis. IP-10 was readily detectable in both plasma and DPS, and correlation was excellent (r(2) = 0.95). QuantiFERON-TB Gold In-Tube (QFT-TB) and IP-10 in DPS and plasma rendered comparable sensitivity (78%, 82% and 84%, respectively), specificity (100%, 97% and 97%, respectively) and indeterminate rates (p>0.55). The DPS-based IP-10 test has comparable diagnostic accuracy to the QFT-TB and samples can be sent via conventional mail over long distances for analysis without affecting the results.

In this clinical audit, we assessed retrospectively the current practice of respiratory physicians with respect to interferon gamma (IFNγ) release assay (IGRA) testing for tuberculosis (TB), as recommended by the 2011 National Institute of Health and Care Excellence (NICE) guidelines for the diagnosis and management of TB. All IGRAs requested by respiratory physicians over a 3-year period were identified retrospectively, and both results and clinical indications analysed. Of the total number of IGRAs carried out, 90% formed part of investigations of suspected active TB. However, 89% of the patients had not had a documented Mantoux test and human immunodeficiency virus (HIV) status was unclear in the 35.2% of patients treated for active TB. Of patients with chest X-rays suggestive of TB, 92.3% were treated for active TB. Of the patients under the age of 35 with reactive IGRAs, 84.6% were treated for active or latent TB and 15.4% had justifiable reasons for not receiving chemoprophylaxis. Based on the results of our audit, IGRAs are commonly being utilised for the investigation of active TB, which is contrary to current guidance.

Rationale: There is uncertainty regarding how to interpret discordance between tests for latent tuberculosis infection., Objectives: The objective of this study was to assess discordance between commercially available tests for latent tuberculosis in a low-prevalence population, including the impact of nontuberculous mycobacteria., Methods: This was a cross-sectional comparison study among 2,017 military recruits at Fort Jackson, South Carolina, from April to June 2009. Several tests were performed simultaneously with a risk factor questionnaire, including (1) QuantiFERON-TB Gold In-Tube test, (2) T-SPOT.TB test, (3) tuberculin skin test, and (4) Battey skin test using purified protein derivative from the Battey bacillus., Measurements and Main Results: In this low-prevalence population, the specificities of the three commercially available diagnostic tests were not significantly different. Of the 88 subjects with a positive test, only 10 (11.4%) were positive to all three tests; 20 (22.7%) were positive to at least two tests. Bacille Calmette-Guérin vaccination, tuberculosis prevalence in country of birth, and Battey skin test reaction size were associated with tuberculin skin test-positive, IFN-γ release assay-negative test discordance. Increasing agreement between the three tests was associated with epidemiologic criteria indicating risk of infection and with quantitative test results., Conclusions: For most positive results the three tests identified different people, suggesting that in low-prevalence populations most discordant results are caused by false-positives. False-positive tuberculin skin test reactions associated with reactivity to nontuberculous mycobacteria and bacille Calmette-Guérin vaccination may account for a proportion of test discordance observed.

Background: We determined the consistency of positive interferon-gamma (IFN-γ) release assays (IGRAs) to detect latent TB infection (LTBI) over one-year postpartum in HIV-1-infected women., Methods: Women with positive IGRAs during pregnancy had four 3-monthly postpartum IGRAs. Postpartum change in magnitude of IFN-γ response was determined using linear mixed models., Results: Among 18 women with positive pregnancy IGRA, 15 (83%) had a subsequent positive IGRA; 9 (50%) were always positive, 3 (17%) were always negative, and 6 (33%) fluctuated between positive and negative IGRAs. Women with pregnancy IGRA IFN-γ>8 spot forming cells (SFCs)/well were more likely to have consistent postpartum IGRA response (odds ratio: 10.0; 95% confidence interval (CI): 0.9-117.0). Change in IFN-γ response over postpartum was 10.2 SFCs/well (95% CI: -1.5-21.8 SFCs/well)., Conclusion: Pregnancy positive IGRAs were often maintained postpartum with increased consistency in women with higher baseline responses. There were modest increases in magnitude of IGRA responses postpartum.

Although interferon-γ release assays (IGRAs) are intended for diagnosing latent tuberculosis (TB), we hypothesised that in a high-burden setting: 1) the magnitude of the response when using IGRAs can distinguish active TB from other diagnoses; 2) IGRAs may aid in the diagnosis of smear-negative TB; and 3) IGRAs could be useful as rule-out tests for active TB. We evaluated the accuracy of two IGRAs (QuantiFERON®-TB Gold In-tube (QFT-GIT) and T-SPOT®.TB) in 395 patients (27% HIV-infected) with suspected TB in Cape Town, South Africa. IGRA sensitivity and specificity (95% CI) were 76% (68-83%) and 42% (36-49%) for QFT-GIT and 84% (77-90%) and 47% (40-53%) for T-SPOT®.TB, respectively. Although interferon-γ responses were significantly higher in the TB versus non-TB groups (p<0.0001), varying the cut-offs did not improve discriminatory ability. In culture-negative patients, depending on whether those with clinically diagnosed TB were included or excluded from the analysis, the negative predictive value (NPV) of QFT-GIT, T-SPOT®.TB and chest radiograph in smear-negative patients varied between 85 and 89, 87 and 92, and 98% (for chest radiograph), respectively. Overall accuracy was independent of HIV status and CD4 count. In a high-burden setting, IGRAs alone do not have value as rule-in or -out tests for active TB. In smear-negative patients, chest radiography had better NPV even in HIV-infected patients.

Background: Imperfect sensitivity of interferon-γ release assay (IGRA) is a potential problem to detect tuberculosis. We made a thorough investigation of the factors that can lead to false negativity of IGRA., Methods: We recruited 543 patients with new smear-positive pulmonary tuberculosis in Hanoi, Viet Nam. At diagnosis, peripheral blood was collected and IGRA (QuantiFERON-TB Gold In-Tube) was performed. Clinical and epidemiological information of the host and pathogen was collected. The test sensitivity was calculated and factors negatively influencing IGRA results were evaluated using a logistic regression model in 504 patients with culture-confirmed pulmonary tuberculosis., Results: The overall sensitivity of IGRA was 92.3% (95% CI, 89.6%-94.4%). The proportions of IGRA-negative and -indeterminate results were 4.8% (95% CI, 3.1%-7.0%) and 3.0% (95% CI, 1.7%-4.9%). Age increased by year, body mass index <16.0, HIV co-infection and the increased number of HLA-DRB1*0701 allele that patients bear showed significant associations with IGRA negativity (OR = 1.04 [95% CI, 1.01-1.07], 5.42 [1.48-19.79], 6.38 [1.78-22.92] and 5.09 [2.31-11.22], respectively). HIV co-infection and the same HLA allele were also associated with indeterminate results (OR = 99.59 [95% CI, 15.58-625.61] and 4.25 [1.27-14.16])., Conclusions: Aging, emaciation, HIV co-infection and HLA genotype affected IGRA results. Assessment of these factors might contribute to a better understanding of the assay.

The purpose of this prospective, cross-sectional observational study was to compare the tuberculin skin testing (TST) with QuantiFERON-TB Gold-In Tube (QTF-GIT) for the detection of latent tuberculosis infection in healthcare workers (HCWs). The study included 78 volunteers who are HCWs at the same tertiary care teaching hospital for chest diseases and tuberculosis. Participants with active tuberculosis, immunodefficiency or malnutrition were not included. The TST was administered by the Mantoux method. Peptides representing ESAT-6, CFP-10 and TB7-7 were used as TB-specific antigens in the whole-blood Interferon-gamma (IFN-g) assay (QTF-GIT). There was a statistically significant relation between the number of Bacillus Calmette-Guerin (BCG) scars and the diameter of TST (p< 0.01). QTF results according to previous BCG vaccinations did not significantly differ (p> 0.05). There was an intermediate concordance between two tests (k: 0.346). QTF-GIT has a sensitivity of 56.14% (both TST and QTF-GIT are positive), specificity of 90.48% (both TST and QTF-GIT are negative); positive predictive value of 94.12% and negative predictive value of 43.18% and accuracy is 65.38%. There was a statistically significant relation between TST diameter and QTF result (p< 0.01). Latent tuberculosis infection prevalance of our study population was 43% according to QTF-GIT test, 73% according to TST and BCG vaccination rate was 87%. In conclusion, TST is affected by previous BCG vaccinations, QTF-GIT is not. We can recommend QTF-GIT test for the detection of latent tuberculosis infection as an alternative to TST in populations with routine BCG vaccination programme.