QFT-GIT Assay Research Articles

Tuberculosis Infection Screening in 5468 Italian Healthcare Students: Investigation of a Borderline Zone Value for the QFT-Test.

Healthcare workers are at an increased risk of contracting Mycobacterium tuberculosis infection. Tuberculin skin test (TST) and interferon gamma release assay (IGRA) represent the available tests most used for the diagnosis of latent tuberculosis infection (LTBI). Different borderline zones have been proposed for defining conversions and reversions to improve the interpretation of the IGRA test results as part of serial testing. From 2012 to 2017, 5468 health students of an Italian University Hospital were screened for tuberculosis infection through the execution of the TST and, in case of positivity, of the QuantiFERON-TB® Gold In-Tube assay (QFT–GIT). The QFT–GIT is considered “borderline” with values from 0.35 to 0.99 IU/mL. Among the students who performed the QFT–GIT assay, 27 subjects presented a range of values defined as borderline. The QFT–GIT was repeated after 90 days on 19 subjects with borderline values and showed a negativization of the values in 14 students and a positive conversion in three cases, while for two students, a borderline value was also found for the second test, with a 74% regression of the borderline cases. The introduction of QuantiFERON borderline values is a useful assessment tool to bring out LTBI case candidates for chemoprophylaxis.

Prevalence of and risk factors associated with latent tuberculosis in Singapore: A cross-sectional survey

ObjectivesThis first cross-sectional survey on latent tuberculosis infection (LTBI) in Singapore was performed by utilizing the QuantiFERON Gold In-tube (QFT-GIT) assay to collect data on the prevalence of LTBI and to identify potential risk factors associated with LTBI. MethodsNationwide household addresses were selected randomly for enumeration, and Singaporeans or Permanent Residents aged 18–79 years were identified. One eligible member per household was selected using the Kish grid. Each participant answered a questionnaire assessing their medical history (including tuberculosis (TB)), socio-economic factors, and lifestyle factors. They also provided a blood specimen for the QFT-GIT assay. Participants with a positive QFT-GIT result were defined as having LTBI if they were asymptomatic. To identify independent risk factors, adjusted hazard ratios were obtained using the multivariable modified Breslow–Cox proportional hazards model. ResultsAn overall QFT-GIT positivity rate of 12.7% was detected amongst 1682 Singapore residents. There was a wide variation in the positivity rate according to the participants’ country of birth. Higher LTBI prevalence was also significantly associated with increasing age, lower educational and socio-economic status, and alcohol use. ConclusionsGiven the high prevalence of LTBI amongst foreign-born residents from regional countries, similar studies should be conducted amongst migrants in Singapore to improve national guidelines on screening and preventive treatment against LTBI.

Diagnostic Utility of New Equation for Active Tuberculosis Based on Parameters of Interferon-γ Release Assay.

We derived a new equation to include interferon-γ (IFN-γ) levels in the QuantiFERON-Gold In-Tube (QFT-GIT) assay to discriminate active tuberculosis (ATB) infection from latent TB, and compared the diagnostic performance of the QFT-GIT assay and the new equation. From January 2013 through May 2015, we retrospectively enrolled 159 and 408 patients with and without ATB, respectively, in this study. Discriminant analysis was performed to derive an equation to distinguish the ATB group from the non-ATB group. The sensitivity and specificity of the QFT-GIT assay for diagnosing ATB were 90.6% and 63.0%, respectively. The positive and negative predictive values of the QFT-GIT assay were 48.8% and 94.5%, respectively. When the optimal cutoff for the new equation [Z = (0.031 × Nil) + (0.007 × TBAg) - 0.978] was set to -0.435, the sensitivity and specificity were 84.3% and 69.1% (positive predictive value, 51.5%; negative predictive value, 91.9%), respectively. The QFT-GIT assay and the equation derived from each IFN-γ could not discriminate ATB from latent TB without considering other cytokines involved in immunity against TB.

Utility of QuantiFERON-TB Gold In-Tube assay in adult, pulmonary and extrapulmonary, active tuberculosis diagnosis

Tuberculosis remains a public health problem in France and the diagnosis of tuberculosis disease (TB) is sometimes difficult. The aim of this study was to analyse the contribution of the QuantiFERON-TB Gold In-Tube assay (QFT-GIT) to TB diagnosis. Sixty patients hospitalized with TB, for whom a QFT-GIT assay had been performed between June 2008 and June 2011 at the University Hospital of Bondy in the north-east of Paris, were identified retrospectively. Clinical and laboratory data were collected. The sensitivity, specificity, predictive values, and likelihood ratios of the QFT-GIT were all calculated. Furthermore, the characteristics of patients testing positive were compared to those of patients testing negative, as well as the QFT-GIT values according to several different factors. The sensitivity of the QFT-GIT was 85% (95% confidence interval (CI) 0.73-0.92) and specificity was 73.3% (95% CI 0.68-0.78). The positive predictive value was 39.5% and the negative predictive value was 97.3%. The positive and negative likelihood ratios were 3.2 and 0.20, respectively. The prevalence of TB in this population was 15% (pre-test probability). After a positive test result, the probability of TB increased to 40% (post-positive probability test); after a negative test result, it decreased to 4.5% (post-negative probability test). The combination of the QFT-GIT test with the tuberculin skin test brought no significant improvement in sensitivity. Factors significantly associated with a negative QFT-GIT result included older age, high C-reactive protein, a low lymphocyte count, and immunosuppressant intake. The test value in quantitative terms was significantly higher in those with lymph node TB than in those with pulmonary TB, and in younger patients (<40 years) than in older patients (>40 years old). On its own, QFT-GIT is an insufficient tool to confirm the diagnosis of TB disease. However, it may form part of an ensemble of tools in combination with clinical, biological, and radiological assessments.

IFN-γ/TNF-α ratio in response to immuno proteomically identified human T-cell antigens of Mycobacterium tuberculosis – The most suitable surrogate biomarker for latent TB infection

The enormous reservoir of latent TB infection (LTBI) poses a major hurdle for global TB control. The existing Tuberculin skin test (TST) and IFN-γ release assays (IGRAs) are found to be suboptimal for LTBI diagnosis. Previously we had taken an immunoproteomic approach and identified 10 protein fractions (contains 16 proteins), which are solely recognized by LTBI. In a cohort of 40 pulmonary TB patients (PTB) and 35 healthy household contacts (HHC), IFN-γ and TNF-α response were measured against 16 antigens by using 1:10 diluted whole blood assay. Among all the antigens, IFN-γ response to Rv2626c has shown positivity of 88.57% in HHC and 7.5% in PTB group. IFN-γ response to combination of Rv2626c+Rv3716c has demonstrated 100% positivity in HHC and 17.5% positivity in PTB respectively. Compared to individual cytokines (i.e. IFN-γ and TNF-α), ratio of IFN-γ/TNF-α has shown promising results for diagnosis of LTBI. IFN-γ/TNF-α ratio against Rv3716c and TrxC has exhibited a positivity of 94.29% in HHC and 5% in PTB group. Accession of Rv2626c and Rv3716c may improve the diagnostic performance of existing QFT-GIT. Independent of QFT-GIT assay, ratio of IFN-γ/TNF-α in response to either Rv3716c or TrxC may acts as suitable surrogate biomarker for LTBI.

Interferon gamma release assays based on M. tuberculosis-specific antigens in sarcoidosis patients.

This study is a part of the project on interferon gamma release assays performed in the group of untreated sarcoidosis patients formerly BCG vaccinated. The aim of the study was to assess the rate of positive commercial interferon g release assays in sarcoidosis patients. We discussed the results in the context of hypothesis that M. tuberculosis antigens may play a role in the pathogenesis of sarcoidosis. 151 patients, mean age 38 ± 10.3, treatment naive, with newly diagnosed pulmonary sarcoidosis were enrolled into the study. All participants underwent QFT-GIT assay. A subgroup of 81 patients underwent also T-SPOT.TB assay. QFT-GIT was positive in 7/151. T-SPOT.TB was positive in 3/81. There were no indeterminate results in both IGRAs. There was no statistically significant relationship between IGRAs results and sarcoidosis parameters such as the radiologic stage, disease duration and the presence of Löfgren's syndrome. In sarcoidosis patients formerly BCG vaccinated, positive rate of IGRAs was 4.6% for QFT-GIT and 3.7% for T-SPOT. TB. We did not find the influence of the selected parameters of sarcoidosis on IGRAs results.

Lymphocyte subpopulations in active tuberculosis: association with disease severity and the QFT-GIT assay [Short communication

Cell-mediated immune response plays an essential role in the pathogenesis of tuberculosis (TB). We retrospectively evaluated lymphocyte subpopulations in 177 active TB patients compared to 93 healthy controls, finding a relevant decrease in total lymphocytes and CD8+ cells. Conversely, activated human leukocyte antigen (HLA-DR+) and CD4+CD57+ cells were higher in the TB group. B-1a (CD5+CD19+) lymphocytes were reduced in TB subjects, particularly those with extended and cavitary pulmonary forms, suggesting increased compartmentalisation at the infection site. QuantiFERON-TB Gold In-Tube positive results were associated with higher HLA-DR+CD4+ and CD4+CD57+ cells, while interferon-gamma response and total lymphocyte levels were lower in advanced pulmonary TB cases.

Diagnosis of latent tuberculosis infection in healthy young adults in a country with high tuberculosis burden and BCG vaccination at birth

BackgroundOne third of the world’s population is thought to have latent tuberculosis infection (LTBI) with the potential for subsequent reactivation of disease. To better characterize this important population, studies comparing Tuberculin Skin Test (TST) and the new interferon-γ release assays including QuantiFERON®-TB Gold In-Tube (QFT-GIT) have been conducted in different parts of the world, but most of these have been in countries with a low incidence of tuberculosis (TB). The aim of this study was therefore to evaluate the use of QFT-GIT assay as compared with TST in the diagnosis of LTBI in Ethiopia, a country with a high burden of TB and routine BCG vaccination at birth.MethodsHealthy medical and paramedical male students at the Faculty of Medicine, Addis Ababa University, Ethiopia were enrolled into the study from December 2008 to February 2009. The TST and QFTG-IT assay were performed using standard methods.ResultsThe mean age of the study participants was 20.9 years. From a total of 107 study participants, 46.7% (95%CI: 37.0% to 56.6%) had a positive TST result (TST≥10 mm), 43.9% (95%CI: 34.3% to 53.9%) had a positive QFT-GIT assay result and 44.9% (95%CI: 35.2% to 54.8%) had BCG scar. There was strong agreement between TST (TST ≥10mm) and QFT-GIT assay (Kappa = 0.83, p value = 0.000).ConclusionThe TST and QFT-GIT assay show similar efficacy for the diagnosis of LTBI in healthy young adults residing in Ethiopia, a country with high TB incidence.

Diagnostic performance of whole-blood interferon-γ assay and enzyme-linked immunospot assay for active tuberculosis,

The aim of this study was to compare the diagnostic performance of 2 interferon-γ release assays, an enzyme-linked immunospot assay (T-SPOT.TB; Oxford Immunotec Ltd., Oxford, UK) and the QuantiFERON-TB Gold in-Tube assay (QFT-GIT; Cellestis Ltd., Carnegie, Australia), in patients with suspected active tuberculosis (TB). From October 2009 to October 2011, a total of 200 patients with suspected TB were enrolled. Clinical and microbiological characteristics of the patients were collected and blood samples were obtained for T-SPOT.TB and QFT-GIT assays. Among the 200 subjects, 98 (49%) had culture-confirmed TB, 18 (9%) had probable TB, and the remaining 84 (42%) subjects did not have TB. The sensitivity, specificity, positive predictive value, and negative predictive value for active TB diagnosis by the T SPOT. TB were 83%, 71%, 81%, and 75%, respectively. For QFT-GIT, the sensitivity, specificity, positive predictive value, and negative predictive value for active TB diagnosis were 66%, 76%, 80%, and 62%, respectively. The QFT-GIT assay resulted in more indeterminate and false-negative results than the T-SPOT.TB assay, especially in immunocompromised patients. In conclusion, T-SPOT.TB had a higher sensitivity and resulted in fewer indeterminate results than the QFT-GIT assay for diagnosing active TB.

Practical Experience With the QFT-GIT Assay for LTBI Annual Testing Among US Health-care Workers in a Large Tertiary Setting

Practical Experience With the QFT-GIT Assay for LTBI Annual Testing Among US Health-care Workers in a Large Tertiary Setting

Predictive factors for the indeterminate result on the QuantiFERON-TB Gold In-Tube test

Background: QuantiFERON-TB Gold In-Tube (QFT-G IT) test is recommended for screening of latent tuberculosis. However, this can reveal the indeterminate results, especially in the immunocompromised patients. Therefore, we investigated the predictive factors that can influence the indeterminate results on QFT-G IT. Methods: We performed a retrospective case-control study with 144 cases with the indeterminate results on QFT-G IT from October 2006 to March 2009 at Severance Hospital. The controls with the positive or negative results were selected by matching 1:1 with the case for date of QFTG IT assay. An indeterminate result was considered when the level in both the tuberculosis antigen and mitogen tube was less than 0.35 IU/ml, or the level in the nil tube was higher than 8.0 IU/ml. Through retrospective review of medical records, age, gender, total lymphocyte count at the QFT-G IT assay, underlying diseases, and medical conditions which can influence the immune function were collected as covariates. The predictive factors for the indeterminate results on QFT-G IT were assessed by multivariate logistic regression models. Results: Age and gender did not show the significant differences between case and control patients (p = 0.105 and 0.906). The percentage of patients with hematologic malignancy (19.4% vs. 11.1%, p = 0.049), chronic renal disease (22.2% vs. 9.7%, p = 0.004), and autoimmune disease (16.0% vs. 6.3%, p = 0.009) in the case group were the significantly higher than those in the control group. Also, the case group had the significantly higher percentage of steroid use (16.0% vs. 8.3%, p = 0.047) and solid organ transplantation (11.1% vs. 2.1%, p = 0.002) than the control group. The total lymphocyte count was the significantly lower in the case group than in the control group (median [interquartile range], 540 [220—1,030] vs. 1,370 [870—1,970], p < 0.001). In the final regression model, clinical factors associated with the indeterminate results were chronic renal disease (odds ratio [OR] 2.26, 95% confidential interval [CI] 1.03—4.94, p = 0.041), autoimmune disease (OR 3.99, 95% CI 1.65—9.66, p = 0.002), and solid organ transplantation (OR 5.06, 95% CI 1.30—19.73, p = 0.020). Conclusion: The patients with lower lymphocyte counts or immunosuppressive condition showed the higher possibility of the indeterminate results on QFT-G IT assay. Therefore, the combined assay such as tuberculin skin test and T-SOPT TB with QFT-G IT may be helpful to screen the latent tuberculosis in the patients with these conditions.

The role of a whole blood interferon-γ assay for the detection of latent tuberculosis infection in Bacille Calmette–Guérin vaccinated children

The tuberculin skin test (TST) has limitations in children who are under the Bacille Calmette–Guérin (BCG) effect. Our aim was to evaluate the QuantiFERON®-TB Gold In-Tube (QFT-G IT) blood test for Mycobacterium tuberculosis infection in children and to compare results with those of the TST. QFT-G IT and TST data were collected from 227 children between 0 and 15 years of age, split into 4 risk groups. Forty-two children were close contacts, 29 were casual contacts, and 65 were controls. The QFT-G IT positivity rates were 19% (8/42), 6.9% (2/29), and 1.5% (1/65), with a significantly higher rate for the close contacts over the controls ( P < 0.05). The high specificity of the QFT-G IT assay and the association of positive results with increasing risk of infection in our study suggest it has major benefits over the TST as a screening test for latent infection with M. tuberculosis in BCG-vaccinated children.

Tuberculosis in a Swiss army training camp: contact investigation using an Interferon gamma release assay.

In tuberculosis (TB), the risk of exposure is determined mainly by the proximity to and the hours of direct contact with an infectious patient. We describe the contact investigation after detection of an infectious form of TB in a military camp using an Interferon-g-Release-Assay (IGRA, QuantiFERON-TB Gold In Tube [QTF-GIT]) eight weeks after detection of the index case. INDEX PATIENT: The index patient presented with fever, cough and weight loss in the military hospital six weeks after entering the camp. TB was suspected and anti-tuberculous therapy given immediately. Subsequently, TB was microbiologically confirmed. Four exposure groups were formed a priori based on the proximity and the hours of direct contact to the index case. 168 (95.5%) agreed to be investigated: - Group A: sharing the same dormitory (15 persons) - Group B: same platoon, but not sharing the dormitory (20 persons) - Group C: staff and patients of the military hospital (22 persons) - Group D: other three platoons and senior military staff (111 persons). 34 (20.2%) out of 168 contacts tested positive in the QFT-GIT assay. For the exposure groups, the respective QFT-GIT testing results were: group A, 14/15 (93%); group B, 4/20 (20%); group C, 5/22 (22.7%); and group D, 11/111 (9.9%). No secondary TB cases were identified. In our study, test results show a correlation with the risk of exposure, suggesting that IGRA may be useful for the assessment of TB infection in TB contacts. The high mobility of recruits reduced traceability of contacts. In this context, QFT-GIT allowed for an efficient screening of contacts at a single time point.

Tuberculosis in a Swiss army training camp: contact investigation using an Interferon gamma release assay.

In tuberculosis (TB), the risk of exposure is determined mainly by the proximity to and the hours of direct contact with an infectious patient. We describe the contact investigation after detection of an infectious form of TB in a military camp using an Interferon-g-Release-Assay (IGRA, QuantiFERON-TB Gold In Tube [QTF-GIT]) eight weeks after detection of the index case. INDEX PATIENT: The index patient presented with fever, cough and weight loss in the military hospital six weeks after entering the camp. TB was suspected and anti-tuberculous therapy given immediately. Subsequently, TB was microbiologically confirmed. Four exposure groups were formed a priori based on the proximity and the hours of direct contact to the index case. 168 (95.5%) agreed to be investigated: - Group A: sharing the same dormitory (15 persons) - Group B: same platoon, but not sharing the dormitory (20 persons) - Group C: staff and patients of the military hospital (22 persons) - Group D: other three platoons and senior military staff (111 persons). 34 (20.2%) out of 168 contacts tested positive in the QFT-GIT assay. For the exposure groups, the respective QFT-GIT testing results were: group A, 14/15 (93%); group B, 4/20 (20%); group C, 5/22 (22.7%); and group D, 11/111 (9.9%). No secondary TB cases were identified. In our study, test results show a correlation with the risk of exposure, suggesting that IGRA may be useful for the assessment of TB infection in TB contacts. The high mobility of recruits reduced traceability of contacts. In this context, QFT-GIT allowed for an efficient screening of contacts at a single time point.

Comparison of a whole blood Interferon-γ assay and A tuberculin skin test for detecting latent tuberculosis infection in children

Purpose : Surveillance for detecting and managing latent tuberculosis infection (LTBI) is a key component of tuberculosis control. The classic surveillance tool, the tuberculin skin test (TST), may have some limitations when used in the Bacillus Calmette-Guerin (BCG)-vaccinated population. The object was to perform a blood test QuantiFERON®-TB Gold In Tube (QFT-G IT) based on the detection of interferon-γ (IFN-γ) released by T cells in response to Mycobacterium tuberculosis-specific antigens, and to compare the efficacy of this new diagnostic tool for LTBI with that of TST. Methods : For six months, between October 1, 2006 and April 30, 2007, data were collected from 111 patients under 15 years of age at Severance Children's Hospital. TST and QFT-G IT tests were performed with children with or without contact histories of tuberculosis. In addition to these tests, we examined comparative data from 29 adults who had tuberculosis, to detect false negative rates in the QFT-G IT method. Results : Thirty-three children had household contact histories. In this group, 15% and 42% of cases were found to be positive using the QFT-G IT assay and TST, respectively. Agreement was low between these two tests (κ=0.39). In the adult active tuberculosis group, the QFT-G IT false negative rate defined as a positive culture and a negative QFT-G IT result was 12.5%. Conclusion : In diagnosing LTBI in children, the usefulness of a whole-blood IFN-γ assay employing TB-specific antigens will be revealed only by examining additional longitudinal clinical data; this study serves as a starting point in that process.