Comparison of Two Interferon-γ Assays and Tuberculin Skin Test for Tracing Tuberculosis Contacts

The pathology biopsy represents the "gold standard" for diagnosis: a case report

A 70-year-old male with previously unknown immunodeficiency presented with multiple pulmonary nodular shadows observed on chest and abdomen radiography. Fungal infection was detected in brushing specimens, bronchial lavage, and transbronchial lung biopsy samples. Through next-generation sequencing (NGS) analysis, the patient was ultimately diagnosed with disseminated Talaromyces marneffei infection. Treatment with voriconazole at a dosage of 200 mg every 12 hours was initiated. However, after three months of treatment, the patient still had enlarged retroperitoneal lymph nodes, and a lymph node aspiration biopsy was performed to further clarify the diagnosis, which ultimately led to the diagnosis of Talaromyces marneffei infection and B-cell non-Hodgkin's lymphoma. The main significance of this study is to emphasize the importance for clinicians to obtain comprehensive specimens from patients presenting with multiple masses in order to ensure accurate clinical diagnosis.

Latent tuberculosis infection prevalence in second generation immigrants from high to low TB burden countries

BACKGROUND

Latent tuberculosis infection (LTBI) diagnosis in a country with a low tuberculosis burden is complicated. Since the prevalence of LTBI in second generation immigrants has not been well recognized, we conducted a cross-sectional study which aimed to explore the differences in LTBI prevalence between offspring of immigrants from high tuberculosis (TB) burden countries and those whose parents were born in countries with a low TB burden.

METHODS

Between May 2014 and April 2018 young native Israelis who were required to perform pre-occupational tuberculin skin tests (TST) (medical and paramedical personnel or teaching assistants of immigrants from high TB burden countries) and who had a TST result of 10mm and above were tested for QuantiFERON-TB In Tube (QFT-GIT). Statistical comparisons were made between second generation immigrants and those with both parents from a low TB burden country.

RESULTS

Of 102 patients, 71 were born to parents both of whom were from low-risk countries, 14 to one parent from a high-risk country and 17 to parents both of whom were from a high-risk country. The odds ratio for LTBI was 4.5 (95% CI, 1.2...17.2; p=0.03) if both parents were born in a high-risk country compared to both parents being from a low-risk country and 4.01 (95% CI, 1.12...14.3; p=0.03) higher compared to persons for whom at least one parent was born in a low-risk country.

CONCLUSION

The risk for latent TB is significantly higher in second generation immigrants if both parents were born in a high-risk country. IGRA should be considered before treatment to patients with a positive TST if at least one parent was born in a low-risk country in order to confirm LTBI.

Tuberculin skin test before biologic and targeted therapies: does the same rule apply for all?

This study aimed to compare Tuberculin Skin Test (TST) and QuantiFERON®-TB Gold In-Tube (QFT-GIT) test in rheumatoid arthritis (RA) and spondyloarthritis (SpA) patients scheduled for biological and targeted synthetic disease modifying anti-rheumatic drugs (DMARDs) in a Bacillus Calmette-Guérin-vaccinated population. Adult RA (n = 206) and SpA (n = 392) patients from the TReasure database who had both TST and QFT-GIT prior to initiation of biological and targeted synthetic DMARDs were included in the study. Demographic and disease characteristics along with pre-biologic DMARD and steroid use were recorded. The distribution of TST and performance with respect to QFT-GIT were compared between RA and SpA groups. Pre-biologic conventional DMARD and steroid use was higher in the RA group. TST positivity rates were 44.2% in RA and 69.1% in SpA for a 5 mm cutoff (p < 0.001). Only 8.9% and 15% of the patients with RA and SpA, respectively, tested positive by QFT-GIT. The two tests poorly agreed in both groups at a TST cutoff of 5 mm and increasing the TST cutoff only slightly increased the agreement. Among age, sex, education and smoking status, pre-biologic steroid and conventional DMARD use, disease group, and QFT-GIT positivity, which were associated with a 5 mm or higher TST, only disease group (SpA) and QFT-GIT positivity remained significant in multiple logistic regression. TST positivity was more pronounced in SpA compared to that in RA and this was not explainable by pre-biologic DMARD and steroid use. The agreement of TST with QFT-GIT was poor in both groups. Using a 5 mm TST cutoff for both diseases could result in overestimating LTBI in SpA.

Resistance to Mycobacterium tuberculosis Infection Among Household Contacts: A Multinational Study

BACKGROUND

Some contacts of patients with tuberculosis remain negative on tests for tuberculosis infection, despite prolonged exposure, suggesting they might be resistant to Mycobacterium tuberculosis infection. The objective of this multinational study was to estimate the proportion of household contacts resistant to M. tuberculosis (resisters).

METHODS

We conducted a longitudinal study enrolling index patients enrolled in treatment for pulmonary multidrug- or rifampin-resistant tuberculosis and their household contacts. Contacts were tested for tuberculosis infection with a tuberculin skin test (TST) and interferon-gamma release assay (IGRA) at baseline and after 1 year. Exposure was quantified based on index patients' infectiousness, index patient and household contact interaction, and age. We explored multiple definitions of resistance to tuberculosis infection by varying TST negativity cutoffs (0 vs <5 mm), classification of missing test results, and exposure level.

RESULTS

In total, 1016 contacts were evaluated from 284 households; 572 contacts aged ≥5 years had TST and longitudinal IGRA results available. And 77 (13%) or 71 (12%) contacts were classified as resisters with a <5 mm or 0 mm TST threshold, respectively. Among 263 highly exposed contacts, 29 (11%) or 26 (10%) were classified as resisters using TST cutoffs of <5 mm and 0 mm, respectively. The prevalence of resisters did not differ substantially by sex, age, human immunodeficiency virus (HIV) coinfection, or comorbid conditions.

CONCLUSIONS

At least 10% of household contacts can be classified as resistant to tuberculosis infection, depending on the definition used, including those with high exposure. Further studies to understand genetic or immunologic mechanisms underlying the resister phenotype may inform novel strategies for therapeutics and vaccines.

Mycobacterial lymphadenitis without granuloma formation in a patient with anti-interferon-gamma antibodies

A previously healthy 49-year-old Japanese woman presented with cervical lymph node swelling and tenderness. Lymph node biopsy revealed reactive lymphadenitis without granulomas. No malignant cells were found, and no acid-fast positive bacilli were identified by Ziehl-Neelsen staining. She was treated unsuccessfully with various antibiotics, and it was very challenging to reach a diagnosis. ¹⁸F-Fluorodeoxyglucose (¹⁸F-FDG) uptake in bones was evaluated using positron emission tomography-computed tomography (PET-CT), and disseminated mycobacterial infection was suspected. The interferon-gamma (IFN-γ) release assays QuantiFERON (QFT) and T-SPOT were used to diagnose tuberculosis infection. On testing, a difference in mitogen response was found between these assays. The response was low for QFT but adequate for T-SPOT, suggesting the presence of anti-IFN-γ antibodies. This difference depended on whether the patient's plasma (including anti-IFN-γ antibodies) was used within the assay system. Mycobacterium abscessus was isolated from lymph node cultures, and plasma anti-IFN-γ antibodies were confirmed. The patient was diagnosed with disseminated M. abscessus infection with underlying adult-onset immunodeficiency caused by anti-IFN-γ antibodies. Granulomas are a pathological hallmark of mycobacterial infection, but may not fully form in immunodeficient patients. Clinicians should be aware of the possibility of mycobacterial infection without granuloma formation due to anti-IFN-γ antibodies.

Predictive value of TNF-α, IFN-γ, and IL-10 for tuberculosis among recently exposed contacts in the United States and Canada

BACKGROUND

We examined cytokine immune response profiles among contacts to tuberculosis patients to identify immunologic and epidemiologic correlates of tuberculosis.

METHODS

We prospectively enrolled 1272 contacts of culture-confirmed pulmonary tuberculosis patients at 9 United States and Canadian sites. Epidemiologic characteristics were recorded. Blood was collected and stimulated with Mycobacterium tuberculosis culture filtrate protein, and tumor necrosis factor (TNF-α), interferon gamma (IFN-γ), and interleukin 10 (IL-10) concentrations were determined using immunoassays.

RESULTS

Of 1272 contacts, 41 (3.2%) were diagnosed with tuberculosis before or < 30 days after blood collection (co-prevalent tuberculosis) and 19 (1.5%) during subsequent four-year follow-up (incident tuberculosis). Compared with contacts without tuberculosis, those with co-prevalent tuberculosis had higher median baseline TNF-α and IFN-γ concentrations (in pg/mL, TNF-α 129 versus 71, P < .01; IFN-γ 231 versus 27, P < .001), and those who subsequently developed incident tuberculosis had higher median baseline TNF-α concentrations (in pg/mL, 257 vs. 71, P < .05). In multivariate analysis, contact age < 15 years, US/Canadian birth, and IFN or TNF concentrations > the median were associated with co-prevalent tuberculosis (P < .01 for each); female sex (P = .03) and smoking (P < .01) were associated with incident tuberculosis. In algorithms combining young age, positive skin test results, and elevated CFPS TNF-α, IFN-γ, and IL-10 responses, the positive predictive values for co-prevalent and incident tuberculosis were 40 and 25%, respectively.

CONCLUSIONS

Cytokine concentrations and epidemiologic factors at the time of contact investigation may predict co-prevalent and incident tuberculosis.

Evolution of Interferon-Gamma Release Assay Results and Submillisievert Chest CT Findings among Close Contacts of Active Pulmonary Tuberculosis Patients

Background

Latent tuberculosis (TB) infection among TB contacts is diagnosed using plain chest radiography and interferon-gamma release assays (IGRAs). However, plain chest radiographs often miss active TB, and the results of IGRA could fluctuate over time. The purpose of this study was to elucidate changes in the results of the serial IGRAs and in the findings of the serial submillisievert chest computed tomography (CT) scans among the close contacts of active pulmonary TB patients.

Methods

Patients age 20 or older with active pulmonary TB and their close contacts were invited to participate in this study. Two types of IGRA (QuantiFERON-TB Gold In-Tube assay [QFT-GIT] and the T-SPOT.TB test [T-SPOT]) and submillisievert chest CT scanning were performed at baseline and at 3 and 12 months after enrollment.

Results

In total, 19 close contacts participated in this study. One was diagnosed with active pulmonary TB and was excluded from further analysis. At baseline, four of 18 contacts (22.2%) showed positive results for QFT-GIT and T-SPOT; there were no discordant results. During the follow-up, transient and permanent positive or negative conversions and discordant results between the two types of IGRAs were observed in some patients. Among the 17 contacts who underwent submillisievert chest CT scanning, calcified nodules were identified in seven (41.2%), noncalcified nodules in 14 (82.4%), and bronchiectasis in four (23.5%). Some nodules disappeared over time.

Conclusion

The results of the QFT-GIT and T-SPOT assays and the CT images may change during 1 year of observation of close contacts of the active TB patients.

Multidrug-resistant tuberculosis transmission among middle school students in Zhejiang Province, China

Background

Despite significant advancements in the treatment and diagnosis of tuberculosis (TB) over the past decade, drug-resistant TB remains an increasing threat to public health. TB outbreaks are most commonly reported in schools considering the delay in TB diagnosis, sustained contact, and overcrowding observed in schools. This report describes multidrug-resistant TB (MDR-TB) transmission in a school in Zhejiang Province. We aimed to raise awareness regarding MDR-TB transmission among students.

Case presentation

The index patient was a 16-year-old girl in the second year of junior middle school in Zhejiang Province, China, who had been experiencing persistent cough and expectoration for 37 days since 1 March 2014. She tested positive for smear pulmonary and extrapulmonary TB on 8 April 2014 and was subsequently diagnosed with MDR-TB on 1 May 2014. However, the patient was resistant to isoniazid, rifampicin, ethambutol, and streptomycin. Thus, she was suspended from school for anti-TB treatment. All 54 students who were in close contact with the index patient in the same class were screened, and 5 tested positive on the tuberculin skin test. Their exposure time to the index patient was approximately 37 days. Three classmates were subsequently diagnosed with MDR-TB, with similar resistance profiles nearly two years later. Their average discovery delay was 55 days. These three classmates were also suspended from school for anti-TB treatment. During the treatment period, four students visited the local TB-designated hospital for further consultation every month and were followed up once a month by the local community health service center until they were completely cured.

Conclusions

Discovery delay for an index patient played a primary role in MDR-TB transmission inside the school. To immediately detect TB, morning examinations in schools should be performed. TB trackers and case managers should work closely with public health workers and physicians in cases of TB outbreaks or transmissions involving students. Moreover, individuals who are in close contact with MDR-TB patients should undergo careful clinical follow-up for at least two years. Implementing a joint examination strategy to ensure early detection, diagnosis, and treatment of MDR-TB transmission is recommended.

QuantiFERON TB Gold Plus for the diagnosis of tuberculosis: a systematic review and meta-analysis

Estimated 2017 tuberculosis (TB) incidence is 10 million and mainly depends on the reservoir of individuals with latent TB infection (LTBI). Quantiferon^Ⓡ-TB Gold in-Tube (QFT-GIT) is one of the tests used for LTBI detection. Since 2015 a new version, Quantiferon^Ⓡ-TB Gold Plus (QFT-Plus) is available.

OBJECTIVES

To perform a systematic review and meta-analysis to assess the diagnostic accuracy for TB of QFT-Plus compared to QFT-GIT.

METHODS

PubMed and Scopus were used to detect records related to predefined strings from 2015 to 2018. Full text articles dealing with the sensitivity and/or specificity of the QFT-Plus vs. QFT-GIT for active-TB and LTBI detection were analyzed. Scientific quality and risk of bias were assessed using QADAS-2.

RESULTS

We selected 15 articles. Studies were mainly observational and cross-sectional, performed in 8 countries. Sample size differed in the TB group (27 to 164) compared to LTBI group (29 to 1031). Pooled sensitivity of QFT-Plus for active-TB was 0.94 (0.91 and 0.95 for TB1 and TB2, respectively), whereas pooled specificity for healthy status was 0.96. Pooled sensitivity and specificity for LTBI was 0.91 and 0.95, respectively.

CONCLUSIONS

We show that QFT-Plus is more sensitive compared to QFT-GIT for detecting M. tuberculosis infection, mainly due to TB2 responses.

Comparative sensitivity of the test with tuberculosis recombinant allergen, containing ESAT6-CFP10 protein, and Mantoux test with 2 TU PPD-L in newly diagnosed tuberculosis children and adolescents in Moscow

BACKGROUND

A group of Russian scientists has developed Diaskintest, which comprises Mycobacterium tuberculosis-specific recombinant proteins CFP10-ESAT6, for skin testing (0.2 μg/0.1 ml).

STUDY PURPOSE

To evaluate the comparative sensitivity of TST with 2 TU PPD-L and a skin test with tuberculous recombinant allergen (Diaskintest) containing the ESAT6-CFP10 protein in children and adolescents with newly diagnosed active tuberculosis during mass screening in the primary medical service in Moscow.

MATERIALS AND METHODS

The trial was a comprehensive retrospective group study of children and adolescents diagnosed in Moscow with active tuberculosis in 2013-2016, aged 0 to 17 years inclusive.

RESULTS

From 441 patients selected for analysis 408 patients had both tests (TST with 2 TU PPD-L and Diaskintest) performed, in 193 patients both tests were given simultaneously, of them 162 patients were BCG-vaccinated. Comparative results of both tests in 408 patients with tuberculosis: at cut-off ≥ 5 mm, both tests has similar sensitivity: Diaskintest 98.3% (95% CI 97.0-99.6%), TST 98.0% (95% CI 96.7-99.4%), at cut-off ≥10 mm, the sensitivity decreases for both tests: Diaskintest 90.0% (95% CI 87.0-93.0%), TST 88.7% (95% CI 85.6-91.9%), but at cut-off ≥ 15 mm, the decrease in sensitivity is statistically significant: for Diaskintest 61.5% (95% CI 56.7-66.3%), and for TST 46.3% (95% CI 41.4-51.3%), p <0.0001. The results of simultaneous setting of tests on different hands in 193 people (including 162 BCG-vaccinated), do not differ from the results for 408 people. The correlation between the results of Diaskintest and TST was significant in all groups.

CONCLUSION

In children and adolescents with active tuberculosis, Diaskintest of 0.2 μg/ml and the Mantoux test with 2 TU PPD-L have high sensitivity (98%) at a cut-off of 5 mm; however, at cut-off ≥ 15 mm sensitivity is significantly reduced, and the decrease is more pronounced in the Mantoux test. The advantage of Diaskintest is that, unlike the Mantoux test, it has high specificity under the conditions of mass BCG vaccination. The test is simple to carry out, and can be used in mass screening.

Evaluation of Immunodiagnostic Tests for Leprosy in Brazil, China and Ethiopia

Leprosy remains persistently endemic in several low- or middle income countries. Transmission is still ongoing as indicated by the unabated rate of leprosy new case detection, illustrating the insufficiency of current prevention methods. Therefore, low-complexity tools suitable for large scale screening efforts to specifically detect M. leprae infection and diagnose disease are required. Previously, we showed that combined detection of cellular and humoral markers, using field-friendly lateral flow assays (LFAs), increased diagnostic potential for detecting leprosy in Bangladesh compared to antibody serology alone. In the current study we assessed the diagnostic performance of similar LFAs in three other geographical settings in Asia, Africa and South-America with different leprosy endemicity. Levels of anti-PGL-I IgM antibody (humoral immunity), IP-10, CCL4 and CRP (cellular immunity) were measured in blood collected from leprosy patients, household contacts and healthy controls from each area. Combined detection of these biomarkers significantly improved the diagnostic potential, particularly for paucibacillary leprosy in all three regions, in line with data obtained in Bangladesh. These data hold promise for the use of low-complexity, multibiomarker LFAs as universal tools for more accurate detection of M. leprae infection and different phenotypes of clinical leprosy.

Screening of healthcare workers for latent tuberculosis infection in the low tuberculosis burden country: QuantiFERON-TB gold in tube test or tuberculin skin test?

Healthcare workers (HCWs) are an important group at increased risk for exposure to various infectious agents including Mycobacterium tuberculosis. Unfortunately, there is very limited data on the prevalence of latent tuberculosis infection (LTBI) among HCWs in Iran. The aim of this study was to analyze the prevalence of LTBI among HCW's of Children Medical Center (CMC), an Iranian referral hospital, and to compare the feasibility of using tuberculin skin test (TST) and QuantiFERON-TB gold in tube test (QFT-GIT) to screen the LTBI among this population. Informed consent was obtained before the study questionnaire was completed. Participants were then evaluated for LTBI using QFT-GIT test followed immediately by TST. The prevalence of latent TB infection in the 101 HCWs, based on QFT-GIT positivity, was 47% (n = 47), while based on TST test a higher prevalence was observed (n = 57, 57%). Forty-five (45%) subjects were positive for both tests, whereas 14 (14%) were positive by either test. Among the TST positive cases, 21% (n = 12) were negative for QFT-GIT. The overall agreement of TST and QFT-GIT was 86% ([45 + 42]/101] and a moderate correlation between these two tests was observed (Kappa value 0.72). The use of QFT-GIT test as a second step in TST-positive cases offers an appropriate tool for LTBI detection in our country where all HCWs are BCG-vaccinated. To enable the effective control and prevention of TB in healthcare settings in Iran, specific and detailed guidelines for dealing with LTBI are highly required. All newly hired HCWs should receive baseline testing for LTBI before commencing employment. In addition, HCWs who work in high-risk departments should receive regular follow-up screening for LTBI.

Comparison of latent tuberculosis infection screening strategies before tumor necrosis factor inhibitor treatment in inflammatory arthritis: IGRA-alone versus combination of TST and IGRA

This study aims to compare the latent tuberculosis infection (LTBI) screening strategy of interferon-gamma release assay (IGRA)-alone and in combination with tuberculin skin tests (TSTs) before the initiation of tumor necrosis factor (TNF) inhibitor treatment in patients with inflammatory arthritis. Between January 2011 and June 2017, we enrolled 476 patients who were followed up for ≥1 year after the TNF inhibitor initiation in a tertiary referral center in South Korea. Inflammatory arthritis comprised rheumatoid arthritis in 266 (55.9%) and ankylosing spondylitis in 210 (44.1%) patients. The following strategies were used for LTBI screening during the study period: (i) from January 2011 to October 2014, the combination of TST and QuantiFERON-TB Gold In-Tube (QFT-GIT); (ii) between November 2014 and February 2015, QFT-GIT-alone and (iii) since March 2015, either the combination of TST and QFT-GIT or QFT-GIT-alone depending on the attending physician's choice. We compared the screening strategies of QFT-GIT alone and in combination with TST. Overall, 338 (71.0%) patients received LTBI screening tests using the combination of TST and QFT-GIT, and 138 (29.0%) received QFT-GIT-alone. In addition, the LTBI tests were positive in 159 (47.0%) of 338 patients using the combination tests, and 43.8% (148/338) required LTBI treatment. Meanwhile, the LTBI tests were positive in 32.6% (45/138) of QFT-GIT-alone patients, and 30.4% (42/138) required LTBI treatment. Among 338 patients who received combination tests, 2 patients developed active tuberculosis within 1 year after the TNF inhibitor initiation. Of patients who received QFT-GIT-alone, no patient developed tuberculosis. In conclusion, among patients who received QFT-GIT-alone, the number of patients who required LTBI treatment declined compared to the TST and QFT-GIT combination, and none developed active tuberculosis within 1 year, suggesting that QFT-GIT-alone could be a potential screening strategy for diagnosing LTBI in patients with inflammatory arthritis in South Korea.

Evaluation of IP-10 in Quantiferon-Plus as biomarker for the diagnosis of latent tuberculosis infection

The QuantiFERON-TB Gold Plus (QFT-Plus) is a new test for latent tuberculosis infection (LTBI) diagnosis, in which has been added a new tube containing shorter peptides stimulating CD8 T-cells and CD4-stimulating-peptides. Measurement of alternative biomarkers to Interferon-γ (IFN-γ) in QFT-Plus may improve its sensitivity. Interferon-γ inducible protein 10 (IP-10), has been proposed as a tuberculosis (TB) biomarker. We aimed to evaluate the IP-10 accuracy in QFT-Plus for LTBI diagnosis. QFT-Plus was performed in 36 active TB, 31 LTBI and 16 healthy donors (HD). IP-10 was detected by ELISA. IP-10 is increased in TB1 and TB2 tubes in subjects with active TB and LTBI compared to HD. A ROC analysis comparing active TB and HD was performed and a cut-off of 1174 pg/mL for TB1 and 928.8 pg/mL for TB2 identified active TB with 86% sensitivity (Se) and 94% specificity (Sp). Moreover, increased IP-10 in response to TB1 was found in subjects with LTBI compared to those with active TB. A cut-off point of ≥16,108 pg/mL was chosen to maximize the test performance. However, the test predicted LTBI only with 58% Se and 61% Sp. These results suggest that IP-10 is an alternative biomarker to IFN-γ in the QFT-Plus format.

Borderline QuantiFERON results and the distinction between specific responses and test variability

BACKGROUND

QuantiFERON (QFT) results near the cut-off are subject to debate. We aimed to investigate which borderline QFT results were due to Mycobacterium tuberculosis (Mtb)-specific responses or to test variability.

METHODS

In a contact investigation, tuberculin skin test (TST), QFT and T-SPOT.TB (T-SPOT) were performed in 785 BCG-unvaccinated contacts. Contacts with a low-negative (<0.15), borderline (0.15-0.35), low-positive (0.35-0.70) or high-positive QFT (≥0.70 IU/mL) were compared with respect to exposure, TST and T-SPOT results. Development of active tuberculosis was assessed.

RESULTS

Borderline QFT results occurred in threefold excess over test variability (p = 0.0027). In contacts with low-negative, borderline or positive QFT results, a positive TST occurred in 24.9%, 62.1% and 91.4% (p < 0.0001) and a positive T-SPOT result in 6.3%, 41.3% and 86.4%, respectively (p < 0.0001). Two-third (20/29) of contacts with a borderline and 14/16 (88%) with a low-positive QFT had a positive TST and/or T-SPOT, indicating probable Mtb-infection. During 12 years of follow-up, seven patients were diagnosed with active tuberculosis, two of whom after a low-positive QFT.

CONCLUSIONS

In this study, most borderline and low-positive QFT results were Mtb-specific, showing the biological significance of a borderline QFT. The clinical relevance, however, will be most distinct in patients who are or will be immunocompromised.

Mycobacterial growth inhibition is associated with trained innate immunity

The lack of defined correlates of protection hampers development of vaccines against tuberculosis (TB). In vitro mycobacterial outgrowth assays are thought to better capture the complexity of the human host/Mycobacterium tuberculosis (Mtb) interaction. Here, we used a mycobacterial growth inhibition assay (MGIA) based on peripheral blood mononuclear cells to investigate the capacity to control outgrowth of bacille Calmette-Guérin (BCG). Interestingly, strong control of BCG outgrowth was observed almost exclusively in individuals with recent exposure to Mtb, but not in (long-term) latent TB infection, and only modestly in BCG vaccinees. Mechanistically, control of mycobacterial outgrowth strongly correlated with the presence of a CD14dim monocyte population, but also required the presence of T cells. The nonclassical monocytes produced CXCL10, and CXCR3 receptor blockade inhibited the capacity to control BCG outgrowth. Expression of CXCR3 splice variants was altered in recently Mtb-exposed individuals. Cytokines previously associated with trained immunity were detected in MGIA supernatants, and CXCL9, CXCL10, and CXCL11 represent new markers of trained immunity. These data indicate that CXCR3 ligands are associated with trained immunity and are critical factors in controlling mycobacterial outgrowth. In conclusion, control of mycobacterial outgrowth early after exposure to Mtb is the result of trained immunity mediated by a CXCL10-producing nonclassical CD14dim monocyte subset.

Interferon-gamma release assay for the diagnosis of latent tuberculosis infection: A latent-class analysis

BACKGROUND

Accurate diagnosis and subsequent treatment of latent tuberculosis infection (LTBI) is essential for TB elimination. However, the absence of a gold standard test for diagnosing LTBI makes assessment of the true prevalence of LTBI and the accuracy of diagnostic tests challenging. Bayesian latent class models can be used to make inferences about disease prevalence and the sensitivity and specificity of diagnostic tests using data on the concordance between tests. We performed the largest meta-analysis to date aiming to evaluate the performance of tuberculin skin test (TST) and interferon-gamma release assays (IGRAs) for LTBI diagnosis in various patient populations using Bayesian latent class modelling.

METHODS

Systematic search of PubMeb, Embase and African Index Medicus was conducted without date and language restrictions on September 11, 2017 to identify studies that compared the performance of TST and IGRAs for LTBI diagnosis. Two IGRA methods were considered: QuantiFERON-TB Gold In Tube (QFT-GIT) and T-SPOT.TB. Studies were included if they reported 2x2 agreement data between TST and QFT-GIT or T-SPOT.TB. A Bayesian latent class model was developed to estimate the sensitivity and specificity of TST and IGRAs in various populations, including immune-competent adults, immune-compromised adults and children. A TST cut-off value of 10 mm was used for immune-competent subjects and 5 mm for immune-compromised individuals.

FINDINGS

A total of 157 studies were included in the analysis. In immune-competent adults, the sensitivity of TST and QFT-GIT were estimated to be 84% (95% credible interval [CrI] 82-85%) and 52% (50-53%), respectively. The specificity of QFT-GIT was 97% (96-97%) in non-BCG-vaccinated and 93% (92-94%) in BCG-vaccinated immune-competent adults. The estimated figures for TST were 100% (99-100%) and 79% (76-82%), respectively. T-SPOT.TB has comparable specificity (97% for both tests) and better sensitivity (68% versus 52%) than QFT-GIT in immune-competent adults. In immune-compromised adults, both TST and QFT-GIT display low sensitivity but high specificity. QFT-GIT and TST are equally specific (98% for both tests) in non-BCG-vaccinated children; however, QFT-GIT is more specific than TST (98% versus 82%) in BCG-vaccinated group. TST is more sensitive than QFT-GIT (82% versus 73%) in children.

CONCLUSIONS

This study is the first to assess the utility of TST and IGRAs for LTBI diagnosis in different population groups using all available data with Bayesian latent class modelling. Our results challenge the current beliefs about the performance of LTBI screening tests, and have important implications for LTBI screening policy and practice. We estimated that the performance of IGRAs is not as reliable as previously measured in the general population. However, IGRAs are not or minimally affected by BCG and should be the preferred tests in this setting. Adoption of IGRAs in settings where BCG is widely administered will allow for a more accurate identification and treatment of LTBI.

Tuberculosis in children with sickle cell anaemia: a retrospective study in French tertiary care centres

Tuberculosis (TB) and sickle cell anaemia (SCA) may affect the same population of patients, particularly in Africa but also in high-TB incidence areas in developed countries. However, few data are available from children with SCA who develop TB. The aim of this study was to describe the clinical features and outcome of TB diagnosed in children with SCA. We conducted a retrospective, descriptive study in three referral centre of Sickle Cell Disease in Paris, France. We included 11 patients with SCA who develop TB. The median age at TB diagnosis was 11 years [7.5-14.5]. Two patients were asymptomatic and nine patients were symptomatic. Six patients had pulmonary TB (pulmonary, pleural and mediastinal lesions). Five patients had extrapulmonary TB (osteoarticular TB, hepatic TB, cervical and mediastinal TB). Mycobacterium tuberculosis was isolated in four of the 11 cases. All patients recovered after a median of 6 months of anti-TB treatment. The localisation of TB and outcome after treatment in our SCA patients were similar to the one observed in an age-and sex-matched control group of non-SCA patient with TB.

CONCLUSION

despite the low number of patients included in our study, SCA does not seem to be a risk factor for severe TB. What is Known: • Tuberculosis (TB) remains a global health problem particularly in developing countries, and Sickle cell anaemia (SCA) is currently one of the most common genetic diseases in the world that mainly affects African populations. • Very few data are available on TB in SCA patients. What is New: • The features of TB in children with SCA seem to be comparable to those expected in general population, with favourable outcomes in response to standard treatment. • Monitoring the dosage of anti-TB treatments could be of interest because of the possible impact of SCA on drug metabolism.

Comparing tuberculin skin test and interferon γ release assay (T-SPOT.TB) to diagnose latent tuberculosis infection in household contacts

BACKGROUND/AIMS

The tuberculin skin test (TST) and interferon γ release assay are currently used as diagnostic tools to detect latent tuberculosis (TB) infection; however, there are inconsistencies about the degree of agreement between the tests. We aimed to evaluate the concordance rate between the two tests in household contacts of a country with intermediate TB burden, where most people were vaccinated.

METHODS

We recruited household contacts who spent > 8 hours daily with patients with microbiologically confirmed active pulmonary TB, and received both TST and T-SPOT.TB (Oxford Immunotec) simultaneously. The degree of agreement was analysed according to TST cutoff and Bacille Calmette-Guerin (BCG) vaccination status. Relevant factors were analysed to establish the association with TST or T-SPOT.TB.

RESULTS

Among 298 household contacts, 122 (40.9%) were spouses, and 250 (83.9%) had received BCG vaccination. In the contact sources, 117 (39.3%) showed a positive result for acid-fast bacillus (AFB) sputum smear and 109 (36.6%) had cavities. The highest agreement rate of 69.5% and κ value of 0.378 were found with a 10 mm cutoff. Spouse, time interval from TB diagnosis to test, and AFB sputum smear positivity were significantly associated with a positive result for T-SPOT.TB. Sex, BCG vaccination, and cavity on chest computed tomography were related to TST positivity.

CONCLUSIONS

The present study suggested it was not possible for TST and T-SPOT.TB to replace each other because of considerable discrepancy between the two tests in household contacts in a country with intermediate TB prevalence.

Qualitative and quantitative results of interferon-γ release assays for monitoring the response to anti-tuberculosis treatment

BACKGROUND/AIMS

The usefulness of interferon-γ release assays (IGRAs) in monitoring to responses to anti-tuberculosis (TB) treatment is controversial. We compared the results of two IGRAs before and after anti-TB treatment in same patients with active TB.

METHODS

From a retrospective review, we selected patients with active TB who underwent repeated QuantiFERON-TB Gold (QFN-Gold, Cellestis Limited) and T-SPOT.TB (Oxford Immunotec) assays before and after anti-TB treatment with first-line drugs. Both tests were performed prior to the start of anti-TB treatment or within 1 week after the start of anti-TB treatment and after completion of treatment.

RESULTS

A total of 33 active TB patients were included in the study. On the QFN-Gold test, at baseline, 23 cases (70%) were early secreted antigenic target 6-kDa protein 6 (ESAT-6) or culture filtrate protein 10 (CFP-10) positive. On the T-SPOT. TB test, at baseline, 31 cases (94%) were ESAT-6 or CFP-10 positive. Most of patients remained both test-positive after anti-TB treatment. Although changes in interferon-γ release responses over time were highly variable in both tests, there was a mean decline of 27 and 24 spot-forming counts for ESAT-6 and CFP-10, respectively on the T-SPOT.TB test (p < 0.05 for all).

CONCLUSIONS

Although limited by the small number of patients and a short-term follow-up, there was significant decline in the quantitative result of the T-SPOT. TB test with treatment. However, both commercial IGRAs may not provide evidence regarding the cure of disease in Korea, a country where the prevalence of TB is within the intermediate range.

Diagnosis and treatment of paediatric tuberculosis: An insight review

Tuberculosis (TB) is a major public health problem, invading all age groups world-wide. It is an opportunistic infection affecting the individuals alone or with co-infections. Childhood TB is a neglected aspect and a significant health problem in epidemic areas. It constitutes more than 20% of TB incidence. Pediatric TB exists in the shadow of adult TB. The clinicians concentrate on pulmonary manifestation of TB, whereas it is a major problem in both pulmonary and extra-pulmonary infections. The rate of infection with this disease is mostly associated with poverty, social disruption and human immunodeficiency virus (HIV) infection. The diagnosis of extra-pulmonary TB (EPTB) is more difficult than pulmonary TB (PTB). Delayed diagnosis and executive treatment contribute to increase in the mortality rate in endemic areas. This article provides the evidence-based simple and safe screening method, indicating rapid, highly sensitive and specific diagnostic tests for pulmonary and EPTB in children. The most important aspect of treatment is the correct course of anti-tubercular drugs. This review serves the purpose of quick reference for microbiologists, epidemiologists, academicians, students and researchers. It provides guidance regarding early diagnosis and treatment accuracy of pediatric TB.

Close contact interferon-gamma response to the new PstS1(285-374):CPF10: a preliminary 1-year follow-up study

Background

The available diagnostic tools for latent tuberculosis (TB) infection (LTBI) via interferon-gamma (IFN-g) release assays (IGRA) are based on ESAT6:CFP10 stimulation. However, the mycobacterial antigen PstS1 is also highly immunogenic and some of its fragments, such as PstS1_(285–374), have shown higher immunoreactivity in LTBI than in active TB. PstS1_(285–374), therefore, could increase the accuracy of the existing IGRA to detect LTBI. Thus, a new chimeric protein has recently been developed (PstS1_(285–374):CFP10) showing potential for LTBI screening of recent close contacts (rCt) exposed to Mycobacterium tuberculosis. The aim of this study was to analyze the PstS1_(285–374):CFP10 longitudinal IFN-g profile in comparison to ESAT6:CFP10 and full PstS1/CFP10 stimulation in a rCt cohort and correlate the responses to these in-house IGRA with any clinical changes/interventions that might occur.

Methods

A free-of-cost, one-year follow up was offered to 120 rCt recruited in Rio de Janeiro, RJ, Brazil. Whole blood short-term (WBA), long-term stimulation (LSA) assays, and the tuberculin skin test (TST) were performed during follow up.

Results

Among the enrolled rCt, 44.2% (53/120) returned for re-evaluation and the control group (TST negative, n = 17) showed low IFN-g reactivity to all antigen stimulations during the entire follow up, except for one participant who had shown radiological evidence of past TB/LTBI. Both incident cases were detected by IGRA-PstS1_(285–374):CFP10 during LTBI and after disease progression. Moreover, subsequent to the prophylactic treatment for LTBI (tLTBI), a significant regression in the LSA response was predominantly observed through stimulation of the new chimeric protein (8/10, 80%) followed by ESAT6:CFP10 (5/10, 50%) and PstS1/CFP10 (4/10, 40%). No clinical or epidemiological characteristics were exclusively shared among IGRA convertors.

Conclusion

It was demonstrated that the TST negative rCt without radiological evidence of LTBI/TB did not develop an IGRA-PstS1_(285–374):CFP10 response during the one-year follow up. Moreover, all incident cases were detected by our new IGRA; and a significant decrement of LSA-PstS1_(285–374):CFP10 reactivity post-prophylactic tLTBI was found. To our knowledge, this is the first study to monitor changes in the immune response profile of IGRA-PstS1_(285–374):CFP10 among rCt during a consecutive one-year period, thus providing additional evidence of its potential in the detection of LTBI.

Electronic supplementary material

The online version of this article (doi:10.1186/s13104-016-2360-4) contains supplementary material, which is available to authorized users.

Elevated Neopterin Levels Are Associated with Increased Tuberculosis Risk in Rheumatoid Arthritis Patients with QuantiFERON Conversion during Biologic Therapy

QuantiFERON-TB-Gold (QFT-G) conversion is frequently observed in rheumatoid arthritis (RA) patients receiving biologic therapy. However, there have not been any known biomarkers available for detecting tuberculosis (TB) in QFT-G converters. We aimed to evaluate clinical utility of cytokines/chemokines for detecting TB in patients with QFT-G conversion. Among a total of 227 RA patients who underwent QFT-G assay, 187 QFT-G-negative patients received biologic therapy without isoniazid prophylaxis. QFT-G assay was repeated at week 52 of biologic therapy or at the time of TB diagnosis. Levels of cytokines/chemokines were determined by magnetic bead array or ELISA in QFT-G converters and 12 non-RA patients with TB (non-RA TB). QFT-G conversion was found in 54 (28.9%) of 187 baseline QFT-G-negative patients, of which 7 (13.0%) developed active TB during the one-year follow-up period. Among the examined cytokines/chemokines, non-stimulated and TB-antigen-stimulated neopterin levels were significantly higher in RA patients who developed TB (RA-TB) (median, 24.5pg/ml and 23053pg/ml, respectively) and non-RA TB patients (12.2pg/ml and 9633pg/ml, respectively) compared with QFT-G converters without TB (3.0pg/ml and 2720pg/ml, respectively, both p<0.001). Rising levels of neopterin relative to baseline (non-stimulated levels, 4.4pg/ml vs. 24.5pg/ml; TB-antigen-stimulated levels, 1801pg/ml vs. 23053pg/ml) were observed in QFT-G converters who developed TB. A high proportion (85.7%) of QFT-G converters with high plasma neopterin levels developed TB during the one-year follow-up period. In conclusion, RA patients with QFT-G conversion during the period of biologic therapy should be carefully monitored for elevation of neopterin levels, which is associated with TB risk in QFT-G converters, particularly in TB-endemic areas.

Differential positive TSPOT assay responses to ESAT-6 and CFP-10 in health care workers

BACKGROUND

The TSPOT.TB (TSPOT) diagnostic test for latent tuberculosis infection is based on a cell-mediated response to the Mycobacteria tuberculosis antigens, ESAT-6 and/or CFP-10, producing an "interferon-gamma footprint". We investigated the within-sample and within-subject variability of positive TSPOT assays due to the individual assay antigens' reactivity.

METHODS

Positive TSPOT assay frequencies due to ESAT-6 or CFP-10 among health care workers (HCWs) at 6-month intervals for 18 months were compared. Differences in result interpretation (positive or negative) for ESAT-6 and CFP10 and potential prognostic factors were investigated.

RESULTS

There were 576 positive results in 8805 TSPOT assays representing 2418 participants. A significant difference was detected in positive TSPOT results due to a positive response to either ESAT-6, CFP-10 or both antigens at baseline through 12 M (p < 0.001), but not for the 18 M follow-up. Gender, ethnicity, occupation, previous positive tuberculin skin test (TST) and study site were significantly associated with specific antigen positivity.

CONCLUSIONS

Among our HCW samples with positive TSPOT assays, CFP-10 induced a larger proportion of positive TSPOT results than ESAT-6. Potential causes for this finding include: BCG vaccinated subpopulations, certain jobs, history of positive TST, U.S. birth, and study site. A high proportion of single-positive specimens may reflect false-positives results.

Discordance Between Tuberculin Skin Test and Interferon-γ Release Assay in Children Younger Than 5 Years Who Have Been Vaccinated With Bacillus Calmette-Guérin

BACKGROUND

Interferon-γ release assays (IGRAs) offer the possibility of improved detection of latent tuberculosis infection (LTBI).

OBJECTIVE

To analyze discordant tuberculin skin testing (TST) and IGRA results in ethnic Croatian children as old as 5 years for whom there is documented exposure to an adult with active tuberculosis (TB) and who have been vaccinated with Bacillus Calmette-Guérin.

METHODS

In specimens from our cohort individuals, we tested the performances of the QuantiFERON-TB Gold In-Tube (QFT-GIT) test and TST and analyzed discordant results.

RESULTS

At the TST cutoff value of 10 mm or greater, the estimated prevalence of M. tuberculosis infection was 18.1% (31/171) using TST and 15.2% (26/171) using QFT-GIT. The results of these 2 tests showed an overall concordance of 87.7%. There was no evidence that subjects' age correlated with discordant results.

CONCLUSIONS

The reasons for discordant results in young children are still unclear, which highlights the importance of further longitudinal studies to better understand the interpretation and any possible clinical implications of the results of these tests.

Improving T-cell assays for diagnosis of latent TB infection: Confirmation of the potential role of testing Interleukin-2 release in Iranian patients

BACKGROUND

Since gamma interferon release assays (IGRAs) cannot differentiate between active tuberculosis and latent tuberculosis infection (LTBI), development of rapid and specific diagnosis tools are essential for discriminating between active tuberculosis (TB) from LTBI. Both IGRAs are based on Mycobacterium tuberculosis-specific antigens, namely, early secretory antigenic target 6 (ESAT-6) and 10kDa culture filtrate (CFP-10). The aim of this study was to evaluate the potential value of IL-2 secretion by whole blood cells after stimulation with rESAT-6 and rCFP-10 for discriminating between active and latent tuberculosis.

METHODS

Interleukin-2 and IFN-γ were measured after blood stimulation of 90 cases (30 with active TB, 30 with LTBI and 30 healthy controls) with recombinant ESAT-6 and CFP-10. Receiver operating characteristic (ROC) curve analysis was conducted to determine the best IL-2 and IFN-γ result thresholds in discriminating between cases with active or latent TB, and the corresponding sensitivity and specificity were recorded.

RESULTS

The IFN-γ release assay demonstrated a good sensitivity and specificity (sensitivity 83-84% and specificity 92%) for diagnosis of tuberculosis. The discrimination performance of IL-2 assay (assessed by the area under ROC curve) between LTBI and patients with active TB were 0.75 and 0.8 following stimulation with rESAT-6 and rCFP-10, respectively. Maximum discrimination was reached at a cut-off of 11.6pg/mL for IL-2 after stimulation with recombinant rESAT-6 with 72% sensitivity and 79% specificity and 10.7pg/mL for IL-2 following stimulation with rCFP-10 with 75% sensitivity and 79% specificity, respectively.

CONCLUSION

This study demonstrates that rESAT-6 and rCFP-10 can provide a sensitive and specific diagnosis of TB. In addition, it was shown that IL-2 may be serving as a marker for discriminating LTBI and active TB.

Interferon-Gamma Release Assays and Pediatric Public Health Tuberculosis Screening: The San Francisco Program Experience 2005 to 2008

BACKGROUND

Interferon-gamma release assay utilization in pediatric tuberculosis (TB) screening is limited by a paucity of longitudinal experience, particularly in low-TB burden populations.

METHODS

We conducted a retrospective review of QuantiFERON (QFT)-TB Gold results in San Francisco children from 2005 to 2008. Concordance with the tuberculin skin test (TST) was analyzed for a subset of children. Progression to active disease was determined through San Francisco and California TB registry matches.

RESULTS

Of 1092 children <15 years of age, 853 (78%) were foreign-born, and 136 (12%) were exposed to active TB cases (contacts). QuantiFERON tests were positive in 72 of 1092 (7%) children; 15 of 136 (11%) recent contacts; 53 of 807 (7%) foreign-born noncontacts; and 4 of 149 (3%) US-born noncontacts. QuantiFERON-negative/TST-positive discordance was seen more often in foreign-born/bacille Calmette-Guerin (BCG)-vaccinated children <5 years of age (52 of 56, 93%) compared to those ≥ 5 years of age (90 of 123, 73%; P = .003). Foreign-born, BCG-vaccinated children were more than twice as likely to have a discordant (79%) result as US-born, non-BCG-vaccinated children (37%; P < .0001). During 5587 person-years of follow-up of untreated children, including 146 TST-positive/QFT-negative children, no cases of active TB were identified, consistent with a negative predictive value of 100%.

CONCLUSIONS

Our experience supports the use of QFT to evaluate latent TB infection in children, particularly young BCG-vaccinated children. The proportion of QFT-positive results correlated with risk of exposure, and none of the untreated QFT-negative children developed TB. The low QFT-positive rate highlights the need for more selective testing based on current epidemiology and TB exposure risk.

A prospective cohort study of latent tuberculosis in adult close contacts of active pulmonary tuberculosis patients in Korea

BACKGROUND/AIMS

The objective of this prospective study was to evaluate the diagnosis and treatment of latent tuberculosis infection (LTBI) in adult close contacts of active pulmonary tuberculosis (TB) patients in Korea.

METHODS

Adult close contacts of active pulmonary TB patients were recruited at a regional tertiary hospital in Korea. The participants were tested for LTBI using the tuberculin skin test (TST) and/or QuantiFERON-TB Gold (QFT-G) test. LTBI patients, who consented to treatment, were randomly assigned to receive isoniazid for 9 months (9INH) or rifampin for 4 months (4RIF).

RESULTS

We examined 189 adult close contacts (> 18 years) of 107 active pulmonary TB patients. The TST and QFT-G were positive (≥ 10 mm) in 75/183 (39.7%) and 45/118 (38.1%) tested participants, respectively. Among 88 TST or QFT-G positive LTBI participants, 45 participants were randomly assigned to receive 4RIF (n = 21) or 9INH (n = 24), respectively. The average treatment duration for the 4RIF and 9INH groups was 3.3 ± 1.3 and 6.1 ± 2.7 months, respectively. Treatment was completed in 25 participants (4RIF, n = 16; 9INH, n = 9). LTBI participants who accepted treatment were more likely to be women and have more cavitary lesions on the chest radiographs of index cases and positive TST and QFT-G results compared to those who refused treatment.

CONCLUSIONS

About 40% of adult close contacts of active pulmonary TB patients had LTBI; about 50% of these LTBI participants agreed to treatment.

Interferon-gamma release assays and tuberculin skin testing for diagnosing latent Mycobacterium tuberculosis infection in at-risk groups in Poland

OBJECTIVE/BACKGROUND

The diagnostics of latent tuberculosis infection in Poland using the tuberculin skin test is challenging due to the obligatory Bacillus Calmette-Guérin vaccinations. Interferon-gamma release assays are still very rarely used for diagnostics. We compared the tuberculin skin test and the QuantiFERON-TB Gold In-Tube test to evaluate the degree of latent tuberculosis infection in at-risk groups for tuberculosis (homeless, close contacts, periodic contacts, nursing-home attendees) and in healthy individuals.

METHODS

QuantiFERON-TB Gold In-Tube tests were carried out on 785 individuals from the homeless (n=150), close contacts (n=171), periodic contacts (n=163), nursing-home attendees (n=152), and healthy individuals (n=149). The tuberculin skin test was performed on 129, 156, 147, 148, and 121 participants, respectively. We evaluated the (a) correlation between serum concentrations of interferon gamma and the tuberculin-skin-test induration diameter; (b) between the number of QuantiFERON-TB Gold In-Tube-positive results and the tuberculin-skin-test diameter in the studied groups; and (c) agreement between both tests and the kappa coefficient using the tuberculin-skin-test diameters of 5, 10, and 15mm.

RESULTS

Larger tuberculin-skin-test induration diameters were associated with elevated serum concentrations of interferon gamma. We found a positive correlation between the number of positive QuantiFERON-TB Gold In-Tube screening results and the tuberculin-skin-test induration diameter. The agreement between QuantiFERON-TB Gold In-Tube and tuberculin-skin-test screening results improved with increasing tuberculin-skin-test induration diameter.

CONCLUSION

Based on measures of tuberculin-skin-test induration diameter alone, it is difficult to diagnose latent tuberculosis infection with certainty. The agreement of the QuantiFERON-TB Gold In-Tube test increases with the tuberculin-skin-test diameter. Tuberculin-skin-test diameters larger than 15mm are more likely to be associated with active infection.

Impact of correcting the lymphocyte count to improve the sensitivity of TB antigen-specific peripheral blood-based quantitative T cell assays (T-SPOT.(®)TB and QFT-GIT)

BACKGROUND

The standardized blood-based TB antigen-specific T cell assay, T-SPOT.(®)TB, is ~10% more sensitive than QuantiFERON(®)-TB-GIT (QFT-GIT) in detecting presumed latent TB infection (LTBI). Whilst T-SPOT.(®)TB uses a fixed number of lymphocytes per well, QFT-GIT uses a fixed volume of blood (~1 mL). However, the person-to-person lymphocyte count can vary by 2 to 3 fold. We hypothesized that this variability could explain the reduced sensitivity of QFT-GIT. The findings could have potential implications for improving case detection.

METHODS

T-SPOT.(®)TB was compared to QFT-GIT readouts before and after normalization of lymphocyte count (by adjusting the blood volume or lymphocyte enrichment within a fixed 1 mL volume) to an arbitrary value of 2.5×10(6) cells/mL. Within-test variability was evaluated to meaningfully interpret results.

RESULTS

In patient-specific optimization experiments IFN-γ concentrations significantly increased when QFT-GIT positive samples were enriched with increasing concentrations of lymphocytes (1×10(6) vs. 2.5×10(6) cells/mL). However, for the group as a whole lymphocyte enrichment whilst maintaining a ~1 mL volume, compared to un-enriched samples, did not significantly increase IFN-γ [median (range): 0.03 (0-4.41) vs. 0.20 (0-2.40) IU/mL; P=0.64]. There was also no increase in IFN-γ readouts when QFT-GIT lymphocyte numbers were corrected (to 2.5×10(6) lymphocytes/mL) using volume adjustment. Interestingly, adjusted values were significantly lower than unadjusted ones [median (range): 0.02 (0-12.93) vs. 0.09 (0-14.23) IU/mL; P=0.008].

CONCLUSIONS

In QFT-GIT negative subjects lymphocyte enrichment did not increase QFT-GIT positivity rates. The reduced clinical sensitivity of the QFT-GIT assay, compared to T-SPOT.(®)TB, is likely to be due to factors other than lymphocyte count alone. Further studies are required to clarify these findings.

A workplace tuberculosis case investigation in the presence of immigrant contacts from high prevalence countries

The highest prevalence of tuberculosis (TB) occurs in foreign born immigrants in the United States. Contact investigations at work sites with mostly immigrant workers present multiple practical problems. Recently 402 contacts were investigated at a meat packing plant in rural Texas by the Texas Department of State Health Services (DSHS). Our objective was to study the approach and effectiveness of this intensive investigation. We reviewed information, including symptoms, BCG status, TB history, X-rays, and treatment, on the sentinel case and 47 contacts managed by the Texas DSHS TB Division in Lubbock, TX. We used a gamma interferon release assay (T-SPOT.TB) to identify contacts with TB infection. The sentinel case was foreign born and had cavitary TB with acid-fast positive smears. Forty-two work site contacts were foreign born, and five were US born. The foreign born contacts were from Sudan, Somalia, Mexico, Burma, and Haiti; 18 contacts had a history of BCG vaccination. T-SPOT.TB tests were positive in 20 contacts, borderline in four, and negative in 23. Contacts with borderline results had negative repeat tests. Twenty-three contacts with negative T-SPOT.TB tests were scheduled for repeat tests in 4 weeks, but only four returned for this testing. Chest X-rays were abnormal in two contacts who were started on treatment. Sputum was collected in three individuals; one was culture positive for pan-sensitive Mycobacterium tuberculosis. Twelve contacts were treated for latent TB. Our investigation established an infection rate of 42.5% in this work site contact cohort, which is similar to the 39% prevalence reported by the Center for Disease Control. The use of T-SPOT.TB assays simplified testing in immigrants with high rates of BCG vaccination. Our investigation was complicated by language barriers, varying and uncertain levels of exposure, and a high rate of drop outs in the negative T-SPOT.TB contacts. This concerted effort provides a model for investigating work site contacts, especially with numerous immigrants, and illustrates the problems associated with these investigations.

Tuberculosis Infection in the United States: Prevalence Estimates from the National Health and Nutrition Examination Survey, 2011-2012

BACKGROUND

Reexamining the prevalence of persons infected with tuberculosis (TB) is important to determine trends over time. In 2011-2012 a TB component was included in the National Health and Nutrition Examination Survey (NHANES) to estimate the reservoir of persons infected with TB.

METHODS

Civilian, noninstitutionalized U.S. population survey participants aged 6 years and older were interviewed regarding their TB history and eligibility for the tuberculin skin test (TST) and interferon gamma release assay (IGRA) blood test. Once eligibility was confirmed, both tests were conducted. Prevalence and numbers of TST positive (10 mm or greater), IGRA positive, and both TST and IGRA positive were calculated by adjusting for the complex survey design after applying corrections for item nonresponse and digit preference in TST induration measurements. To examine TST positivity over time, data from NHANES 1999-2000 were reanalyzed using the same statistical methods. The TST was performed using Tubersol, a commercially available purified protein derivative (PPD), rather than PPD-S, which was the antigen used in NHANES 1999-2000. Prior patient history of TB vaccination was not collected in this study nor were patients examined for the presence of a Bacillus of Calmette and Guerin (BCG) vaccine scar.

RESULTS

For NHANES 2011-2012, TST and IGRA results were available for 6,128 (78.4%) and 7,107 (90.9%) eligible participants, respectively. There was no significant difference between the percentage of the U.S. population that was TST positive in 2011-2012 (4.7% [95% CI 3.4-6.3]; 13,276,000 persons) compared with 1999-2000 (4.3%; 3.5-5.3). In 2011-2012 the percentage that was IGRA positive was 5.0% (4.2-5.8) and double TST and IGRA positivity was 2.1% (1.5-2.8). The point estimate of IGRA positivity prevalence in foreign-born persons (15.9%; 13.5-18.7) was lower than for TST (20.5%; 16.1-25.8) in 2011-2012. The point estimate of IGRA positivity prevalence in U.S.-born persons (2.8%; 2.0-3.8) was higher than for TST (1.5%; 0.9-2.6).

CONCLUSIONS

No statistically significant decline in the overall estimated prevalence of TST positivity was detected from 1999-2000 to 2011-2012. The prevalence of TB infection, whether measured by TST or IGRA, remains lower among persons born in the United States compared with foreign-born persons.

Do the tuberculin skin test and the QuantiFERON-TB Gold in-tube test agree in detecting latent tuberculosis among high-risk contacts? A systematic review and meta-analysis

OBJECTIVES:

The QuantiFERON-TB Gold in-tube test (QFT-GIT) and the tuberculin skin test (TST) are used to diagnose latent tuberculosis infection (LTBI). However, conclusive evidence regarding the agreement of these two tests among high risk contacts is lacking. This systematic review and meta-analysis aimed to estimate the agreement between the TST and the QFT-GIT using kappa statistics.

METHODS:

According to the Preferred Reporting Items for Systematic Review and Meta-Analyses guidelines, scientific databases including PubMed, Scopus, and Ovid were searched using a targeted search strategy to identify relevant studies published as of June 2015. Two researchers reviewed the eligibility of studies and extracted data from them. The pooled kappa estimate was determined using a random effect model. Subgroup analysis, Egger’s test and sensitivity analysis were also performed.

RESULTS:

A total of 6,744 articles were retrieved in the initial search, of which 24 studies had data suitable for meta-analysis. The pooled kappa coefficient and prevalence-adjusted bias-adjusted kappa were 0.40 (95% confidence interval [CI], 0.34 to 0.45) and 0.45 (95% CI, 0.38 to 0.49), respectively. The results of the subgroup analysis found that age group, quality of the study, location, and the TST cutoff point affected heterogeneity for the kappa estimate. No publication bias was found (Begg’s test, p=0.53; Egger’s test, p=0.32).

CONCLUSIONS:

The agreement between the QFT-GIT and the TST in diagnosing LTBI among high-risk contacts was found to range from fair to moderate.

Cough Aerosol Cultures of Mycobacterium tuberculosis: Insights on TST / IGRA Discordance and Transmission Dynamics

Rationale

The diagnosis of latent tuberculosis (TB) infection (LTBI) is complicated by the absence of a gold standard. Discordance between tuberculin skin tests (TST) and interferon gamma release assays (IGRA) occurs in 10–20% of individuals, but the underlying mechanisms are poorly understood.

Methods

We analyzed data from a prospective household contact study that included cough aerosol culture results from index cases, environmental and contact factors. We assessed contacts for LTBI using TST and IGRA at baseline and six weeks. We examined TST/IGRA discordance in qualitative and quantitative analyses, and used multivariable logistic regression analysis with generalized estimating equations to analyze predictors of discordance.

Measurements and Results

We included 96 TB patients and 384 contacts. Discordance decreased from 15% at baseline to 8% by six weeks. In adjusted analyses, discordance was related to less crowding (p = 0.004), non-cavitary disease (OR 1.41, 95% CI: 1.02–1.96; p = 0.03), and marginally with BCG vaccination in contacts (OR 1.40, 95% CI: 0.99–1.98, p = 0.06).

Conclusions

We observed significant individual variability and temporal dynamism in TST and IGRA results in household contacts of pulmonary TB cases. Discordance was associated with a less intense infectious exposure, and marginally associated with a BCG-mediated delay in IGRA conversion. Cough aerosols provide an additional dimension to the assessment of infectiousness and risk of infection in contacts.

Study of the BCG Vaccine-Induced Cellular Immune Response in Schoolchildren in Antananarivo, Madagascar

Objective

Although the Bacillus Calmette-Guérin vaccine (BCG) protects young children against serious forms of TB, protection against pulmonary TB is variable. We assessed BCG vaccine-induced cellular immune responses and determined for how long they could be detected during childhood in Antananarivo, Madagascar.

Methods

We assessed BCG vaccine-induced cellular immune responses by TST and IGRA (in-house ELISPOT assay) using BCG and PPD as stimulation antigen, and compared results between vaccinated and non-vaccinated schoolchildren of two age groups, 6-7 and 13-14 years old.

Results

Three hundred and sixty-three healthy schoolchildren were enrolled. TST was performed on 351 children and IGRA on 142. A high proportion (66%; 229/343) of the children had no TST reactivity (induration size 0 mm). TST-positive responses (≥15 mm) were more prevalent among 13-14 year-old (31.7%) than 6-7 year old (16.5%) children, both in the non-vaccinated (43% vs. 9%, p<0.001) and vaccinated (29% vs. 13%, p=0.002) subgroups. There were no significant differences in TST responses between vaccinated and non-vaccinated children in either of the age groups. The IGRA response to BCG and to PPD stimulation was not significantly different according to BCG vaccination record or to age group. A high rate (15.5%; 22/142) of indeterminate IGRA responses was observed. There was very poor agreement between TST and IGRA-PPD findings (k= 0.08) and between TST and IGRA-BCG findings (k= 0.02)

Conclusion

Analysis of TST and IGRA response to stimulation with BCG and PPD revealed no difference in immune response between BCG-vaccinated and non-vaccinated children; also no decrease of the BCG vaccine-induced cellular immune response over time was observed. We conclude that TST and IGRA have limitations in assessing a role of BCG or tuberculosis-related immunity.

Diagnostic values of the QuantiFERON-TB Gold In-tube assay carried out in China for diagnosing pulmonary tuberculosis

BACKGROUND

Interferon-release assays (IGRAs) for diagnosing active pulmonary tuberculosis (PTB) are not yet fully validated, particularly in high TB-endemic areas as the People's Republic of China (PRC). The aim of this report was to assess the performance of the QuantiFERON-TB Gold In-tube (QFT-GIT) and tuberculin skin test (TST), in addition to microbiological results, as contributors for diagnosing active PTB in the PRC.

METHODS/PRINCIPAL FINDINGS

A total of 300 PTB patients, 41 disease controls (DC) and 59 healthy community controls (HCC) were included prospectively between May 2010 and April 2011 from two provinces of the PRC (Heilongjiang and Zhejiang). The QFT-GIT and TST yielded an overall sensitivity for active TB of 80.9% and 86.2%, and a specificity of 36.6% and 26.8%, respectively. The province of origin and smear microscopy status did not significantly impact the diagnostic values for PTB. However, using the TST with a 10 mm cut-off point, a significantly higher proportion of LTBI was observed in the DC than the HCC (p=0.01). Discordant results between the QFT-GIT and TST were found among 1/3 of the PTB, HCC and DC. Two-thirds of the individuals presented TST-positive/QFT-GIT-negative discordant results. The TST-negative/QFT-GIT-positive result was not associated with age or bacillary load. Cumulative QFT-GIT and TST positive results increased the overall sensitivity (95.9%), but it was associated with a dramatic decrease of the overall specificity (24.8%) leading to a suboptimal PPV (80.1%) and a low NPV (61.1%).

CONCLUSIONS/SIGNIFICANCE

The usefulness of the QFT-GIT to diagnose active TB in high TB-endemic countries remains doubtful because like the TST, the QFT-GIT cannot distinguish between LTBI and active TB. Used as single stand-alone tests, both the QFT-GIT and TST have very limited roles in the diagnosis of active PTB. However, the combined use of SM, the TST and QFT-GIT may allow for the exclusion of ATB.

Optimizing the detection of recent tuberculosis infection in children in a high tuberculosis-HIV burden setting

RATIONALE

Children who are young, malnourished, and infected with HIV have significant risk of tuberculosis (TB) morbidity and mortality following TB infection. Treatment of TB infection is hindered by poor detection and limited pediatric data.

OBJECTIVES

Identify improved testing to detect pediatric TB infection.

METHODS

This was a prospective community-based study assessing use of the tuberculin skin test and IFN-γ release assays among children (n = 1,343; 6 mo to <15 yr) in TB-HIV high-burden settings; associations with child characteristics were measured.

MEASUREMENTS AND MAIN RESULTS

Contact tracing detects TB in 8% of child contacts within 3 months of exposure. Among children with no documented contact, tuberculin skin test and QuantiFERON-TB Gold In-Tube positivity was greater than T-SPOT.TB. Nearly 8% of children had IFN-γ release assay positive and skin test negative discordance. In a model accounting for confounders, all tests correlate with TB contact, but IFN-γ release assays correlate better than the tuberculin skin test (P = 0.0011). Indeterminate IFN-γ release assay results were not associated with age. Indeterminate QuantiFERON-TB Gold In-Tube results were more frequent in children infected with HIV (4.7%) than uninfected with HIV (1.9%), whereas T-SPOT.TB indeterminates were rare (0.2%) and not affected by HIV status. Conversion and reversion were not associated with HIV status. Among children infected with HIV, tests correlated less with contact as malnutrition worsened.

CONCLUSIONS

Where resources allow, use of IFN-γ release assays should be considered in children who are young, recently exposed, and infected with HIV because they may offer advantages compared with the tuberculin skin test for identifying TB infection, and improve targeted, cost-effective delivery of preventive therapy. Affordable tests of infection could dramatically impact global TB control.

Role of QuantiFERON(®)-TB Gold In-Tube in tuberculosis contact investigation: experience in a tuberculosis unit

BACKGROUND

Interferon-γ release assays (IGRAs) are increasingly used for the diagnosis of latent tuberculosis infection (LTBI). Because of the lack of a gold standard for the diagnosis of LTBI, IGRAs are compared to the tuberculin skin test (TST) and yield conflicting results. We assessed the usefulness of an IGRA test, QuantiFERON(®)-TB Gold In-Tube (QFT-G-IT), for diagnosing LTBI compared with TST in the setting of a contact screening study.

METHODS

A prospective comparison between the QFT-G-IT and the TST in TB contact subjects in a low TB burden area was conducted sequentially between January 2006 and December 2012.

RESULTS

A moderate concordance between the two tests (κ = 0.44 for TST cut-off of 5 mm and κ = 0.56 for TST cut-off of 15 mm) was found. A better agreement was shown in younger contacts and in non-vaccinated contacts when using a TST of 15 mm. Independent risk factors for a TST(+)/QFT-G-IT(-) discordance were history of BCG vaccination and age between 31 and 59 years. Discordance was also more frequent using a TST cut-off value of 5 mm. QFT-G-IT(+)/TST(-) was infrequent and was found in older contacts.

CONCLUSIONS

Based on our data, we cannot recommend the use of QFT-G-IT as the only test to rule out LTBI, especially in older patients.

IP-10 is an accurate biomarker for the diagnosis of tuberculosis in children

OBJECTIVE

Performance of IFN-γ assays in children is compromised. Therefore, we investigated the utility of IP-10 for the detection of active tuberculosis (TB) and latent tuberculosis infection (LTBI) diagnosis in children; comparing its positivity with QuantiFERON-TB Gold In-Tube (QFN-G-IT) and T-SPOT.TB.

METHODS

We studied 230 children from three groups: active TB, screening (healthy children without known exposure to active TB patient screened at school or by their paediatrician) and contact-tracing studies. IFN-γ release was determined by QFN-G-IT and T-SPOT.TB. IP-10 was detected in QFN-G-IT supernatants by ELISA.

RESULTS

When combining QFN-G-IT and IP-10 assays, positive results improved significantly from 38.3% in QFN-G-IT and 33.9% in IP-10 to 41.3%. Age and type of contact were significant risk factors associated with positive QFN-G-IT and IP-10 results. IP-10 levels after antigen-specific stimulation were significantly higher in comparison to IFN-γ levels. Correlation between the three assays was good (κ = 0.717-0.783).

CONCLUSIONS

IP-10 cytokine is expressed in response to TB specific-antigens used in QFN-G-IT. In conclusion, the use of IFN-γ T-cell based assays in combination with an additional IP-10 assay detection could be useful for diagnosing active TB and LTBI in children.

Serologic diagnosis of tuberculosis by combining Ig classes against selected mycobacterial targets

INTRODUCTION

Accurate, simple and cost-effective diagnostic tests are needed for diagnosis of active tuberculosis (TB). Serodiagnosis is attractive as it can be harnessed for point-of-care tests.

METHODS

We evaluated, in a blinded fashion, the sensitivity and specificity of serologic immunoglobulin (Ig)G, IgA and/or IgM responses to Apa, heat shock protein (HSP) 16.3, HSP20, PE35, probable thiol peroxidase Tpx and lipoarabinomannan (LAM) in 42 HIV-negative South African pulmonary TB patients and 67 control individuals. The status of latent Mycobacterium tuberculosis infection (LTBI) among controls was defined through the TST and IFN-γ release assays (IGRAs). We evaluated 47 definite LTBI (IGRA(+)/LTBI), 8 putative LTBI (IGRA(-)/TST(+)) and 12 TB-uninfected (non-LTBI) subjects.

RESULTS

In contrast to anti-PE35 IgA, anti-PE35 IgG and particularly anti-Apa IgA, performances of anti-LAM IgG and selected anti-protein antibodies were less affected by inclusion of LTBI participants into the analysis. Anti-LAM IgG showed with a sensitivity/specificity of 71.4%/86.6% (p < 0.001) the best discrimination between TB and non-TB subjects. Selected five-antibody-combinations (including anti-LAM IgG, anti-LAM IgA and anti-Tpx IgG) further improved this performance to an accuracy exceeding 86%.

CONCLUSIONS

Antibody responses to some Mycobacterium tuberculosis antigens often also reflect latent infection explaining the poor performance of antibody-based tests for active TB in TB-endemic settings. Our results suggest that rather a combination of serological responses against selected protein and non-protein antigens and different Ig classes should be investigated for TB serodiagnostics.

Discordance of tuberculin skin test and interferon gamma release assay in recently exposed household contacts of pulmonary TB cases in Brazil

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.

Performance of QuantiFERON-TB Gold In-Tube test and Tuberculin Skin Test for diagnosis of latent tuberculosis infection in BCG vaccinated health care workers

Background

Tuberculin skin test (TST) has been used for years as an aid in diagnosing latent tuberculosis infection (LTBI) but it suffers from a number of well-documented performance and logistic problems. Quantiferon-TB Gold In Tube test (QFT-GIT) has been reported to have better sensitivity and specifity than TST. In this study, it was aimed to compare the performance of a commercial IFN-γ release assay (QFT-GIT) with TST in the diagnosis of HCWs at risk for latent TB infection in BCG vaccinated population.

Material/Methods

Hundred healthy volunteer health care workers were enrolled. All were subjected to TST and QFT-GIT. Results were compared among Health Care Workers (HCWs) groups in terms of profession, workplace, working duration.

Results

TST is affected by previous BCG vaccinations and number of cases with QFT-GIT positivity is increased in accordance with the TST induration diameter range. QFT-GIT result was negative in 17 of 32 TST positive (≥15 mm) cases and positive in 4 of 61 cases whose TST diameters are between 6–14 mm, that is attritutable to previous BCG vaccination(s). It was negative in all cases with TST diameters between 0–5 mm.

HCWs with positive QFT-GIT results were significantly older than the ones with negative results. Furthermore duration of work was significantly longer in QFT-GIT positive than in negative HCWs.

Conclusions

There was a moderate concordance between QFT-GIT and TST, when TST result was defined as positive with a ≥15 mm diameter of induration. We suggest that QFT-GIT can be used as an alternative to TST for detection of LTBI, especially in groups with high risk of LTBI and in population with routine BCG vaccination program.