Interferon-gamma release assay improves the diagnosis of tuberculosis in children

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

CLINICAL TRIAL REGISTRATION

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

Antigen-specific chemokine profiles as biomarkers for detecting Mycobacterium tuberculosis infection

Background

Latent tuberculosis (TB) infection can progress to active TB, which perpetuates community transmission that undermines global TB control efforts. Clinically, interferon-γ release assays (IGRAs) are commonly used for active TB case detection. However, low IGRA sensitivity rates lead to false-negative results for a high proportion of active TB cases, thus highlighting IGRA ineffectiveness in differentiating MTB-infected individuals from healthy individuals.

Methods

Participants enrolled at Beijing Chest Hospital from May 2020-April 2022 were assigned to healthy control (HC), LTBI, IGRA-positive TB, and IGRA-negative TB groups. Screening cohort MTB antigen-specific blood plasma chemokine concentrations were measured using Luminex xMAP assays then were verified via testing of validation cohort samples.

Results

A total of 302 individuals meeting study inclusion criteria were assigned to screening and validation cohorts. Testing revealed significant differences in blood plasma levels of CXCL9, CXCL10, CXCL16, CXCL21, CCL1, CCL19, CCL27, TNF-α, and IL-4 between IGRA-negative TB and HC groups. Levels of CXCL9, CXCL10, IL-2, and CCL8 biomarkers were predictive for active TB, as reflected by AUC values of ≥0.9. CXCL9-based enzyme-linked immunosorbent assay sensitivity and specificity rates were 95.9% (95%CI: 91.7-98.3) and 100.0% (92.7-100.0), respectively. Statistically similar AUC values were obtained for CXCL9 and CXCL9-CXCL10 assays, thus demonstrating that combined analysis of CXCL10 and CXCL9 levels did not improve active TB diagnostic performance.

Conclusion

The MTB antigen stimulation-based CXCL9 assay may compensate for low IGRA diagnostic accuracy when used to diagnose IGRA-negative active TB cases and thus is an accurate and sensitive alternative to IGRAs for detecting MTB infection.

Advanced drug delivery and therapeutic strategies for tuberculosis treatment

Tuberculosis (TB) remains a significant global health challenge, necessitating innovative approaches for effective treatment. Conventional TB therapy encounters several limitations, including extended treatment duration, drug resistance, patient noncompliance, poor bioavailability, and suboptimal targeting. Advanced drug delivery strategies have emerged as a promising approach to address these challenges. They have the potential to enhance therapeutic outcomes and improve TB patient compliance by providing benefits such as multiple drug encapsulation, sustained release, targeted delivery, reduced dosing frequency, and minimal side effects. This review examines the current landscape of drug delivery strategies for effective TB management, specifically highlighting lipid nanoparticles, polymer nanoparticles, inorganic nanoparticles, emulsion-based systems, carbon nanotubes, graphene, and hydrogels as promising approaches. Furthermore, emerging therapeutic strategies like targeted therapy, long-acting therapeutics, extrapulmonary therapy, phototherapy, and immunotherapy are emphasized. The review also discusses the future trajectory and challenges of developing drug delivery systems for TB. In conclusion, nanomedicine has made substantial progress in addressing the challenges posed by conventional TB drugs. Moreover, by harnessing the unique targeting abilities, extended duration of action, and specificity of advanced therapeutics, innovative solutions are offered that have the potential to revolutionize TB therapy, thereby enhancing treatment outcomes and patient compliance.

Comparison of IGRA and TST in the diagnosis of latent tuberculosis among women of reproductive age in South India

BACKGROUND

Latent tuberculosis infection (LTBI) is a mycobacterial infection defined on the basis of cellular immune response to mycobacterial antigens. The tuberculin skin test (TST) and the Interferon-Gamma Release Assay (IGRA) are the two tests currently used to establish the diagnosis of LTB. Literature suggests that a study regarding tuberculosis (TB) infection among women of reproductive age group is limited.

METHODS

Female household contact, married, aged 18-49 years underwent written consent form and are screened for LTBI using the TST and IGRA. Participants are injected with TST [5 tuberculin unit (TU), purified protein derivative (PPD)] and IGRA [QuantiFERON®-TB Gold Plus kit (QFT-Plus)]. All the household contacts were followed-up for one year for incident TB cases. Statistical analysis was done using STATA version 14 (StataCorp., Texas, USA). Cohen's kappa test was used to determine the agreement between two tests.

RESULTS

The prevalence of LTBI was found to be 69% (either TST or IGRA positive). Positivity rate of IGRA was higher when compared to that of TST. Out of 139 participants, 68 (49%) tested positive for TST, 80 (57.6%) tested positive for IGRA and 52 (37.4%) tested positive for both. Discordant results were observed in about two fifth of the study population and there was poor agreement between the two tests.

CONCLUSION

Longitudinal studies are required to detect incident TB cases to evaluate the usefulness of these tests. The study was found that IGRA is more consistent to diagnosis of latent tuberculosis infection than the TST. Such studies can also be performed in varied settings among different populations which would help us to improve the diagnosis of LTBI and consequently help in TB control.

Host, technical, and environmental factors affecting QuantiFERON-TB Gold In-Tube performance in children below 5 years of age

Interferon-gamma release assays performance can be impaired by host-related, technical and environmental factors, but data in young children are limited. We performed a cross-sectional study of children < 5 years-of-age at risk of tuberculosis (TB), using QuantiFERON-TB Gold In-Tube (QFT-GIT) assays. The impact of the following was evaluated: (i) host-related [age; hematological parameters; erythrocyte sedimentation rate (ESR); C-reactive protein (CRP); and tobacco smoke exposure (TSE) based on serum cotinine concentrations], (ii) technical (pre-analytical delay) and (iii) environmental factors (annual season; monthly temperatures). Of 204 children, 35 (17.2%) were diagnosed with latent TB infection or TB disease. QFT-GIT results were indeterminate in 14 (6.9%) patients. In multivariate analysis, younger age and higher ESR were associated with lower positive control responses (beta: 0.247, p = 0.002 and - 0.204, p = 0.007, respectively), and increasing age was associated with lower rates of indeterminate QFT-GIT results [OR (95% CI) 0.948 (0.903-0.996) per month, p = 0.035]. In children with positive QFT-GIT results, average monthly temperatures correlated with antigen responses (r = 0.453, p = 0.020); also, antigen responses were lower in winter than in other seasons (p = 0.027). Serum cotinine concentrations determined in a subgroup of patients (n = 41) indicated TSE in 36 (88%), positive control responses being lower in children with TSE (p = 0.034). In children < 5 years-of-age, young age, elevated ESR, temperature, annual season and TSE can affect the performance of QFT-GIT assays.

A prevalence study in Guadalajara, Mexico, comparing tuberculin skin test and QuantiFERON-TB Gold In-Tube

Background

Tuberculosis (TB) is a prevalent disease throughout the world. The extent of TB illness in childhood is not clear; recent data shows that 10–20% of the cases are found in children under 15 years old. In 2017, 1 million children developed the disease, of which 9% were co-infected with HIV.

Methods

A cross-sectional study that analyzed 48 children diagnosed with HIV-infection in Guadalajara, Mexico. The tuberculin skin test (TST) and QuantiFERON-TB Gold In-Tube test (QFT) were performed and compared to diagnose latent TB infection (LTBI).

Results

The average age was 9 years old (± 4), with an age range of 1–16 years; the 6-12-year-old group predominated with 50% of cases. 27 patients (56%) were male; 83% had received the BCG vaccination and 23% had a history of being contacts of TB cases. In the study, 40 patients (83%) were without immunosuppression; seven (15%) with moderate immunosuppression, and only one patient had severe immunodeficiency. Overall, 3 of the 48 children (6.2%) had a positive TST, while 8 out of 48 (16.6%) had a positive QFT. The concordance between the two tests was 89.6% (43/48) with Kappa = 0.5 (95% CI, 0.14–0.85).

Conclusions

The QFT test represents an opportunity in the diagnosis of LTBI, particularly in pediatric HIV- patients. This is the first study that compares the two tests (TST and QFT) in children with HIV-infection in Guadalajara, Mexico.

Tuberculosis Infection in Children and Adolescents: Testing and Treatment

Tuberculosis (TB) remains an important problem among children in the United States and throughout the world. There is no diagnostic reference standard for latent tuberculosis infection (also referred to as tuberculosis infection [TBI]). The tuberculin skin test (TST) has many limitations, including difficulty in administration and interpretation, the need for a return visit by the patient, and false-positive results caused by cross-reaction with Mycobacterium bovis-bacille Calmette-Guerin vaccines and many nontuberculous mycobacteria. Interferon-gamma release assays (IGRAs) are blood tests that use antigens specific for M tuberculosis; as a result, IGRAs yield fewer false-positive results than the TST. Both IGRAs and the TST have reduced sensitivity in immunocompromised children, including children with severe TB disease. Both methods have high positive predictive value when applied to children with risk factors for TBI, especially recent contact with a person who has TB disease. The advantages of using IGRAs and diminished experience with the placement and interpretation of the TST favor expanded use of IGRAs in children in the United States. There are now several effective and safe regimens for the treatment of TBI in children. For improved adherence to therapy, the 3 rifamycin-based regimens are preferred because of their short duration. Daily isoniazid can be used if there is intolerance or drug interactions with rifamycins. A TB specialist should be involved when there are questions regarding testing interpretation, selection of an appropriate treatment regimen, or management of adverse effects.

Surface-enhanced Raman spectroscopy for comparison of serum samples of typhoid and tuberculosis patients of different stages

BACKGROUND

Surface-enhanced Raman spectroscopy (SERS) is a reliable tool for the identification and differentiation of two different human pathological conditions sharing the same symptomology, typhoid and tuberculosis (TB).

OBJECTIVES

To explore the potential of surface-enhanced Raman spectroscopy for differentiation of two different diseases showing the same symptoms and analysis by principal component analysis (PCA) and partial least square discriminate analysis (PLS-DA).

METHODS

Serum samples of clinically diagnosed typhoid and tuberculosis infected individuals were analyzed and differentiated by SERS using silver nanoparticles (Ag NPs) as a SERS substrate. For this purpose, the collected serum samples were analyzed under the SERS instrument and unique SERS spectra of typhoid and tuberculosis were compared showing notable spectral differences in protein, lipid and carbohydrates features. Different stages of the diseased class of typhoid (Early acute and late acute stage) and tuberculosis (Pulmonary and extra-pulmonary stage) were compared with each other and with healthy human serum samples, which were significantly separated. Moreover, SERS data was analyzed using multivariate data analysis techniques including principal component analysis (PCA) and partial least square discriminate analysis (PLS-DA) and differences were so prominent to observe.

RESULTS

SERS Spectral data of typhoid and tuberculosis showed clear differences and were significantly separated using PCA. SERS spectral data of both stages of typhoid and tuberculosis were separated according to 1st principle component. Moreover, by analyzing data using partial least square discriminate analysis, differentiation of two disease classes were considered more valid with a 100% value of sensitivity, specificity and accuracy.

CONCLUSION

SERS can be employed for identification and comparison of two different human pathological conditions sharing same symptomology.

Performance of a lymphocyte t interferon gamma test (Quantiferon-TB gold in tube) in the diagnosis of active tuberculosis in HIV-infected children

OBJECTIVE

Evaluate the performance of QuantiFERON ® -TB Gold In-Tube test (QFT-GIT), to improve the diagnosis of active tuberculosis (TB) in Human Immuno-Deficiency Virus (HIV)-infected children.

METHOD

Sensitivity, specificity, Positive Predictive Value (PPV), Negative Predictive Value (NPV) of QFT-GIT were assessed in 58/63 HIV-infected children who were suspected of having TB.

RESULTS

Sensitivity of QFT-GIT was 20.69%, specificity 96.55%, PPV/NPV respectively 85.71% and 54.90%.

CONCLUSION

QFT-GIT appears to be of little contribution to the diagnosis of active TB in children living with HIV in a TB-endemic country.

Pediatric Tuberculosis: The Impact of "Omics" on Diagnostics Development

Tuberculosis (TB) is a major public health concern for all ages. However, the disease presents a larger challenge in pediatric populations, partially owing to the lack of reliable diagnostic standards for the early identification of infection. Currently, there are no biomarkers that have been clinically validated for use in pediatric TB diagnosis. Identification and validation of biomarkers could provide critical information on prognosis of disease, and response to treatment. In this review, we discuss how the “omics” approach has influenced biomarker discovery and the advancement of a next generation rapid point-of-care diagnostic for TB, with special emphasis on pediatric disease. Limitations of current published studies and the barriers to their implementation into the field will be thoroughly reviewed within this article in hopes of highlighting future avenues and needs for combating the problem of pediatric tuberculosis.

Tuberculosis infection in under-2-year-old refugees: Should we be screening? A systematic review and meta-regression analysis

AIM

Refugees are at increased risk of tuberculosis infection due to time spent in crowded camps, decreased nutrition and originating from countries whose own tuberculosis control systems may have been disturbed. In Australia, tuberculosis is screened for in for all refugees aged 11-34 years old and in those aged 2-10 years arriving from high-incidence countries. Our aims were to determine if refugee children aged under 2 years of age should also be screened.

METHODS

A systematic literature review and meta-regression was carried out on studies in refugee children under 18 years old, involving screening for tuberculosis (active or latent tuberculosis infection (LTBI)). Studies were extracted from the last 10 years from a range of bibliographic databases using the search terms 'tuberculosis', 'children', 'screening' and 'refugee', which tested for tuberculosis using the tuberculin skin test (TST) or QuantiFERON-Gold (Interferon Gamma Release Assay (IGRA)).

RESULTS

Of the 15 included studies, prevalence of LTBI in < 2-year-olds was 5% using IGRA and 15% using TST (P < 0.05). Prevalence increased with age (odds ratio 1.12; 95% confidence interval: 1.06-1.17) cumulatively and decreased where IGRA was used for screening compared to TST (odds ratio 0.38; 95% confidence interval: 0.25-0.58). Prevalence of LTBI did not differ between general versus clinic refugee cohorts.

CONCLUSIONS

Refugees are a particularly vulnerable group in their susceptibility to tuberculosis, and LTBI management is a critical part of tuberculosis disease control due to the lifetime risk of developing active tuberculosis. A prevalence of 5-15% for LTBI in the under 2 years age group would support them being included in screening programmes.

Evaluation of QuantiFERON tuberculosis Gold In-Tube assay for diagnosis of active tuberculosis in children

AIM

Tuberculin skin test (TST) is still used in diagnostic algorithms of childhood tuberculosis (TB). QuantiFERON TB Gold In-Tube assay (QFT-GIT) is an alternative test to TST based on the detection of interferon-gamma release upon in vitro induction of peripheral mononuclear cells by TB antigens. In this study, we aimed to determine the diagnostic value and performance of QFT-GIT for active childhood TB.

METHODS

This retrospective study was conducted between January 2005 and December 2011 in three referral hospitals in Turkey with 124 children who were diagnosed with definite active TB. Sensitivity values of TST and QFT-GIT were determined by accepting the microbiological confirmation as the gold standard of diagnosis of TB.

RESULTS

In our study, sensitivity of QFT-GIT and TST was found to be 65 and 66% respectively. However, combined usage of QFT-GIT and TST was found to be more sensitive (85%) than TST or QFT-GIT alone (P < 0.0001). Although negative results of QFT-GIT or TST did not exclude the diagnosis of active TB in children, their positivity supported the diagnosis. Specificity could not be measured as only microbiologically confirmed cases of Mycobacterium tuberculosis disease were enrolled in the study.

CONCLUSION

Although sensitivities of TST and QFT-GIT are too low to exclude active TB, their positivity supports diagnosis of active TB in children concomitant with signs and symptoms. QFT-GIT and TST should be used together to enhance diagnostic sensitivity and could help exclude a diagnosis of TB if the pretest probability is low.

Comparison of tuberculin skin test and QuantiFERON-TB Gold In-Tube test in Bacillus Calmette-Guerin-vaccinated children

Objectives:

The aim of this study is to determine the concordance between QuantiFERON-TB Gold In-Tube (QFT-GIT) and tuberculin skin test (TST) in children vaccinated with Bacillus Calmette–Guerin (BCG).

Methods:

This cross-sectional study was done at a pediatric tertiary care center in 33 BCG-vaccinated children aged 6 months–15 years suspected of Mycobacterium tuberculosis infection or in contact with a patient with open tuberculosis (TB). All patients were tested for TST with purified protein derivative-S 5 tuberculin units and QFT-GIT assays. Concordance was evaluated between TST and QFT assay by kappa coefficient (k). Agreement between the tests was classified into categories: poor if k < 0.20, fair (k = 0.21–0.40), moderate (k = 0.41–0.60), good (k = 0.61–0.80), and very good (k = 0.81–1.00).

Results:

Both the TST and QFT assay were positive in 13 and negative in eight children, respectively, resulting in an agreement of 63% (κ = 0.31). Eight children were <4 years of age of which only one patient had a positive TST and QFT-GIT, and TST and QFT-GIT were negative in two patients resulting in an agreement of 37.5% (κ = 0.063). Among children 4 years of age and older, 12 patients had a positive TST and QFT-GIT and 6 patients had a negative TST and QFT-GIT resulting in an agreement of 72% (κ = 0.41). Among 12 children who had been in contact with an adult having open TB, both the TST and QFT-GIT were positive in 6 patients and negative in two patients, respectively, resulting in an agreement of 66% (κ = 0.41). TST specificity was only 29.6% with a positive predictive value of 42.4% as compared to QFT-GIT. Among children <4 years of age, TST specificity was only 28.6% with a positive predictive rate of 16.7%, and among children >4 years of age, TST specificity was 50% with a positive predictive value of 66.7%. In patients with contact with a patient having TB, TST specificity was 33.3%. Considering TST of 15 mm and above as positive, TST specificity increased to 63.2% and a positive predictive value was 56.3%.

Conclusion:

The concordance of TST and QFT-GIT is low in children with previous BCG vaccination and especially in children <4 years of age. QFT-GIT may help to rule out false-positive TST.

QuantiFERON-TB Performs Better in Children, Including Infants, than in Adults with Active Tuberculosis: a Multicenter Study

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

Comparative performance of QuantiFERON-TB Gold versus skin test with tuberculosis recombinant allergen (Diaskintest) among patients with suspected pulmonary tuberculosis in Russia

BACKGROUND

The early identification of Mycobacterium tuberculosis infection can prevent tuberculosis (TB) transmission. A skin test with a tuberculosis recombinant allergen (Diaskintest) is a new method for identification that has been implemented in Russia. This study was performed to compare the performances of Diaskintest and QuantiFERON-TB Gold (QFT) in adults and children with suspected TB in Moscow, Russia.

METHODS

Adults (n=85) and children (n=96) were tested using Diaskintest and QFT. Concordance and comparative analyses were performed.

RESULTS

Diaskintest and QFT were concordant in 84% of adults and 90% of children (overall concordance 87%, κ>0.6, K_c>0.5). The concordance between QFT, Diaskintest, and the final diagnosis was good in adults (86% and 81%, respectively) and moderate in children (77% and 79%, respectively). In adults, QFT had a higher sensitivity for detecting TB than Diaskintest (82% and 68%, respectively); in children, Diaskintest was more sensitive (73% and 65%, respectively). In patients with a confirmed TB diagnosis, negative Diaskintest/QFT results were associated with low disease activity. Combined Diaskintest/QFT results identified TB patients with higher sensitivity and specificity than each test separately.

CONCLUSIONS

Diaskintest is a low-cost diagnostic tool that shows a test positivity rate similar to QFT and can be used in combination with QFT as an adjunctive test for TB diagnosis.

Immunologic-based Diagnosis of Latent Tuberculosis Among Children Younger Than 5 Years of Age Exposed and Unexposed to Tuberculosis in Tanzania

BACKGROUND

Childhood tuberculosis (TB) is acquired after exposure to an infectious TB case, often within the household. We prospectively screened children 6-59 months of age, exposed and unexposed to an infectious TB case within the same household, for latent tuberculosis infection (LTBI), in Dar es Salaam, Tanzania.

METHODS

We collected medical data and clinical specimens (to evaluate for helminths, TB and HIV coinfections) and performed physical examinations at enrollment and at 3-month and 6-month follow-up surveys. LTBI was assessed using QuantiFERON-TB Gold (QFT) at enrollment and at 3 months.

RESULTS

In total, 301 children had complete data records (186 with TB exposure and 115 without known TB exposure). The median age of children was 26 months (range: 6-58); 52% were females, and 4 were HIV positive. Eight children (3%) developed TB during the 6-month follow-up. We found equal proportions of children with LTBI among those with and without exposure: 20% (38/186) versus 20% (23/115) QFT-positive, and 2% (4/186) versus 4% (5/115) indeterminate QFT. QFT conversion rate was 7% (22 children) and reversion 8% (25 children). Of the TB-exposed children, 72% initiated isoniazid preventive therapy, but 61% of parents/caregivers of children with unknown TB exposure and positive QFT refused isoniazid preventive therapy.

CONCLUSIONS

In this high burden TB setting, TB exposure from sources other than the household was equally important as household exposure. Nearly one third of eligible children did not receive isoniazid preventive therapy. Evaluation for LTBI in children remains an important strategy for controlling TB but should not be limited to children with documented TB exposure.

Risk Factors for Indeterminate Interferon-Gamma Release Assay for the Diagnosis of Tuberculosis in Children-A Systematic Review and Meta-Analysis

Background: Interferon-gamma release assays (IGRA) are well-established immunodiagnostic tests for tuberculosis (TB) in adults. In children these tests are associated with higher rates of false-negative and indeterminate results. Age is presumed to be one factor influencing cytokine release and therefore test performance. The aim of this study was to systematically review factors associated with indeterminate IGRA results in pediatric patients. Methods: Systematic literature review guided by the preferred reporting items for systematic reviews and meta-analyses (PRISMA) searching PubMed, EMBASE, and Web of Science. Studies reporting results of at least one commercially available IGRA (QuantiFERON-TB, T-SPOT.TB) in pediatric patient groups were included. Random effects meta-analysis was used to assess proportions of indeterminate IGRA results. Heterogeneity was assessed using the I² value. Risk differences were calculated for studies comparing QuantiFERON-TB and T-SPOT.TB in the same study. Meta-regression was used to further explore the influence of study level variables on heterogeneity. Results: Of 1,293 articles screened, 133 studies were included in the final analysis. These assessed QuantiFERON-TB only in 77.4% (103/133), QuantiFERON-TB and T-SPOT.TB in 15.8% (21/133), and T-SPOT.TB only in 6.8% (9/133) resulting in 155 datasets including 107,418 participants. Overall 4% of IGRA results were indeterminate, and T-SPOT.TB (0.03, 95% CI 0.02-0.05) and QuantiFERON-TB assays (0.05, 95% CI 0.04-0.06) showed similar proportions of indeterminate results; pooled risk difference was-0.01 (95% CI -0.03 to 0.00). Significant differences with lower proportions of indeterminate assays with T-SPOT.TB compared to QuantiFERON-TB were only seen in subgroup analyses of studies performed in Africa and in non-HIV-infected immunocompromised patients. Meta-regression confirmed lower proportions of indeterminate results for T-SPOT.TB compared to QuantiFERON-TB only among studies that reported results from non-HIV-infected immunocompromised patients (p < 0.001). Conclusion: On average indeterminate IGRA results occur in 1 in 25 tests performed. Overall, there was no difference in the proportion of indeterminate results between both commercial assays. However, our findings suggest that in patients in Africa and/or patients with immunocompromising conditions other than HIV infection the T-SPOT.TB assay appears to produce fewer indeterminate results.

Interferon-γ Release Assay Performance for Tuberculosis in Childhood

BACKGROUND

Interferon-γ release assays (IGRAs) are important adjunctive tests for diagnosing tuberculosis (TB) disease in children.

METHODS

We analyzed California TB registry data for patients ≤18 years with laboratory-confirmed TB disease during 2010-2015 to identify case characteristics associated with test selection and performance and measure IGRA sensitivity.

RESULTS

In total, 778 cases of TB were reported; 360 were laboratory confirmed. Indeterminate IGRAs were associated with being <1 year old (prevalence rate ratio 9.23; 95% confidence interval 2.87 to 29.8) and having central nervous system disease (prevalence rate ratio 2.69; 95% confidence interval 1.06 to 6.86) on multivariable analysis. Ninety-five children had both an IGRA and tuberculin skin test (TST) performed. Among those, the sensitivity of IGRA in 5- to 18-year-olds was 96% (66 out of 69) vs 83% (57 out of 69) for TST (P = .01); IGRA sensitivity compared with TST in children ages 2 to 4 was 91% (10 out of 11) vs 91% (10 out of 11) (P > .99), and the sensitivity compared with TST in children aged <2 years was 80% (12 out of 15) vs 87% (13 out of 15) (P > .99).

CONCLUSIONS

This is the largest North American analysis of IGRA use and performance among children with TB disease. In children <5 years old, IGRA sensitivity is similar to TST, but sensitivity of both tests are reduced in children <2 years old. Indeterminate results are higher in children <1 year old and in central nervous system disease. In children ≥5 years old with laboratory-confirmed TB, IGRA has greater sensitivity than TST and should be considered the preferred immunodiagnostic test..

Is secretion of IFN-gamma in response to Mycobacterium tuberculosis antigens in youngest children sufficient to play a role in TB diagnostics?

OBJECTIVES

To assess whether children ≤5 years of age, produce sufficient amounts of interferon gamma (IFN-ɣ) in response to phytohaemagglutinin (mitogen), and Mycobacterium tuberculosis antigens (TB antigens) in the QuantiFERON-TB Gold in-Tube test (QFT-GIT), (Cellestis Ltd., Australia).

WORKING HYPOTHESIS

Is TB-antigen-induced IFN-ɣ response in children ≤5 years sufficient to consider QFT-GIT a possible tool for TB diagnostics? Study design, patient-subject selection, and methods: We recruited children 0-17 years old suspected of TB infection to this cross-sectional study, in whom QFT-GIT and TST were performed. We analyzed the median IFN-ɣ levels in mitogen and TB antigen tubes in children ≤5 years and >5 years, and the correlation between IFN-ɣ level in both tubes and age.

RESULTS

A total of 153 children were enrolled, age median was 7.8 (IQR:8), 45 (29.4%) aged ≤5 years (median 3.4, IQR:1.7), 108 > 5 years (median 10.55, IQR:5.93). In the mitogen tubes, the median IFN-ɣ level was higher in children >5 years (median 17.87, IQR:2.1 vs 16.77, IQR:7.6), but surprisingly in the TB antigen tubes it was higher in the younger group (median 0.12, IQR:0.21vs 0.06, IQR:0.09, P = 0.04). We proved a positive correlation between IFN-ɣ level and age in mitogen tubes (r = 0.18, P = 0.03) and a negative correlation in TB antigen tubes (r = -0.17, P = 0.04). In latent tuberculosis infection patients, the latter correlation was found to be even stronger (r = -0.39, P = 0.01).

CONCLUSIONS

The youngest children release sufficient amount of IFN-ɣ in response to TB antigens thus QFT-GIT might be a useful tool for TB diagnostics in this age group.

Quantitative Analysis of Gamma Interferon Release Assay Response in Children with Latent and Active Tuberculosis

The use of interferon gamma (IFN-γ) release assays (IGRAs) for the diagnosis of tuberculosis (TB) infection in children is still under debate because of concerns about the immature immune response in children. The aim of this study was to investigate quantitative values of the QuantiFERON-TB Gold In-Tube (QFT-IT) test, a commercially available IGRA, in a large cohort of children screened for TB infection. A retrospective analysis was conducted on samples from 517 children aged 0 to 14 years old at the Pediatric Unit of S. Orsola-Malpighi University Hospital of Bologna (Italy); quantitative responses to QFT-IT stimuli were analyzed according to diagnosis and age. Elevated IFN-γ values in the QFT-IT nil (background) tube were statistically associated with diagnosis of active TB. Quantitative IFN-γ response to Mycobacterium tuberculosis-specific antigens (TB Ag) was not significantly different in children with active TB compared to those with latent TB infection (LTBI), even though the median values were higher in the first group. When children were grouped by age, those less than 5 years old produced significantly higher levels of IFN-γ in response to TB Ag if they had active TB (median 10 IU/ml) than those with LTBI (median 1.96 IU/ml). IFN-γ response to mitogen increased with age. The overall rate of indeterminate results was low (3.9%), and no indeterminate QFT-IT values were observed in active or latent TB patients. In conclusion, quantitative QFT-IT values could provide further information to clinicians to manage TB in children, and these observations could be transferred to the new version of the test, QuantiFERON-TB Gold Plus, which to date lacks data from the pediatric population.

Optimizing Blood Collection and Processing for Quantiferon-TB Gold in-Tube Testing Gives Low Rates of Indeterminate Results: Clinical Implications

The rate of low-mitogen indeterminate interferon-gamma release assay results at a hospital with expert pediatric phlebotomy and rapid incubation of specimens was 0.96%. All low-mitogen indeterminate results were found to be associated with an immunocompromised or anergic state. We describe a child where an unexpected indeterminate interferon-gamma release assay test pointed to an underlying anergic condition and was of diagnostic significance.

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.

Testing of tuberculosis infection among Chinese adolescents born after terminating the Bacillus Calmette-Guérin booster vaccination: subgroup analysis of a population-based cross-sectional study

The prevalence of tuberculosis infection among adolescents born after terminating the Bacillus Calmette-Guérin (BCG) booster vaccination in China was estimated using tuberculin skin testing (TST) and QuantiFERON-TB Gold assay (QFT) to investigate the influence of neonatal BCG vaccination on the performance of TST. Data analysis was conducted for 2831 eligible participants aged 5-15 years from the baseline survey of a population-based multi-center prospective study. The prevalence rates of TST (induration = 10 mm) and QFT positivity were 9.3% (264/2827) and 2.5% (71/2831), respectively. The rate of QFT indeterminate result was 2.2% (62/2831). The overall agreement between TST and QFT was low (concordance = 88.0%; ? coefficient = 0.125). Only TST was positively associated with BCG vaccination with an adjusted odds ratio of 1.71 [95% confidence interval, 1.26-2.31]. A history of close contact with patients of active TB was significantly associated with positivity for TST and QFT. Our results suggested that BCG neonatal vaccination still affects TST performance, and a twostep approach might be considered for TB infection testing among adolescents in China.

Tuberculosis in Infants and Children

One million children develop tuberculosis disease each year, and 210,000 die from complications of tuberculosis. Childhood tuberculosis is very different from adult tuberculosis in epidemiology, clinical and radiographic presentation, and treatment. This review highlights the many unique features of childhood tuberculosis, with special emphasis on very young children and adolescents, who are most likely to develop disease after infection has occurred.

Field evaluation of a blood based test for active tuberculosis in endemic settings

Over 9 million new active tuberculosis (TB) cases emerge each year from an enormous pool of 2 billion individuals latently infected with Mycobacterium tuberculosis (M. tb.) worldwide. About 3 million new TB cases per year are unaccounted for, and 1.5 million die. TB, however, is generally curable if diagnosed correctly and in a timely manner. The current diagnostic methods for TB, including state-of-the-art molecular tests, have failed in delivering the capacity needed in endemic countries to curtail this ongoing pandemic. Efficient, cost effective and scalable diagnostic approaches are critically needed. We report a multiplex TB serology panel using microbead suspension array containing a combination of 11 M.tb. antigens that demonstrated overall sensitivity of 91% in serum/plasma samples from TB patients confirmed by culture. Group wise sensitivities for sputum smear positive and negative patients were 95%, and 88%, respectively. Specificity of the test was 96% in untreated COPD patients and 91% in general healthy population. The sensitivity of this test is superior to that of the frontline sputum smear test with a comparable specificity (30–70%, and 93–99%, respectively). The multiplex serology test can be performed with scalability from 1 to 360 patients per day, and is amenable to automation for higher (1000s per day) throughput, thus enabling a scalable clinical work flow model for TB endemic countries. Taken together, the above results suggest that well defined antibody profiles in blood, analyzed by an appropriate technology platform, offer a valuable approach to TB diagnostics in endemic countries.

Quantiferon-TB Gold In-Tube Improves Tuberculosis Diagnosis in Children

BACKGROUND

The diagnostic accuracy of Quantiferon-TB Gold In-Tube (QFT-IT) is uncertain in the pediatric population, while tuberculin skin test (TST) is still conventionally used despite its limitations. The aim of this study was to compare the performance of QFT-IT with TST in a large cohort of children screened for tuberculosis (TB) infection because of contact tracing, suspected TB, arrival from endemic country or immunosuppressive therapy.

METHODS

A retrospective analysis was conducted on 517 children 0-14 years of age evaluated at the pediatric unit of the S. Orsola-Malpighi University Hospital of Bologna, Italy; 366 of them were also tested with TST. Results were analyzed for Calmette-Guérin bacillus vaccination, country of origin, reason for testing, diagnosis and age.

RESULTS

The overall agreement between the 2 tests was 89.9%, but it was highly affected by Calmette-Guérin bacillus vaccination (P < .0001). According to diagnosis and age, QFT-IT detected latent tuberculous infection cases better than TST in all age groups. Sensitivity for diagnosing active TB in symptomatic children was higher for QFT-IT than TST (93.3% vs. 86.5%), especially in children younger than 2 years, while specificity was high for both tests (99.3% and 98.8%, respectively). Low rate of indeterminate QFT-IT results (3.9%) was not differently distributed among age groups, but was associated with diagnosis of TB exclusion (P < 0.0001), mainly pneumonia (35%), and to Italian children (P = 0.0024).

CONCLUSIONS

Despite the concern about the use of QFT-IT in children because of their immature immune system, our results suggest the preferential use of QFT-IT as a support tool for diagnosis and management of TB, even in infants.

Recommendations for the diagnosis of pediatric tuberculosis

Tuberculosis (TB) is still the world's second most frequent cause of death due to infectious diseases after HIV infection, and this has aroused greater interest in identifying and managing exposed subjects, whether they are simply infected or have developed one of the clinical variants of the disease. Unfortunately, not even the latest laboratory techniques are always successful in identifying affected children because they are more likely to have negative cultures and tuberculin skin test results, equivocal chest X-ray findings, and atypical clinical manifestations than adults. Furthermore, they are at greater risk of progressing from infection to active disease, particularly if they are very young. Consequently, pediatricians have to use different diagnostic strategies that specifically address the needs of children. This document describes the recommendations of a group of scientific societies concerning the signs and symptoms suggesting pediatric TB, and the diagnostic approach towards children with suspected disease.

Relation between BCG vaccine scar and an interferon-gamma release assay in immigrant children with "positive" tuberculin skin test (≥10 mm)

Background

Immigrants from countries with high incidence of tuberculosis (TB) are usually offered screening when they arrive to low incidence countries. The tuberculin skin test (TST) is often used. The interferon gamma release assays (IGRAs) are more specific and not affected by BCG vaccination. The aims of this study were 1. To see if there if there is a correlation between a positive IGRA (QFT) and presence of a BCG scar in children with TST ≥10 mm, 2. To compare the TST diameter with QFT result, 3. To see if chest X-ray can be omitted in QFT negative children despite TST ≥10 mm.

Methods

762 healthy children/adolescents (median age 14 years) arriving to Gothenburg and surroundings with TST ≥10 mm were tested with QFT.

Results

A total of 163/492 (33 %) children with BCG scar had positive QFT, whereas 205/270 (76 %) without BCG scar had positive QFT (p < 0.0001). The median TST was 12 mm in QFT negative and 18 mm in QFT positive children (p < 0.0001) but with considerable overlap. Median TST was the same (12 mm) in QFT negative children with and without BCG scar. Among the QFT positive children 25/368 had chest X-ray changes compared to 2/393 among the QFT negative children (p < 0.0007).

Conclusions

Previous BCG vaccination had an effect on the TST diameter so an IGRA is recommended to diagnose latent TB. Using only TST for screening of latent TB would lead to overdiagnosis. The TST diameter was larger in QFT positive than in QFT negative children but could not predict QFT in the individual patient. Chest X ray contributes little to the diagnosis of TB in QFT negative children but can not be omitted because of late seroconversion of QFT in some patients.

Trial registration

Not applicable.

Pott's disease in Moroccan children: clinical features and investigation of the interleukin-12/interferon-γ pathway

SETTING

Tuberculosis spondylodiscitis (TS), or Pott's disease, an extra-pulmonary form of tuberculosis (TB), is rare and difficult to diagnose in children. Some cases of severe TB in children were recently explained by inborn errors of immunity affecting the interleukin-12/interferon-gamma (IL-12/IFN-γ) axis.

OBJECTIVE

To analyse clinical data on Moroccan children with TS, and to perform immunological and genetic explorations of the IL-12/IFN-γ axis.

DESIGN

We studied nine children with TS diagnosed between 2012 and 2014. We investigated the IL-12/IFN-γ circuit by both whole-blood assays and sequencing of the coding regions of 14 core genes of this pathway.

RESULTS

A diagnosis of TS was based on a combination of clinical, biological, histological and radiological data. QuantiFERON(®)-TB Gold In-Tube results were positive in 75% of patients. Whole-blood assays showed normal IL-12 and IFN-γ production in all but one patient, who displayed impaired decreased response to IL-12. No candidate disease-causing mutations were detected in the exonic regions of the 14 genes.

CONCLUSIONS

TS diagnosis in children remains challenging, and is based largely on imaging. Further investigations of TS in children are required to determine the role of genetic defects in pathways that may or may not be related to the IL-12/IFN-γ axis.

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.

Usefulness of interferon-γ release assay for the diagnosis of latent tuberculosis infection in young children

Purpose

Latent tuberculosis infection (LTBI) in young children may progress to severe active tuberculosis (TB) disease and serve as a reservoir for future transmission of TB disease. There are limited data on interferon-γ release assay (IGRA) performance in young children, which our research aims to address by investigating the usefulness of IGRA for the diagnosis of LTBI.

Methods

We performed a tuberculin skin test (TST) and IGRA on children who were younger than 18 years and were admitted to Chung-Ang University Hospital during May 2011–June 2015. Blood samples for IGRA were collected, processed, and interpreted according to manufacturer protocol.

Results

Among 149 children, 31 (20.8%) and 10 (6.7%) were diagnosed with LTBI and active pulmonary TB, respectively. In subjects lacking contact history with active TB patients, TST and IGRA results were positive in 41.4% (29 of 70) and 12.9% (9 of 70) subjects, respectively. The agreement (kappa) of TST and IGRA was 0.123. The control group, consisting of non-TB-infected subjects, showed no correlation between age and changes in interferon-γ concentration after nil antigen, TB-specific antigen, or mitogen stimulation in IGRAs (P=0.384, P=0.176, and P=0.077, respectively). In serial IGRAs, interferon-γ response to TB antigen increased in IGRA-positive LTBI subjects, but did not change considerably in initially IGRA-negative LTBI or control subjects.

Conclusion

The lack of decrease in interferon-γ response in young children indicates that IGRA could be considered for this age group. Serial IGRA tests might accurately diagnose LTBI in children lacking contact history with active TB patients.

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.

High Discordance Between Pre-US and Post-US Entry Tuberculosis Test Results Among Immigrant Children: Is it Time to Adopt Interferon Gamma Release Assay for Preentry Tuberculosis Screening?

BACKGROUND

Since 2007, immigration applicants 2-14 years old with a tuberculin skin test (TST) ≥10 mm and an otherwise negative evaluation for tuberculosis (TB) are assigned a classification for TB infection and instructed to seek domestic evaluation upon arrival in the US in accordance with Centers for Disease Control and Prevention instructions. We examined the characteristics and outcome of domestic evaluation of immigrant children who arrived in California with a positive TST on preimmigration examination to inform the preimmigration TB screening process.

METHODS

Retrospective analysis of the characteristics and results of domestic evaluation of immigrants 2-14 years old who arrived in California with a classification for TB infection during October 1, 2008-September 30, 2013 was performed. TB disease was determined by matching preimmigration records with the California TB registry.

RESULTS

Among a total of 12,544 immigrant children included, 7786 (62%) were evaluated for TB postentry. Of these, 5243 (67%) were tested with TST or interferon gamma release assay (IGRA), and 2371 (45%) had a positive test. Of those tested with IGRA (n = 4035), 914 (23%) were positive. The proportion with positive IGRA increased significantly with age (years): 2-4 (11%), 5-9 (19%), 10-14 (28%), P < 0.0001; was lowest among arrivers from China (6%) and highest among arrivers from Mexico (48%). Nine children (0.07%) had TB disease within 5 years after arrival.

CONCLUSIONS

The majority of immigrant children with a positive preimmigration TST tested negative for TB infection on domestic evaluation using TST or IGRA. Inclusion of IGRA in preimmigration TB screening is likely to reduce subsequent testing, treatment and cost of evaluations among immigrant children to the US.

Guidelines for the use of interferon-γ release assays in the diagnosis of tuberculosis infection

INTRODUCTION

Interferon-gamma release assays are widely used for the diagnosis of tuberculosis infection in low-prevalence countries. However, there is no consensus on their application. The objective of this study was to develop guidelines for the use of interferon-gamma release assays in specific clinical scenarios in Spain.

METHODS

A panel of experts comprising specialists in infectious diseases, respiratory diseases, microbiology, pediatrics and preventive medicine, together with a methodologist, formulated the clinical questions and outcomes of interest. They conducted a systematic literature search, summarized the evidence and rated its quality, and prepared the recommendations following the GRADE (Grading of Recommendations of Assessment Development and Evaluations) methodology.

RESULTS

The panel prepared recommendations on the use of interferon-gamma release assays for the diagnosis of tuberculosis infection in the contact-tracing study (both adults and children), health care workers, immunosuppressed patients (patients infected with human immunodeficiency virus, patients with chronic immunomediated inflammatory diseases due to start biological therapy and patients requiring organ transplant) and for the diagnosis of active tuberculosis. Most recommendations were weak, mainly due to the lack of good quality evidence to balance the clinical benefits and disadvantages of the interferon-gamma release assays as compared with the tuberculin skin test.

CONCLUSION

This document provides evidence-based guidance on the use of interferon-gamma release assays for the diagnosis of tuberculosis infection in patients at risk of tuberculosis or with suspicion of active disease. The guidelines will be applicable in specialist and primary care and in public health settings.

Health Profiles of Newly Arrived Refugee Children in the United States, 2006-2012

OBJECTIVES

We conducted a large-scale study of newly arrived refugee children in the United States with data from 2006 to 2012 domestic medical examinations in 4 sites: Colorado; Minnesota; Philadelphia, Pennsylvania; and Washington State.

METHODS

Blood lead level, anemia, hepatitis B virus (HBV) infection, tuberculosis infection or disease, and Strongyloides seropositivity data were available for 8148 refugee children (aged < 19 years) from Bhutan, Burma, Democratic Republic of Congo, Ethiopia, Iraq, and Somalia.

RESULTS

We identified distinct health profiles for each country of origin, as well as for Burmese children who arrived in the United States from Thailand compared with Burmese children who arrived from Malaysia. Hepatitis B was more prevalent among male children than female children and among children aged 5 years and older. The odds of HBV, tuberculosis, and Strongyloides decreased over the study period.

CONCLUSIONS

Medical screening remains an important part of health care for newly arrived refugee children in the United States, and disease risk varies by population.

Accuracy of the QuantiFERON-TB Gold in Tube for diagnosing tuberculosis in a young pediatric population previously vaccinated with Bacille Calmette-Guérin

Objective:

To evaluate the accuracy of an interferongamma release assay (QuantiFERON-TB Gold in Tube) for diagnosing Mycobacterium tuberculosis infection in a young pediatric population.

Methods:

195 children previously vaccinated with BCG were evaluated, being 184 healthy individuals with no clinical or epidemiological evidence of mycobacterial infection, and 11 with Mycobacterium tuberculosis infection, according to clinical, radiological, and laboratory parameters. A blood sample was obtained from each child and processed according to the manufacturer's instructions. The assay performance was evaluated by a Receiver Operating Characteristic (ROC) curve.

Results:

In the group of 184 non-infected children, 130 (70.6%) were under the age of four years (mean age of 35 months). In this group, 177 children (96.2%) had negative test results, six (3.2%) had indeterminate results, and one (0.5%) had a positive result. In the group of 11 infected children, the mean age was 58.5 months, and two of them (18%) had negative results. The ROC curve had an area under the curve of 0.88 (95%CI 0.82-0.92; p<0.001), disclosing a predictive positive value of 81.8% for the test (95%CI 46.3-97.4). The assay sensitivity was 81.8% (95%CI 48.2-97.2) and the specificity was 98.8% (95%CI 96-99.8).

Conclusions:

In the present study, the QuantiFERON-TB Gold in Tube performance for diagnosing M. tuberculosis infection was appropriate in a young pediatric population.

Evaluation of QuantiFERON-TB gold in-tube and tuberculin skin tests among immigrant children being screened for latent tuberculosis infection

BACKGROUND

Centers for Disease Control and Prevention requirements for pre-immigration tuberculosis (TB) screening of children 2- to 14-years old permit a tuberculin skin test (TST) or an interferon-gamma release assay (IGRA). Few data are available on the performance of IGRAs versus TSTs in foreign-born children.

METHODS

We compared the performance of TST and QuantiFERON-TB (QFT) Gold In-Tube in children 2- to 14-years old applying to immigrate to the United States from Mexico, the Philippines and Vietnam, using diagnosis of TB in immigrating family members as a measure of potential exposure.

RESULTS

We enrolled 2520 children: 664 (26%) were TST+ and 142 (5.6%) were QFT+. One hundred and eleven (4.4%) were TST+/QFT+, 553 (21.9%) were TST+/QFT- and 31 (1.2%) were TST-/QFT+. Agreement between tests was poor (κ = 0.20). Although positive results of both tests were significantly associated with older age (relative risks [RR] TST+, 1.64; 95% confidence interval [CI]: 1.36-1.97; RR QFT+, 3.05; 95% CI: 1.72-5.38) and with the presence of TB in at least 1 immigrating family member (RR TST+, 1.40; 95% CI: 1.12-1.75; RR QFT+ 2.24; 95% CI: 1.18-4.28), QFT+ results were more strongly associated with both predictive variables.

CONCLUSIONS

The findings support the preferential use of QFT over TST for pre-immigration screening of foreign-born children 2 years of age and older and lend support to the preferential use of IGRAs in testing foreign-born children for latent TB infection.

Interferon-γ release assays for diagnosis of tuberculosis infection and disease in children

Tuberculosis (TB) remains an important problem among children in the United States and throughout the world. Although diagnosis and treatment of infection with Mycobacterium tuberculosis (also referred to as latent tuberculosis infection [LTBI] or TB infection) remain the lynchpins of TB prevention, there is no diagnostic reference standard for LTBI. The tuberculin skin test (TST) has many limitations, including difficulty in administration and interpretation, the need for a return visit by the patient, and false-positive results caused by significant cross-reaction with Mycobacterium bovis-bacille Calmette-Guérin (BCG) vaccines and many nontuberculous mycobacteria. Interferon-γ release assays (IGRAs) are blood tests that measure ex vivo T-lymphocyte release of interferon-γ after stimulation by antigens specific for M tuberculosis. Because these antigens are not found on M bovis-BCG or most nontuberculous mycobacteria, IGRAs are more specific tests than the TST, yielding fewer false-positive results. However, IGRAs have little advantage over the TST in sensitivity, and both methods have reduced sensitivity in immunocompromised children, including children with severe TB disease. Both methods have a higher positive predictive value when applied to children with risk factors for LTBI. Unfortunately, neither method distinguishes between TB infection and TB disease. The objective of this technical report is to review what IGRAs are most useful for: (1) increasing test specificity in children who have received a BCG vaccine and may have a false-positive TST result; (2) using with the TST to increase sensitivity for finding LTBI in patients at high risk of developing progression from LTBI to disease; and (3) helping to diagnose TB disease.

Interferon-gamma release assay sensitivity in children younger than 5 years is insufficient to replace the use of tuberculin skin test in western countries

Tuberculin skin test, QuantiFERON-TB Gold In-Tube and T-SPOT.TB were performed in 338 children at risk for tuberculosis (TB), including 70 active TB cases. In children <5 years of age, QuantiFERON-TB Gold In-Tube sensitivity was 73.3% [95% confidence interval (CI): 57.5-89.1]; and T-SPOT.TB sensitivity was 59.3% (95% CI: 40.1-77.8); both were inferior to tuberculin skin test sensitivity (90.0%; 95% CI: 79.3-100). In children ≥ 5 years QuantiFERON-TB Gold In-Tube sensitivity was 92.5% (95% CI: 84.4-100); T-SPOT.TB sensitivity was 73.0% (95% CI: 58.6-87.3) ; and tuberculin skin test sensitivity was 97.5% (95% CI: 92.6-100).Test specificities were similar in all age groups.

Effect of BCG vaccination against Mycobacterium tuberculosis infection in children: systematic review and meta-analysis

OBJECTIVES

To determine whether BCG vaccination protects against Mycobacterium tuberculosis infection as assessed by interferon γ release assays (IGRA) in children.

DESIGN

Systematic review and meta-analysis. Searches of electronic databases 1950 to November 2013, checking of reference lists, hand searching of journals, and contact with experts.

SETTING

Community congregate settings and households.

INCLUSION CRITERIA

Vaccinated and unvaccinated children aged under 16 with known recent exposure to patients with pulmonary tuberculosis. Children were screened for infection with M tuberculosis with interferon γ release assays.

DATA EXTRACTION

Study results relating to diagnostic accuracy were extracted and risk estimates were combined with random effects meta-analysis.

RESULTS

The primary analysis included 14 studies and 3855 participants. The estimated overall risk ratio was 0.81 (95% confidence interval 0.71 to 0.92), indicating a protective efficacy of 19% against infection among vaccinated children after exposure compared with unvaccinated children. The observed protection was similar when estimated with the two types of interferon γ release assays (ELISpot or QuantiFERON). Restriction of the analysis to the six studies (n=1745) with information on progression to active tuberculosis at the time of screening showed protection against infection of 27% (risk ratio 0.73, 0.61 to 0.87) compared with 71% (0.29, 0.15 to 0.58) against active tuberculosis. Among those infected, protection against progression to disease was 58% (0.42, 0.23 to 0.77).

CONCLUSIONS

BCG protects against M tuberculosis infection as well as progression from infection to disease.Trial registration PROSPERO registration No CRD42011001698 (www.crd.york.ac.uk/prospero/).

[Tuberculosis screening program for undocumented immigrant teenagers using the QuantiFERON(®)-TB Gold In-Tube test]

BACKGROUND AND OBJECTIVE

The aim of this study was to determine the prevalence of tuberculosis infection in undocumented immigrant teenagers using a tuberculin skin test (TST) for initial screening and QuantiFERON(®)-TB Gold In-Tube (QFT-GIT) as a confirmatory test.

PATIENT AND METHOD

From 2007 to 2012, under 19 year-old immigrant teenagers from 2 accommodation centers of the Basque Country (Spain) were included in the study. The TST was done in all of them and the QFT-GIT was done in selected patients with a TST≥5mm.

RESULTS

Eight hundred and forty-five immigrants were included, most of them from Africa (99.5%). Fifty-one percent of immigrants with TST ≥ 5 mm has a positive QFT-GIT. We found 2 cases of active tuberculosis (2/845: 0.24%). The concordance between TST (≥ 10 mm) and QFT-GIT was 63%, with 57% of positive concordance cases and 96% of negative concordances. There were 246 cases with TST ≥ 10 mm (29%), with significant differences between Magrebis (21.5%) and Subsaharians (67%) (P<.001). Vaccination with Calmette-Guéin bacille was an independent predictor for having a TST ≥ 10 mm (OR: 2.11; P<.001) and for the discordance TST+/QFT-GIT-, both for a TST≥5 and a TST≥10mm (OR 2.16, 95% confidence interval [95% CI] 1.46-3.20, and OR 1.91 95% CI 1.23-2.97, respectively). The positive value of QFT-GIT increased significantly as the TST increased, with a positive association in all the cut-off points analyzed: 10-14 mm (OR 7.95, 95% CI 1.79-35.33), 15-19 mm (OR 35, 95% CI 7.93-154.52) and ≥ 20 mm (OR 91.3, 95% CI 18.20-458.11).

CONCLUSION

Due to the high prevalence of latent tuberculosis infection in Subsaharian immigrants, we recommend implementing screening programs in this population. Using QFT-GIT, the number of candidates for chemoprophylaxis was reduced to 43% compared with TST alone (≥ 10 mm).

Comparison of Tuberculin Skin Test result and interferon gamma response to human PPD in BCG scar positive and negative children

BACKGROUND

The aim of this study is to compare Tuberculin Skin Test (TST) result and interferon gamma response to human PPD (purified protein derivative), in scar positive and scar negative BCG-vaccinated children.

METHODS

Between August 2007 and May 2008 a total of 236 children aged 1-168 months (mean 21 months) admitted to Mofid Children's Hospital, Tehran, Iran, were enrolled in a cross-sectional study. Each patient was examined for BCG vaccine scar and tested with TST and human PPD-based Interferon Gamma Release Assay (IGRA).

RESULTS

Two hundred and twenty one cases out of 236 (44% female, 1-168 months, mean age 21 months) were scar positive of whom 95% TST result was negative. Human PPD-based IGRA was positive in 110 (49.8%), negative in 85 (38.4 %) and indeterminate in 26 (11.8%) of scar positive patients. Fifteen children (40% female, 1-156 months; mean age 42 months) were scar negative. All the scar negative cases were TST negative. Human PPD-based IGRA was positive in 10 (66.7%), negative in 4 (26.7%) and indeterminate in 1 (6.7%) of scar negative patients.

CONCLUSIONS

Immune responsiveness to human PPD antigens in scar positive and negative children may not correspond with results of the Tuberculin Skin Test.

The sensitivity of an interferon-γ release assay in microbiologically confirmed pediatric tuberculosis

This study aimed at determining the sensitivity of a whole blood interferon-γ release assay (IGRA) among children with microbiologically confirmed tuberculosis in a high-burden country. Children with a diagnosis of tuberculosis based on clinical and radiographic assessment were tested with an IGRA in addition to microbiologic examination of appropriate specimens for acid-fast bacilli, mycobacterial rRNA, and observation for growth of Mycobacterium tuberculosis on appropriate culture media. Of the 405 children with a clinical diagnosis of tuberculosis, 91 (22.5 %) had microbiologically confirmed tuberculosis, of whom 81 were tested with an IGRA. A positive result was obtained in 43 (sensitivity 53.1 %, 95 % confidence interval 42.3 to 63.6 %), uninfluenced by age, sex, or disease manifestation.

CONCLUSIONS

The sensitivity of a whole blood interferon-γ release assay in microbiologically confirmed pediatric tuberculosis was low. An IGRA cannot, thus, be used as rule-in test, but it might be useful to rule in tuberculosis among children in whom tuberculosis is notoriously difficult to confirm microbiologically.

Systematic review and meta-analysis on the utility of Interferon-gamma release assays for the diagnosis of Mycobacterium tuberculosis infection in children: a 2013 update

Background

Previous meta-analyses regarding the performance of interferon-gamma release assays (IGRAs) for tuberculosis diagnosis in children yielded contrasting results, probably due to different inclusion/exclusion criteria.

Methods

We systematically searched PubMed, EMBASE and Cochrane databases and calculated pooled estimates of sensitivities and specificities of QuantiFERON-TB Gold In Tube (QFT-G-IT), T-SPOT.TB, and tuberculin skin test (TST). Several sub-analysis were performed: stratification by background (low income vs. high income countries); including only microbiological confirmed TB cases; including only studies performing a simultaneous three-way comparison of the three tests, and including immunocompromised children.

Results

Overall, 31 studies (6183 children) for QFT-G-IT, 14 studies (2518 children) for T-SPOT.TB and 34 studies (6439 children) for TST were included in the analyses. In high income countries QFT-G-IT sensitivity was 0.79 (95%IC: 0.75-0.82) considering all the studies, 0.78 (95%CI:0.70-0.84) including only studies performing a simultaneous three-way comparison and 0.86 (95%IC 0.81-0.90) considering only microbiologically confirmed studies. In the same analyses T-SPOT.TB sensitivity was 0.67 (95%IC 0.62-0.73); 0.76 (95%CI: 0.68 to 0.83); and 0.79 (95%IC 0.69-0.87), respectively. In low income countries QFT-G-IT pooled sensitivity was significantly lower: 0.57 (95%IC:0.52-0.61), considering all the studies, and 0.66 (95%IC 0.55-0.76) considering only microbiologically confirmed cases; while T-SPOT.TB sensitivity was 0.61 (95%IC 0.57-0.65) overall, but reached 0.80 (95%IC 0.73-0.86) in microbiologically confirmed cases. In microbiologically confirmed cases TST sensitivity was similar: 0.86 (95%IC 0.79-0.91) in high income countries, and 0.74 (95%IC 0.68-0.80) in low income countries. Higher IGRAs specificity with respect to TST was observed in high income countries (97-98% vs. 92%) but not in low income countries (85-93% vs. 90%).

Conclusions

Both IGRAs showed no better performance than TST in low income countries.

Clinical peculiarities of tuberculosis

The ongoing spread of tuberculosis (TB) in poor resource countries and the recently increasing incidence in high resource countries lead to the need of updated knowledge for clinicians, particularly for pediatricians. The purpose of this article is to provide an overview on the most important peculiarities of TB in children. Children are less contagious than adults, but the risk of progression to active disease is higher in infants and children as compared to the subsequent ages. Diagnosis of TB in children is more difficult than in adults, because few signs are associated with primary infection, interferon-gamma release assays and tuberculin skin test are less reliable in younger children, M. tuberculosis is more rarely detected in gastric aspirates than in smears in adults and radiological findings are often not specific. Treatment of latent TB is always necessary in young children, whereas it is recommended in older children, as well as in adults, only in particular conditions. Antimycobacterial drugs are generally better tolerated in children as compared to adults, but off-label use of second-line antimycobacterial drugs is increasing, because of spreading of multidrug resistant TB worldwide. Given that TB is a disease which often involves more than one member in a family, a closer collaboration is needed between pediatricians and clinicians who take care of adults.