T cell-based diagnosis of childhood tuberculosis infection

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).

Screening for Latent Tuberculosis in Children With Immune-mediated Inflammatory Diseases Treated With Anti-tumor Necrosis Factor Therapy: Comparison of Tuberculin Skin and T-SPOT Tuberculosis Tests

Objectives

This study aims to analyze the coherence between T-SPOT tuberculosis test (T-SPOT.TB) and tuberculin skin test (TST) with different cut-off values in screening latent tuberculosis infection (LTBI) both prior to and at the sixth month of anti-tumor necrosis factor (anti-TNF) treatment.

Patients and methods

This prospective multicentric study included 57 children (34 girls, 23 boys, mean age 12.4±3.9 years; range, 6 to 18 years) diagnosed with immune-mediated inflammatory diseases (IMIDs) evaluated with TST and T-SPOT.TB for screening LTBI both prior to and at the sixth month of treatment with anti-TNF agents. Coherence between two tests was analyzed for TST cut-off values suggested by the local guidelines and also for different possible cut-off values of TST.

Results

Tuberculin skin test was positive (≥5 mm) in 28.1% (n=16) of patients in the screening prior to treatment and in 33.3% (n=19) at the sixth month of treatment. T-SPOT.TB test was positive in 8.8% (n=5) of patients both prior to and at the sixth month of treatment. Coherence between two tests was poor or fair when compared with all possible TST cut-off values both prior to and at the sixth month of anti-TNF therapy.

Conclusion

Our results show poor coherence between T-SPOT.TB and TST for all possible cut-off values of TST. Thus, using both tests would be beneficial in screening LTBI until further studies bring new evidence on the subject.

Performance of Tuberculin Skin Tests and Interferon-γ Release Assays in Children Younger Than 5 Years

BACKGROUND

Available data to assess the optimal diagnostic approach in infants and preschool children at risk of tuberculosis (TB) are limited.

METHODS

We conducted a prospective observational study in children younger than 5 years undergoing assessment with both tuberculin skin tests (TST) and QuantiFERON-TB Gold In-Tube (QFT-GIT) assays at 2 tertiary TB units in Barcelona, Spain.

RESULTS

A total of 383 children were included. One of 304 participants considered uninfected developed active TB during follow-up {median [interquartile range (IQR)]: 47 [30; 48] months}, compared with none of 40 participants with latent TB infection [follow-up since completion of anti-TB treatment: 42 (32; 45) months]. Overall test agreement between TST and QFT-GIT was moderate (κ = 0.551), but very good in children screened after TB contact (κ = 0.801) and in Bacillus Calmette-Guérin (BCG)-unvaccinated children (κ = 0.816). Discordant results (16.8%, all TST+/QFT-GIT-) were mainly observed in new-entrant screening and in BCG-vaccinated children. Children with indeterminate QFT-GIT results were on average younger than those with determinate results (median age: 12 vs. 30 months; P < 0.001). The sensitivity of TSTs and QFT-GIT assays in children with confirmed active TB was 100% (95% confidence interval: 79.4%-100%) and 93.7% (95% confidence interval: 69.8%-99.8%), respectively. In patients with latent TB infection or active TB, there was no correlation between age and antigen-stimulated interferon-γ responses (r = -0.044; P = 0.714).

CONCLUSIONS

In young BCG-unvaccinated children with recent TB contact, a dual testing strategy using TST and QFT-GIT in parallel may not be necessary. However, TST+/QFT-GIT- discordance is common, and it remains uncertain if this constellation indicates TB infection or not. In active TB, QFT-GIT assays do not perform better than TSTs.

GradDock: rapid simulation and tailored ranking functions for peptide-MHC Class I docking

Motivation

The identification of T-cell epitopes has many profound translational applications in the areas of transplantation, disease diagnosis, vaccine/therapeutic protein development and personalized immunotherapy. While data-driven methods have been widely used for the prediction of peptide binders with notable successes, the structural modeling of peptide binding to MHC molecules is crucial for understanding the underlying molecular mechanism of the immunological processes.

Results

We developed GradDock, a structure-based method for the rapid and accurate modeling of peptide binding to MHC Class I (pMHC-I). GradDock explicitly models diverse unbound peptides in vacuo and inserts them into the MHC-I groove through a steered gradient descent with a topological correction process. The simulation process yields diverse structural conformations including native-like peptides. We completely revised the Rosetta score terms and developed a new ranking function specifically for pMHC-I. Using the diverse peptides, a linear programming approach is applied to find the optimal weights for the individual Rosetta score terms. Our examination revealed that a refinement of the dihedral angles and a modification of the repulsion can dramatically improve the modeling quality. GradDock is five-times faster than a Rosetta-based docking approach for pMHC-I. We also demonstrate that the predictive capability of GradDock with the re-weighted Rosetta ranking function is consistently more accurate than the Rosetta-based method with the standard Rosetta score (approximately three-times better for a cross-docking set).

Availability and implementation

GradDock is freely available for academic purposes. The program and the ranking score weights for Rosetta are available at http://bel.kaist.ac.kr/research/GradDock.

Contact

hskim76@kaist.ac.kr.

Supplementary information

Supplementary data are available at Bioinformatics online.

A systematic approach to diagnosing intra-thoracic tuberculosis in children

Children suffer a huge and often underappreciated burden of disease in tuberculosis (TB) endemic countries. Major hurdles include limited awareness among health care workers, poor integration of TB into maternal and child health approaches, diagnostic difficulties and a lack of child-friendly treatment options. Accurate disease diagnosis is particularly difficult in young and vulnerable children who tend to develop paucibacillary disease and are unable to produce an expectorated sputum sample. In addition, access to chest radiography is problematic in resource-limited settings. Differentiating between TB exposure and M. tuberculosis infection, and especially between M. tuberculosis infection and TB disease is crucial to guide clinical management. TB represents a dynamic continuum from well-contained "latent" infection to incipient and ultimately severe disease. The clinical spectrum of disease in children is broad and can be confused with a myriad of common infections. We provide a pragmatic 4-step approach to diagnose intra-thoracic TB in children and demonstrate how classifying clinical, radiological and laboratory findings into recognised clinical syndromes may provide a more refined diagnostic approach, even in resource-limited settings.

Tuberculosis exposure, infection and disease in children: a systematic diagnostic approach

The accurate diagnosis of tuberculosis (TB) in children remains challenging. A myriad of common childhood diseases can present with similar symptoms and signs, and differentiating between exposure and infection, as well as infection and disease can be problematic. The paucibacillary nature of childhood TB complicates bacteriological confirmation and specimen collection is difficult. In most instances intrathoracic TB remains a clinical diagnosis. TB infection and disease represent a dynamic continuum from TB exposure with/without infection, to subclinical/incipient disease, to non-severe and severe disease. The clinical spectrum of intrathoracic TB in children is broad, and the classification of clinical, radiological, endoscopic, and laboratory findings into recognized clinical syndromes allows a more refined diagnostic approach in order to minimize both under- and over-diagnosis. Bacteriological confirmation can be improved significantly by collecting multiple, high-quality specimens from the most appropriate source. Mycobacterial testing should include traditional smear microscopy and culture, as well as nucleic acid amplification testing. A systematic approach to the child with recent exposure to TB, or with clinical and radiological findings compatible with this diagnosis, should allow pragmatic classification as TB exposure, infection, or disease to facilitate timely and appropriate management. It is important to also assess risk factors for TB disease progression and to undertake follow-up evaluations to monitor treatment response and ongoing evidence supporting a TB, or alternative, diagnosis.

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.

Performance of interferon-γ release assays in the diagnosis of confirmed active tuberculosis in immunocompetent children: a new systematic review and meta-analysis

Background

Tuberculosis (TB) is a global public health problem, causing morbidity and mortality in adults and children. The most reliable diagnostic tools currently available are the in vivo Tuberculin Skin Test (TST) and the ex vivo Interferon-γ release assays (IGRAs). Several clinical, radiological, and bacteriological features make the detection of active (overt disease) TB in children difficult. Although recently developed immunological assays such as QuantiFERON-TB Gold In-Tube (QFT-IT) and T-SPOT®.TB are commonly used to identify active TB in adults, different evidence is required for diagnosis in children. The purpose of this study was to reassess the sensitivity and specificity of IGRAs in detecting microbiologically confirmed active TB in immunocompetent children.

Methods

A systematic review and meta-analysis of studies reporting on the diagnostic accuracy of tests for TB in immunocompetent children aged 0–18 years, with confirmation by positive M. tuberculosis cultures, were undertaken. Electronic databases were searched up to September 2015 and study quality assessment was performed using QUADAS-2.

Results

Fifteen studies were included in our meta-analysis. Results showed that there were no significant differences in sensitivity between TST (88.2 %, 95 % confidence interval [CI] 79.4–94.2 %), QFT-IT (89.6 %, 95 % CI 79.7–95.7 %) and T SPOT (88.5 %, 95 % CI 80.4–94.1 %). However, both QFT-IT (95.4 %, 95 % CI 93.8–96.6 %) and T-SPOT (96.8 %, 95 % CI 94.2–98.5 %) have significantly higher specificity than TST (86.3 %, 95 % CI 83.9–88.6 %).

Conclusions

QFT-IT and T-SPOT have higher specificity than TST for detecting active TB cases in immunocompetent children.

Comparison of tuberculin skin test and QuantiFERON®-TB Gold In-Tube for the diagnosis of childhood tuberculosis

BACKGROUND

Tuberculosis (TB) is an important worldwide ongoing health issue. To be able to control TB, one should not only cure active TB but also identify childhood TB patients who have the possibility to develop active disease in the future. The aim of this study was to compare a century-old tuberculin skin test (TST) and QuantiFERON-TB Gold In-Tube (QFT-GIT) test, developed as an alternative to TST and which has been claimed to be superior to TST in several ways, in the diagnosis of childhood TB.

METHODS

Fifty-three children with TB between 5 months and 17.5 years of age and 92 healthy children from the same age group with no risk factors for TB were recruited into the study. All children underwent TST and QFT-GIT test and their demographic, clinic and laboratory data were recorded. Data were analyzed using SPSS 14.

RESULTS

A total of 53 patients were diagnosed with TB. Mean patient age was 8.5 ± 4.3 years (range, 5 months-17.5 years). A total of 41.7% of the patients were female. Sixteen of 53 patients had confirmation on culture. QFT-GIT test was positive in 16 and TST was positive in 15 among 16 children with culture-confirmed TB. The sensitivity of TST and QFT-GIT were 93.8% and 100.0%, and the specificity of TST and QFT-GIT were 100.0% and 97.8%, respectively. With regard to the 53 TB children including those without bacteriological confirmation, QFT-GIT was positive in 33 children, and TST was positive in 44 children. The sensitivity of TST and QFT-GIT was then 83.0% and 62.3%, and the specificity, 100.0% and 97.8%, respectively.

CONCLUSION

Although positive QFT-GIT test is very significant for TB, negative results will not exclude TB infection. TST and QFT-GIT used together may provide more efficient results.

Challenging Mycobacterium tuberculosis dormancy mechanisms and their immunodiagnostic potential

Mycobacterium tuberculosis is the etiologic agent of tuberculosis, one of the world's greatest cause of morbidity and mortality due to infectious disease. Many evolutionary mechanisms have contributed to its high level of adaptation as a host pathogen. Prior to become dormant, a group of about 50 genes related to metabolic changes are transcribed by the DosR regulon, one of the most complex and important systems of host-pathogen interaction. This genetic mechanism allows the mycobacteria to persist during long time periods, establishing the so-called latent infection. Even in the presence of a competent immune response, the host cannot eliminate the pathogen, only managing to keep it surrounded by an unfavorable microenvironment for its growth. However, conditions such as immunosuppression may reestablish optimal conditions for bacterial growth, culminating in the onset of active disease. The interactions between the pathogen and its host are still not completely elucidated. Nonetheless, many studies are being carried out in order to clarify this complex relationship, thus creating new possibilities for patient approach and laboratory screening.

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.

Relating Tuberculosis (TB) Contact Characteristics to QuantiFERON-TB-Gold and Tuberculin Skin Test Results in the Toronto Pediatric TB Clinic

BACKGROUND

Few data relate interferon-γ-release-assay results in children to source case sputum status, the best predictor of infectiousness of tuberculosis (TB) patients. We evaluated the QuantiFERON-Gold-in-tube assay (QFT) and tuberculin skin test (TST) in children with different types of TB exposure.

METHODS

The TST and QFT were performed in referred TB-exposed children and adolescents who had not undergone prior TST screening (tested in parallel), and the QFT was performed in referred TST-positive individuals. Source case characteristics were obtained from referring public health units. We excluded children with known immunocompromising conditions and those known to have TB disease at the time of evaluation.

RESULTS

For 103 patients tested in parallel, overall test agreement was very good in the Bacillus Calmette-Guerein (BCG) unimmunized contacts (κ = 0.83) and contacts of household smear-positive (HS+) cases (κ = 0.67), but test agreement was poor in those with lower-risk contact (κ = 0.34). Only 3 of 59 HS+ patients were QFT-positive and TST-negative. On multivariate analysis, a positive QFT was strongly associated with HS+ exposure (odds ratio [OR], 6.6; 95% confidence interval [CI], 2.2-20]) but not BCG; and a positive TST was associated with BCG alone. For 92 referred TST-positive individuals, the QFT was negative in 21% of HS+ contacts, 65% of lower-risk contacts (OR, 6.8; 95% CI, 1.9-25), and 82% of the patients with unknown contact history (OR, 15.5; 95% CI, 5-54). Application of the Canadian 2010 guidelines would exclude from treatment 43 (72%) of the 73 TST+, QFT- patients.

CONCLUSIONS

For close contacts of HS+ individuals, the QFT added little sensitivity to the TST for detection of TB infection. The QFT correlated much better with exposure than the TST, especially in BCG-immunized children, and it has the greatest potential benefit for evaluation of those at lower risk of latent TB infection.

Performance of an interferon-gamma release assay in the diagnosis of tuberculous meningitis in children / Performanţa testului bazat pe eliberarea interferonului gamma în diagnosticul meningitei tuberculoase la copil

The new immunodiagnostic tests based on the Mycobacterium tuberculosis specific antigen, early secretory antigenic target 6 (ESAT-6) and culture filtrate protein 10 (CFP-10), showed promising results in the diagnosis of tuberculosis infection. However, there are only few studies in the published literature on performance tests in cerebrospinal fluid. We investigated whether a rapid diagnosis of tuberculous meningitis (TBM) could be established by interferon-γ blood and cerebrospinal fluid (CSF) tests in children.

We used the QuantiFERON-TB Gold in Tube test (QFT-IT) on blood and the QuantiFERON-TB Gold test (QFT-G) on the CSF of 63 subjects with TBM (including 25 case of definite TBM and 38 cases of probable TBM) and 62 controls.

The CSF analyses indicated possible TBM in 63.4% of cases. The sensitivity of the CSF culture for Mycobacterium tuberculosis was only 39.6%. The sensitivity of the tuberculin skin test (TST) was 49.2% and the specificity was 88.6%. The estimated sensitivities of the QFT-G for the CSF and QFT-IT for the blood in culture confirmed TBM cases (gold standard) were 84% and 80%, respectively. The estimated specificities were 98.2% for the CSF and 87.9% for the blood. This study showed that the sensitivity of QFT for the CSF could be higher than TST and culture and slightly higher in CSF than in blood. The specificity of QFT-G for the CSF was higher those of the TST, but the specificity of QFT-IT is lower.

QFT-G of the CSF is a useful diagnostic marker of tuberculosis that may improve the management of TBM, but the test results must be correlated with clinical, radiological and characteristics of CSF. New researches are needed to investigate the performance of QFT-G in the CSF compared with ELISPOT and PCR

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.

The role of interferon gamma release assays in the monitoring of response to anti-tuberculosis treatment in children

Successful control of childhood TB requires early diagnosis, effective chemotherapy and a method of evaluating the response to therapy. Identification of suitable biomarkers that predict the response to anti-TB therapy may allow the duration of treatment to be shortened. The majority of biomarker studies in paediatric TB have focused on the role of T cell-based interferon-gamma (IFN-γ) release assays (IGRAs) in the diagnosis of either latent or active disease. Little has been published on the role of IGRAs in the monitoring response to therapy in children. We reviewed the available literature to ascertain the value of IGRAs in the monitoring of response to anti-TB therapy in children. We explored the results of the few studies that have investigated the role of IGRAs as markers of response to anti-TB treatment in children. We conclude that the role of IGRAs as surrogate markers appears promising. Robust clinical trials are, however, needed to entrench the value of IGRAs as surrogate biomarkers of response to anti-TB therapy in children.

Comparing interferon-gamma release assays to tuberculin skin test in Thai children with tuberculosis exposure

Background

Data on the performance of interferon-gamma release assays (IGRAs), QuantiFERON TB Gold In-tube (QFNGIT) and T-Spot.TB, in diagnosing tuberculosis (TB) are limited in Southeast Asia. This study aims to compare the performances of the two IGRAs and TST in Thai children with recent TB exposure.

Methods

This multicenter, prospective study enrolled children with recent exposure to active TB adults. Children were investigated for active TB. TST was performed and blood collected for T-Spot.TB and QFNGIT.

Results

158 children were enrolled (87% TB-exposed and 13% active TB, mean age 7.2 years). Only 3 children had HIV infection. 66.7% had TST≥10 mm, while 38.6% had TST≥15 mm. 32.5% had positive QFNGIT; 29.9% had positive T-Spot.TB. QFNGIT and T-Spot.TB positivity was higher among children with active TB compared with TB-exposed children. No indeterminate IGRA results were detected. No statistically significant differences between the performances of the IGRAs and TST at the two cut-offs with increasing TB exposure were detected. Concordance for positive IGRAs and TST ranged from 42–46% for TST≥10 mm and 62–67% for TST≥15 mm. On multivariable analyses, exposure to household primary/secondary caregiver with TB was associated with positive QFNGIT. Higher TB contact score and active TB were associated with positive T-Spot.TB.

Conclusions

Both QFNGIT and T-Spot.TB performed well in our Thai pediatric study population. No differences in the performances between tests with increasing TB exposure were found. Due to accessibility and low cost, using TST may more ideal than IGRAs in diagnosing latent and active TB in healthy children in Thailand and other similar settings.

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/).

Agreement between QuantiFERON®-TB Gold In-Tube and the tuberculin skin test and predictors of positive test results in Warao Amerindian pediatric tuberculosis contacts

Background

Interferon-gamma release assays have emerged as a more specific alternative to the tuberculin skin test (TST) for detection of tuberculosis (TB) infection, especially in Bacille Calmette-Guérin (BCG) vaccinated people. We determined the prevalence of Mycobacterium tuberculosis infection by TST and QuantiFERON^®-TB Gold In-Tube (QFT-GIT) and assessed agreement between the two test methods and factors associated with positivity in either test in Warao Amerindian children in Venezuela. Furthermore, progression to active TB disease was evaluated for up to 12 months.

Methods

163 HIV-negative childhood household contacts under 16 years of age were enrolled for TST, QFT-GIT and chest X-ray (CXR). Follow-up was performed at six and 12 months. Factors associated with TST and QFT-GIT positivity were studied using generalized estimation equations logistic regression models.

Results

At baseline, the proportion of TST positive children was similar to the proportion of children with a positive QFT-GIT (47% vs. 42%, p = 0.12). Overall concordance between QFT-GIT and TST was substantial (kappa 0.76, 95% CI 0.46-1.06). Previous BCG vaccination was not associated with significantly increased positivity in either test (OR 0.68, 95% CI 0.32-1.5 for TST and OR 0.51, 95% CI 0.14-1.9 for QFT-GIT). Eleven children were diagnosed with active TB at baseline. QFT-GIT had a higher sensitivity for active TB (88%, 95% CI 47-98%) than TST (55%, 95% CI 24-83%) while specificities were similar (respectively 58% and 55%). Five initially asymptomatic childhood contacts progressed to active TB disease during follow-up.

Conclusion

Replacement of TST by the QFT-GIT for detection of M. tuberculosis infection is not recommended in this resource-constrained setting as test results showed substantial concordance and TST positivity was not affected by previous BCG vaccination. The QFT-GIT had a higher sensitivity than the TST for the detection of TB disease. However, the value of the QFT-GIT as an adjunct in diagnosing TB disease is limited by a high variability in QFT-GIT results over time.

Tuberculin skin test and ELISPOT/T. SPOT.TB in children and adolescents with juvenile idiopathic arthritis

BACKGROUND

There are controversies regarding the accuracy of the tuberculin skin test (TST) and methods based on the production of interferon gamma by sensitized T cells for the diagnosis of latent tuberculosis infection (LTBI) in pediatrics and immunosuppressed patients. Our objectives are to study TST and ELISPOT/T. SPOT.TB in the diagnosis of LTBI in children and adolescents with JIA undergoing methotrexate, the correlation between both and the sensitivity and specificity of T. SPOT.TB.

METHODS

This is an observational prospective longitudinal study in which children and adolescents with JIA undergoing methotrexate therapy were assessed for clinical and epidemiological data for LTBI, in addition to performing TST and T. SPOT.TB at baseline and after 3 and 12months.

RESULTS

There were 24 patients. The prevalence of LTBI at inclusion was 20.8%, the incidence after initiation of immunosuppressions 26.3% and the prevalence at the end of the study 41.6%. Epidemiological history positive for TB showed a relative risk of 2.0 for the development of LTBI. Only 2 patients had positive T. SPOT.TB but only in one it was useful for detecting early LTBI. T. SPOT.TB presented a sensitivity of 10%, specificity of 92.8%, and low correlation with TST. No patient developed TB disease at a mean follow-up of 47months.

CONCLUSIONS

We found a high prevalence of ILTB that doubled with immunosuppression and that epidemiological history was an important relative risk. T. SPOT.TB showed low sensitivity and high specificity, and no superiority over TST. There was low agreement and little influence of immunosuppression on the results of both tests.

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.

Effect of micronutrient deficiency on QuantiFERON-TB Gold In-Tube test and tuberculin skin test in diagnosis of childhood intrathoracic tuberculosis

BACKGROUND/OBJECTIVES

Data on performance of QuantiFERON-TB Gold In-Tube test (QFT) and tuberculin skin test (TST) in children with active tuberculosis from high burden countries in the context of micronutrient deficiency are scarce. The objective of this study was to evaluate the effect of micronutrient deficiency on the performance of TST and QFT in children with intrathoracic tuberculosis.

SUBJECTS/METHODS

Children with probable intrathoracic tuberculosis underwent TST, QFT, gastric lavages and induced sputum examination for AFB (Acid-Fast Bacilli) smear and culture. Zinc, copper, ferritin and vitamin D were measured on stored serum samples. The study used cross-sectional data at initiation of anti-tubercular therapy.

RESULTS

Three hundred and sixty-two children (median age 115.5 months (interquartile range: 73, 144), 200 (55.3%) girls) were enrolled in the study. Microbiological confirmation of tuberculosis could be obtained in 128 patients. TST and QFT were positive in 337 (93%) and 297 (82%) children, respectively. Performance of both the tests was unaffected by weight-for-age and height-for-age 'z-scores' or by serum copper levels. TST was not affected by serum zinc and ferritin levels. Children with negative QFT results had lower mean serum zinc level (P=0.01) and higher ferritin levels (P=0.007) as compared to those with positive test. Higher proportion of children with positive TST were vitamin D deficient/insufficient (P=0.003).

CONCLUSION

Micronutrient status, especially serum levels of zinc, may influence the performance of QFT in children with intrathoracic tuberculosis. Considering the high prevalence of zinc deficiency in developing countries, QFT should be used cautiously for diagnosing tuberculosis.

Point of care investigations in pediatric care to improve health care in rural areas

The good quality laboratory services in developing countries are often limited to major urban centers. As a result, many commercially available high-quality diagnostic tests for infectious diseases are neither accessible nor affordable to patients in the rural areas. Health facilities in rural areas are compromised and this limits the usability and performance of the best medical diagnostic technologies in rural areas as they are designed for air-conditioned laboratories, refrigerated storage of chemicals, a constant supply of calibrators and reagents, stable electrical power, highly trained personnel and rapid transportation of samples. The advent of new technologies have allowed miniaturization and integration of complex functions, which has made it possible for sophisticated diagnostic tools to move out of the developed-world laboratory in the form of a "point of care"(POC) tests. Many diagnostic tests are being developed using these platforms. However, the challenge is to develop diagnostics which are inexpensive, rugged and well suited to the medical and social contexts of the developing world and do not compromise on accuracy and reliability. The already available POC tests which are reliable and affordable, like for HIV infection, malaria, syphilis, and some neglected tropical diseases, and POC tests being developed for other diseases if correctly used and effectively regulated after rigorous evaluation, have the potential to make a difference in clinical management and improve surveillance. In order to use these tests effectively they would need to be supported by technically competent manpower, availability of good-quality reagents, and healthcare providers who value and are able to interpret laboratory results to guide treatment; and a system for timely communication between the laboratory and the healthcare provider. Strengthening the laboratories at the rural level can enable utilization of these diagnostics for improving the diagnosis and management of infectious diseases among children which require prompt treatment and thus, considerably reduce morbidity and mortality among the pediatric age group.

Interferon-γ release assays for the diagnosis of Mycobacterium tuberculosis infection in children: a systematic review and meta-analysis

Data regarding the use of interferon-gamma release assays (IGRAs) for tuberculosis diagnosis are accumulating. We systematically searched PubMed, EMBASE and Cochrane and performed pooled estimates of sensitivity and specificity of QuantiFERON-TB Gold In Tube (QFT-G-IT) and T-SPOT.TB compared to tuberculin skin test (TST). For studies assessing sensitivity, children had to have active tuberculosis. Specificity data were derived from children classified as non-infected. Eleven studies were included in the sensitivity analysis for TST, 10 for QFT-G-IT, and 9 for T-SPOT.TB. Eight studies were included in specificity analysis for TST, 8 for QFT-G-IT, and 7 for T-SPOT.TB. Pooled QFT-G-IT sensitivity was 0.79 (95% CI:0.70-0.89) pooled T-SPOT.TB sensitivity was 0.74 (95% CI:0.59-0.90) and pooled TST sensitivity was 0.82 (95% CI:0.72-0.93). Pooled QFT-G-IT and T-SPOT.TB specificities were 0.95 (95% CI:0.93- 0.97) and 0.96 (95% CI:0.93-1.00), respectively. Pooled TST specificity was significantly lower 0.83 (95% CI:0.74-0.92). IGRA performance in children showed no better sensitivity than TST, but higher specificity.

Interferon γ assays in the diagnosis of tuberculosis infection in psoriasis patients who are candidates for biologic therapies

Although there is no doubt that biologic agents are an effective alternative for the treatment of moderate and severe psoriasis, anti-tumor necrosis factor α therapy has been associated with reactivation of latent tuberculosis infection. Tuberculin skin testing (TST) is used to diagnose tuberculosis infection but it has low specificity in patients who have received the Mycobacterium bovis BCG vaccine and low sensitivity in patients with altered cell-mediated immunity. In vitro assays based on the detection of interferon γ released by T cells stimulated by specific Mycobacterium tuberculosis antigens have emerged as an option for the diagnosis of tuberculosis infection. The results to date show that they are a viable alternative to TST thanks to their higher specificity and sensitivity. Furthermore, these assays are also proving to have high negative predictive value, meaning that we might be able to use them without TST in the short to medium term.

Interferon γ Assays in the Diagnosis of Tuberculosis Infection in Psoriasis Patients Who Are Candidates for Biologic Therapies

Although there is no doubt that biologic agents are an effective alternative for the treatment of moderate and severe psoriasis, anti-tumor necrosis factor α therapy has been associated with reactivation of latent tuberculosis infection. Tuberculin skin testing (TST) is used to diagnose tuberculosis infection but it has low specificity in patients who have received the Mycobacterium bovis BCG vaccine and low sensitivity in patients with altered cell-mediated immunity. In vitro assays based on the detection of interferon γ released by T cells stimulated by specific Mycobacterium tuberculosis antigens have emerged as an option for the diagnosis of tuberculosis infection. The results to date show that they are a viable alternative to TST thanks to their higher specificity and sensitivity. Furthermore, these assays are also proving to have high negative predictive value, meaning that we might be able to use them without TST in the short to medium term.

The effect of age on whole blood interferon-gamma release assay response among children investigated for latent tuberculosis infection

OBJECTIVE

To evaluate the effect of age upon QuantiFERON-TB Gold-In-Tube (QFT-IT) assay outcome among children examined for latent tuberculosis infection (LTBI).

STUDY DESIGN

A cross-sectional study was conducted among 761 children (mean age ± SD: 7.84 ± 4.68 years) evaluated for LTBI. Participants were examined with both tuberculin skin test and QFT-IT (Cellestis, Australia) and categorized into 4 age groups. Multivariate logistic and linear regressions were used to evaluate the association between selected demographic and patient characteristics upon the qualitative and quantitative QFT-IT outcomes. Agreement between the tuberculin skin test and QFT-IT within groups was evaluated with the κ statistic.

RESULTS

QFT-IT indeterminate results occurred more frequently among young children (8.1%; P < .0001) and children (2.7%; P = .025) than adolescents (0.7%). Among QFT-IT positive patients, infants had higher mean (± SD) interferon-gamma (IFNγ) concentration than adolescents. QFT-IT positive (vs negative) outcome was associated with origin from a high tuberculosis endemicity setting (AOR = 4.54; 95% CI, 3.22-6.25) and lack of previous Bacille Calmette Guerin immunization (AOR = 2.70; 95% CI, 1.89-3.85), but not patient age (AOR = 0.96; 95% CI, 0.92-0.99). However, among QFT-IT positive patients, the IFNγ concentration was inversely associated with patient age (P = .009) and positively with mitogen response (P = .0002). Agreement between tests was not significantly different between younger and older children in the different risk groups.

CONCLUSIONS

Qualitative QFT-IT assay results are not affected by patient age. However, indeterminate results occur more frequently among younger children. Among patients with LTBI the quantitative QFT-IT result (ie, IFNγ) is inversely associated with patient age.

Identifying predictors of interferon-γ release assay results in pediatric latent tuberculosis: a protective role of bacillus Calmette-Guerin?: a pTB-NET collaborative study

RATIONALE

Interferon-γ (IFN-γ) release assays are widely used to diagnose latent infection with Mycobacterium tuberculosis in adults, but their performance in children remains incompletely evaluated to date.

OBJECTIVES

To investigate factors influencing results of IFN-γ release assays in children using a large European data set.

METHODS

The Pediatric Tuberculosis Network European Trials group pooled and analyzed data from five sites across Europe comprising 1,128 children who were all investigated for latent tuberculosis infection by tuberculin skin test and at least one IFN-γ release assay. Multivariate analyses examined age, bacillus Calmette-Guérin (BCG) vaccination status, and sex as predictor variables of results. Subgroup analyses included children who were household contacts.

MEASUREMENTS AND MAIN RESULTS

A total of 1,093 children had a QuantiFERON-TB Gold In-Tube assay and 382 had a T-SPOT.TB IFN-γ release assay. Age was positively correlated with a positive blood result (QuantiFERON-TB Gold In-Tube: odds ratio [OR], 1.08 per year increasing age [P < 0.0001]; T-SPOT.TB: OR, 1.14 per year increasing age [P < 0.001]). A positive QuantiFERON-TB Gold In-Tube result was shown by 5.5% of children with a tuberculin skin test result less than 5 mm, by 14.8% if less than 10 mm, and by 20.2% if less than 15 mm. Prior BCG vaccination was associated with a negative IFN-γ release assay result (QuantiFERON-TB Gold In-Tube: OR, 0.41 [P < 0.001]; T-SPOT.TB: OR, 0.41 [P < 0.001]). Young age was a predictor of indeterminate IFN-γ release assay results, but indeterminate rates were low (3.6% in children < 5 yr, 1% in children > 5 yr).

CONCLUSIONS

Our data show that BCG vaccination may be effective in protecting children against Mycobacterium tuberculosis infection. To restrict use of IFN-γ release assays to children with positive skin tests risks underestimating latent infection.

Classic and new diagnostic approaches to childhood tuberculosis

Tuberculosis in childhood differs from the adult clinical form and even has been suggested that it is a different disease due to its differential signs. However, prevention, diagnostics, and therapeutic efforts have been biased toward adult clinical care. Sensibility and specificity of new diagnostic approaches as GeneXpert, electronic nose (E-nose), infrared spectroscopy, accelerated mycobacterial growth induced by magnetism, and flow lateral devices in children populations are needed. Adequate and timely assessment of tuberculosis infection in childhood could diminish epidemiological burden because underdiagnosed pediatric patients can evolve to an active state and have the potential to disseminate the etiological agent Mycobacterium tuberculosis, notably increasing this worldwide public health problem.

Interferon-gamma inducible protein 10 as a biomarker for active tuberculosis and latent tuberculosis infection in children: a case-control study

BACKGROUND

Interferon-gamma (IFN-γ) release assays (IGRAs) are suboptimally sensitive to diagnose tuberculosis (TB) and latent TB infection (LTBI) in young children. In this study we compared Mycobacterium tuberculosis antigen-stimulated IFN-γ inducible protein 10 (IP-10) responses in children with active TB and LTBI to responses from children with non-tuberculous mycobacterial (NTM) lymphadenopathy and respiratory tract infection (RTI). We also assessed test agreement between IP-10 and the QuantiFERON(®)-TB Gold In-Tube (QFT-IT) test results, and investigated whether IP-10 release upon mitogen stimulation is associated with age.

METHODS

We recruited 48 children (median age 54 months) diagnosed in Germany with either active TB (n = 11), LTBI (n = 14), NTM lymphadenopathy (n = 8), or common RTI (n = 15). IFN-γ levels were measured using the QFT-IT. These plasma supernatants were used to determine IP-10 concentrations using an in-house enzyme-linked immunosorbent assay (ELISA).

RESULTS

The median antigen-stimulated IP-10 levels in children with active TB, LTBI, NTM lymphadenopathy, and RTI were 12,702 pg/ml, 9109 pg/ml, 97 pg/ml, and 84 pg/ml, respectively. We observed a strong correlation between IP-10 and IFN-γ plasma concentration in children with active TB and LTBI (r(2) = 0.69). Overall agreement between IP-10 and QFT-IT assays was high (kappa = 0.95). IP-10 levels after mitogen stimulation showed no association with age.

CONCLUSIONS

IP-10 and IFN-γ were both induced with antigen stimulation in blood from children in the TB and LTBI groups, in contrast to the NTM and RTI groups. Compared to IFN-γ the IP-10 levels were higher and IP-10 was released independently of age. IP-10 therefore may represent an additional biomarker in the paediatric population.

The utility of an interferon gamma release assay for diagnosis of latent tuberculosis infection and disease in children: a systematic review and meta-analysis

BACKGROUND

The utility of interferon gamma release assays (IGRAs) has been assessed in adults, but remains unclear in children. We reviewed the literature on the use of a commercial IGRA in immunocompetent children for the diagnosis of both latent tuberculosis infection (LTBI) and TB disease.

METHODS

We searched PubMed for studies published before January 2010 on the diagnosis of TB in children using an IGRA. We compared the specificity and sensitivity of the tuberculin skin test (TST) and the IGRA for LTBI and conducted a random effects meta-analysis on sensitivity of the IGRA for TB disease.

RESULTS

Of 68 studies identified, 20 were included in this review. There was increased specificity of the IGRA for LTBI in children compared with TST, but varying sensitivities. Sensitivity of the IGRA in detecting TB disease in children also varied when compared with TST (mean κ score, 0.57). For all TB cases, the pooled sensitivity was 66% (95% confidence interval [CI], 53%-78%) with heterogeneity (I² = 74.8%). Stratification by background TB incidence highlighted a significantly reduced IGRA sensitivity of 55% (95% CI, 37%-73%) in high incidence settings when compared with low incidence settings, 70% (95% CI, 53%-84%).

CONCLUSIONS

There was no clear evidence that IGRAs should replace TST for detecting LTBI in children. Sensitivity of the IGRA for TB disease was no different from TST, and a significantly reduced IGRA sensitivity was found in high-burden TB settings compared with low-burden TB settings. Further studies are needed to determine the value of IGRAs in LTBI and TB disease diagnosis in children.

Revival of the identification of cytotoxic T-lymphocyte epitopes for immunological diagnosis, therapy and vaccine development

Immunogenic T-cell epitopes have a central role in the cellular immunity against pathogens and tumors. However, in the early stage of cellular immunity studies, it was complicated and time-consuming to identify and characterize T-cell epitopes. Currently, the epitope screening is experiencing renewed enthusiasm due to advances in novel techniques and theories. Moreover, the application of T-cell epitope-based diagnoses for tuberculosis and new data on epitope-based vaccine development have also revived the field. There is a growing knowledge on the emphasis of epitope-stimulated T-cell immune responses in the elimination of pathogens and tumors. In this review, we outline the significance of the identification and characterization of T-cell epitopes. We also summarize the methods and strategies for epitope definition and, more importantly, address the relevance of cytotoxic T-lymphocyte epitopes to clinical diagnoses, therapy and vaccine development.

Latent tuberculosis detection by interferon γ release assay during pregnancy predicts active tuberculosis and mortality in human immunodeficiency virus type 1-infected women and their children

BACKGROUND

We evaluated the prognostic usefulness of interferon γ release assays (IGRAs) for active tuberculosis and mortality in Kenyan human immunodeficiency virus type 1 (HIV-1)-infected women and their infants.

METHODS

Prevalence and correlates of Mycobacterium tuberculosis-specific T-SPOT.TB IGRA positivity were determined during pregnancy in a historical cohort of HIV-1-infected women. Hazard ratios, adjusted for baseline maternal CD4 cell count (aHR(CD4)), were calculated for associations between IGRA positivity and risk of active tuberculosis and mortality over 2-year postpartum follow-up among women and their infants.

RESULTS

Of 333 women tested, 52 (15.6%) had indeterminate IGRA results. Of the remaining 281 women, 120 (42.7%) had positive IGRA results, which were associated with a 4.5-fold increased risk of active tuberculosis (aHR(CD4), 4.5; 95% confidence interval [CI], 1.1-18.0; P = .030). For immunosuppressed women (CD4 cell count, <250 cells/μL), positive IGRA results were associated with increased risk of maternal mortality (aHR(CD4), 3.5; 95% CI, 1.02-12.1;), maternal active tuberculosis or mortality (aHR(CD4), 5.2; 95% CI, 1.7-15.6; P = .004), and infant active tuberculosis or mortality overall (aHR(CD4), 3.0; 95% CI, 1.0-8.9; P = .05) and among HIV-1-exposed uninfected infants (aHR(CD4), 7.3; 95% CI, 1.6-33.5; P = .01).

CONCLUSIONS

Positive IGRA results for HIV-1-infected pregnant women were associated with postpartum active tuberculosis and mortality among mothers and their infants.

IFN-gamma release assays in tuberculosis management in selected high-risk populations

Tuberculosis (TB) is the most deadly infectious disease in the world. TB control relies on passive case findings and targeted treatment of latently infected individuals at high risk of disease progression. Tuberculin skin testing (TST) is conventionally used for detection of TB infection. Recently, blood assays measuring the release of IFN-gamma by TB-specific effector memory T cells have been developed to overcome TST limitations. Overall, IFN-gamma release assays are more specific than TST, more sensitive in detecting active TB and correlate better with TB exposure in immune-competent patients, at least in low-burden settings. There are three US FDA-approved assays commercially available: the ELISpot-based assay T-SPOT.TB (Oxford Immunotech, UK) and two ELISA-based formats, QuantiFERON TB Gold (QFT) and QFT-in tube (Cellestis, Australia). Recent international guidelines and consensus statements recommend the use of IFN-gamma release assays at different levels in TB management. However, conclusive evidence-based information targeting populations at high TB risk, including HIV-infected individuals, children and patient candidates for biotherapy with TNF-alpha blockers, are lacking. The aim of this review is to focus our attention on studies addressing the performance of commercial IFN-gamma release assays in clinical management of TB infection in these highly selected settings to provide a more comprehensive picture of the actual scenario and to identify areas to be investigated further.

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

BACKGROUND

Interferon-gamma release assays (IGRAs) have been recently developed for the diagnosis of tuberculosis (TB) infection. The aim of the present study was to evaluate the performance of an enzyme-linked immunosorbent assay (ELISA)-based IGRA for detecting TB in children.

METHODS

A prospective study in 336 children at risk for TB infection was carried out. All children were tested with tuberculin skin test (TST) and a commercial ELISA-based IGRA [QuantiFERON-TB Gold In-Tube (Cellestis)].

RESULTS

TST were positive in 58 of 336 (17.3%) and IGRA in 60 of 336 (17.9%) children. Two (0.6%) IGRA results were indeterminate. The overall agreement between the 2 tests was intermediate (86.2%, kappa= 0.533). IGRA was positive in 15 of 16 (93.8%) children with active pulmonary TB. The discordant pattern IGRA-/TST+ was significantly associated with Bacille Calmette-Guérin (BCG) vaccination. Among IGRA+ children (excluding cases of TB disease), TST- were significantly younger than TST+ children.

CONCLUSIONS

The good agreement between positive IGRA and active TB disease suggests a good sensitivity of IGRA. Discrepancies between IGRA and TST can be a result of higher specificity of IGRA that is not influenced by previous BCG vaccination. IGRA may be more sensitive in children younger than 48 months.

Detection of tuberculosis in HIV-infected children using an enzyme-linked immunospot assay

OBJECTIVE

To evaluate an enzyme-linked immunospot assay (ELISPOT) for the diagnosis of tuberculosis (TB) in HIV-infected children with suspected TB and to compare the performance of ELISPOT with the tuberculin skin test (TST).

METHODS

Interferon-gamma responses to Mycobacterium tuberculosis-specific antigens were measured by ELISPOT in HIV-infected children with suspected TB. HIV-infected and HIV-uninfected children without TB were taken for comparison.

RESULTS

Results were available for 188 children, of whom 139 (74%) were HIV-infected. Of these, 22 were classified as having definite TB: 24 probable TB, 14 possible TB and 128 not having TB. The median (range) age of patients was 20 (10-54.1) months. Median interferon-gamma responses to early-secreted antigenic target-6 and culture filtrate protein-10 were higher in children with definite or probable TB compared with children without TB (P < 0.002). In HIV-infected children with an interpretable ELISPOT result, the ELISPOT was positive in 14/21 (66%) with definite TB. A significantly higher proportion of HIV-infected children with definite or probable TB had a positive ELISPOT compared with a positive TST [25/39 (64%) vs. 10/34 (29%), P = 0.005]. In contrast to TST, results from ELISPOT were not affected by young age or severe immunosuppression. In HIV-infected children without active TB disease, 27% had a positive ELISPOT, suggesting latent TB infection.

CONCLUSION

ELISPOT is more sensitive than TST for the detection of active TB in HIV-infected children. However, the sensitivity of current ELISPOT assays is not sufficiently high to be used as a rule out test for TB.

Use of T cell-based diagnosis of tuberculosis infection to optimize interpretation of tuberculin skin testing for child tuberculosis contacts

BACKGROUND

Treatment of recent tuberculosis infection in children aged <2 years is essential, because of high risk of progression to disease, but diagnosis is hindered by the inaccuracy of the tuberculin skin test (TST). More-accurate T cell-based tests of infection could enhance diagnosis by optimizing interpretation of the TST results.

METHODS

A total of 979 child tuberculosis contacts in Istanbul underwent the TST and enzyme-linked immunospot assay. Using enzyme-linked immunospot test results as a reference standard, we assessed the effect of age and bacille Calmette-Guérin (BCG) vaccination on the sensitivity and specificity of the TST, and we computed the optimal TST cutoff points, using receiver operating characteristic curves.

RESULTS

With a TST cutoff point of >or=10 mm, the sensitivity of the TST was 66% for children aged <2 years, which was lower than that for older children (P= .006). Specificity was 75% for BCG-vaccinated children, compared with 92% for unvaccinated children (P= .001). Optimal cutoff points improved TST specificity for children with 1 BCG scar, with little loss of sensitivity. Despite the use of optimal cutoff points, TST sensitivity remained <70% for children aged <2 years, specificity remained <87% for BCG-vaccinated children aged >or=2 years, and overall accuracy was low for children with >1 BCG scar.

CONCLUSIONS

Negative results of the TST cannot exclude tuberculosis infection for child tuberculosis contacts aged <2 years, which supports the use of preventive therapy regardless of the TST results for this age group. In children aged >or=2 years, the accuracy of the TST can be improved by adjustment of cutoff points for BCG-vaccinated children but remains poor for children with >1 BCG scar. This methodology can define optimal TST cutoff points for diagnosis of tuberculosis infection tailored to target populations.

IGRA tests perform similarly to TST but cause no adverse reactions: pediatric experience in Finland

Background

Two commercial interferon gamma release assays (IGRAs) (QuantiFERON^®-TB Gold in Tube and T SPOT^®-TB) to detect a contact with M. tuberculosis have recently become available. The majority of studies agree that the sensitivity and specificity of these methods are superior to the Tuberculin Skin Tests (TSTs) in detecting an exposure to bacteria in latently infected individuals and in clinical tuberculosis. However, the data in children remains limited.

Findings

Consecutively collected samples from children (n = 99) representing age range from zero to 18 years were analyzed in a retrospective non-blinded study. The two IGRAs were modified and adapted to the needs of Finland, a country of a low tuberculosis incidence. For 27 children, both tests were performed simultaneously and compared with the TST and clinician's diagnosis. The sensitivity, specificity, and accuracy of both IGRAs was determined. QuantiFERON TB Gold and T SPOT-TB performed (respectively) as follows: sensitivities 0.92 (95% confidence interval, CI, 0.67–0.99) and 0.85 (0.64–0.95); specificities 0.91 (0.77–0.97) and 1.00 (0.93–1.00); accuracies 0.91 (0.80–0.97) and 0.96 (0.88–0.99). This compares favorably to the TST whose known figures are 0.90, 0.95, and 0.95, respectively. The agreement between the IGRAs was high, k = 0.89. Finally, both methods agreed well with the TST, k = 0.86 for TST/QuantiFERON-TB Gold and k = 0.76 for TST/T SPOT-TB.

Conclusion

The sensitivity and specificity of IGRA methods compares well with the TST without the inconveniences and complications associated with TST, including exaggerated delayed type hypersensitivity reactions. These properties place them as acceptable substitutes for TST.

Temporal dynamics of interferon gamma responses in children evaluated for tuberculosis

Background

Development of T-cells based-Interferon gamma (IFNγ) assays has offered new possibilities for the diagnosis of latent tuberculosis infection (LTBI) and active disease in adults. Few studies have been performed in children, none in France. With reference to the published data on childhood TB epidemiology in the Paris and Ile de France Region, we considered it important to evaluate the performance of IGRA (QuantiFERON TB Gold In Tube®, QF-TB-IT) in the diagnosis and the follow-up through treatment of LTBI and active TB in a cohort of French children.

Methodology/Principal Findings

131 children were recruited during a prospective and multicentre study (October 2005 and May 2007; Ethical Committee St Louis Hospital, Paris, study number 2005/32). Children were sampled at day 0, 10, 30, 60 (except Healthy Contacts, HC) and 90 for LTBI and HC, and a further day 120, and day 180 for active TB children. Median age was 7.4 years, with 91% of the children BCG vaccinated. LTBI and active TB children undergoing therapy produced significant higher IFNγ values after 10 days of treatment (p = 0.035). In addition, IFNγ values were significantly lower at the end of treatment compared to IFNγ values at day 0, although the number of positive patients was not significantly different between day 0 and end of treatment.

Conclusions/ Significance

By following quantitative IFNγ values in each enrolled child with LTBI or active TB and receiving treatment, we were able to detect an increase in the IFNγ response at day 10 of treatment which might allow the confirmation of a diagnosis. In addition, a decline in IFNγ values during treatment makes it possible for clinicians to monitor the effect of preventive or curative therapy.

Is IP-10 a better biomarker for active and latent tuberculosis in children than IFNgamma?

BACKGROUND

The blood based interferon-gamma release assays (IGRA) for the diagnosis of tuberculosis do not discriminate between active TB disease and latent TB infection (LTBI). The search for distinguishing biomarkers therefore continues, as the accurate diagnosis of tuberculosis is particularly challenging in children. IFN-gamma-inducible protein 10 (IP-10/CXCL10) has recently been evaluated as a marker for active TB in adults with promising results.

AIM

To investigate this new biomarker for active TB and LTBI in paediatrics.

METHOD

We measured IP-10 levels using ELISA in supernatants of whole blood samples stimulated with TB-specific-antigens and negative control antigen.

RESULTS

IP-10 is produced in high levels following mycobacterial antigen stimulation in active TB (n = 17) and LTBI (n = 16) compared to controls (n = 16) and to IFN-gamma. The baseline levels of IP-10 are increased in active TB and in LTBI, but there is no significant difference of stimulated levels of IP-10 between active TB and LTBI.

CONCLUSIONS

IP-10 is a biomarker for tuberculosis in children. However like IFNgamma, IP-10 also does not distinguish between active TB and LTBI.

Enhancement of human antigen-specific memory T-cell responses by interleukin-7 may improve accuracy in diagnosing tuberculosis

Children and immunocompromised adults are at an increased risk of tuberculosis (TB), but diagnosis is more challenging. Recently developed gamma interferon (IFN-gamma) release assays provide increased sensitivity and specificity for diagnosis of latent TB, but their use is not FDA approved in immunocompromised or pediatric populations. Both populations have reduced numbers of T cells, which are major producers of IFN-gamma. Interleukin 7 (IL-7), a survival cytokine, stabilizes IFN-gamma message and increases protein production. IL-7 was added to antigen-stimulated lymphocytes to improve IFN-gamma responses as measured by enzyme-linked immunosorbent assay (ELISA) and enzyme-linked immunospot (ELISPOT) assay. Antigens used were tetanus toxoid (n = 10), p24 (from human immunodeficiency virus [HIV], n = 9), and TB peptides (n = 15). Keyhole limpet hemocyanin was used as a negative control, and phytohemagglutinin was the positive control. IL-7 improved antigen-specific responses to all antigens tested including tetanus toxoid, HIV type 1 p24, and TB peptides (ESAT-6 and CFP-10) with up to a 14-fold increase (mean = 3.8), as measured by ELISA. Increased IFN-gamma responses from controls, HIV-positive patients, and TB patients were statistically significant, with P values of <0.05, 0.01, and 0.05, respectively. ELISPOT assay results confirmed ELISA findings (P values of <0.01, 0.02, and 0.03, respectively), with a strong correlation between the two tests (R(2) = 0.82 to 0.99). Based on average background levels, IL-7 increased detection of IFN-gamma by 39% compared to the level with antigen alone. Increased production of IFN-gamma induced by IL-7 improves sensitivity of ELISA and ELISPOT assays for all antigens tested. Further enhancement of IFN-gamma-based assays might improve TB diagnosis in those populations at highest risk for TB.