Performance of commercial blood tests for the diagnosis of latent tuberculosis infection in children and adolescents

QuantiFERON to diagnose infection by Mycobacterium tuberculosis: performance in infants and older children

OBJECTIVES

QuantiFERON value to diagnose tuberculosis (TB) in young children remains to be clarified. To this aim QF-TB-IT performance was evaluated in a large series of immunocompetent children that were stratified according to age and clinical conditions.

METHODS

QF-TB-IT reactivity was analyzed in 226 immunocompetent children (0-15 years old): 31 were uninfected despite TB contact; 51 presented TB disease; 39 had Latent TB (LTBI) and 105 had TB disease suspected but an alternative diagnosis (TB excluded).

RESULTS

QF-TB-IT specificity was 100% in TB excluded. In TB disease, low sensitivity of QF-TB-IT in infants (40%) increased with aging (77% in 1-<5 years and 82% in 5-<15 years old subgroups). In LTBI, agreement between TST and QF-TB-IT was 0% in infants, 40% in 1-<5 years and 57% in children >5 years old. Finally, the incidence of indeterminate results was high (24%) in children <5 years old with TB excluded, especially with non-TB pneumonitis (61%), but was low (0-6%) regardless of age group in TB disease, LTBI and uninfected contact cases.

CONCLUSIONS

In our low burden country, i) QF-TB-IT specificity was 100%, ii) QF-TB-IT sensitivity was low in infants but commensurable to adult values in older children, and iii) indeterminate results mostly relied on ongoing infections unrelated to TB.

Contact investigation based on serial interferon-gamma release assays (IGRA) in children from the hematology-oncology ward after exposure to a patient with pulmonary tuberculosis

BACKGROUND

Interferon-gamma release assays (IGRAs) have high specificity and sensitivity for the diagnosis of tuberculosis (TB) infection. However, their role as a screening tool in children with immunodeficiency disorders is still unclear. In the present study, we performed a contact investigation using serial IGRAs on children with immunodeficiency conditions exposed to a contagious TB patient.

METHODS

Children who were exposed to a contagious TB case underwent serial QuantiFERON(®) TB Gold In-Tube (QFT-GIT) and T-SPOT(®).TB (T-SPOT) testing.

RESULTS

Eighteen children were tested. At the first testing, only two children (11 %) were positive to T-SPOT. Indeterminate results were more frequent with QFT-GIT (35 %) than with T-SPOT (12 %). In the multivariable analysis, a statistically significant association of lymphocyte count <500 cells/mm(3) (p < 0.00005) and low age (p = 0.03) with indeterminate results for the QFT-GIT test but not for T-SPOT (p = 0.10 and p = 0.88, respectively) was found. At the end of October 2012, 15 of the 18 children were alive and none developed active TB disease.

CONCLUSION

T-SPOT provided more determinate results and was less influenced by low age and lymphocytopenia than QFT-GIT in this population of immunodeficient children. These findings suggest that T-SPOT is a more accurate test for the identification of TB infection in young children with lymphocytopenia and should be preferred to QFT-GIT under such specific conditions.

Circulating biomarkers of pulmonary and extrapulmonary tuberculosis in children

Tuberculosis (TB) in children is not only more likely to cause more severe disease than that seen in adults, it is also more likely to be extrapulmonary. Moreover, pediatric TB is very difficult to diagnose and suffers from a lack of understanding of host biomarkers for monitoring the progression of disease. Hence, we sought to identify the expression patterns of a variety of biomarkers in the plasma of children with pulmonary TB (PTB) and extrapulmonary TB (ETB), as well as in healthy control (HC) children. Thus, we examined a variety of circulating markers reflecting tissue inflammation, oxidative stress, innate immune activation, fibrosis, and the cytokine response. Children with active TB, compared to HC children, showed markedly elevated plasma levels of matrix metalloproteinases and their endogenous inhibitors. In addition, children with active TB had significantly elevated levels of C-reactive protein, α-2 macroglobulin, and haptoglobin, as well as hemoxygenase 1. Markers of innate immune activation (lipopolysaccharide [LPS] and lipopolysaccharide-binding protein [LBP]) were significantly lower in ETB than in PTB children. Although there were no significant differences between the two groups in their levels of cytokines (type 1 [gamma interferon (IFN-γ), tumor necrosis factor α (TNF-α), interleukin 2 (IL-2), and IL-12], type 2 [IL-4, IL-5, IL-13, and IL-33], and most type 17 [IL-17A, IL-22, IL-1β, and IL-6] and type 1 interferons [IFN-α and IFN-β]) or most of the cytokines associated with immune modulation (IL-10 and IL-20), pediatric TB was associated with elevated plasma transforming growth factor β (TGF-β), IL-21, and IL-23 levels. Thus, pediatric TB is characterized by elevated levels of a variety of biomarkers at homeostasis, suggesting that these responses may play a crucial role in disease pathogenesis.

Updated diagnosis and treatment of childhood tuberculosis

BACKGROUND

Childhood tuberculosis (TB) accounts for a significant proportion of the global tuberculosis disease burden. However, current and previous efforts to develop better diagnostic, therapeutic, and preventive interventions have focused on TB in adults, and childhood TB has been relatively neglected. The purpose of this review is to provide an update on the diagnostic and therapeutic recommendations for childhood TB with an emphasis on intrathoracic disease.

DATA SOURCES

The literature from a range of sources was reviewed and synthesized to provide an overview of the contemporary approaches for the diagnosis and treatment of childhood TB.

RESULTS

This review summarizes the clinical, radiological, bacteriological, and immunological approaches to diagnose TB infection and disease in children. In addition, we summarize the updated guidelines for the treatment of TB in children.

CONCLUSIONS

The development of better diagnostic and therapeutic methods for childhood TB remains a significant challenge. As the strategies for diagnosis and treatment of childhood TB continue to improve and the knowledge base increases, the implementation of these strategies will be crucial.

Cost-effectiveness of latent tuberculosis screening before steroid therapy for idiopathic nephrotic syndrome in children

BACKGROUND

Guidelines differ on screening recommendations for latent tuberculosis infection (LTBI) prior to immunosuppressive therapy. We aimed to determine the most cost-effective LTBI screening strategy before long-term steroid therapy in a child with new-onset idiopathic nephrotic syndrome.

STUDY DESIGN

Markov state-transition model.

SETTING & POPULATION

5-year-old boy with new-onset idiopathic nephrotic syndrome.

MODEL, PERSPECTIVE, & TIMEFRAME

The Markov model took a societal perspective over a lifetime horizon.

INTERVENTION

3 strategies were compared: universal tuberculin skin testing (TST), targeted screening using a risk-factor questionnaire, and no screening. A secondary model included the newer interferon γ release assays (IGRAs), requiring only one visit and having greater specificity than TST.

OUTCOMES

Marginal cost-effectiveness ratios (2010 US dollars) with effectiveness measured as quality-adjusted life-years (QALYs).

RESULTS

At an LTBI prevalence of 1.1% (the average US childhood prevalence in our base case), a no-screening strategy dominated ($2,201; 29.3356 QALYs) targeted screening ($2,218; 29.3356 QALYs) and universal TST ($2,481; 29.3347 QALYs). At a prevalence >10.3%, targeted screening with a risk-factor questionnaire was the most cost-effective option. Higher than a prevalence of 58.5%, universal TST was preferred. In the secondary model, targeted screening with a questionnaire followed by IGRA testing was cost-effective compared with no screening in the base case when the LTBI prevalence was >4.9%.

LIMITATIONS

There is no established gold standard for the diagnosis of LTBI. Results of any modeling task are limited by the accuracy of available data.

CONCLUSIONS

Prior to starting steroid therapy, only patients in areas with a high prevalence of LTBI will benefit from universal TST. As more evidence becomes available about the use of IGRA testing in children, the assay may become a component of cost-effective screening protocols in populations with a higher burden of LTBI.

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.

Diagnosis and management of tuberculosis in transplant donors: a donor-derived infections consensus conference report

Mycobacterium tuberculosis is a ubiquitous organism that infects one-third of the world's population. In previous decades, access to organ transplantation was restricted to academic medical centers in more developed, low tuberculosis (TB) incidence countries. Globalization, changing immigration patterns, and the expansion of sophisticated medical procedures to medium and high TB incidence countries have made tuberculosis an increasingly important posttransplant infectious disease. Tuberculosis is now one of the most common bacterial causes of solid-organ transplant donor-derived infection reported in transplant recipients in the United States. Recognition of latent or undiagnosed active TB in the potential organ donor is critical to prevent emergence of disease in the recipient posttransplant. Donor-derived tuberculosis after transplantation is associated with significant morbidity and mortality, which can best be prevented through careful screening and targeted treatment. To address this growing challenge and provide recommendations, an expert international working group was assembled including specialists in transplant infectious diseases, transplant surgery, organ procurement and TB epidemiology, diagnostics and management. This working group reviewed the currently available data to formulate consensus recommendations for screening and management of TB in organ donors.

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.

The role of interferon-gamma release assay in tuberculosis control

Tuberculosis is still one of the major global public health threats. Countries with low incidence must focus on exhausting the reservoir of future cases by preventing reactivation. Therefore, it is important to identify and effectively treat those individuals who have latent tuberculosis infection and who may develop active disease. The tuberculin skin test has been the standard for detection of immune response against M. tuberculosis since the beginning of the 20th century. The new millennium has brought advancement in the diagnosis of latent tuberculosis infection. The name of the new blood test is interferon-gamma release assay (IGRA). Croatia is a middle-incidence country with a long decreasing trend and developed tuberculosis control. To reach low incidence and finally eliminate tuberculosis, its tuberculosis programme needs a more aggressive approach that would include intensive contact investigation and treatment of persons with latent tuberculosis infection. This article discusses the current uses of IGRA and its role in tuberculosis control.

Preventive therapy in children exposed to Mycobacterium tuberculosis: problems and solutions

Young children living with a tuberculosis patient are at high risk of Mycobacterium tuberculosis infection and disease. WHO guidelines promote active screening and isoniazid (INH) preventive therapy (PT) for such children under 5 years, yet this well-established intervention is seldom used in endemic countries. We review the literature regarding barriers to implementation of PT and find that they are multifactorial, including difficulties in screening, poor adherence, fear of increasing INH resistance and poor acceptability among primary caregivers and healthcare workers. These barriers are largely resolvable, and proposed solutions such as the adoption of symptom-based screening and shorter drug regimens are discussed. Integrated multicomponent and site-specific solutions need to be developed and evaluated within a public health framework to overcome the policy-practice gap and provide functional PT programmes for children in endemic settings.

Interferon-γ release assays for the diagnosis of Mycobacterium tuberculosis infection in children: a literature review

The role of interferon-gamma release assays (IGRAs) for immunologic diagnosis of tuberculosis in children is under debate. We carried out a narrative review on the studies on IGRAs in paediatric populations. A literature search was conducted using multiple keywords and standardized terminology in Medline, EMBASE and Cochrane databases, up to January 27th, 2011. Study quality was assessed using the MOOSE checklist and results of relevant studies were summarized. Sixty-seven paediatric studies (study population ranging from 14 to 5,244 children) were identified. Non-commercial ELISPOT assay (by means of ESAT-6 and CFP-10 antigens) had been carried out in 11 studies. QuantiFERON-TB Gold (QFT-G), QuantiFERON-TB Gold In-tube (QFT-G-IT), and T-SPOT.TB assays had been performed in 10, 44 and 18 studies, respectively. Most studies reported higher specificity of IGRA than tuberculin skin test (TST), but interpretation of the results is complicated by the fact that a gold standard for the diagnosis of latent TB is lacking. The reported sensitivity for active TB ranged from 51-93 percent for QFT-G/QFT-G-IT and 40-100 percent for ELISPOT assays, suggesting that a negative IGRA result may not exclude tuberculosis. Combining TST and IGRA results increased the diagnostic sensitivity. Rates of indeterminate results largely varied (0 to 35 percent). Most of the studies on young (less than 5 years) or immune-compromised children reported a proportion of indeterminate results exceeding 4 percent. Agreement among TST and IGRA, assessed by the k statistics, ranged from -0.03 to 0.87. Higher rates of discordance were reported in BCG-vaccinated than in non-BCG-vaccinated children. Studies on children less than 5 years and immunocompromised children reported conflicting results, as did studies on serial IGRA determinations. Despite the large amount of literature data, the role of IGRA in the pediatric population is still unclear, especially in young children. Combined use of TST/IGRA may increase diagnostic sensitivity but interpretation of discordant results remains a challenging issue.

QuantiFERON®-TB gold in-tube performance for diagnosing active tuberculosis in children and adults in a high burden setting

AIM

To determine whether QuantiFERON®-TB Gold In-Tube (QFT) can contribute to the diagnosis of active tuberculosis (TB) in children in a high-burden setting and to assess the performance of QFT and tuberculin skin test (TST) in a prospective cohort of TB suspect children compared to adults with confirmed TB in Tanzania.

METHODS

Sensitivity and specificity of QFT and TST for diagnosing active TB as well as indeterminate QFT rates and IFN-γ levels were assessed in 211 TB suspect children in a Tanzanian district hospital and contrasted in 90 adults with confirmed pulmonary TB.

RESULTS

Sensitivity of QFT and TST in children with confirmed TB was 19% (5/27) and 6% (2/31) respectively. In adults sensitivity of QFT and TST was 84% (73/87) and 85% (63/74). The QFT indeterminate rate in children and adults was 27% and 3%. Median levels of IFN-γ were lower in children than adults, particularly children <2 years and HIV infected. An indeterminate result was associated with age <2 years but not malnutrition or HIV status. Overall childhood mortality was 19% and associated with an indeterminate QFT result at baseline.

CONCLUSION

QFT and TST showed poor performance and a surprisingly low sensitivity in children. In contrast the performance in Tanzanian adults was good and comparable to performance in high-income countries. Indeterminate results in children were associated with young age and increased mortality. Neither test can be recommended for diagnosing active TB in children with immature or impaired immunity in a high-burden setting.

Factors associated with the performance of a blood-based interferon-γ release assay in diagnosing tuberculosis

Background

Indeterminate results are a recognised limitation of interferon-γ release assays (IGRA) in the diagnosis of latent tuberculosis (TB) infection (LTBI) and TB disease, especially in children. We investigated whether age and common co-morbidities were associated with IGRA performance in an unselected cohort of resettled refugees.

Methods

A retrospective cross-sectional study of refugees presenting for their post-resettlement health assessment during 2006 and 2007. Refugees were investigated for prevalent infectious diseases, including TB, and for common nutritional deficiencies and haematological abnormalities as part of standard clinical screening protocols. Tuberculosis screening was performed by IGRA; QuantiFERON-TB Gold in 2006 and QuantiFERON-TBGold In-Tube in 2007.

Results

Complete data were available on 1130 refugees, of whom 573 (51%) were children less than 17 years and 1041 (92%) were from sub-Saharan Africa. All individuals were HIV negative. A definitive IGRA result was obtained in 1004 (89%) refugees, 264 (26%) of which were positive; 256 (97%) had LTBI and 8 (3%) had TB disease. An indeterminate IGRA result was obtained in 126 (11%) refugees (all failed positive mitogen control). In multivariate analysis, younger age (linear OR  = 0.93 [95% CI 0.91–0.95], P<0.001), iron deficiency anaemia (2.69 [1.51–4.80], P = 0.001), malaria infection (3.04 [1.51–6.09], P = 0.002), and helminth infection (2.26 [1.48–3.46], P<0.001), but not vitamin D deficiency or insufficiency, were associated with an indeterminate IGRA result.

Conclusions

Younger age and a number of common co-morbidities are significantly and independently associated with indeterminate IGRA results in resettled predominantly African refugees.

Utility of interferon-γ release assay results to monitor anti-tubercular treatment in adults and children

BACKGROUND

Interferon-γ release assays (IGRAs), including the commercially available T-SPOT.TB, QuantiFERON-TB Gold (QFT-G), and QuantiFERON-TB Gold In-Tube (QTF-G-IT), enable detection of circulating T lymphocytes responsive to specific Mycobacterium tuberculosis antigens. Studies of the potential role of serial IGRAs for assessment of response to anti-tubercular therapy are accumulating.

OBJECTIVE

The objective of this systematic review was to evaluate the potential clinical utility of serial IGRAs in anti-tubercular therapy.

METHODS

We conducted a literature search of the Cochrane Library and MEDLINE by PubMed, from database inception through October 1, 2011, for serial IGRA results in anti-tubercular therapy, in adults and children, using commercial stardardized assays. All types of articles in the English language were included. Meta-analysis was performed to estimate the pooled percentage of reversion from a positive to a negative IGRA value at 3- to 6-month follow-up.

RESULTS

According to inclusion and exclusion criteria, three T-SPOT.TB-based (n = 319 patients), three QFT-G-based (n = 75 patients), and seven QFT-G-IT-based (n = 558 patients) longitudinal studies were included. The percentage of patients with reversion from a positive to a negative IGRA value ranged from 5.71% to 13.93% for T-SPOT.TB, 5.26% to 71.05% for QFT-G, and 14.28% to 41.89% for QFT-G-IT assays. Meta-analysis estimation of reversion was feasible only for the QFT-G-IT assay, at 30.54% (95% CI, 22.89-38.75). In two pediatric studies, which were QFT-G-IT based (n = 122 children), the reported reversion rates were 14.28% and 20.33%, respectively.

CONCLUSIONS

Because IGRAs require time and cost resources, and reversion from positive to negative IGRA values occurs in a minority of treated patients, monitoring IGRA changes over time seems to have only speculative value in adults. Data in children are poor, but are in line with results reported in adults.

The diagnosis of tuberculosis

Childhood tuberculosis accounts for a significant proportion of the global tuberculosis disease burden. However, tuberculosis in children is difficult to diagnose, because disease tends to be paucibacillary and sputum samples are often not easy to obtain. The diagnosis of tuberculosis in children is traditionally based on chest radiography, tuberculin skin testing, and mycobacterial staining/culture from appropriate samples. Newer diagnostic strategies have included improved bacteriologic and molecular methods, as well as new methods for sample collection from children. Recently, immune-based diagnostics, such as the interferon-gamma release assays, have been introduced for clinical use. These tests do not offer substantial improvements in sensitivity over tuberculin skin testing for the diagnosis of active disease but may be useful in excluding false-positive tuberculin skin tests. Further research is needed to develop better diagnostic tests for tuberculosis in children.

Evaluation of an Interferon Gamma Release Assay to Detect Tuberculosis Infection in Children in San Diego, California

QuantiFERON-TB Gold In-Tube (QFT-GIT) and tuberculin skin test (TST) results are reported in 23 children with active tuberculosis due to Mycobacterium tuberculosis and Mycobacterium bovis. Overall QFT-GIT (96%) was more sensitive than TST (74%) for detecting tuberculosis infection in these patients.

Diagnostic value of interferon- gamma release assays (QuantiFERON-TB Gold® In Tube) in childhood tuberculosis

OBJECTIVE

To evaluate the efficacy and diagnostic potential of interferon- gamma release assays QuantiFERON-TB Gold® In Tube (QFT-TB-IT) for the detection of gamma interferon against the antigen ESAT-6, CFP-10, TB 7.7(p4) of Mycobacterium tuberculosis and compare the reactivity with other methods (smear, culture and IS6110 targeting PCR).

METHODS

The study was carried out on children with pulmonary and extra pulmonary tuberculosis along with matching and PPD+ controls (82 cases, 48 matching controls and 20 PPD+ controls).

RESULTS

QFT-TB-IT showed a significantly higher sensitivity (51.2%) as compared with LJ medium culture method (11.0%; p < 0.001), BacT/Alert 3D system (12.1%; p < 0.001), ZN staining (19.5%; p < 0.001) and PCR (45.1%; p < 0.05). Specificity of QFT-TB-IT was 48.0%.

CONCLUSIONS

Less specificity of this assay may be due to high endemicity of tuberculosis. However, further studies are recommended.

Latent tuberculosis infection in children: diagnostic approaches

Tuberculosis (TB) remains an important public health problem and a leading infectious cause of death. Diagnosis and treatment of latent tuberculosis infection (LTBI) is important for TB control and elimination. Nevertheless, the diagnosis of LTBI in both adults and children remains complex, since there is no gold standard. The development of interferon gamma release assays was a major breakthrough in the diagnosis of LTBI. The evaluation of IGRAs in the diagnosis of LTBI in children is proven to be difficult since childhood TB differs from adults as immune responses vary with age. Separate studies assessing IGRAs performance in children are still limited, and only a few of them divide results by narrow age groups Nevertheless, new approaches are being exploited by the ongoing research for the development of more efficient diagnostic tools. It is likely that many changes in both the diagnosis and management of LTBI will occur in the near future. We believe that better understanding of the immunopathology of latency can ultimately lead to the development of more effective strategies in TB control. In the present review we summarize current data on diagnosis of LTBI in children, underscoring the existing challenges and limitations.

Diagnostic features associated with culture of Mycobacterium tuberculosis among young children in a vaccine trial setting

OBJECTIVES

To identify diagnostic features associated with culture of Mycobacterium tuberculosis (MTB), the standard for tuberculosis (TB) diagnosis, to inform clinical end point definitions for new TB vaccine trials.

METHODS

Children <2 years of age (n = 1445) were screened and investigated for TB during a Bacille Calmette Guerin vaccine trial in South Africa. Standardized clinical, radiologic, and microbiologic data were collected, including paired gastric lavage and induced sputum for MTB liquid culture. Adjusted odds ratios (AORs) were calculated using a multivariate logistic regression model.

RESULTS

Adjusted odds of positive MTB culture increased by 90% with history of wheezing (AOR, 1.9) and by 4% with each 1-mm increase in Mantoux diameter (AOR, 1.04). Odds of positive MTB culture doubled if the chest radiograph was suggestive of pulmonary TB (AOR, 2.16) and more than tripled if lower chest retraction was observed clinically (AOR, 3.37). Fever, night sweats, and presence of lymphadenopathy were negatively associated with MTB culture (AOR: 0.5, 0.62, and 0.2, respectively). Persistent cough, weight loss, and failure to thrive were not significantly associated with MTB culture in this study population.

CONCLUSIONS

Wheezing and lower chest retraction, consistent with intrathoracic airway obstruction; chest radiography suggestive of pulmonary tuberculosis; and Mantoux diameter were predictive of positive MTB culture. These variables should be considered for inclusion in composite clinical end point definitions for infant TB vaccine trials. Several clinical features, commonly used for TB diagnosis in older children, were not associated with positive MTB culture among children younger than 2 years.

Advances in the diagnosis of pulmonary tuberculosis in HIV-infected and HIV-uninfected children

The identification of improved diagnostic tests for tuberculosis has been identified as a global research priority. Over the past decade, there has been renewed interest in the development and validation of novel diagnostic tools for pulmonary tuberculosis that are applicable to resource-poor settings. These techniques are aimed primarily at improving detection of the organism or a specific host immune response. Although most studies have focused on determining the accuracy of novel tests in adults, it is likely they will also have the capacity to significantly improve the diagnosis of childhood tuberculosis. Improving the quality of clinical samples obtained from children with suspected tuberculosis remains an important research priority while awaiting validation of novel diagnostic tests. This review will focus on a number of recent developments for the diagnosis of tuberculosis, with a specific emphasis on the application of these new tests to children in settings where tuberculosis is endemic.

Concordance between tuberculin skin test and interferon-γ assay and interferon-γ response to mitogen in pediatric tuberculosis contacts

There is paucity of data on the usefulness of Interferon (IFN)-γ release assays in the diagnosis of latent tuberculosis infection (LTBI) in children. The aim of this study was to evaluate the concordance between tuberculin skin test (TST) and QuantiFERON®-TB Gold in-tube (QFT-GIT) test, when used in contact screening to diagnose LTBI in asymptomatic children. We also aimed to determine if there is any correlation between age and the IFN-γ response to the mitogen. Children assessed at Leicester Royal Infirmary and Glenfield hospital (Leicester, United Kingdom) as part of tuberculosis contact screening were studied. Two hundred and eighty three children (mean [SD] age 5.3 [4.1] years, 148 males) underwent clinical examination, chest radiograph, TST, and QFT-GIT test. In this group, there was good agreement (κ = 0.70 [95%CI = 0.57-0.83], P < 0.0001) between TST and QFT-GIT. Of the 18 children in this group with an indeterminate QFT-GIT test result, all except one were < 5-years-old. To study the correlation between age and the IFN-γ response to the mitogen, results of 282 children who had QFT-GIT test as part of tuberculosis contact screening during the study period were analyzed. A significant correlation was observed between age and the IFN-γ response to the mitogen (r = 0.47, P < 0.001). Whilst our study re-emphasizes the good overall concordance between TST and QFT-GIT, the high rate of indeterminate results and the low IFN-γ response to the mitogen seen in young children raise some concerns about the performance of IGRAs in this group.

Indeterminate results of QuantiFERON-TB Gold In-Tube assay in nonimmunosuppressed children

BACKGROUND AND AIMS

QuantiFERON-TB Gold In-Tube (QFT-IT) assay is a highly sensitive and specific test for the diagnosis of latent tuberculosis infection. Data on the use of QFT-IT assay in children are scarce and contradictory. The aim of the study was to assess the rate of indeterminate test results and to identify factors contributing to indeterminate results on routine use of QFT-IT assay in nonimmunosuppressed children.

METHODS

This retrospective study included 2173 children with ages ranging from 1 month to 18 years. Determination of interferon-gamma (IFN-γ) in peripheral blood was performed by commercial QFT-IT assay.

RESULTS

Indeterminate test results were recorded in ten (0.46%) subjects with ages ranging from 15 months to 15 years. The value of negative control was >8.0 kIU/L in one subject, whereas in the remaining nine subjects indeterminate results were consequential to positive control (<0.50 kIU/L). None of these subjects had any history data on congenital or acquired immunodeficiency disorders. Bacterial infection (with elevated body temperature and therapy with β-lactam antibiotics) was present in eight subjects with indeterminate results, one subject had exacerbation of asthma (therapy with inhalation corticosteroids), and one subject was clinically healthy. Repeat IFN-γ determination performed in seven subjects did not yield indeterminate results.

CONCLUSIONS

Study results showed the rate of indeterminate QFT-IT results in nonimmunosuppressed children of all age groups to be very low. QFT-IT should preferably be performed upon resolution of acute inflammation in order to avoid repeat testing of indeterminate results in a new blood sample and to reduce the cost of testing.

Interferon-γ release assay for the diagnosis of latent tuberculosis in children younger than 5 years of age

BACKGROUND

There are limited data available on interferon-γ release assay (IGRA) performance in children up to 5 years of age, with documented exposure to active tuberculosis (TB). The aim of this study was to evaluate (1) the influence of infectivity of adult source cases on test results, (2) the impact of age, and (3) the level of agreement, between IGRA and tuberculin skin test (TST) results.

METHODS

A total of 142 Bacille Calmette-Guerin-vaccinated children up to 5 years of age were investigated because of a history of exposure to active TB. QuantiFERON-TB Gold In-Tube IGRA (QFT) and TST assays were performed.

RESULTS

Test results were significantly influenced by positive finding of cavitary lesions (QFT, odds ratio [OR] = 6.15; TST, OR = 7.48) and positive acid-fast bacilli (QFT, OR = 4.01; TST, OR = 4.47) in active TB contacts. QFT resulted in 1 indeterminate response (0.7%), attributable to low mitogen. There was no evidence for age having any effect on QFT performance. The 2 tests showed a moderate overall concordance (89%; κ = 0.591) at a TST cutoff value of ≥ 10 mm.

CONCLUSIONS

Association of positive QFT and TST results with risk factors for infection in child contacts (presence of cavitary lesions and acid-fast bacilli smear positivity in index cases) suggests that both the tests have good diagnostic accuracy. However, there was significant discord between results of the 2 tests that could not be definitively resolved. Thus, in a high-risk population of children up to 5 years of age, both tests (QFT and TST) should be performed and the child should be considered infected if either or both tests are positive.

The tuberculin skin test is unreliable in school children BCG-vaccinated in infancy and at low risk of tuberculosis infection

BACKGROUND

The tuberculin skin test (TST) is often used to screen for latent tuberculosis infection (LTBI) in school children, many of whom were bacille Calmette-Guérin (BCG)-vaccinated in infancy. The reliability of the TST in such children is unknown.

METHODS

TSTs performed in low-risk BCG-vaccinated and -nonvaccinated grade 1 and grade 6 First Nations (North American Indian) school children in the province of Alberta, Canada, were evaluated retrospectively. To further assess the specificity of the TST, BCG-vaccinated children with a positive TST (≥10 mm of induration) and no treatment of LTBI were administered a QuantiFERON-TB Gold In-Tube test (QFT-GIT, Cellestis International).

RESULTS

A total of 3996 children, 2063 (51.6%) BCG-vaccinated and 1933 (48.4%) BCG-nonvaccinated, were screened for LTBI. Vaccinated children were more likely than nonvaccinated children to be TST positive (5.7% vs. 0.2%, P < 0.001). Vaccinated children with a positive TST were more likely to have a recent past TST as compared with those with a negative TST (6.8% versus 2.8%, P = 0.01). Among 65 BCG-vaccinated TST-positive children who underwent a QFT-GIT, only 5 (7.7%; 95% CI: 2.5%, 17.0%) were QFT-GIT positive. A TST of ≥15 mm was more likely to be associated with a positive QFT-GIT than a TST of 10 to 14 mm, 16.0% (95% CI: 4.5%, 36.1%) versus 2.5% (95% CI: 0.1%, 13.2%), P = 0.047.

CONCLUSION

The TST is unreliable in school children, BCG-vaccinated in infancy, and who are at low risk of infection. The QFT-GIT is a useful confirmatory test for LTBI in BCG-vaccinated TST-positive school children.

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.

[Specific features of tuberculosis in childhood]

Primary infection with Mycobacterium tuberculosis usually occurs during childhood. The source of infection is most often an adult. The risk of infection in exposed children is modulated by various factors related to the infectiousness of the index case, exposure conditions, and the child himself. This review aims to describe the specific diagnostic and therapeutic features of latent TB infection and TB disease in childhood.

A multicentre evaluation of the accuracy and performance of IP-10 for the diagnosis of infection with M. tuberculosis

IP-10 has potential as a diagnostic marker for infection with Mycobacterium tuberculosis, with comparable accuracy to QuantiFERON-TB Gold In-Tube test (QFT-IT). The aims were to assess the sensitivity and specificity of IP-10, and to evaluate the impact of co-morbidity on IP-10 and QFT-IT. 168 cases with active TB, 101 healthy controls and 175 non-TB patients were included. IP-10 and IFN-γ were measured in plasma of QFT-IT stimulated whole blood and analyzed using previously determined algorithms. A subgroup of 48 patients and 70 healthy controls was tested in parallel with T-SPOT.TB IP-10 and QFT-IT had comparable accuracy. Sensitivity was 81% and 84% with a specificity of 97% and 100%, respectively. Combining IP-10 and QFT-IT improved sensitivity to 87% (p < 0.0005), with a specificity of 97%. T-SPOT.TB was more sensitive than QFT-IT, but not IP-10. Among non-TB patients IP-10 had a higher rate of positive responders (35% vs 27%, p < 0.02) and for both tests a positive response was associated with relevant risk factors. IFN-γ but not IP-10 responses to mitogen stimulation were reduced in patients with TB and non-TB infection. This study confirms and validates previous findings and adds substance to IP-10 as a novel diagnostic marker for infection with M. tuberculosis. IP-10 appeared less influenced by infections other than TB; further studies are needed to test the clinical impact of these findings.

Latent tuberculosis in children: diagnosis and management

Control of tuberculosis in children often escapes attention because of the paucibacillary nature of the illness. However, they contribute much of the morbidity, mortality and future reservoir of the disease which reiterates the importance of risk-factor based screening for latent infection and appropriate treatment. We review the modalities and importance of diagnosis and treatment of latent tuberculosis infection in children. At this time, the role for interferon-gamma release assays in low-income, high-burden settings is rather limited but further research in the coming years might clear their role in children. An important emerging area of research is the development of an improved skin test for TB that uses specific mycobacterial antigens rather than tuberculin, thus is more feasible and useful in resource limited settings.

[Study of contacts in children and adolescents using the QuantiFERON®-TB Gold In-Tube]

OBJECTIVE

To compare the results of the Mantoux Tuberculin Test (TT) and the QuantiFERON TB® Gold In-Tube (QFT-GIT) in a population of children and adolescents with TB contacts.

MATERIAL AND METHODS

A prospective study using data collected on children and adolescents (< 17years) from a Health District of 300,000 inhabitants in the Basque Country (Spain) recruited into a TB contact study over a period of almost three years. The study included performing the Tuberculin Test using the Mantoux technique (with 2-TU of RT-23 PPD RT23 and Tween 80), and the QFT-GIT simultaneously, and collecting the demographic and clinical data.

RESULTS

Of the 160 children included in the study, 14% had a positive TT (≥ 5mm) and 11% a positive QFT-GIT. There was 95%-96% agreement between the tests, depending on the TT cut-off point chosen, and was higher in non-vaccinated children (100%) and in children less than 5 years-old (100%). A significant relationship was observed between a positive result for both tests with exposure in the home. The use of QFT-GIT in the screening of latent TB infection could reduce preventive treatments by 28%-34% compared with conventional screening with the TT.

CONCLUSIONS

The behaviour of QFT-GIT was comparable to the TT in identifying children with a tuberculosis infection; therefore it could potentially replace the TT.

Immune-based diagnostics for TB in children: what is the evidence?

Childhood TB is difficult to diagnose, since disease tends to be paucibacillary and sputum specimens are not easy to obtain in children. Thus, blood-based immune assays are an attractive option. Systematic reviews of serological assays suggest that these tests produce highly inconsistent estimates of sensitivity and specificity, but much of the serology literature is based on adults. In children, there is insufficient evidence to recommend the use of serological tests for active TB diagnosis. Interferon-gamma release assays (IGRA) do not offer substantial improvements in sensitivity over the TST for the diagnosis of active disease. For latent TB infection, the IGRA correlates well with the exposure gradient and seems to have utility in reducing the number of children who undergo preventive therapy due to false-positive TST. Although IGRAs can be used as evidence of TB infection in children, appropriate specimen collection and microbiological confirmation of TB disease should remain a priority.

Recent advances in testing for latent TB

After more than a century of relying on skin testing for the diagnosis of latent TB infection, clinicians now have access to blood-based diagnostics in the form of interferon γ release assays (IGRAs). These tests are generally associated with higher sensitivity and specificity for diagnosis of latent TB infection. This article reviews the indications for testing and treatment of latent TB infection in the overall context of a TB control program and describes how IGRAs might be used in specific clinical settings and populations, including people having close contact with an active case of TB, the foreign born, and health-care workers.

Comparing the tuberculin skin test and T-SPOT.TB blood test in children

BACKGROUND

Interferon-γ-release assays (IGRAs) have been developed for the diagnosis of tuberculosis infection, but few data are available for children. There currently is no reference standard for the diagnosis of tuberculosis infection.

OBJECTIVE

To compare the performance of 1 IGRA, the T-SPOT.TB assay with the tuberculin skin test (TST) in children with different epidemiologic risk factors for tuberculosis.

METHODS

We conducted a prospective study of 210 patients referred to 3 pediatric tuberculosis clinics, including those with no risk factors for tuberculosis (low risk, n = 27), risk factors but no identifiable source case (intermediate risk, n = 78), contact with a known source case (high risk, n = 74), and active disease (n = 31). Children were tested with TST and T-SPOT.TB. Concordance analyses were performed, and assay outcomes were modeled by multivariate logistic regression.

RESULTS

For 13 children with culture-confirmed tuberculosis disease, sensitivity of TST and T-SPOT.TB was 77% and 92%, respectively, and concordance was 69%. For high-risk children, concordance was 94% for BCG-unimmunized children and 88% for BCG-immunized children. For intermediate-risk children, concordance was 74% for BCG-unimmunized children and 33% for BCG-immunized children. For low-risk children, concordance was 74% for BCG-unimmunized children and 20% for BCG-immunized children. Multivariate analysis revealed that contact with a source case was associated with T-SPOT.TB result, but age and BCG immunization were not.

CONCLUSIONS

T-SPOT.TB is comparable to the TST in the diagnosis of tuberculosis disease and identification of high-risk children with tuberculosis infection and is more specific than the TST in children who have received the BCG vaccine.

Malnutrition and helminth infection affect performance of an interferon gamma-release assay

OBJECTIVE

We sought to compare the tuberculin skin test (TST) to the QuantiFERON-TB Gold In-Tube assay (QFT-IT) and assess the effects of malnourishment and intestinal helminth infection on QFT-IT results.

METHODS

In this population-based cross-sectional study from Dhaka, Bangladesh, we screened children for latent tuberculosis infection with the QFT-IT and TST. We assess the agreement between the TST and QFT-IT, risk factors associated with indeterminate QFT-IT results, and magnitude of interferon γ (IFN-γ) production.

RESULTS

Three hundred and two children (aged 11-15.3 years) were enrolled, including 93 (30.8%) who were malnourished. Of 251 participants who provided stool samples, 117 (46.6%) were infected with Ascaris lumbricoides and/or Trichuris trichiura. TST results were positive (≥10 mm) for 101 (33.4%) children and negative for 201 (66.6%) children. QFT-IT results were positive for 107 (35.4%) children, negative for 121 (40.1%) children, and indeterminate for 74 (24.5%) children. Agreement between the tests was moderate (κ = 0.55 [95% confidence interval: 0.44-0.65]; P < .0001) when excluding indeterminate results. Children with indeterminate QFT-IT results were separately compared with children with positive and negative QFT-IT results; malnutrition (P = .0006 and .0003), and helminth infection (P = .05 and .02), and the statistical interaction between these 2 terms (P = .03 and .004) were associated with indeterminate results. Higher levels of IFN-γ in response to tuberculosis antigens were associated with positive TST results (P < .0001); lower levels were associated with malnutrition (P = .02).

CONCLUSIONS

Malnutrition and helminth infections were associated with indeterminate QFT-IT results. Therefore, the presence of such conditions may limit the interpretability of QFT-IT results in children.

Overlap, common features, and essential differences in pediatric granulomatous inflammatory bowel disease

Overlap in the clinical presentation of pediatric granulomatous inflammatory bowel disease may be substantial, depending on the mode of presentation. Chronic granulomatous disease (CGD) may present with granulomatous colitis, perianal abscesses, hepatic abscesses or granulomas, failure to thrive, and obstruction of the gastrointestinal tract (including esophageal strictures and dysmotility, delayed gastric emptying, and small bowel obstruction). Anemia, thrombocytosis, elevated C-reactive protein and erythrocyte sedimentation rate, and hypoalbuminemia are nonspecific and may occur in any of the granulomatous inflammatory bowel diseases. In histology, macrophages with cytoplasmic inclusions will be rather specific for CGD. Sarcoidosis may present with abdominal pain or discomfort, diarrhea, weight loss, growth failure, delayed puberty, erythema nodosum, arthritis, uveitis, and hepatic granulomata. Only in 55% of the patients will angiotensin-converting enzyme be elevated. The noncaseating epithelioid granulomata will be unspecific. Bronchoalveolar lymphocytosis and abnormalities in pulmonary function are reported in sarcoidosis and in Crohn disease (CD) and CGD. Importantly, patients with CD may present with granulomatous lung disease, fibrosing alveolitis, and drug-induced pneumonitis. Sarcoidosis and concomitant gastrointestinal CD have been reported in patients, as well as coexistence of CD and sarcoidosis in siblings. Common susceptibility loci have been identified in CD and sarcoidosis. CD and CGD share defects in the defense mechanisms against different microbes. In the present review, common features and essential differences are discussed in clinical presentation and diagnostics--including histology--in CGD, sarcoidosis, and CD, together with 2 other granulomatous inflammatory bowel diseases, namely abdominal tuberculosis and Hermansky-Pudlak syndrome. Instructions for specific diagnosis and respective treatments are provided.

Diagnosis of pulmonary tuberculosis in children: new advances

The global burden of childhood pulmonary TB has been underappreciated, in part due to difficulties in obtaining microbiological confirmation of disease. Most HIV-uninfected children can be diagnosed using a combination of clinical and epidemiological features, tuberculin skin testing and chest radiography, as represented in different scoring systems. However, accurate microbiologic diagnosis has become increasingly important for timely use of effective treatment. Mycobacterial culture confirms the diagnosis of TB and provides drug susceptibility data but is not available in most areas with a high TB prevalence. Moreover, culture has poor sensitivity in children who usually have paucibacillary disease. The HIV epidemic has made definitive diagnosis even more challenging due to nonspecific clinical and radiological signs. In high HIV-prevalence areas, scoring systems have been especially variable, lacking sensitivity and specificity. Newer methods for diagnosis are aimed either at detecting the organism or a specific host immune response. Methods for organism detection have focused on collection of better samples, improved culture techniques, molecular methods or antigen detection. Recent advances include the use of sputum induction for obtaining a more reliable specimen, faster and more sensitive culture methods, and rapid detection of the organism and drug resistance based on nucleic acid amplification. Improved methods for detecting a specific host response have largely focused on the use of IFN-g release assays. Even with newer methods, accurately diagnosing childhood TB may be challenging. Greater efforts to obtain a microbiologic diagnosis should be made in children, even in primary care settings. Further research to develop a more accurate, cost-effective and simple diagnostic test for childhood TB is urgently needed.

[Diagnosis of tuberculosis in pediatrics. Consensus document of the Spanish Society of Pediatric Infectology (SEIP) and the Spanish Society of Pediatric Pneumology (SENP)]

Tuberculosis is one of the most important health problems worldwide. There are an increased number of cases, including children, due to different reasons in developed countries. The most likely determining cause is immigration coming from high endemic areas. Measures to optimize early and appropriate diagnosis of the different forms of tuberculosis in children are a real priority. Two Societies of the Spanish Pediatric Association (Spanish Society of Pediatric Infectology and Spanish Society of Pediatric Pneumology) have agreed this Consensus Document in order to homogenize diagnostic criteria in pediatric patients.

Interferon-gamma release assays: new diagnostic tests for Mycobacterium tuberculosis infection, and their use in children

PURPOSE OF REVIEW

The testing and treatment of children at risk for Mycobacterium tuberculosis infection represents an important public health priority in the United States. Until recently, diagnosis has relied upon the tuberculin skin test (TST). New interferon-gamma release assays (IGRAs) offer improvements over TST, but these tests have not been studied in children until recently.

RECENT FINDINGS

Evidence regarding IGRA performance in children is accumulating rapidly. Overall, the findings demonstrate performance of IGRAs equivalent or superior to that of the TST. However, IGRAs have biological limitations similar to TST and some technical problems of their own, and critical gaps in our knowledge remain.

SUMMARY

Current evidence supports usage of IGRAs in children aged 5 years or older. IGRAs are preferred over TST when specificity is paramount or wherein patients might fail to return for TST reading. Evidence for use in children aged less than 5 years is insufficient at this time: the sensitivity is poorly defined, and TST is preferred for testing these children. Future IGRA research should focus on children aged less than 5 years for informing expanded usage in this vulnerable population.

Evidence-based comparison of commercial interferon-gamma release assays for detecting active TB: a metaanalysis

Test accuracy of interferon-gamma release assays (IGRAs) for diagnosing TB differs when using older or precommercial tools and inconsistent diagnostic criteria. This metaanalysis critically appraises studies investigating sensitivity and specificity of the commercial T-Spot.TB and the QuantiFERON-TB Gold In-Tube Assay (QFT-IT) among definitely confirmed TB cases. We searched Medline, EMBASE, and Cochrane bibliographies of relevant articles. Sensitivities, specificities, and indeterminate rates were pooled using a fixed effect model. Sensitivity of the tuberculin skin test (TST) was evaluated in the context of IGRA studies. In addition, the rates of indeterminates of both IGRAs were assessed. The pooled sensitivity of TST was 70% (95% CI, 0.67-0.72) compared with 81% (95% CI, 0.78-0.83) for the QFT-IT and 88% (95% CI, 0.85-0.90) for the T-Spot.TB. Sensitivity increased to 84% (95%CI, 0.81-0.87) and 89% (95% CI, 0.86-0.91) for the QFT-IT and T-Spot.TB, respectively, when restricted to performance in developed countries. In contrast, specificity of the QFT-IT was 99% (95% CI, 0.98-1.00) vs 86% for the T-Spot.TB (95% CI, 0.81-0.90). The pooled rate of indeterminate results was low, 2.1% (95% CI, 0.02-0.023) for the QFT-IT and 3.8% (95% CI, 0.035-0.042) for the T-Spot.TB, increasing to 4.4% (95% CI, 0.039-0.05) and 6.1% (95% CI, 0.052-0.071), respectively, among immunosuppressed hosts. The newest commercial IGRAs are superior, in comparison with the TST, for detecting confirmed active TB disease, especially when performed in developed countries.