Comparison of T-SPOT.TB assay and tuberculin skin test for the evaluation of young children at high risk for tuberculosis in a community setting

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).

Low secondary attack rate after prolonged exposure to sputum smear positive miliary tuberculosis in a neonatal unit

BACKGROUND

Several neonatal intensive care units (NICU) have reported exposure to sputum smear positive tuberculosis (TB). NICE guidelines give support regarding investigation and treatment intervention, but not for contact definitions. Data regarding the reliability of any interferon gamma release assay (IGRA) in infants as a screening test for TB infection is scarce. We report an investigation and management strategy and evaluated the viability of IGRA (T-Spot) in infants and its concordance to the tuberculin skin test (TST).

METHODS

We performed an outbreak investigation of incident TB infection in a NICU after prolonged exposure to sputum smear positive miliary TB by an infant's mother. We defined individual contact definitions and interventions and assessed secondary attack rates. In addition, we evaluated the technical performance of T-Spot in infants and compared the results with the TST at baseline investigation.

RESULTS

Overall, 72 of 90 (80%) exposed infants were investigated at baseline, in 51 (56.7%) of 54 (60%) infants, follow-up TST at the age of 6 months was performed. No infant in our cohort showed a positive TST or T-Spot at baseline. All blood samples from infants except one responded to phytohemagglutinin (PHA), which was used as a positive control of the T-Spot, demonstrating that cells are viable and react upon stimulation. 149 of 160 (93.1%) exposed health care workers (HCW) were investigated. 1 HCW was tested positive, having no other reason than this exposure for latent TB infection. 5 of 92 (5.5%) exposed primary contacts were tested positive, all coming from countries with high TB incidences. In total, 1 of 342 exposed contacts was newly diagnosed with latent TB infection. The secondary attack rate in this study including pediatric and adult contacts was 0.29%.

CONCLUSION

This investigation highlighted the low transmission rate of sputum smear positive miliary TB in a particularly highly susceptible population as infants. Our expert definitions and interventions proved to be helpful in terms of the feasibility of a thorough outbreak investigation. Furthermore, we demonstrated concordance of T-Spot and TST. Based on our findings, we assume that T-Spot could be considered a reliable investigation tool to rule out TB infection in infants.

Prevalence of latent tuberculosis infection and incidence of active tuberculosis in school close contacts in Shanghai, China: Baseline and follow-up results of a prospective cohort study

Background

The management of latent tuberculosis infection (LTBI) is a key action for the realization of the “End tuberculosis (TB) Strategy” worldwide, and it is important to identify priority populations. In this prospective cohort study, we evaluated the prevalence of LTBI and incidence of active TB among close contacts and explored the suitable TB control strategy in schools.

Methods

We designed a cohort with 2 years of follow-up, recruiting freshman/sophomore TB patients’ close contacts from three administrative districts in Shanghai. These were chosen based on different levels of TB incidence reported in 2019. Questionnaires were included and all participants received both tuberculin skin test (TST) and QuantiFERON-TB Gold (QFT) at baseline, then tracked the outcomes of them during the follow-up period.

Results

The prevalence of LTBI was 4.8% by QFT. Univariate analysis showed that the risk of LTBI was higher in those contacting bacteriologically confirmed patients or did not have BCG scars, including smokers. The risk increased with poor lighting and ventilation conditions at contact sites. Multivariate analysis showed that those contacting with bacteriologically confirmed patients (OR=4.180; 95%CI, 1.164-15.011) or who did not have BCG scars (OR=5.054; 95%CI, 2.278-11.214) had a higher risk of being LTBI, as did the current smokers (OR=3.916; 95%CI, 1.508-10.168) and those who had stopped smoking (OR=7.491; 95%CI, 2.222-25.249). During the 2-year follow-up period, three clinically diagnosed cases of TB were recorded, the 2-year cumulative incidence was 0.4% (95%CI 0.1-1.2), the median duration for TB occurrence was 1 year, the incidence rate of active TB was 2.0 per 1000 person-years with a total of 1497.3 observation person-years. For those LTBI, no one initiated preventive treatment, in the QFT (+) cohort, 1 TB case was observed, 71 person-years with an incidence rate of 14.1 14.1 (95%CI 2.5-75.6) per 1000 person-years, in the TST (+++) cohort, 2 TB cases were observed 91.5 person-years with an incidence rate of 21.9 (95%CI 6.0-76.3) per 1000 person-years.

Conclusions

The results suggest that school close contacts are one of the key populations for LTBI management. Measures should be taken to further reduce the prevalence of LTBI and the incidence of active TB among them.

Increased Expression of IL-10 in Peripheral Blood Mononuclear Cells Correlates with Negative Interferon-γ Release Assay Results in Culture-Confirmed Tuberculosis Patients

Introduction

Interferon-γ release assays (IGRAs) can have high false-negative rates for active tuberculosis (TB) cases. Here we investigated factors, including potential anti-inflammatory mechanisms, that contributed to false-negative IGRA results.

Methods

We established two cohorts. In the first cohort, we reviewed IGRA results for confirmed TB cases diagnosed in our hospital in 2018. Cases with false-negative IGRA results were analysed to identify factors contributing to false-negative results. In the second cohort, we prospectively studied IL-10 expression levels in peripheral blood mononuclear cells (PBMCs) of IGRAs-positive and IGRAs-negative TB cases after antigenic stimulation to correlate IL-10 expression with IGRAs results.

Results

Of 1232 culture-confirmed TB cases, 1124 produced true-positive IGRA results and 108 had false-negative IGRA results. Multivariate logistic regression analysis identified glucocorticoid use and extrapulmonary TB as independent risk factors for false-negative IGRA results. Notably, IL-10 expression of the IGRA-negative group was significantly up-regulated as compared to that of the IGRA-positive group. The average cell supernatant IL-10 concentration of the IGRA-negative group was 4.77 pg/mL, a value that was statistically greater than the IGRA-positive group concentration (1.47 pg/mL, P = 0.007). After PBMCs pretreatment with BRD6989 (to enhance IL-10 secretion), average IFN-γ concentrations in cell supernatants from the IGRA-positive group significantly decreased from 59.73 pg/mL to 33.79 pg/mL (P = 0.011). By contrast, addition of AS101 (to inhibit IL-10 secretion) to false-negative group PBMCs led to an increase of average IFN-γ concentration in cell supernatants from 19.01 pg/mL to 45.10 pg/mL (P = 0.030), a result that was inversely correlated with IL-10 concentration.

Conclusion

Our data demonstrate that increased IL-10 secretion by PBMCs is inversely correlated with IGRA assay results in culture-confirmed TB patients. Glucocorticoids use and extrapulmonary TB are significantly associated with false-negative IGRA results. Combination testing to measure IL-10 secretion and IFN-γ release is recommended to improve IGRAs specificity.

Diagnostic values of peripheral blood T-cell spot of tuberculosis assay (T-SPOT.TB) and magnetic resonance imaging for osteoarticular tuberculosis: a case-control study

OBJECTIVE

Early diagnosis of osteoarticular tuberculosis helps improve patients' outcomes, but little is known about the accuracy of noninvasive diagnostic methods. This case-control study aimed to assess the diagnostic value of peripheral blood T-cell spot of tuberculosis assay (T-SPOT.TB) and magnetic resonance imaging (MRI).

METHODS

Patients suspected with osteoarticular tuberculosis were retrospectively included and diagnosed according to the composite reference standard. T-SPOT.TB was used to detect the number of cells secreting Interferon gamma. Diagnostic performance of T-SPOT.TB and MRI alone and combined were evaluated.

RESULTS

Among the suspected patients, 92 had osteoarticular tuberculosis and 137 non- osteoarticular tuberculosis. T-SPOT.TB assay alone had a higher sensitivity (0.73 vs. 0.60) but a lower specificity (0.69 vs. 0.91 P>0.05) in diagnosing osteoarticular tuberculosis. Combined serial test showed a sensitivity and specificity 0.47, 0.97, respectively, whereas combined parallel test showed a sensitivity and specificity of 0.86, 0.65, respectively. Specificity was higher in the combined serial test than in the T-SPOT.TB assay (P=0.007) or MRI alone (P < 0.001). Furthermore, sensitivity was higher in the combined parallel test than in the T-SPOT.TB assay (P < 0.001) or MRI alone (P < 0.001).

CONCLUSIONS

Combined blood T-cell spot of tuberculosis assay and osteoarticular MRI have higher sensitivity and specificity for noninvasive osteoarticular tuberculosis diagnosis, compared with either method alone.

Culture-confirmed Tuberculosis in South African Infants Younger Than 3 Months of Age: Clinical Presentation and Management of Respiratory Complications

BACKGROUND

Little is known about the course and management of perinatal tuberculosis (TB). We describe the presentation, medical and surgical management of culture-confirmed TB in infants younger than 3 months of age.

METHODS

We conducted a retrospective study including all infants younger than 3 months of age with culture-confirmed TB admitted to Tygerberg Hospital, Cape Town, South Africa, from March 2003 to June 2015.

RESULTS

During the study period, 106 of 2017 (5%) children younger than 13 years of age with culture-confirmed TB were infants younger than 3 months of age. The median age on admission was 67 days (interquartile range, 40-79). Intrathoracic TB was present in 101 (95%) infants; of these, 34 (32%) had extrathoracic TB. Two (2%) infants had extrathoracic TB only, while 3 (3%) infants were asymptomatic and diagnosed as having TB infection only. Forty (38%) infants were HIV-exposed, and 14 (13%) were HIV-infected. The mother was identified as the source case in 53 (50%) infants. Mycobacterium tuberculosis was cultured in a median of 2 (interquartile range, 1-7) specimens per infant; 9 (9%) had drug-resistant TB. Bronchoscopy was done in 37 (35%) infants, and 27 (26%) underwent intrathoracic lymph node decompression. Twelve (11%) infants died during admission, 81(76%) were clinically stable on transfer or discharge from hospital, and outcome was not documented in 13 (12%) infants.

CONCLUSIONS

TB in young infants often presents with severe intrathoracic disease, including airway compression. Bronchoscopy may aid confirmation of the diagnosis and management; decompression of intrathoracic lymph nodes was common. Mortality in this age group remains high.

Congenital Tuberculosis: A New Concern in the Neonatal Intensive Care Unit

BACKGROUND

Congenital tuberculosis (TB) is rare in the United States. Recent immigration patterns to the United States have made the diagnosis of congenital TB an important public health issue.

PURPOSE

To explore the epidemiology, pathophysiology, diagnostic evaluation, treatment, and prognosis for congenital TB. The implications for exposed healthcare professionals in the neonatal intensive care unit (NICU) setting are also explored.

METHODS/SEARCH STRATEGY

Relevant articles were accessed via PubMed, CINAHL, and Google Scholar.

FINDINGS/RESULTS

Until 1994, fewer than 400 cases of confirmed congenital TB had been reported in the literature worldwide. An additional 18 cases were reported from 2001 to 2005. Neonatal providers need to be aware of the potential for congenital TB infection as the immigrant population in the United States continues to increase, many of whom originate from TB endemic countries.

IMPLICATIONS FOR PRACTICE

The interpretation of TB-specific tests is problematic in newborns due to decreased sensitivity and specificity. Congenital TB should be ruled out in infants with signs and symptoms of sepsis or pneumonia and in whom broad-spectrum antibiotic therapy does not improve their clinical status.

IMPLICATIONS FOR RESEARCH

The interpretation of TB-specific tests is problematic in newborns due to decreased sensitivity and specificity; more research is needed regarding best practice in diagnosis. Established protocols are needed to address the healthcare of TB-exposed providers in the NICU.

Tuberculosis in Infants and Children

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

Official American Thoracic Society/Infectious Diseases Society of America/Centers for Disease Control and Prevention Clinical Practice Guidelines: Diagnosis of Tuberculosis in Adults and Children

BACKGROUND

Individuals infected with Mycobacterium tuberculosis (Mtb) may develop symptoms and signs of disease (tuberculosis disease) or may have no clinical evidence of disease (latent tuberculosis infection [LTBI]). Tuberculosis disease is a leading cause of infectious disease morbidity and mortality worldwide, yet many questions related to its diagnosis remain.

METHODS

A task force supported by the American Thoracic Society, Centers for Disease Control and Prevention, and Infectious Diseases Society of America searched, selected, and synthesized relevant evidence. The evidence was then used as the basis for recommendations about the diagnosis of tuberculosis disease and LTBI in adults and children. The recommendations were formulated, written, and graded using the Grading, Recommendations, Assessment, Development and Evaluation (GRADE) approach.

RESULTS

Twenty-three evidence-based recommendations about diagnostic testing for latent tuberculosis infection, pulmonary tuberculosis, and extrapulmonary tuberculosis are provided. Six of the recommendations are strong, whereas the remaining 17 are conditional.

CONCLUSIONS

These guidelines are not intended to impose a standard of care. They provide the basis for rational decisions in the diagnosis of tuberculosis in the context of the existing evidence. No guidelines can take into account all of the often compelling unique individual clinical circumstances.

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSION

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

Performance of the Interferon Gamma Release Assays in Tuberculosis Disease in Children Five Years Old or Less

Interferon Gamma Release Assays (IGRAs) were developed for the indirect or immunologic diagnosis of tuberculosis infection; however, they have also been used to assist in difficult to diagnose cases of tuberculosis disease in adults, and to a lesser extent, in children, especially in those under 5 years old. We evaluated the utility of using an IGRA in pediatric tuberculosis in younger children in a hospital setting. The diagnostic accuracy of T-SPOT.TB and TST was assessed in 117 children with active tuberculosis and 413 children with respiratory tract infection. Sensitivity and specificity were calculated for the tests used individually and together. Concordance was also calculated. Sensitivity of T-SPOT.TB (82.9%) was higher than TST (78.6% using a 5mm cut-off), especially in children confirmed to have TB. T-SPOT.TB was more specific than TST using a 5mm cut-off (96.1% vs. 70.9%). Combining T-SPOT.TB and TST results improved the sensitivity to 96.6%. In conclusion, the results of the current study indicate that T-SPOT.TB has good sensitivity and specificity, supporting its use among patients of this age. A combination of IGRA and TST would be useful additions to assist in the diagnosis of childhood TB.

[Primary infection and pulmonary tuberculosis]

Tuberculosis is a major public health problem worldwide. Indeed, a third of the world population is infected with Mycobacterium tuberculosis and more than 8 million new cases of tuberculosis each year. Pulmonary tuberculosis is the most common location. Its diagnosis is difficult and often established with a delay causing a spread of infection. The diagnosis of tuberculosis infection is mainly based on immunological tests represented by the tuberculin skin test and detection of gamma interferon, while the diagnosis of pulmonary tuberculosis is suspected on epidemiological context, lasting general and respiratory symptoms, contrasting usually with normal lung examination, and a chest radiography showing suggestive lesions. The radioclinical feature may be atypical in patients with extreme ages and in case of immunodeficiency. Confirmation of tuberculosis is bacteriological. Conventional bacteriological methods remain the reference. Innovative tests using the technique of molecular biology have improved the diagnosis of tuberculosis in terms of sensitivity and especially speed. However, those techniques are of limited use.

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

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

Congenital tuberculosis detected by T-SPOT.TB assay in a male infant after in vitro fertilization and followed up with radiography

Congenital tuberculosis (TB) is a rare disease with a high mortality rate, and is difficult to diagnose. Here we present a case of congenital TB detected by the T-SPOT.TB assay in a male infant after in vitro fertilization. He ultimately survived after anti-TB therapy despite a delayed diagnosis, and underwent radiological follow-up. The delay in diagnosis of congenital TB resulted in a severe lung lesion, as evidenced by prolonged oxygen dependence, predisposing to recurrent pneumonia. Radiological follow-up revealed uniform rim calcification of multiple enlarged lymph nodes in the mediastinum, and long-term consolidation in the bilateral lung, with slow radiographic regression of the lung lesion. To the best of our knowledge, this is the first report on using the T-SPOT.TB assay in the detection of congenital TB, and no case of congenital TB with such clinical features and image findings has been described in previous reports.

Interferon-γ release assay for the diagnosis of latent Mycobacterium tuberculosis infection in children younger than 5 years: a meta-analysis

BACKGROUND

Interferon-γ release assays (IGRAs) have been widely used for the diagnosis of latent and active tuberculosis in adults, but their role in diagnosing latent tuberculosis infection (LTBI) in children younger than 5 years remains unclear.

OBJECTIVE

To evaluate the diagnostic performance of IGRAs for LTBI in children younger than 5 years.

METHODS

We searched the PubMed, EMBASE, Cochrane Library, and Web of Knowledge databases. According to inclusion criteria, the diagnostic studies of IGRAs for LTBI in children younger than 5 years were included. The study quality was assessed using the 14-item Quality Assessment of Diagnostic Accuracy Studies instrument. The Meta-Analyst software was used to analyze the data.

RESULTS

Seven studies (627 patients) were included. Meta-analysis showed that compared with tuberculin skin test (TST), the pooled sensitivity (Sen), specificity (Spe), positive likelihood ratio (PLR), negative likelihood ratio (NLR), positive predictive value (PPV), negative predictive value (NPV), accuracy and diagnosis odds ratio (DOR), and summary receiver operating characteristic (SROC) curve of QuantiFERON-TB (values in parentheses are 95% confidence intervals) were 0.841 (0.733-0.911), 0.895 (0.861-0.922), 8.046 (5.953-10.876), 0.192 (0.113-0.326), 0.622 (0.527-0.709), 0.970 (0.946-0.983), 0.891 (0.861-0.916), 50.718 (24.201-106.287), and 0.809 respectively. The pooled Sen, Spe, PLR, NLR, PPV, NPV, accuracy, DOR, and SROC curve of T-SPOT.TB test were 0.931 (0.760-0.983), 0.767 (0.684-0.833), 3.947 (2.854-5.459), 0.095 (0.026-0.354), 0.523 (0.398-0.645), 0.977 (0.914-0.994), 0.806 (0.737-0.860), 65.270 (13.463-316.434), and 0.855, respectively.

CONCLUSION

This meta-analysis showed that the sensitivity and specificity of IGRAs were slightly higher than TST and can be used as supporting tools to detect LTBI in children younger than 5 years. The methodological quality of diagnostic test needs to be improved.

Influence of age and nutritional status on the performance of the tuberculin skin test and QuantiFERON-TB gold in-tube in young children evaluated for tuberculosis in Southern India

BACKGROUND

Reliable identification of Mycobacterium tuberculosis infection or tuberculosis (TB) disease in young children is vital to assure adequate preventive and curative treatment. The tuberculin skin test (TST) and IFNγ-release assays may supplement the diagnosis of pediatric TB as cases are typically bacteriologically unconfirmed. However, it is unclear to what extent the performance of TST and QuantiFERON-TB Gold In-Tube (QFT; Cellestis' IFNγ-release assay test) depends on the demographic, clinical and nutritional characteristics of children in whom they are tested.

METHODS

During a 2-year prospective observational study of 4382 neonates in Southern India, children with suspected TB were investigated and classified by a standard TB diagnostic algorithm.

RESULTS

Clinical TB was diagnosed in 13 of 705 children referred for case verification with suspected TB. TST and QFT had a susceptibility for clinical TB of 31% and 23%, respectively, in this group. Children <2 years were more likely to test QFT indeterminate. A height-for-age Z score within the lowest quartile increased the odds ratio (OR) for a positive or indeterminate QFT result [OR 2.46 (1.19-5.06), OR 3.08 (1.10-8.58)], whereas the OR for a positive TST was reduced with a weight-for-height Z score within the lowest quartile [OR 0.17 (0.06-0.47)].

CONCLUSION

The sensitivities of the TST and QFT for clinical TB in children <3 years of age were equally poor in this population. Stunted children were more susceptible to Mycobacterium tuberculosis infection and more prone to indeterminate QFT results. TST was less reliable in children with wasting.

Influencial factors of the performance of interferon-γ release assays in the diagnosis of childhood tuberculosis

Diagnosis of active tuberculosis (TB) in children remains difficult. This study aimed at evaluating the ability of interferon-gamma release assays (IGRAs) in the detection of active TB in human immunodeficiency virus-negative children vaccinated with Bacille Calmette–Guérin and investigating the effect of prednisolone treatment on the IGRAs performance. Among the 162 children with suspected TB disease recruited in China, 60 were tested with QuantiFERON-TB Gold In Tube (QFT-GIT) and 102 were tested with T-SPOT.TB. QFT-GIT presented a sensitivity of 83.9 % (95 % CI 66.9–93.4 %) and a specificity of 88.5 % (95 % CI 70.2–96.8 %), while T-SPOT.TB had a sensitivity of 75.9 % (95 % CI 63.4–85.2 %) and a specificity of 94.7 % (95 % CI 81.8–99.5 %). The positive predictive value was high in both assays, 92.9 % for QFT-GIT and 95.7 % for T-SPOT.TB. In total of these two kinds of IGRAs, false negative rate was significantly higher in children receiving systemic prednisolone (1 mg/kg/day) therapy for >1 week (two tested with T-SPOT.TB and five tested with QFT-GIT) than in those with ≤1 week of prednisolone therapy and without prednisolone therapy (57.1 vs. 18.3 %, p = 0.035). There was no significant difference of the positive rate of both tests in children <5 years old compared with those ≥5 years old. Both types of IGRAs showed good diagnostic values in detecting childhood TB before microbiological evidence was available. Glucocorticoids had a significant negative influence on IGRAs if treated for >1 week. Age made no difference on the performance of these tests in children.

The sensitivity of T-SPOT.TB assay in diagnosis of pediatric tuberculosis

This study was performed aiming to evaluate the sensitivity of T-SPOT.TB assay in diagnosis of pediatric TB and investigate the association between age and results of T-SPOT.TB assay. Between March 2012 and September 2013, 102 patients, who aged ≤15 years old, were enrolled in this retrospective study and then were grouped into three age categories: Group 1, aged ≤2 years; Group 2, aged 3 to 12 years; and Group 3, aged 13 to 15 years. The χ(2) test was used to compare the sensitivities of T-SPOT.TB between groups with different ages. The overall sensitivity of T-SPOT.TB assay was 58.8% (95% confidence interval: 49.1-67.9%) and low in diagnosis of pediatric TB. Although the sensitivities varied in the three groups, the difference did not reach statistical significance (p > 0.05). Therefore, in high burden countries, T-SPOT.TB assay wasn't accurate in diagnosis of pediatric TB, and age was not associated with the results of T-SPOT.TB.

Performance of Tuberculin Skin Test Measured against Interferon Gamma Release Assay as Reference Standard in Children

Objectives. International guidelines differ in the threshold of tuberculin skin test (TST) induration regarded as indicating Mycobacterium (M.) tuberculosis infection. Interferon gamma release assay (IGRA) results were used as reference to assess performance of TST induration thresholds for detection of M. tuberculosis infection in children. Design. Systematic review which included studies containing data on TST, IGRA, and Bacillus Calmette-Guérin (BCG) status in children. Data bases searched were PubMed, EMBASE, and the Cochrane library. Specificities and sensitivities were calculated for TST thresholds 5, 10, and 15 mm and correlated with age and geographical latitude. Results. Eleven studies with 2796 children were included. For BCG immunised children diameters of 5, 10, and 15 mm had median sensitivities of 87, 70, and 75% and specificities of 67, 93, and 90%, respectively. In non-BCG immunised children median sensitivities were 94, 95, and 83% and specificities 91, 95, and 97%. At the 10 mm threshold age correlated negatively with sensitivity of TST (r = −0.65, P = 0.04) and latitude correlated positively (r = 0.71, P = 0.02). Conclusions. For the 10 mm threshold the sensitivity of the TST is lower in BCG immunised children. Younger age and higher geographical latitude were associated with higher sensitivity of the TST.

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.

Long-incubation-time gamma interferon release assays in response to purified protein derivative, ESAT-6, and/or CFP-10 for the diagnosis of Mycobacterium tuberculosis infection in children

The diagnosis of childhood active tuberculosis (aTB) and latent Mycobacterium tuberculosis (M. tuberculosis) infection (LTBI) remains a challenge, and the replacement of tuberculin skin tests (TST) with commercialized gamma interferon (IFN-γ) release assays (IGRA) is not currently recommended. Two hundred sixty-six children between 1 month and 15 years of age, 214 of whom were at risk of recent M. tuberculosis infection and 51 who were included as controls, were prospectively enrolled in our study. According to the results of a clinical evaluation, TST, chest X ray, and microbiological assessment, each children was classified as noninfected, having LTBI, or having aTB. Long-incubation-time purified protein derivative (PPD), ESAT-6, and CFP-10 IGRA were performed and evaluated for their accuracy in correctly classifying the children. Whereas both TST and PPD IGRA were suboptimal for detecting aTB, combining the CFP-10 IGRA with a TST or with a PPD IGRA allowed us to detect all the children with aTB with a specificity of 96% for children who were positive for the CFP-10 IGRA. Moreover, the combination of the CFP-10 IGRA and PPD IGRA detected 96% of children who were eventually classified as having LTBI, but a strong IFN-γ response to CFP-10 (defined as >500 pg/ml) was highly suggestive of aTB, at least among the children who were <3 years old. The use of long-incubation-time CFP-10 IGRA and PPD IGRA should help clinicians to quickly identify aTB or LTBI in young children.

Evaluation of an enzyme-linked immunospot assay for the immunodiagnosis of atypical spinal tuberculosis (atypical clinical presentation/atypical radiographic presentation) in China

Background

Methods

Results

Conclusions

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.

Updating a Tuberculosis Surveillance Program

Tuberculosis surveillance programs have used the same testing methods for almost a century. New testing methods have been approved and are available, but how does a health care provider determine which diagnostic test is best in a given situation? Reviewing research statistics can be confusing, and the types of studies conducted may not be similar to a particular application. Development of an organizational needs assessment based on Centers for Disease Control and Prevention (CDC) requirements, organizational resources, the needs of the employee population, and the logistics of multiple campus sites prior to evaluating the available testing methods can assist occupational health nurses navigate the decision-making process. This article presents an example of a moderately sized health care facility to illustrate how to conduct a needs assessment that results in a decision as to which program best suits the organization.

Interferon-Gamma Release Assays versus Tuberculin Skin Testing for the Diagnosis of Latent Tuberculosis Infection: An Overview of the Evidence

A profusion of articles have been published on the accuracy and uses of interferon-gamma releasing assays. Here we review the clinical applications, advantages, and limitations of the tuberculin skin test and interferon-gamma release assays and provide an overview of the most recent systematic reviews conducted for different indications for the use of these tests. We conclude that both tests are accurate to detect latent tuberculosis, although interferon-gamma release assays have higher specificity than tuberculin skin testing in BCG-vaccinated populations, particularly if BCG is received after infancy. However, both tests perform poorly to predict risk for progression to active tuberculosis. Interferon-gamma release assays have significant limitations in serial testing because of spontaneous variability and lack of a validated definition of conversion and reversion, making it difficult for clinicians to interpret changes in category (conversions and reversions). So far, the most important clinical evidence, that is, that isoniazid preventive therapy reduces the risk for progression to disease, has been produced only in tuberculin skin test-positive individuals.

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.

Tuberculin skin test in bacille Calmette-Guérin-vaccinated children: how should we interpret the results?

BACKGROUND

The tuberculin skin test (TST) is the most useful method for the diagnosis of tuberculosis (TB). There is no evidence about the effect of bacillus Calmette-Guerin (BCG) vaccine on the interpretation of TST results.

OBJECTIVE

The aim of this study was to evaluate TST results in a population of immigrants and adopted children, analyzing the effect of the vaccine on TST.

METHODS

Cross-sectional observational study including immigrants or adopted children evaluated in our unit between January 2003 and December 2008 was made. Children diagnosed with TB, live attenuated virus vaccinated 2 months earlier, HIV-infected, chronically ill, or under treatment with immunosuppressive agents were excluded. TST was considered the dependent variable. Independent variables were gender, age, geographical origin, BCG scar, nutritional status, immune status, and intestinal parasites infestation.

RESULTS

One thousand seventy-four children were included, 69.6 % are female; their origin includes China (34.7 %), Latin America (20.8 %), India/Nepal (19.4 %), Eastern Europe (15.7 %), and Africa (9.3 %). BCG scar was present in 79 % of children. Mantoux = 0 mm in 84.4 %, <10 mm in 4.1 %, and ≥10 mm in 11.4 %. Only two variables, age and BCG scar, influenced TST result. Risk of a TST false-positive due to BCG disappears 3 years after vaccine administration.

CONCLUSIONS

A history of BCG vaccination at birth does not interfere with TST results in children >3 years old. Under 3 years of age, BCG does interfere with and may cause a false-positive TST result. In these cases, the use of interferon-gamma release assays (IGRAs) is recommended. If IGRAs are not available or when results are indeterminate, ignoring the antecedent of the vaccine is recommended.

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.

Evaluation of interferon-gamma release assays for the diagnosis of tuberculosis: an updated meta-analysis

The objective of this investigation was to systematically evaluate the diagnostic accuracy of interferon-gamma release assays (IGRAs) for tuberculosis disease. Both English and Chinese databases were searched for relevant articles through January 2012. We included studies that were restricted to diagnostic applications of IGRAs in patients with active tuberculosis and excluded studies performed in the immune-compromised population. We used Meta-DiSc software to handle the data. We calculated the sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR), and 95 % confidence interval (CI) for each study. We also calculated the pooled sensitivity, specificity, PLR, NLR, DOR, and produced forest plots and summary receiver operating characteristic (SROC) curves. A total of 61 papers (73 studies) were eligible for meta-analysis, including 36 published in English and 25 published in the Chinese language. The overall sensitivity, specificity, PLR, NLR, DOR, and 95 % CI of IGRAs were 0.85 (95 % CI: 0.84-0.86), 0.84 (95 % CI: 0.83-0.85), 7.82 (95 % CI: 6.01-10.19), 0.17 (95 % CI: 0.14-0.21), and 59.27 (95 % CI: 40.19-87.42), respectively. For ten studies evaluating T-SPOT.TB in China, the combined sensitivity, specificity, PLR, NLR, DOR, and 95 % CI were 0.88 (95 % CI: 0.86-0.91), 0.89 (95 % CI: 0.86-0.92), 8.86 (95 % CI: 5.42-14.46), 0.13 (95 % CI: 0.10-0.17), and 88.15 (95 % CI: 41.76-186.07), respectively. The SROC area under the curve (AUC) was 0.9548 (95 % CI: 0.9323-0.9773). Though IGRAs showed good sensitivity and specificity for the detection of tuberculosis in this meta-analysis, the decision to use an IGRA should be based on the local prevalence of the disease and the country guidelines, as well as resources and logistical considerations.

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.

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.

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.

Interferon release does not add discriminatory value to smear-negative HIV-tuberculosis algorithms

Clinical algorithms for evaluating HIV-infected individuals for tuberculosis (TB) prior to isoniazid preventive therapy (IPT) perform poorly, and interferon-γ release assays (IGRAs) have moderate accuracy for active TB. It is unclear whether, when used as adjunct tests, IGRAs add any clinical discriminatory value for active TB diagnosis in the pre-IPT assessment. 779 sputum smear-negative HIV-infected persons, established on or about to commence combined antiretroviral therapy (ART), were screened for TB prior to IPT. Stepwise multivariable logistic regression was used to develop clinical prediction models. The discriminatory ability was assessed by receiver operator characteristic area under the curve (AUC). QuantiFERON-TB Gold in-tube (QFT-GIT) was evaluated. The prevalence of smear-negative TB by culture was 6.4% (95% CI 4.9-8.4%). Used alone, QFT-GIT and the tuberculin skin test (TST) had comparable performance; the post-test probability of disease based on single negative tests was 3-4%. In a multivariable model, the QFT-GIT test did not improve the ability of a clinical algorithm, which included not taking ART, weight <60 kg, no prior history of TB, any one positive TB symptom/sign (cough ≥ 2 weeks) and CD4+ count <250 cells per mm(3), to discriminate smear-negative culture-positive and -negative TB (72% to 74%; AUC comparison p=0.33). The TST marginally improved the discriminatory ability of the clinical model (to 77%, AUC comparison p=0.04). QFT-GIT does not improve the discriminatory ability of current TB screening clinical algorithms used to evaluate HIV-infected individuals for TB ahead of preventive therapy. Evaluation of new TB diagnostics for clinical relevance should follow a multivariable process that goes beyond test accuracy.

Diagnosing latent tuberculosis in high-risk individuals: rising to the challenge in high-burden areas

A key challenge to greater progress in tuberculosis (TB) control is the reservoir of latent TB infection (LTBI), which represents a huge long-lived reservoir of potential TB disease. In parts of Africa, as many as 50% of 15-year-olds and 77%-89% of adults have evidence of LTBI. A second key challenge to TB control is the human immunodeficiency virus (HIV)-associated TB epidemic, and Africa alone accounts for one-quarter of the global burden of HIV-associated TB. HIV co-infection promotes both reactivation TB from LTBI and rapidly progressive primary TB following recent exposure to Mycobacterium tuberculosis. Preventing active TB and tackling latent infection in addition to the Directly Observed Treatment, Short-Course (DOTS) strategy could improve TB control in high-burden settings, especially where there is a high prevalence of HIV co-infection. Current strategies include intensified case finding (ICF), TB infection control, antiretroviral therapy (ART), and isoniazid preventive therapy (IPT). Although ART has been widely rolled out, ICF and IPT have not. A key factor limiting the rollout and effectiveness of IPT and ICF is the limitations of existing tools to both diagnose LTBI and identify those persons most at risk of progressing to active TB. In this review, we examine the obstacles and consider current progress toward the development of new tools to address this pressing global problem.

T-SPOT.TB assay usage in adults and children

The diagnosis and treatment of TB infection is one of the public health priorities. Until recently, diagnosis of TB infection has been based on the tuberculin skin test (TST). However, this is neither 100% sensitive nor specific for the diagnosis of TB infection owing to its many drawbacks. More recently, T-cell-based IFN-γ release assays (IGRAs) have been developed. In this article, we review the clinical performance of one of the IGRAs, T-SPOT.TB assay, for the diagnosis of TB infection in adults and children. We discuss the principle of the assay, its utility in active TB diseases, latent TB infection and the performance of the test in specialized subgroups of patients, such as immunocompromised individuals. When compared with the TST, the T-SPOT.TB assay has better specificity in bacillus Calmette-Guérin-vaccinated individuals, and data suggest that T-SPOT.TB may be more sensitive than the TST. Data in groups at high risk of progression to disease support the idea that T-SPOT.TB performs better than the TST. In addition, application of T-SPOT.TB by using bodily fluids such as cerebrospinal fluid, bronchoalveolar lavage fluid and pleural fluid may offer new diagnostic approaches in extrapulmonary TB disease. Although IGRAs cannot distinguish active TB disease from latent TB infection, these assays perform better than the TST for the detection of TB infection.

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.

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.

Opportunities for chemoprophylaxis in children with culture-confirmed tuberculosis

BACKGROUND AND OBJECTIVES

Chemoprophylaxis is an effective strategy to prevent progression of tuberculosis (TB) in vulnerable children who have had contact with an infectious source of TB. However, many operational gaps prevent implementation of routine chemoprophylaxis in high-burden settings. The TB exposure status and disease spectrum in children diagnosed with culture-confirmed TB are described and missed opportunities for chemoprophylaxis are highlighted.

METHODS

All children <13 years of age diagnosed with culture-confirmed TB at a tertiary referral hospital between March 2003 and February 2007 were included. Clinical data were collected from retrospective review of files. TB was classified as pulmonary and extra-pulmonary; disseminated TB included miliary disease and TB meningitis.

RESULTS

During the study period, 614 children (327, 53·3% boys, median age 32 months) were diagnosed with culture-confirmed TB. Contact with an infectious adult source case was documented in 333 (54·2%), 237 (71·2%) of whom were <5 years of age, and 24 (7·2%) were HIV-infected and ≥5 years of age. Of those eligible for chemoprophylaxis, missed opportunities were identified in 156/221 (70·6%) children; 127 (81·4%) were <3 years of age, 39 (25%) had disseminated TB and 8 (5·1%) died. The TB source case was the mother or father in 74/156 (47·4%) children.

CONCLUSION

Opportunities for initiation of chemoprophylaxis in vulnerable children following TB exposure are often missed. Awareness should be increased among health-care workers and in the community at large regarding the importance of chemoprophylaxis in young and HIV-infected children. Health system strengthening is required to improve delivery of chemoprophylaxis to vulnerable children in close contact with newly diagnosed infectious TB cases.