The impact of BCG vaccination on tuberculin skin test responses in children is age dependent: evidence to be considered when screening children for tuberculosis infection

Predictors of positive tuberculin skin test in neonates exposed to pulmonary tuberculosis

BACKGROUND

Neonates are at risk of nosocomial tuberculosis (TB) infection from health care workers (HCWs) in neonatal care facilities, which can progress to severe TB diseases. Tuberculin skin test (TST) is commonly used for TB diagnosis, but its accuracy in neonates is influenced by various factors, including bacilli Calmette-Guérin (BCG) vaccination. This study aimed to identify predictors of positive TSTs in neonates exposed to HCWs with pulmonary TB.

METHODS

A retrospective observational study was conducted to compare the frequency of predictors between TST-positive and TST-negative neonates. Demographic, epidemiological, and clinical data of neonates exposed to TB, along with that of HCW and household contacts, were collected retrospectively through contact investigations with the Korean National TB Surveillance System (KNTSS) database. TSTs using 2 tuberculin units of purified protein derivative RT23 were performed on exposed neonates at the end of preventive TB treatment. Firth logistic regression was performed to identify predictors of TST positivity.

RESULTS

Contact investigations revealed that 152 neonates and 54 HCWs were exposed to infectious TB index cases in 3 neonatal care facilities. Of 152 exposed neonates, 8 (5.3%) had positive TST results. Age of 6 days or more at the initial exposure is a statistically significant predictor of positive TST (Firth coefficient 2.1, 95% confidence interval 0.3-3.9, P = 0.024); BCG vaccination showed no statistical significance in both univariable and multivariable analysis. Sex, prematurity, exposure duration, duration from initial exposure to contact investigation, and isoniazid preventive treatment duration were not significant predictors.

CONCLUSION

Age at the initial exposure is a significant predictor of positive TST in neonates exposed to active pulmonary TB. Given the complexities of TST interpretation, including false positives due to BCG vaccination, careful risk assessment is necessary for appropriate decision-making and resource allocation in the management of neonatal TB exposure.

Timing of maternal isoniazid preventive therapy on tuberculosis infection among infants exposed to HIV in low-income and middle-income settings: a secondary analysis of the TB APPRISE trial

BACKGROUND

Infants born to women with HIV in settings with a high tuberculosis burden are at risk of tuberculosis infection and rapid progression to active disease. Maternal isoniazid preventive therapy might mitigate this risk, but optimal timing of therapy remains unclear. The TB APPRISE trial showed that initiation of isoniazid during pregnancy resulted in more frequent adverse pregnancy outcomes than when initiated postpartum. We aimed to determine the proportion of infants testing positive for tuberculosis infection born to mothers who initiated isoniazid therapy antepartum compared with postpartum using two commonly used tests, the test agreement, and predictors of test positivity.

METHODS

TB APPRISE was a randomised, double-blind, placebo-controlled, non-inferiority trial done at 13 study sites across eight countries (Botswana, Haiti, India, South Africa, Tanzania, Thailand, Uganda, and Zimbabwe). Pregnant women with HIV on antiretroviral therapy were randomly assigned to receive immediate isoniazid preventive therapy (28 weeks isoniazid [300 mg daily], then placebo until week 40 after delivery) or deferred treatment (placebo until week 12 after delivery, then isoniazid [300 mg daily] for 28 weeks). Mother-infant pairs were followed up until 48 weeks after delivery. We included all liveborn infants with a tuberculin skin test or interferon-γ release assay (IGRA) at 44 weeks. The outcomes assessed in this secondary analysis were tuberculosis test positivity by study group, test agreement, and predictors of test positivity. This study was registered with ClinicalTrials.gov, NCT01494038.

FINDINGS

Between Aug 19, 2014, and April 4, 2016, 956 mothers were randomly assigned, and 749 mother-child pairs were included in this secondary analysis. Of 749 infants, 694 (93%) received Bacille Calmette-Guérin (BCG) vaccination, 675 (90%) were born to mothers who had completed isoniazid treatment, 20 (3%) were exposed to tuberculosis, seven (1%) became HIV positive, and one (<1%) developed probable tuberculosis. 43 (6%; 95% CI 4-8]) of 732 infants had a positive IGRA test result and 55 (8%; 6-10) of 727 infants had a positive tuberculin skin test result. Test positivity did not differ by study group (p=0·88 for IGRA; p=0·44 for tuberculin skin test). Test agreement was poor (κ=0·107 [95% CI 0·002-0·212]). Infant tuberculin skin test positivity was associated with breastfeeding (adjusted odds ratio 6·63 [95% CI 1·57-27·9]), BCG vaccination (4·97 [1·50-16·43]), and maternal tuberculin skin test positivity at delivery (3·28 [1·70-6·33]); IGRA positivity was associated with female sex (2·09 [1·06-4·14]).

INTERPRETATION

Deferral of maternal isoniazid preventive therapy to early postpartum had no effect on infant tuberculosis acquisition in our trial population, regardless of the diagnostic test used; however, tuberculosis test agreement is poor during infancy.

FUNDING

US National Institutes of Health.

Contact Investigations With a Single Tuberculin Skin Test on Infants Exposed to Tuberculosis in a Postpartum Care Center During the Neonatal Period

BACKGROUND

Tuberculosis (TB) exposure in congregate settings related to neonates is a serious medical and social issue. TB exposure happens during the neonatal period, but contact investigations for exposed infants are usually conducted after the neonatal period. Generally, recommendations for screening and managing close contact are different for neonates and children. Thus, there are challenges in contact investigations. We aimed to report contact investigations with a single tuberculin skin test (TST) on infants exposed to infectious TB in a postpartum care center.

METHODS

The index case was a healthcare worker with active pulmonary TB: sputum acid-fast bacilli smear negative, culture positive, and no cavitary lesion. All exposed infants underwent medical examinations and chest X-ray. After TB disease was ruled out, contacts received window period prophylaxis with isoniazid (INH) until three months after the last exposure. TST was performed only once after completing the prophylaxis.

RESULTS

A total of 288 infants were selected as high-priority contacts. At the initial contact investigation, the age of infants ranged from 8 to 114 days. None of these exposed infants had TB disease. The prevalence of latent TB infection (LTBI) was 25.3% (73/288; 95% confidence interval [CI], 20.7-30.7). There were no serious adverse events related to the window period prophylaxis or LTBI treatment with INH. During the 1-year follow-up period, no infants progressed to overt TB disease. The size of TST induration in infants vaccinated with percutaneous Bacillus Calmette-Guérin (BCG) vaccine was significantly larger than that of infants vaccinated with intradermal BCG vaccine (median, 8 mm vs. 5 mm; P = 0.002). In multiple logistic regression analysis, independent factors associated with TST positivity (≥ 10 mm induration) were male (adjusted odds ratio [aOR], 2.98; 95% CI, 1.6-5.64), percutaneous BCG vaccination (aOR, 3.30; 95% CI, 1.75-6.48), TST reading between 60 and 72 hours after injecting purified protein derivative (aOR, 2.87; 95% CI, 1.53-5.49), and INH prophylaxis more than four weeks (aOR, 0.49; 95% CI, 0.25-0.94).

CONCLUSION

A single TST at three months after the last TB exposure with INH prophylaxis could be used as a main protocol in contact investigations for infants exposed to infectious TB during the neonatal period in congregate settings in Korea.

Use of Interferon-Gamma Release Assays in Children <2 Years Old

While interferon-gamma release assays (IGRAs) are widely used for detecting tuberculosis (TB) infection, tuberculin skin tests (TSTs) remain preferred for children under the age of 2 years. The preference for TST stems from concern over IGRA sensitivity in young children. However, TSTs are susceptible to false-positive results following Bacille Calmette-Guérin (BCG) vaccination, which is common in infancy, and exposure to nontuberculous mycobacteria. We reviewed available data for IGRA performance in children under age 2 years. Across four cohorts of high-risk children under age 2 (mostly case contacts or those born in tuberculosis endemic regions), 0 of 575 untreated children with negative IGRA test results progressed to tuberculosis disease-including 0 of 70 who were TST positive but IGRA negative. While neither TSTs nor IGRAs are perfectly sensitive for the diagnosis of tuberculosis infection, IGRAs are an acceptable alternative to TST in children <2 years of age.

Pulmonary Tuberculosis in Children: A Forgotten Disease?

Even today, tuberculosis in childhood is a disease that is often undiagnosed and undertreated. In the absence of therapy with antituberculosis drugs, children in the first years of life have a high degree of severe forms and mortality. In these children, symptoms are often not very specific and can easily be confused with other diseases of bacterial, viral or fungal etiology, making diagnosis more difficult. Nevertheless, the introduction of new diagnostic techniques has allowed a more rapid identification of the infection. Indeed, Interferon gamma release assay (IGRA) is preferred to the Mantoux, albeit with obvious limitations in children aged <2 years. While the Xpert Mtb/RIF Ultra test is recommended as an initial diagnostic investigation of the gastric aspirate and/or stools in children with signs and symptoms of pulmonary tuberculosis. The drugs used in the treatment of susceptible and resistant TB are the same as those used in adults but doses and combinations are different in the pediatric age. In children, brief therapy is preferable in both the latent infection and the active disease, as a significant reduction in side effects is obtained.

Interferon-γ release assay and mantoux response in infants with tuberculous meningitis in low and intermediate burden countries

AIM

Until now, the performance of interferon-γ release assay (IGRA) and Mantoux tests remains unclear in infant tuberculous meningitis (TBM). Therefore, a systematic review is performed to evaluate the sensitivity of IGRA and Mantoux tests for the diagnosis of infant TBM in low and intermediate tuberculosis (TB) burden countries, while following PRISMA.

METHODS

Several databases, including PubMed, EBSCO, Embase, Scopus, Web of Science, ClinicalTrials.gov, and Cochrane Central Register of Controlled Trials, were searched. Articles describing the results of IGRA or Mantoux tests among infant TBM were included for analysis. Data, such as age, sex, Mantoux test or IGRA, and cerebrospinal fluid (CSF) microbiological examinations (such as acid-fast bacilli (AFB) smear, TB PCR, and TB culture), were extracted from each study.

RESULTS

A total of 31 articles were enrolled for further analysis, including 48 cases. The mean age was 9.4 ± 5.8 months and boys accounted for 57.1% of infants (24/42). Mantoux test was positive in 57.4% (27/47) of tested infants and IGRA was positive in 77.8% (7/9) of infants. In addition, among the infants with confirmed TB, 18 (52.9%, 18/34) of them have positive Mantoux responses and 7 (20.0%, 7/35) have positive IGRA results.

CONCLUSIONS

In low or intermediate TB burden countries, the Mantoux test has a poor performance for diagnosing TBM among infants, and IGRAs appear to have a moderate sensitivity for the diagnosis of infant TBM.

Determining the Need for Additional Testing With Quantiferon TB Gold in Patients With Positive Tuberculin Skin Tests and a History of BCG Vaccination

OBJECTIVE

 To determine if the QuantiFERON-TB Gold (QFT) testing can be obviated for the diagnosis of latent tuberculosis infection (LTBI) in patients with a positive tuberculin skin test (TST) and a history of Bacillus Calmette-Guerin (BCG) vaccination by identifying high-risk features in patients with positive TST and a history of BCG vaccination who are associated with positive QFT.

METHODS

 Retrospective chart review was done for 76 adult patients by dividing them into two groups. Group 1 consisted of true positive TST patients who had BCG vaccination and were positive for QFT. Group 2 consisted of false positive TST patients who had BCG vaccination but were negative for QFT. The two groups were compared to determine if the high-risk features of TST induration diameter of 15mm and more, TST induration of 20mm and more, recent immigration to the US, the advanced age of more than 65 years, country of origin with high TB burden, known exposure to active TB, and smoking history were more prevalent in Group 1 compared to Group 2.

RESULTS

 Group 1 had 23 patients and Group 2 had 53 patients. Group 1 had a higher prevalence of patients with PPD induration of more than 10mm than Group 2, which was statistically significant with a P value of 0.03. Other risk factors of advanced age, exposure to active TB and smoking did not show statistically significant differences between Groups 1 and 2.  Conclusion: This study also confirms that if the TST induration is more than 10mm in patients with a history of BCG vaccination, the TST induration is likely because of LTBI and is less likely because of cross-reaction with BCG vaccination.

Optimizing the Threshold to Treat Children for Latent Tuberculosis Infection: A North-East England Experience

We assessed the impact of the updated guidelines on tuberculin skin test interpretation in the North East of England. Data on 241 children screened for latent tuberculosis infection (LTBI) between January 2011 and July 2018 were analyzed; 12.4% of children screened under the previous guidelines were treated for LTBI, compared to 33.3% under the new ones ( P < 0.001).

Tuberculosis Infection in Children and Adolescents

The burden of tuberculosis (TB) in children and adolescents remains very significant. Several million children and adolescents are infected with TB each year worldwide following exposure to an infectious TB case and the risk of progression from TB infection to tuberculosis disease is higher in this group compared to adults. This review describes the risk factors for TB infection in children and adolescents. Following TB exposure, the risk of TB infection is determined by a combination of index case characteristics, contact features, and environmental determinants. We also present the recently recommended approaches to diagnose and treat TB infection as well as novel tests for infection. The tests for TB infection have limitations and diagnosis still relies on an indirect immunological assessment of cellular immune response to Mycobacterium tuberculosis antigens using immunodiagnostic testing. It is recommended that TB exposed children and adolescents and those living with HIV receive TB preventive treatment (TPT) to reduce the risk of progression to TB disease. Several TPT regimens of similar effectiveness and safety are now available and recommended by the World Health Organisation.

Tuberculin test versus interferon gamma release assay in pregnant women with household contacts of tuberculosis patients

Background

Pregnant women who live in tuberculosis (TB)-affected households are more likely to develop latent TB infection (LTBI), which often escapes treatment. This study aims to determine if Interferon-gamma release (IGRA) is reliable in screening for LTBI in pregnant women, compare to the tuberculin skin test (TST).

Methods

It was a cross-sectional study that involved 60 pregnant women with TB contact history as a proxy for LTBI and 30 pregnant women without contact history. Latent TB was detected using the TST 5 tuberculin units and IGRA using the QuantiFERON Gold Plus TB Test kit (QFT-Plus). The sensitivity and specificity of the two diagnostic methods and the agreement between them were estimated using SPSS version 20.0.

Results

The sensitivity 95% (95% confidence interval [CI]: 86.08%-98.96%) and specificity 26.7% (95% CI: 12.28%-45.89%) of TST were compared to that of the IGRA with 60% (95% CI: 46.54%-72.44%) and 73.3% (95% CI: 54.11%-87.72%) sensitivity and specificity, respectively in detecting LTBI in pregnancy. Although there was a significant difference (P < 0.05) between TST and IGRA, the agreement was fair (kappa 0.39; 95% CI: 0.24-0.45).

Conclusion

TST assay is more sensitive than IGRA; however, the specificity of IGRA was superior to the TST method. In this study, a fair agreement of TST and IGRA was observed for detecting latent TB infection in pregnant women with household contact with TB patients.

Detecting Mycobacterium tuberculosis Infection in Children Migrating to Australia

In 2015, Australia updated premigration screening for tuberculosis (TB) disease in children 2-10 years of age to include testing for infection with Mycobacterium tuberculosis and enable detection of latent TB infection (LTBI). We analyzed TB screening results in children <15 years of age during November 2015-June 2017. We found 45,060 child applicants were tested with interferon-gamma release assay (IGRA) (57.7% of tests) or tuberculin skin test (TST) (42.3% of tests). A total of 21 cases of TB were diagnosed: 4 without IGRA or TST, 10 with positive IGRA or TST, and 7 with negative results. LTBI was detected in 3.3% (1,473/44,709) of children, for 30 applicants screened per LTBI case detected. LTBI-associated factors included increasing age, TB contact, origin from a higher TB prevalence region, and testing by TST. Detection of TB and LTBI benefit children, but the updated screening program's effect on TB in Australia is likely to be limited.

Study of CD27, CD38, HLA-DR and Ki-67 immune profiles for the characterization of active tuberculosis, latent infection and end of treatment

Background

Current blood-based diagnostic tools for TB are insufficient to properly characterize the distinct stages of TB, from the latent infection (LTBI) to its active form (aTB); nor can they assess treatment efficacy. Several immune cell biomarkers have been proposed as potential candidates for the development of improved diagnostic tools.

Objective

To compare the capacity of CD27, HLA-DR, CD38 and Ki-67 markers to characterize LTBI, active TB and patients who ended treatment and resolved TB.

Methods

Blood was collected from 45 patients defined according to clinical and microbiological criteria as: LTBI, aTB with less than 1 month of treatment and aTB after completing treatment. Peripheral blood mononuclear cells were stimulated with ESAT-6/CFP-10 or PPD antigens and acquired for flow cytometry after labelling with conjugated antibodies against CD3, CD4, CD8, CD27, IFN-γ, TNF-α, CD38, HLA-DR, and Ki-67. Conventional and multiparametric analyses were done with FlowJo and OMIQ, respectively.

Results

The expression of CD27, CD38, HLA-DR and Ki-67 markers was analyzed in CD4⁺ T-cells producing IFN-γ and/or TNF-α cytokines after ESAT-6/CFP-10 or PPD stimulation. Within antigen-responsive CD4⁺ T-cells, CD27⁻ and CD38⁺ (ESAT-6/CFP-10-specific), and HLA-DR⁺ and Ki-67⁺ (PPD- and ESAT-6/CFP-10-specific) populations were significantly increased in aTB compared to LTBI. Ki-67 demonstrated the best discriminative performance as evaluated by ROC analyses (AUC > 0.9 after PPD stimulation). Data also points to a significant change in the expression of CD38 (ESAT-6/CFP-10-specific) and Ki-67 (PPD- and ESAT-6/CFP-10-specific) after ending the anti-TB treatment regimen. Furthermore, ratio based on the CD27 median fluorescence intensity in CD4⁺ T-cells over Mtb-specific CD4⁺ T-cells showed a positive association with aTB over LTBI (ESAT-6/CFP-10-specific). Additionally, multiparametric FlowSOM analyses revealed an increase in CD27 cell clusters and a decrease in HLA-DR cell clusters within Mtb-specific populations after the end of treatment.

Conclusion

Our study independently confirms that CD27⁻, CD38⁺, HLA-DR⁺ and Ki-67⁺ populations on Mtb-specific CD4⁺ T-cells are increased during active TB disease. Multiparametric analyses unbiasedly identify clusters based on CD27 or HLA-DR whose abundance can be related to treatment efficacy. Further studies are necessary to pinpoint the convergence between conventional and multiparametric approaches.

A CD4+ TNF+ monofunctional memory T-cell response to BCG vaccination is associated with Mycobacterium tuberculosis infection in infants exposed to HIV

BACKGROUND

The immunologic correlates of risk of Mycobacterium tuberculosis (Mtb) infection after BCG vaccination are unknown. The mechanism by which BCG influences the tuberculin skin test (TST) remains poorly understood. We evaluated CD4+ T-cell responses in infants exposed to HIV and uninfected (HEU) who received BCG at birth and examined their role in susceptibility to Mtb infection and influence on TST induration.

METHODS

HEU infants were enrolled in a randomised clinical trial of isoniazid (INH) to prevent Mtb infection in Kenya. We measured mycobacterial antigen-specific Th1 and Th17 cytokine responses at 6-10 weeks of age prior to INH randomisation and compared responses between Mtb infected and uninfected infants. Outcomes at 14 months of age included TST, QuantiFERON-Plus (QFT-Plus), and ESAT-6/CFP-10-specific non-IFN-γ cytokines measured in QFT-Plus supernatants.

FINDINGS

A monofunctional mycobacterial antigen-specific TNF+ CD4+ effector memory (CCR7-CD45RA-) T-cell response at 6-10 weeks of age was associated with Mtb infection at 14 months of age as measured by ESAT-6/CFP-10-specific IFN-γ and non-IFN-γ responses (Odds Ratio 2.26; Confidence Interval 1.27-4.15; P = 0.006). Mycobacterial antigen-specific polyfunctional effector memory Th1 responses at 6-10 weeks positively correlated with TST induration in infants without evidence of Mtb infection at 14 months, an association which was diminished by INH therapy.

INTERPRETATION

Induction of monofunctional TNF+ CD4+ effector memory T-cell responses may be detrimental in TB vaccine development. This study also provides mechanistic insight into the association of BCG-induced immune responses with TST induration and further evidence that TST-based diagnoses of Mtb infection in infants are imprecise.

FUNDING

Thrasher Research Fund.

Correlation between innate and adaptive immunity response in TB children post BCG vaccination. Is it effective or not?: Cross-sectional study

Background

How far the role of innate immunity and adaptive immunity do in children who have been BCG vaccinated in controlling the course and the severity of the TB disease has not been completely known. Mycobacterium tuberculosis entry to the body will be recognized by Toll-like receptors found on macrophages, neutrophils, and dendritic cells as part of the innate immune response, after which the dendritic cells will then present the antigen to lymphocyte T0 cells and initiate the adaptive immune response (of which CD4 T cells have an important role in). Was one or were both of these immune responses function well or not in a BCG Vaccinated Children with TB?

Objective

This study aim to find a better understanding of the role of innate immune response assessed by TLR2/TLR4 mRNA gene expression and serum TLR2/TLR4 levels, while the role of adaptive immune response is assessed by analyzing serum CD4 level in children with TB who have had BCG vaccination.

Methods

This cross-sectional study was conducted among children with TB at the outpatient and inpatient wards at Bhakti Medicare and Jakarta Islamic Hospital. Expression of mRNA gene was measured using the Boom method and protein serum levels were measured using the ELISA method. The results were analyzed by using the SPSS v.23 program.

Results

Sixty-nine children were recruited as subjects. In this study, 68.1% of whom had BCG scars. TLR4 mRNA gene expression was found to be higher than TLR2 mRNA gene expression. Serum CD4 level was found to be highest out of TLR2 and TLR4 level, but serum TLR2 level was higher than TLR4 level. TLR2/TLR4 mRNA gene expression, serum TLR2/TLR4 levels, and CD4 levels in subjects with BCG scar were also found to be significantly higher than in subjects without BCG scar (p < 0.001). There was a significant positive correlation between TLR2/TLR4 mRNA gene expression and serum TLR2/TLR4 levels (r = 0.860; r = 0.864; p < 0.001) and between serum levels TLR2/TLR4 with serum CD4 levels (r = 0.822; r = 0.832 p < 0.001).

Conclusion

As early as possible, BCG vaccine administration is needed in endemic countries, but it must be ensured that scars can be formed. It is also important to control Latent TB Infection (LTBI) to prevent transmission and relapse of disease.

•

For the prevention of TB disease, it is important to understand the innate and adaptive immune responses according BCG scar.

•

Mycobacterium tuberculosis recognition by TLR as the innate immune response followed by the adaptive immune response by CD4 cells.

•

There is a strong positive correlation between the expression of mRNA gene and the concentration of TLR and CD4 in BCG-vaccinated subjects.

•

BCG vaccination should be done as early as possible in endemic countries, as it provides better protection against TB infection.

QuantiFERON-TB Gold Plus Test in Diagnostics of Latent Tuberculosis Infection in Children Aged 1-14 in a Country with a Low Tuberculosis Incidence

The aim of the study was to evaluate the QuantiFERON-TB Gold Plus (QFT-Plus) test usability in the identification of latent tuberculosis infection (LTBI) in children and the determination of features associated with tuberculin skin test (TST) and QFT-Plus-positive results concerning LTBI. Two-hundred thirteen children aged 1–14 were screened for LTBI due to household contact with TB, suspected TB, or were qualified for biological therapy. The objective of this study was to evaluate the QFT-Plus affectivity as a diagnostic test in the absence of a gold standard (GS) test for the diagnosis of LTBI. The children were diagnosed with QFT-Plus, TST, and culture of TB. The QFT-Plus results were analyzed depending on the children’s age, TST size, and type. In children aged 1–4, the positive predictive value of QFT-Plus was 1, the negative predictive value was 0.94, QFT-Plus sensitivity was 75%, and specificity was 100%. It was observed that in children aged 5–14 years, the level of agreement decreased to the substantial, i.e., 87.2%. Moreover, the negative predictive value was 0.83. QFT-Plus sensitivity was 64%, and specificity was 100%. Statistical analysis of QFT-Plus and TST results showed substantial and almost perfect agreements. Our study suggests that QFT-Plus is helpful in a pediatric practice showing good sensitivity and specificity for LTBI. The BCG vaccine, infections, and concomitant morbidities do not affect QFT-Plus results.

Impact of Latent Tuberculosis on Severity and Outcomes in Admitted COVID-19 Patients

Background

There is limited data on coronavirus disease 2019 (COVID-19) and latent tuberculosis infection (LTBI).

Methodology

We analyzed data of admitted COVID-19 patients evaluated for LTBI to examine the impact of LTBI on severity, laboratory parameters, and COVID-19 outcome. Prospectively collected data were analyzed for 60 patients who were administered the Mantoux tuberculosis skin test (TST) using five tuberculin units of purified protein derivative. All patients were administered TST irrespective of Bacille Calmette-Guérin (BCG) vaccination status. Comorbidities, clinical features, radiologic involvement, laboratory parameters, and clinical course were analyzed concerning LTBI.

Results

The mean age was 45.9 (±15.2) years, and 35 (58.3%) patients had non-severe disease. The vast majority (n = 56/60; 93.3%) had been vaccinated with single-dose BCG in infancy or early childhood, as per national immunization guidelines. LTBI was diagnosed in 15 (25%) patients. LTBI prevalence was lower in severe (n = 1/25; 4%) than non-severe (n = 14/35; 40%) COVID-19 (p = 0.01) patients. LTBI patients had lower percentage neutrophil count, higher lymphocyte percentage, higher monocyte count, lower neutrophil-lymphocyte (NL) ratio, lower alanine aminotransferase, lower C-reactive protein, and lesser radiologic involvement compared to those without LTBI (p < 0.05). Similarly, among the mild COVID-19 subgroup, those with LTBI had higher lymphocyte and monocyte counts and lesser radiologic involvement than those without LTBI (p < 0.05).

Conclusions

LTBI patients appear to have milder disease, higher lymphocyte and monocyte count, higher NL ratio, and lesser radiographic involvement. This observation needs to be studied in larger studies using interferon release assays.

Tuberculosis Infection in Children and Adolescents: Testing and Treatment

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

Paediatric management of a tuberculosis outbreak in an Irish Direct Provision Centre

Direct Provision in Ireland provides basic needs of food and shelter to asylum seekers while their refugee status is processed. There are a number of issues associated with living conditions in these centres including overcrowding, nutrition and play facilities (1,2). This article outlines the protocol of contact tracing and management of latent tuberculosis infection in the paediatric setting after a confirmed adult case of tuberculosis within a Direct Provision centre in Ireland. This is a retrospective case series of 82 children living in the centre. Twenty-two children were deemed at risk of infection, all asymptomatic. Sixteen children (20%) were treated for possible latent tuberculosis infection with isoniazid for 6-9 months; compliance was good with no side effects reported. This article highlights the risk to vulnerable populations, especially children, when residing in Direct Provision facilities. Initial migrant screening on entry is essential, in addition to improving living conditions and time spent by families in this living environment.

Infectious Risk Mitigation in Patients with Multiple Sclerosis under Disease-Modifying Therapies - the Experience of a Collaborative Neurology-Infectious Diseases Approach

Background

Multiple sclerosis treatment has changed in the last years with the emergence of new disease-modifying therapies (DMTs). Despite a better efficacy profile, these drugs raise concerns about infectious risk, which needs to be mitigated.

Objective

To analyze the results of a systematic collaborative approach between Neurology and Infectious Diseases (ID) Departments in the management of infectious risk and complications in MS patients treated with DMT.

Methods

Retrospective collection of MS patients’ demographic and clinical data from clinical records of MS and ID outpatient clinics (2011–2017).

Results

We included 149 patients: most had evidence of previous contact with Herpesviridae, and half of them were not immune to hepatitis A and B viruses (HAV and HBV). Vaccines for HAV, HBV, and Streptococcus pneumoniae were administered in 91%, 78%, and 88% of non-immune patients, respectively. JC virus serology monitoring prevented natalizumab (NTZ) initiation or prompted its switch in 34/122 patients. Forty patients had latent tuberculosis, in which 88% were treated. Infectious events occurred in 33 patients, mostly mild urinary, respiratory, and herpes virus group infections. Only three patients required inpatient care.

Conclusion

Facing the expansion of the new DMT, we highlight the benefits of an interdisciplinary approach for safer use of the chosen treatment.

Assessment of Interferon Gamma-Induced Protein 10 mRNA Release Assay for Detection of Latent Tuberculosis Infection in Egyptian Pediatric Household Contacts

OBJECTIVES

Current diagnostic tests for tuberculosis (TB) in children living in low-endemic countries are limited by low specificity and the inability of the current tests to differentiate between active TB and latent TB infection (LTBI). This study aimed to evaluate the blood IP-10 mRNA expression level to detect LTBI in Egyptian pediatric household contacts (PHC).

METHODS

TB-specific IP-10 and IFN-γ mRNA levels were assessed by real-time quantitative PCR (RT-qPCR) in 72 Egyptian PHC of active pulmonary TB cases. All study participants were also assessed by Tuberculin Skin Test (TST) and Quantiferon gold in tube (QFN-GIT) assay.

RESULTS

IP-10 and IFN-γ mRNA expression levels were significantly higher in PHC with active TB or LTBI than TB negative (p < 0.0001). The level of IP-10 mRNA expression was significantly higher in PHC with active TB than LTBI (p = 0.0008). In contrast, there was no significant differences in the IFN-γ mRNA expression between PHC with active TB compared to LTBI (p = 0.49). The sensitivity and specificity of the IP-10 RT-qPCR were 94.2% and 95.2%, respectively, in PHC with active TB compared to 85.7% and 81.8% in PHC with LTBI. The negative and positive predictive values and accuracy of IP-10 RT-qPCR for distinguishing active TB from LTBI were 85.2%, 58.3%, and 72.6% respectively.

CONCLUSION

Blood IP-10 mRNA expression level may be a potential diagnostic marker to help distinguish active TB from LTBI in PHC.

TB contact tracing for young children: an Australian cascade of care review

OBJECTIVE

To evaluate care cascades for programmatic active case finding and latent TB infection (LTBI) management in young child TB contacts (aged <5 years) in Victoria, Australia.

DESIGN

This was a retrospective review of public health surveillance data to identify contacts of all pulmonary TB cases notified from 2016 to 2019.

RESULTS

Contact tracing identified 574 young child contacts of 251 pulmonary TB cases. Active TB was found in 28 (4.9%) contacts, none of whom had previously received bacille Calmette-Guérin vaccination, and 529 were tested for TB infection using the tuberculin skin test (TST). The overall TST positivity was 15.3% (95% CI 0.1-0.2). Among the 574 children, 150 (26.1%) were close contacts of sputum smear-positive cases and 25 (16.7%) of these were not referred to TB clinics. Of the 125 referred, 81 were considered to have LTBI, 79 agreed to commence TB preventive treatment (TPT) and 71 (89.9%) completed TPT. Following completion of TPT, no child was subsequently diagnosed with active TB.

CONCLUSION

There was a high yield from active case finding and uptake of TPT. Notable losses in the cascade of care occurred around referral to tertiary clinics, but high treatment completion rates and good outcomes were found in those prescribed treatment.

Tuberculosis in Internationally Displaced Children Resettling in Harris County, Texas, USA, 2010-20151

US guidelines have recommended testing children emigrating from high tuberculosis-incidence countries with interferon-gamma release assays (IGRAs) or tuberculin skin tests (TSTs). We describe the Harris County (Texas) Public Health Refugee Health Screening Program's testing results during 2010-2015 for children <18 years of age: 5,990 were evaluated, and 5,870 (98%) were tested. Overall, 364 (6.2%) children had >1 positive test: 143/1,842 (7.8%) were tested with TST alone, 129/3,730 (3.5%) with IGRA alone, and 92/298 (30.9%) with both TST and IGRA. Region of origin and younger age were associated with positive TST or IGRA results. All children were more likely to have positive results for TST than for IGRA (OR 2.92, 95% CI 2.37-3.59). Discordant test results were common (20%) and most often were TST+/IGRA- (95.0%), likely because of bacillus Calmette-Guérin vaccination. Finding fewer false positives supports the 2018 change in US immigration guidelines that recommends using IGRAs for recently immigrated children.

Immunological Aspects of Diagnosis and Management of Childhood Tuberculosis

The diagnosis of tuberculosis (TB) in children is difficult because of the low sensitivity and specificity of traditional microbiology techniques in this age group. Whereas in adults the culture of Mycobacterium tuberculosis (M. tuberculosis), the gold standard test, detects 80% of positive cases, it only detects around 30-40% of cases in children. The new methods based on the immune response to M. tuberculosis infection could be affected by many factors. It is necessary to evaluate the medical record, clinical features, presence of drug-resistant M. tuberculosis strains, comorbidities, and BCG vaccination history for the diagnosis in children. There is no ideal biomarker for all TB cases in children. A new strategy based on personalized diagnosis could be used to evaluate specific molecules produced by the host immune response and make therapeutic decisions in each child, thereby changing standard immunological signatures to personalized signatures in TB. In this way, immune diagnosis, prognosis, and the use of potential immunomodulators as adjunct TB treatments will meet personalized treatment.

TST conversions and systemic interferon-gamma increase after methotrexate introduction in psoriasis patients

Background

Tuberculosis screening in psoriasis patients is complex due to the immunological alterations associated with psoriasis, the presence of comorbidities, and the effect of immunosuppressive treatment. However, it is not established whether the results of screening tests are affected by these factors in psoriasis patients.

Objectives

To determine whether there is a change in the results of the tuberculin skin test (TST) or the interferon-gamma release assay (IGRA) in psoriasis patients living in tuberculosis (TB)-endemic area after 12 weeks of methotrexate (MTX) treatment and to investigate the association of the test results with clinical and inflammatory markers.

Methods

Forty-five patients were selected for a prospective single-arm self-controlled study and followed for at least 18 months. The TST, IGRA, Psoriasis Area and Severity Index (PASI), and inflammatory factors (erythrocyte sedimentation rate (ESR), C-reactive protein, interferon-gamma (IFN-γ), and tumor necrosis factor-alpha levels), were determined before and after 12 weeks of oral 15 mg per week MTX administration and compared. The associations between the IGRA and TST results were verified before and after treatment according to inflammatory factors and clinical characteristics (age, blood glucose, weight, body mass index, disease duration, and PASI).

Results

We collected data on 25 patients who completed the full course of therapy and the follow-up. None of the patients developed TB. TST positivity was significantly elevated at week 12 (25% baseline vs 44% at week 12, P < 0.037). Three IGRAs followed the TST conversions. There was no difference between TST and IGRA pre- or posttreatment. Serum IFN-γ increased significantly in week 12 (15.95 pg/ml baseline vs 18.82 pg/ml at week 12, P < 0.005) and tended to be higher among TST-positive patients (P = 0.072). The baseline IGRA was associated with a higher ESR (P = 0.038). None of the test results were associated with clinical characteristics.

Conclusions

In addition to the classic booster effect, TST conversions in patients using MTX can occur due to an increase in IFN-γ. However, it is not possible to exclude true TST conversions. Therefore, other diagnostic methods, like IGRA or chest tomography, should be used when the TST has intermediate results.

Discovery and validation of a personalized risk predictor for incident tuberculosis in low transmission settings

The risk of tuberculosis (TB) is variable among individuals with latent Mycobacterium tuberculosis infection (LTBI), but validated estimates of personalized risk are lacking. In pooled data from 18 systematically identified cohort studies from 20 countries, including 80,468 individuals tested for LTBI, 5-year cumulative incident TB risk among people with untreated LTBI was 15.6% (95% confidence interval (CI), 8.0-29.2%) among child contacts, 4.8% (95% CI, 3.0-7.7%) among adult contacts, 5.0% (95% CI, 1.6-14.5%) among migrants and 4.8% (95% CI, 1.5-14.3%) among immunocompromised groups. We confirmed highly variable estimates within risk groups, necessitating an individualized approach to risk stratification. Therefore, we developed a personalized risk predictor for incident TB (PERISKOPE-TB) that combines a quantitative measure of T cell sensitization and clinical covariates. Internal-external cross-validation of the model demonstrated a random effects meta-analysis C-statistic of 0.88 (95% CI, 0.82-0.93) for incident TB. In decision curve analysis, the model demonstrated clinical utility for targeting preventative treatment, compared to treating all, or no, people with LTBI. We challenge the current crude approach to TB risk estimation among people with LTBI in favor of our evidence-based and patient-centered method, in settings aiming for pre-elimination worldwide.

Application of antigenic biomarkers for Mycobacterium tuberculosis

The study and characterization of biomolecules involved in the interaction between mycobacteria and their hosts are crucial to determine their roles in the invasion process and provide basic knowledge about the biology and pathogenesis of disease. Promising new biomarkers for diagnosis and immunotherapy have emerged recently. Mycobacterium is an ancient pathogen that has developed complex strategies for its persistence in the host and environment, likely based on the complexity of the network of interactions between the molecules involved in infection. Several biomarkers have received recent attention in the process of developing rapid and reliable detection techniques for tuberculosis. Among the most widely investigated antigens are CFP-10 (10-kDa culture filtrate protein), ESAT-6 (6-kDa early secretory antigenic target), Ag85A, Ag85B, CFP-7, and PPE18. Some of these antigens have been proposed as biomarkers to assess the key elements of the response to infection of both the pathogen and host. The design of novel and accurate diagnostic methods is essential for the control of tuberculosis worldwide. Presently, the diagnostic methods are based on the identification of molecules in the humoral response in infected individuals. Therefore, these tests depend on the capacity of the host to develop an immune response, which usually is heterogeneous. In the last 20 years, special attention has been given to the design of multiantigenic diagnostic methods to improve the levels of sensitivity and specificity. In this review, we summarize the state of the art in the study and use of mycobacterium biomolecules with the potential to support novel tuberculosis control strategies.

Interferon-Gamma Release Assay Testing in Children Younger Than 2 Years in a US-Based Health System

BACKGROUND

Use of interferon-gamma releasing assays (IGRAs) in children <2 years old may derive many of the same advantages, which have led to preference over tuberculin skin test (TST) in older children, but data are limited. Since 2011, we have tested children <2 years old with Quantiferon-TB Gold/Gold Plus (QFT)) in select clinical scenarios at Denver Health, a health system encompassing a TB clinic, refugee and immigrant screening and primary care.

METHODS

We identified patients <2 years old tested with QFT between February, 2011 and August, 2019. The primary outcome measure was incident cases of TB among tested patients. Test results and in vitro characteristics were analyzed, as were demographic, epidemiologic and clinical outcomes.

RESULTS

We analyzed 116 QFTs ordered in children age 7-23 months. Two were positive, 3 indeterminate, 3 failed/refused phlebotomy and the remainder (93%) were negative. Mitogen tube results were robust. Thirteen patients were TST-positive: 11 were QFT-negative, 1 QFT-positive and 1 failed phlebotomy. Eight patients received some form of TB medication, including 4 QFT-negative patients who were treated for active TB or latent TB infection based on positive TST or clinical findings. Among QFT-negative patients, including 6 TST-positive, not treated for active TB or latent TB infection, no TB disease has been identified over a median follow-up time of 2.96 years.

CONCLUSIONS

IGRA use was not limited by barriers of phlebotomy, indeterminate result or gamma-interferon production. The risk of missing an infected but IGRA-negative patient can be reduced by treatment of select patients at higher risk. Current recommendations against IGRA use in children <2 years old could be amended to allow careful introduction, particularly among well-appearing BCG-vaccinated patients.

Performance of a household tuberculosis exposure survey among children in a Latin American setting

OBJECTIVE: To evaluate the performance of a survey that quantifies the intensity of household tuberculosis (TB) exposure among children.METHODS: Children aged 0-14 years in Lima, Peru, with ≥1 signs and/or symptoms of TB and a history of contact with an adult TB patient were included. The 10-question survey was administered to caregivers and addressed sleep proximity, frequency of exposure, and infectiousness of the contact. Infection status was determined using tuberculin skin tests (TSTs). The exposure scale was evaluated for association with TST positivity using mixed-effects regression analyses.RESULTS: The exposure score was significantly associated with TST positivity (age-adjusted odds ratio [aOR] 1.14, 95%CI 1.02-1.28). We observed a stronger association with TST positivity in children aged ≤5 years; (aOR 1.23, 95%CI 1.07-1.41) and no association in children 6-14 years of age (aOR 0.99, 95%CI 0.82-1.20).CONCLUSION: This survey was easy to use and modestly successful in predicting TST positivity in children aged ≤5 years. It may be a useful resource for clinicians for diagnosing TB in children, and for national TB programs aiming to scale up preventive therapy initiatives.

Performance of metabonomic serum analysis for diagnostics in paediatric tuberculosis

We applied a metabonomic strategy to identify host biomarkers in serum to diagnose paediatric tuberculosis (TB) disease. 112 symptomatic children with presumptive TB were recruited in The Gambia and classified as bacteriologically-confirmed TB, clinically diagnosed TB, or other diseases. Sera were analysed using ¹H nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS). Multivariate data analysis was used to distinguish patients with TB from other diseases. Diagnostic accuracy was evaluated using Receiver Operating Characteristic (ROC) curves. Model performance was tested in a validation cohort of 36 children from the UK. Data acquired using ¹H NMR demonstrated a sensitivity, specificity and Area Under the Curve (AUC) of 69% (95% confidence interval [CI], 56-73%), 83% (95% CI, 73-93%), and 0.78 respectively, and correctly classified 20% of the validation cohort from the UK. The most discriminatory MS data showed a sensitivity of 67% (95% CI, 60-71%), specificity of 86% (95% CI, 75-93%) and an AUC of 0.78, correctly classifying 83% of the validation cohort. Amongst children with presumptive TB, metabolic profiling of sera distinguished bacteriologically-confirmed and clinical TB from other diseases. This novel approach yielded a diagnostic performance for paediatric TB comparable to that of Xpert MTB/RIF and interferon gamma release assays.

Tuberculosis in childhood and adolescence: a view from different perspectives

OBJECTIVE

To describe the epidemiological situation of tuberculosis in children under 19 years of age in Brazil and to review the latest publications on disease risk, diagnosis, treatment, and prevention.

SOURCE OF DATA

Notifiable Diseases Information System (2018), World Health Organization estimates, and PubMed articles selected using the descriptor "Tuberculosis," delimited by type of study, period, age, and language.

SYNTHESIS OF DATA

In 2018, in Brazil, 9.4% of notifications were in children under 19 years. The pulmonary form predominated in 80.1% of the cases. The cure rate was 76.8%, lethality was 0.8%, and abandonment was 10.4%. The prevalence of drug-resistant tuberculosis (2011-2016) was 0.5%. It has been found that the risk of disease can reach up to 56% in children under 5 years, influenced by helminth co-infections, malaria, chronic viral infections, live attenuated virus vaccines, and hypovitaminosis D. Exposure to a bacilliferous patient for periods shorter than 30minutes is sufficient for the development of infection and/or disease. In Brazil, microbiological screening is recommended, but the use of the scoring system, modified in 2019, has been maintained. Studies on infection detection have supported the use of the tuberculin skin test. In the treatment, the great advance was the introduction of dispersible formulations, adjustment of the recommended doses, and shortened regimens for latent infection. Several vaccine studies (stages 1-3) are ongoing, but no BCG-licensed substitute has been implemented yet.

CONCLUSIONS

There has been progress in treatment, but major challenges need to be overcome to improve diagnosis, monitoring, and outcome of cases, aiming to eliminate tuberculosis.

Optimizing the Design of Latent Tuberculosis Treatment Trials: Insights from Mathematical Modeling

Rationale: Noninferiority trials of treatment for latent tuberculosis infection (LTBI) are challenging because of imperfect LTBI diagnostic tests.Objectives: To assess the effect on study outcomes of different enrollment strategies for a noninferiority trial of LTBI treatment.Methods: We mathematically simulated a two-arm randomized clinical trial of LTBI in which the experimental therapy was 50% efficacious and the control was 80% efficacious, with an absolute 0.75% noninferiority margin. Five enrollment strategies were assessed: 1) enroll based on no LTBI diagnostic test; 2) enroll based on a positive tuberculin skin test (TST); 3) enroll based on a positive IFN-γ release assay (IGRA); 4) enroll based on either a positive TST or IGRA; and 5) enroll regardless of test result, assuming 70% had negative TSTs, 20% positive TSTs, and 10% unknown results.Measurements and Main Results: Under most LTBI prevalence assumptions, enrolling based on a positive IGRA was least likely to result in falsely declaring noninferiority of the experimental regimen. Enrolling based on no test or regardless of test result led to falsely declaring noninferiority unless LTBI prevalence in the underlying population was higher than 45%. Enrolling based on a mix of TST and IGRA substantially reduced the likelihood of falsely declaring noninferiority over enrolling based on TST alone, even if as many as 70% of participants were enrolled based on positive TST.Conclusions: Noninferiority trials of LTBI should enroll based on the most specific diagnostic tests available (i.e., IGRAs) to avoid misclassifying inferior treatment regimens as noninferior.

The age-specific burden and household and school-based predictors of child and adolescent tuberculosis infection in rural Uganda

BACKGROUND

The age-specific epidemiology of child and adolescent tuberculosis (TB) is poorly understood, especially in rural areas of East Africa. We sought to characterize the age-specific prevalence and predictors of TB infection among children and adolescents living in rural Uganda, and to explore the contribution of household TB exposure on TB infection.

METHODS

From 2015-2016 we placed and read 3,121 tuberculin skin tests (TST) in children (5-11 years old) and adolescents (12-19 years old) participating in a nested household survey in 9 rural Eastern Ugandan communities. TB infection was defined as a positive TST (induration ≥10mm or ≥5mm if living with HIV). Age-specific prevalence was estimated using inverse probability weighting to adjust for incomplete measurement. Generalized estimating equations were used to assess the association between TB infection and multi-level predictors.

RESULTS

The adjusted prevalence of TB infection was 8.5% (95%CI: 6.9-10.4) in children and 16.7% (95% CI:14.0-19.7) in adolescents. Nine percent of children and adolescents with a prevalent TB infection had a household TB contact. Among children, having a household TB contact was strongly associated with TB infection (aOR 5.5, 95% CI: 1.7-16.9), but the strength of this association declined among adolescents and did not meet significance (aOR 2.3, 95% CI: 0.8-7.0). The population attributable faction of TB infection due to a household TB contact was 8% for children and 4% among adolescents. Mobile children and adolescents who travel outside of their community for school had a 1.7 (95% CI 1.0-2.9) fold higher odds of TB infection than those who attended school in the community.

CONCLUSION

Children and adolescents in this area of rural eastern Uganda suffer a significant burden of TB. The majority of TB infections are not explained by a known household TB contact. Our findings underscore the need for community-based TB prevention interventions, especially among mobile youth.

Expression of USP18 and IL2RA Is Increased in Individuals Receiving Latent Tuberculosis Treatment with Isoniazid

BACKGROUND

The treatment of latent tuberculosis infection (LTBI) in individuals at risk of reactivation is essential for tuberculosis control. However, blood biomarkers associated with LTBI treatment have not been identified.

METHODS

Blood samples from tuberculin skin test (TST) reactive individuals were collected before and after one and six months of isoniazid (INH) therapy. Peripheral mononuclear cells (PBMC) were isolated, and an in-house interferon-γ release assay (IGRA) was performed. Expression of chemokine ligand 4 (CCL4), chemokine ligand 10 (CXCL10), chemokine ligand 11 (CXCL11), interferon alpha (IFNA), radical S-adenosyl methionine domain-containing 2 (RSAD2), ubiquitin-specific peptidase 18 (USP18), interferon-induced protein 44 (IFI44), interferon-induced protein 44 like (IFI44L), interferon-induced protein tetratricopeptide repeats 1(IFIT1), and interleukin 2 receptor subunit alpha (IL2RA) mRNA levels were assessed by qPCR before, during, and after INH treatment.

RESULTS

We observed significantly lower relative abundances of USP18, IFI44L, IFNA, and IL2RA transcripts in PBMC from IGRA-positive individuals compared to levels in IGRA-negative individuals before INH therapy. Also, relative abundance of CXCL11 was significantly lower in IGRA-positive than in IGRA-negative individuals before and after one month of INH therapy. However, the relative abundance of CCL4, CXCL10, and CXCL11 mRNA was significantly decreased and that of IL2RA and USP18 significantly increased after INH therapy, regardless of the IGRA result. Our results show that USP18, IFI44L, IFIT1, and IL2RA relative abundances increased significantly, meanwhile the relative abundance of CCL4, CXCL11, and IFNA decreased significantly after six months of INH therapy in TST-positive individuals.

CONCLUSIONS

Changes in the profiles of USP18, IL2RA, IFNA, CCL4, and CXCL11 expressions during INH treatment in TST-positive individuals, regardless of IGRA status, are potential tools for monitoring latent tuberculosis treatment.

The evolving research agenda for paediatric tuberculosis infection

Following exposure to tuberculosis and subsequent infection, children often progress to tuberculosis disease more rapidly than adults. And yet the natural history of tuberculosis in children, as a continuum from exposure to infection and then to disease, is poorly understood. Children are rarely diagnosed with tuberculosis infection in routine care in international settings and few receive tuberculosis infection treatment. In this Personal View, we review the most up-to-date knowledge in three areas of childhood tuberculosis infection-namely, pathophysiology, diagnosis, and treatment. We then outline what is missing in each of these three areas to generate a priority research agenda. Finally, we suggest potential study designs that might answer these questions. Understanding of pathophysiology could be improved through animal models, laboratory studies assessing the immunological responses of blood or respiratory samples to Mycobacterium spp in vitro, as well as investigating immune responses in children exposed to tuberculosis. Identification of children with sub-clinical disease and at high risk of progression to clinically overt disease, would allow treatment to be targeted at those most likely to benefit. Optimisation and discovery of novel treatments for tuberculosis infection in children should account for mechanisms of action of tuberculosis drugs, as well as child-specific factors including pharmacokinetics and appropriate formulations. To conduct these studies, a change in mindset is required, with a recognition that the diagnosis and treatment of tuberculosis infection in children is a necessary component in addressing the overall tuberculosis epidemic. Collaboration between stakeholders will be required and funding will need to increase, both for research and implementation. The consequences of inaction, however, will lead to further decades of children suffering from what should increasingly be recognised as a preventable disease.

Evaluating UK National Guidance for Screening of Children for Tuberculosis. A Prospective Multicenter Study

RATIONALE

To identify infected contacts of tuberculosis (TB) cases, the UK National Institute for Health and Care Excellence (NICE) recommended the addition of IFN-γ release assays (IGRA) to the tuberculin skin test (TST) in its 2006 TB guidelines. Treatment for TB infection was no longer recommended for children who screened TST-positive but IGRA-negative.

OBJECTIVES

We performed a cohort study to evaluate the risk of TB disease in this group.

METHODS

Children exposed to an infectious case of TB in their household were recruited from 11 pediatric TB clinics. TST and IGRA were performed at baseline, with IGRA repeated at 8 weeks and TST repeated if initially negative. Children were treated according to 2006 NICE guidelines and followed for 24 months.

MEASUREMENTS AND MAIN RESULTS

Of 431 recruited children, 392 completed the study. We diagnosed 48 (12.2%) cases of prevalent TB disease, 105 (26.8%) with TB infection, and 239 (60.9%) without TB infection or disease. Eighteen children aged 2 years and above had a positive TST but persistently negative IGRA. None received TB infection treatment and none developed TB disease. Ninety (26.1%) children qualified for TB infection treatment according to 2006 NICE guidelines. In contrast, 147 (42.7%) children would have qualified under revised NICE guidance, issued in 2016.

CONCLUSIONS

In this low-prevalence setting we saw no incident cases of TB disease in children who were TST-positive but IGRA-negative and did not receive treatment for TB infection. Following the latest NICE guidance, significantly more children will require medication.

Contribution of QuantiFERON-TB Gold-in-Tube to the Diagnosis of Mycobacterium tuberculosis Infection in Young Children in a Low TB Prevalence Country

Introduction: Interferon Gamma Release Assay (IGRA) has proven to be a useful test to evaluate the immune response to Mycobacterium tuberculosis antigens in children over the age of 5 years as an alternative to tuberculin skin testing (TST). Much less is known about its performance in younger children, who are at higher risk for developing tuberculosis (TB) disease after exposure. We aimed to evaluate the accuracy of using IGRA in TB screening in this population. Methods: Children below the age of 5 years at high risk for TB infection were prospectively enrolled, to compare the performance of TST and the QuantiFERON-TB Gold-In-Tube test (QFT). Children were treated in accordance with the diagnosis made at baseline and followed-up for 12 months. Results: We included a total of 60 children of which 97 blood samples were available for analysis. There was 90.72% agreement between TST and QFT (Kappa test 0.59, moderate agreement). With TST as a reference, the QFT positive predictive value was 0.72 and the negative predictive value 0.93. Discordant results were observed with 6% TST+/QFT- paired tests. When we restricted the comparison of TST and QFT to non-BCG-vaccinated children, the degree of agreement was more substantial (95%, Kappa test 0.75) and the negative predictive value was 0.99. We observed 3% discordant TST-/QFT+ results. All children with active TB disease had concordant positive QFT results, with QFT values above 4.00 IU/ml. Conclusion: In a low TB prevalence country, serial testing of QFT was found to produce a moderate agreement with TST results. False positive QFT results would have been eliminated by using a higher cutoff without misdiagnosing the children with TB disease. Some of the false negative QFT results could be explained by false positive TST results on consecutive testing. For now the most prudent approach would be to consider discordant QFT-/TST+ results as false negative QFT results, taking into account the young age of our population and the potential risk for evolution to active TB disease.

Synergy between tuberculin skin test and proliferative T cell responses to PPD or cell-membrane antigens of Mycobacterium tuberculosis for detection of latent TB infection in a high disease-burden setting

Tuberculin skin test (TST) is used most widely for the detection of latent tuberculosis infection (LTBI), even though evidences suggest that it could be underreporting the prevalence of LTBI particularly in high disease-burden settings. We have explored whether in vivo (TST) and in vitro (cell-proliferative) T cell responses to PPD can serve as complementary measures. In addition, we also probed whether in vitro T cell response to cell-membrane antigens (Mem) of Mycobacterium tuberculosis (MTB) can serve as a biomarker for LTBI. Study subjects comprised 43 healthcare workers (HCWs), and 9 smear-positive TB patients served as ‘disease control’. To measure proliferative T cell responses, 0.1 ml blood (diluted 1:10) was incubated (5 days) with test or control antigen. Cells were stained with fluorescent antibodies to T cell (CD3+/CD4+/CD8+) surface markers and, after fixation and permeabilization, to nuclear proliferation marker Ki67. Data was acquired on a flow cytometer. HCWs who had an intimate exposure to MTB showed significantly higher TST positivity (85%) than the rest (43%), notwithstanding their BCG vaccination status. The proliferative responses of CD4+ and CD8+ subsets of T cells were comparable. Sixty seven and 100% TST-negative HCWs, respectively, were positive for proliferative T cell response to PPD and MTBMem. Cumulative positivity (TST or in vitro) was 86% with PPD and 100% with MTBMem indicating complementarity of the two responses. As standalone in vitro assay, MTBMem provided a significantly higher positivity (95%) than PPD (67%). T cell responses of TB patients were ‘generally’ depressed, having implications for the development of immunological assays for ‘progressive’ LTBI. Altogether, these results demonstrate that in vivo and in vitro T cell responses to PPD are complementary and in vitro response to MTBMem can be developed as a highly sensitive biomarker for LTBI.

C-Tb skin test to diagnose Mycobacterium tuberculosis infection in children and HIV-infected adults: A phase 3 trial

Background

C-Tb, an ESAT-6/CFP-10-based skin test, has similar sensitivity for active TB compared to tuberculin skin test (TST) and QuantiFERON-TB-Gold-In-Tube (QFT). However, data are limited in children and HIV-infected persons.

Methods

Asymptomatic South African contacts <5 years (n = 87; HIV-uninfected), or symptomatic individuals of all ages presenting to clinics with suspected TB (n = 1003; 30% HIV-infected) were recruited from eight South African centres. C-Tb and TST were allocated to either forearm double blinded. Samples for QFT were collected in parallel, and test-positivity rates were compared.

Results

In participants with microbiologically confirmed TB (n = 75; 45% HIV-infected) sensitivity of C-Tb, TST and QFT were similar (72% versus 75% versus 73%; p>0.5). All 3 tests had similar positivity rates in HIV-infected participants with active TB, however, positivity rates were reduced when CD4 counts were <100 cells/μL. In participants where active TB was excluded (n = 920), C-Tb (41%), TST (43%), and QFT (44%) also had similar test-positivity rates. Among asymptomatic contacts aged below five, 32% (28/87) tested positive with C-Tb and 32% (28/87) with TST (concordance 89%). Overall, C-Tb and TST showed a similar safety profile.

Conclusion

C-Tb was safe and showed similar test-positivity rates, compared to TST and QFT, in children and HIV-infected persons with active or latent M. tuberculosis infection. These data inform the utility of C-Tb in clinical practice.

Trial registration

ClinicalTrials.gov NCT01642888.

EudraCT 2011-005078-40.

Recommendations for the screening of paediatric latent tuberculosis infection in indigenous communities: a systematic review of screening strategies among high-risk groups in low-incidence countries

Background

Tuberculosis (TB) continues to be a global public health concern. Due to the presence of multiple risk factors such as poor housing conditions and food insecurity in Canadian Indigenous communities, this population is at particularly high risk of TB infection. Given the challenges of screening for latent TB infection (LTBI) in remote communities, a synthesis of the existing literature regarding current screening strategies among high-risk groups in low-incidence countries is warranted, in order to provide an evidence base for the optimization of paediatric LTBI screening practices in the Canadian Indigenous context.

Methods

A literature search of the Embase and Medline databases was conducted, and studies pertaining the evaluation of screening strategies or screening tools for LTBI in paediatric high-risk groups in low-incidence countries were included. Studies focusing on LTBI screening in Indigenous communities were also included, regardless of whether they focused on a paediatric population. Their results were summarized and discussed in the context of their relevance to screening strategies suitable to the Canadian Indigenous setting. Grey literature sources such as government reports or policy briefs were also consulted.

Results

The initial literature search returned 327 studies, with 266 being excluded after abstract screening, and 36 studies being included in the final review (original research studies: n = 25, review papers or policy recommendations: n = 11). In the examined studies, case identification and cost-effectiveness of universal screening were low in low-incidence countries. Therefore, studies generally recommended targeted screening of high-risk groups in low-incidence countries, however, there remains a lack of consensus regarding cut-offs for the incidence-based screening of high-risk communities, as well as regarding the utility and prioritization of individual risk-factor-based screening of high-risk groups. The utility of the TST compared to IGRAs for LTBI detection in the pediatric population also remains contested.

Conclusions

Relevant strategies for targeted screening in the Canadian Indigenous context include community-level incidence-based screening (screening based on geographic location within high-incidence communities), as well as individual risk-factor-based screening, taking into account pertinent risk factors in Indigenous settings, such as poor housing conditions, malnutrition, contact with an active case, or the presence of relevant co-morbidities, such as renal disease.

Screening for tuberculosis in migrants and visitors from high-incidence settings: present and future perspectives

In most settings with a low incidence of tuberculosis (TB), foreign-born people make up the majority of TB cases, but the distribution of the TB risk among different migrant populations is often poorly quantified. In addition, screening practices for TB disease and latent TB infection (LTBI) vary widely. Addressing the risk of TB in international migrants is an essential component of TB prevention and care efforts in low-incidence countries, and strategies to systematically screen for, diagnose, treat and prevent TB among this group contribute to national and global TB elimination goals.This review provides an overview and critical assessment of TB screening practices that are focused on migrants and visitors from high to low TB incidence countries, including pre-migration screening and post-migration follow-up of those deemed to be at an increased risk of developing TB. We focus mainly on migrants who enter the destination country via application for a long-stay visa, as well as asylum seekers and refugees, but briefly consider issues related to short-term visitors and those with long-duration multiple-entry visas. Issues related to the screening of children and screening for LTBI are also explored.

Evaluating latent tuberculosis infection diagnostics using latent class analysis

BACKGROUND

Lack of a gold standard for latent TB infection has precluded direct measurement of test characteristics of the tuberculin skin test and interferon-γ release assays (QuantiFERON Gold In-Tube and T-SPOT.TB).

OBJECTIVE

We estimated test sensitivity/specificity and latent TB infection prevalence in a prospective, US-based cohort of 10 740 participants at high risk for latent infection.

METHODS

Bayesian latent class analysis was used to estimate test sensitivity/specificity and latent TB infection prevalence among subgroups based on age, foreign birth outside the USA and HIV infection.

RESULTS

Latent TB infection prevalence varied from 4.0% among foreign-born, HIV-seronegative persons aged <5 years to 34.0% among foreign-born, HIV-seronegative persons aged ≥5 years. Test sensitivity ranged from 45.8% for the T-SPOT.TB among foreign-born, HIV-seropositive persons aged ≥5 years to 80.7% for the tuberculin skin test among foreign-born, HIV-seronegative persons aged ≥5 years. The skin test was less specific than either interferon-γ release assay, particularly among foreign-born populations (eg, the skin test had 70.0% specificity among foreign-born, HIV-seronegative persons aged ≥5 years vs 98.5% and 99.3% specificity for the QuantiFERON and T-SPOT.TB, respectively). The tuberculin skin test's positive predictive value ranged from 10.0% among foreign-born children aged <5 years to 69.2% among foreign-born, HIV-seropositive persons aged ≥5 years; the positive predictive values of the QuantiFERON (41.4%) and T-SPOT.TB (77.5%) were also low among US-born, HIV-seropositive persons aged ≥5 years.

CONCLUSIONS

These data reinforce guidelines preferring interferon-γ release assays for foreign-born populations and recommending against screening populations at low risk for latent TB infection.

TRIAL REGISTRATION NUMBER

NCT01622140.

Use of tuberculin skin test for assessment of immune recovery among previously malnourished children in Ethiopia

OBJECTIVE

To compare levels of immunity in children recovering from severe acute malnutrition (cases) against those of community controls (controls).

RESULTS

At baseline children recovering from severe acute malnutrition had lower, mid upper arm circumference (122 mm for cases and 135 mm for controls; p < 0.001), weight-for-height Z-score (- 1.0 for cases and - 0.5 for controls; p < 0.001), weight-for-age Z-score (- 2.8 for cases and - 1.1 for controls; p < 0.001) and height/length-for-age Z-score (- 3.6 for cases and - 1.4 for controls; p < 0.001), than controls. Age and gender matched community controls. At baseline, prevalence of a positive tuberculin skin test, assessed by cutaneous delayed-type hypersensitivity reaction skin test, was very low in both cases (3/93 = 3.2%) and controls (2/94 = 2.1%) and did not significantly increase at 6 months follow up (6/86 = 7.0% in cases and 3/84 = 3.4% in controls). The incidences of common childhood morbidities, namely fever, diarrhoea and cough, were 1.7-1.8 times higher among cases than controls. In conclusion, these results show that tuberculin skin test does not enable any conclusive statements regarding the immune status of patients following treatment for severe acute malnutrition. The increased incidence of infection in cases compared to controls suggests persistence of lower resistance to infection even after anthropometric recovery is achieved.

International adoption from Ethiopia: An overview of the health status at arrival in Belgium

BACKGROUND

Ethiopia is a densely populated country with a fast growing economy. Still socioeconomic and health issues render many children parentless. One thousand and twenty eight Ethiopian children have been adopted in Belgium from September 2005 to September 2015. Little has been published about their health status at arrival.

METHODS

Three hundred and fifteen children adopted from Ethiopia were clinically evaluated at the Institute of Tropical Medicine in Antwerp from 1 January 2008 until 31 December 2014. Epidemiological and medical data were collected and analysed retrospectively.

RESULTS

Data about 164 boys and 151 girls with a mean age of three years were analysed. Twenty per cent was adequately vaccinated, for 66.7% of children these data were absent. About 8.6% of the children were wasted/thin, 28.9% stunted. Skin abnormalities were seen in 40.3%, especially Tinea capitis. No children tested positive for HIV, syphilis or hepatitis C. Four children had an acute or chronic hepatitis B (HBV) infection, eight children had a cured HBV infection. Two children tested positive for malaria. Active pulmonary tuberculosis was found in six children. Sixty-two per cent had one or more intestinal parasite. Giardia lamblia (41.9%) and Blastocystis hominis (27.0%) were most frequently isolated. There is a statistically relevant association between the number of intestinal parasites and age at presentation. In this group eosinophilia had a sensitivity of 30.2%, a specificity of 79.1% for intestinal parasites and a positive likelihood ratio of 1.44 with a negative likelihood ratio of 0.88.

CONCLUSION

Apart from the high prevalence of stunting and intestinal parasites important medical problems were infrequent. A systematic clinical examination and screening for infectious diseases remain important to ensure a healthy start of a new life in Belgium.

Optimizing the management of children with latent tuberculosis infection

INTRODUCTION

The management of latent tuberculosis (LTBI) in children represents an important issue for paediatricians because of the disease burden, the lack of a gold standard for the diagnosis and the high annual risk of progression to active disease. Areas covered: A review of English language articles on LTBI in children, published between the 1st of January 2010 and the 1st of July 2016, was conducted using multiple keywords and standardized terminology in PubMed database. This review provides an updated overview of the available tests for LTBI diagnosis in children, management strategies and treatment options. Expert commentary: Two tests are available for LTBI diagnosis: tuberculin skin test and interferon-gamma release assays, both with a suboptimal specificity and sensitivity, and both with the lack of capability in distinguishing between infection and disease. Several new markers have been identified but further studies are needed. Among all treatment regimes, because of the high safety and efficacy profile showed and to avoid the poor completion rate, the treatment with a three-month course of isoniazid and rifampicin is currently recommended. New vaccines are needed because of the spread of the disease despite BCG vaccination in high risk countries. Currently, 15 new vaccines are in the pipeline.

Preventive therapy for latent tuberculosis infection-the promise and the challenges

Around one third of the world's population may harbour latent tuberculosis infection (LTBI), an asymptomatic immunological state that confers a heightened risk of subsequently developing tuberculosis (TB). Effectively treating LTBI will be essential if the End TB Strategy is to be realized. This review evaluates the evidence in relation to the effectiveness of preventive antibiotic therapy to treat LTBI due to both drug-susceptible and drug-resistant bacteria. Current national and international preventive therapy guidelines are summarized, as well as ongoing randomized trials evaluating regimens to prevent drug-resistant TB. Populations that may benefit most from screening and treatment for LTBI include close contacts of patients with TB (particularly children under 5 years of age) and individuals with substantial immunological impairment. The risks and benefits of treatment must be carefully balanced for each individual. Electronic decision support tools offer one way in which clinicians can help patients to make informed decisions. Modelling studies indicate that the expanded use of preventive therapy will be essential to achieving substantial reductions in the global TB burden. However, the widespread scale-up of screening and treatment will require careful consideration of cost-effectiveness, while ensuring the drivers of ongoing disease transmission are also addressed.

Prevalence and Diagnosis of Latent Tuberculosis Infection in Young Children in the Absence of a Gold Standard

INTRODUCTION

For adequate disease control the World Health Organization has proposed the diagnosis and treatment of latent tuberculous infection (LTBI) in groups of risk of developing the disease such as children. There is no gold standard (GS) test for the diagnosis of LTBI. The objective of this study was to estimate the prevalence of LTBI in young children in contact with a household case of tuberculosis (TB-HCC) and determine the accuracy and precision of the Tuberculin Skin Test (TST) and QuantiFERON-TB Gold in-tube (QFT) used in the absence of a GS.

METHODS

We conducted a cross-sectional study in children up to 6 years of age in Manaus/Brazil during the years 2009-2010. All the children had been vaccinated with the BCG and were classified into two groups according to the presence of a TB-HCC or no known contact with tuberculosis (TB). The variables studied were: the TST and QFT results and the intensity and length of exposure to the index tuberculosis case. We used the latent class model to determine the prevalence of LTBI and the accuracy of the tests.

RESULTS

Fifty percent of the children with TB-HCC had LTBI, with the prevalence depending on the intensity and length of exposure to the index case. The sensitivity and specificity of TST were 73% [95% confidence interval (CI): 53-91] and 97% (95%CI: 89-100), respectively, versus 53% (95%CI: 41-66) and 81% (95%CI:71-90) for QFT. The positive predictive value of TST in children with TB-HCC was 91% (95%CI: 61-99), being 74% for QFT (95%CI: 47-95).

CONCLUSIONS

This is one of the first studies to estimate the prevalence of LTBI in children and the parameters of the main diagnostic tests using a latent class model. Our results suggest that children in contact with an index case have a high risk of infection. The accuracy and the predictive value of the two tests did not significantly differ. Combined use of the two tests showed scarce improvement in the diagnosis of LTBI.