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.

Latent Tuberculosis Infection in Haematopoietic Stem Cell Transplant Recipients: A Retrospective Italian Cohort Study in Tor Vergata University Hospital, Rome

The results of tuberculosis (TB) screening and reactivation in a cohort of 323 adult patients undergoing haematopoietic stem cell transplantation (HSCT) from 2015 to 2019 at the University Hospital of Tor Vergata, Rome, Italy, were reported. A total of 260 patients, 59 (18.3%) autologous and 264 (81.7%) allogeneic transplants, underwent Interferon Release (IFN)-γ (IGRA) test screening: 228 (87.7%) were negative, 11 (4.2%) indeterminate and 21 (8.1%) positive. Most of the IGRA-positive patients were of Italian origin (95.2%) and significantly older than the IGRA-negative (p < 0.001); 22 (8.5%) patients underwent a second IGRA during the first year after transplantation, and 1 tested positive for IGRA. Significantly lower monocyte (p = 0.044) and lymphocyte counts (p = 0.009) were detected in IGRA negative and IGRA indeterminate patients, respectively. All latent TB patients underwent isoniazid prophylaxis, and none of them progressed to active TB over a median follow-up period of 63.4 months. A significant decline in TB screening practices was shown from 2015 to 2019, and approximately 19% of patients were not screened. In conclusion, 8.1% of our HSCT population had LTBI, all received INH treatment, and no reactivation of TB was observed during the follow-up period. In addition, 19% escaped screening and 8% of these came from countries with a medium TB burden, therefore at higher risk of possible development of TB.

Biomarkers to identify Mycobacterium tuberculosis infection among borderline QuantiFERON results

BACKGROUND

Screening for tuberculosis (TB) infection often includes QuantiFERON-TB Gold Plus (QFT) testing. Previous studies showed that two-thirds of patients with negative QFT results just below the cut-off, so-called borderline test results, nevertheless had other evidence of TB infection. This study aimed to identify a biomarker profile by which borderline QFT results due to TB infection can be distinguished from random test variation.

METHODS

QFT supernatants of patients with a borderline (≥0.15 and <0.35 IU·mL-1), low-negative (<0.15 IU·mL-1) or positive (≥0.35 IU·mL-1) QFT result were collected in three hospitals. Bead-based multiplex assays were used to analyse 48 different cytokines, chemokines and growth factors. A prediction model was derived using LASSO regression and applied further to discriminate QFT-positive Mycobacterium tuberculosis-infected patients from borderline QFT patients and QFT-negative patients RESULTS: QFT samples of 195 patients were collected and analysed. Global testing revealed that the levels of 10 kDa interferon (IFN)-γ-induced protein (IP-10/CXCL10), monokine induced by IFN-γ (MIG/CXCL9) and interleukin-1 receptor antagonist in the antigen-stimulated tubes were each significantly higher in patients with a positive QFT result compared with low-negative QFT individuals (p<0.001). A prediction model based on IP-10 and MIG proved highly accurate in discriminating patients with a positive QFT (TB infection) from uninfected individuals with a low-negative QFT (sensitivity 1.00 (95% CI 0.79-1.00) and specificity 0.95 (95% CI 0.74-1.00)). This same model predicted TB infection in 68% of 87 patients with a borderline QFT result.

CONCLUSIONS

This study was able to classify borderline QFT results as likely infection-related or random. These findings support additional laboratory testing for either IP-10 or MIG following a borderline QFT result for individuals at increased risk of reactivation TB.

Correlation between tuberculosis-specific interferon-γ release assay and intrathoracic calcification: A cross-sectional study

Background

Although persistent tuberculosis (TB) infection is known to cause calcification in the lungs, the relationship between intrathoracic calcification and the results of the interferon-γ release assay (IGRA) has not been fully elucidated. This study aimed to assess the association between intrathoracic calcification and IGRA results.

Methods

We retrospectively included consecutive patients who concurrently underwent chest X-ray, chest computed tomography (CT), and an IGRA. Patients with a current diagnosis of active TB or treatment history of active TB or latent tuberculosis infection (LTBI) were excluded. The association between calcification according to the chest X-ray or CT and IGRA results were analyzed using binomial logistic regression.

Results

This study included 574 patients, and 38 (7%) patients had a positive IGRA result. Patients with a positive result were significantly older and had a higher proportion of comorbidities, and history of tuberculosis exposure compared to those with a negative result. Calcification of the lung field and mediastinal lymph nodes according to chest CT was more frequently observed in patients with a positive IGRA result, whereas no significant difference was observed concerning the proportion of lung field calcification on chest X-ray between patients with positive and negative IGRA results. In multivariate analysis, calcification of mediastinal lymph nodes alone (adjusted odds ratio [OR] = 3.82, 95% confidence interval [CI] = 1.76–8.26) and the combination of lung field and mediastinal lymph node calcification (adjusted OR = 4.12, 95% CI = 1.51–11.76) on chest CT was independently associated with positive IGRA results.

Conclusions

The finding of mediastinal lymph node calcification, with or without lung field calcification, on chest CT was associated with positive IGRA results independent of TB exposure history. Previous TB infection including eliminated TB infection and LTBI can be suspected when calcified lymph nodes in are observed the mediastinum on chest CT.

Variability of interferon-γ release assays in people at high risk of tuberculosis infection or progression to tuberculosis disease living in the United States

OBJECTIVES

Interferon-γ release assays, including T-SPOT.TB (TSPOT) and QuantiFERON Gold In-Tube (QFT), are important diagnostic tools for tuberculosis infection, but little work has been done to study the performance of these tests in populations prioritized for tuberculosis testing in the United States, especially those other than health care personnel.

METHODS

Participants were enrolled as part of a large, prospective cohort of people at high risk of tuberculosis infection or progression to tuberculosis disease. All participants were administered a tuberculin skin test, TSPOT, and QFT test. A subset of participants had their QFT (n = 919) and TSPOT (n = 885) tests repeated when they returned to get their tuberculin skin test read 2 to 3 days later (repeat study). A total of 531 participants had a TSPOT performed twice on the same sample taken at the same time (split study).

RESULTS

The QFT repeat test interpretations were discordant (one test positive and the other negative) for 6.4% of participants (59 of 919), and the TSPOT tests were discordant for 60 of 885 participants in the repeat study (6.8%) and 41 of 531 participants in the split study (7.7%). There was a high degree of variability in the quantitative test results for both QFT and TSPOT, and discordance was not associated with both test results being near the established cut-offs. Furthermore, the proportion of discordance was similar when comparing participants in both the TSPOT repeat and TSPOT split studies.

DISCUSSION

Both QFT and TSPOT were 6% to 8% discordant. The results should be interpreted with caution, particularly when seeing a conversion or reversion in serial testing.

Interferon gamma release assays for diagnosis of osteoarticular tuberculosis: A systematic review and meta-analysis

Background

Although the Interferon Gamma Release Assays (IGRA) is often used to identify latent tuberculosis, it also plays a crucial role in diagnosing active extrapulmonary tuberculosis. Some studies have assessed the use of IGRA as a biomarker for osteoarticular tuberculosis (OATB), which is elevated following TB infection. Still, conclusive results about its effectiveness have not been reported.

Method

We searched PubMed, Embase, and Cochran databases. We obtained literature related to the diagnosis of OATB by IGRA, and the retrieval period was from the establishment of the database to June 2021. The bivariate random effect model was used to summarize the sensitivity, specificity, and accuracy of other indicators in diagnosing OATB by IGRA, and the forest plot and receiver operating characteristic (ROC) curve were used for testing.

Results

We included seven studies involving 643 subjects in diagnosing OATB by IGRA. The comprehensive sensitivity and specificity were 0.84 (95% CI, 0.70–0.92) and 0.78 (95% CI, 0.66–0.87), respectively. The area under the curve (AUC) was 0.87.

Conclusion

In blood samples, the diagnostic accuracy of IGRAS is poor in patients with suspected OAT. We conclude that IGRA may not be appropriate for patients with OATB.

A retrospective analysis of the tuberculin skin test reactions of a single source population of Mauritian Macaca fascicularis held in quarantine during 2017

A published range of reactions to the tuberculin skin test (TST) using mammalian (human) old tuberculin (MOT) in a population of Mauritius origin Macaca fascicularis in US laboratory animal medicine does not exist. The objectives of this report are to quantify the reactions among juvenile, adolescent, and male adult cynomolgus macaques and to provide the laboratory animal medicine practitioner with a reference range of reactions to MOT in Mauritian juvenile macaques. Monkeys in a US foreign animal quarantine must be tested negative for mycobacterial infection including Mycobacterium tuberculosis (Mtb) using MOT as required by the CDC Division of Global Migration and Quarantine. The TST relies on visual observation post injection of an individual animal’s reaction or nonreaction. During 2017, 933 Mauritius origin macaques from one supplier were quarantined in nine separate cohorts in our facility. 848 or > 90% of the animals were juveniles between 1.5 to 3 years of age, comprised of 425 males and 423 females. The population also included 46 adolescents (21 males, 25 females) and 39 adult males. A total of 33 TST sets were performed on the nine cohorts, resulting in 3418 individual TSTs being administered. 1595 (46.6%) injections were made in juvenile males and 1529 (44.7%) in juvenile females. A total of 172 reactions to the TST were recorded at the final assessment completed at the 72-hour post injection time point from all animal ages and sexes. 162 reactions (94.2% of all reactions) occurred in juvenile animals, consisting of 96 bruises (59.3% of all juvenile reactions) in males and 58 bruises (35.8% of all juvenile reactions) in females. Bruising was the most common reaction in juvenile animals and in all animals regardless of age or sex. Bruising occurred within all 33 TST sets ranging from a low of 0% to a high of 30% in male juveniles and a low of 0% to a high of 17% in female juveniles. Bruising was the only finding in the adolescents and adult males. Erythema was observed only in juvenile animals, two males and three females. Generalized eyelid edema was observed only in juvenile animals, one male and one female. These animals had concurrent erythema in the affected eyelid. Animals with generalized eyelid edema and erythema are considered suspect for active tuberculosis and warrant further diagnostics. In this report, the most observed reaction among all age groups and sexes was bruising. Erythema and edema were rarely observed. Only juvenile animals were observed with either erythema, edema or both.

Updates in Pediatric Tuberculosis in International Settings

Childhood tuberculosis (TB) has been underreported and underrepresented in TB statistics across the globe. Contributing factors include health system barriers, diagnostic barriers, and community barriers leading to an underdetected epidemic of childhood tuberculosis. Despite considerable progress in childhood TB management, there is a concerning gap in policy and practice in high-burden countries leading to missed opportunities for active case detection, early diagnosis and treatment of TB exposure, and infection and disease in children regardless of human immunodeficiency virus status. Bridging this gap requires multisectoral coordination and political commitment along with an eye to research and innovation with potential to scale.

Prevalence of Latent Tuberculosis Infection Among Healthy Young Children and Adolescents and a Two-step Approach for the Diagnosis of Tuberculosis Infection in Chengdu, China

BACKGROUND

China has a high burden of tuberculosis and latent tuberculosis infection (LTBI). The aim of this study was to estimate the prevalence of LTBI among healthy young children and adolescents and test a 2-step approach to explore the threshold for the diagnosis of tuberculosis infection in Chengdu, China.

METHODS

Healthy preschool children and school-going children in Chengdu, Sichuan Province, were screened for LTBI using the tuberculin skin test (TST). Preschool children with TST ≥ 5 mm also underwent interferon-γ release assay (IGRA) to explore the threshold of this 2-step approach.

RESULTS

In total, 5667 healthy young children and adolescents completed TST test between July 2020 and January 2021 and were included in the present analysis. The age of the participants ranged from 2.4 to 18 years (median 7.25 ± 4.514 years), of which 2093 (36.9%) were younger than 5 years. The overall prevalence of LTBI was 6.37% and 6.64% in children younger than 5 years old. Fourteen of the 341 preschool children with TST ≥5 mm were interferon-γ release assay positive, of which 4 showed a TST result of 5-10 mm, and 6 preschool children received preventive treatment for LTBI.

CONCLUSIONS

Healthy young children and adolescents should also be considered as important target populations for LTBI screening. TST can be recommended for first-line screening as part of a 2-step approach for LTBI screening using a positive threshold of 5 mm.

Tuberculin skin tests following Bacille Calmette Guerin vaccination in Africa: a protocol for systematic review and meta-analysis

Tuberculin reactivity following tuberculin skin test which is the most common measure of the effect of the Bacille Calmette Guerin (BCG) vaccination has remained complex. This protocol is aimed to assess the effect of BCG vaccine on tuberculin skin test in Africa as a guide to better understanding or resolving this complexity. A search strategy is developed using MeSH, key words, text words, and entry terms. Five databases will be searched, including PubMed, African Journals Online (AJOL), Google Scholar, Research Gate, and Cochrane Library. Only observational studies conducted in Sub-Saharan Africa and retrievable in English language will be included. The primary measurable outcome of this study is pooled prevalence of positive tuberculin skin tests. Secondary outcomes are factors that influence Tuberculin Skin Test (TST) positivity such as BCG type, the dose of BCG, age at BCG vaccinates, time/interval between BCG vaccination and TST, and type of tuberculin unit used for TST. Identified studies will be screened and selected based on inclusion criteria. Data will be extracted into Zotero, Microsoft Excel and CMA software. Both quality scores and the risk of bias for individual studies will be reported. Studies will be assessed for methodological, clinical, and statistical heterogeneity. Funnel Plots will be used for assessing publication bias. The results will be presented in tabular format in addition to a narrative synthesis. The pooled prevalence of effect of BCG vaccine on TST in Africa will be examined in relation to factors that influence TST positivity.

Cost-effectiveness of testing for latent tuberculosis infection in people with HIV

OBJECTIVE

The aim of this study was to estimate the cost-effectiveness of screening strategies for predicting LTBI that progresses to active tuberculosis (TB) in people with HIV.

DESIGN

We developed a decision-analytical model that constituted a decision tree covering diagnosis of LTBI and a Markov model covering progression to active TB. The model represents the lifetime experience following testing for LTBI, and discounting costs, and benefits at 3.5% per annum in line with UK standards. We undertook probabilistic and one-way sensitivity analyses.

SETTING

UK National Health Service and Personal Social Service perspective in a primary care setting.

PARTICIPANTS

Hypothetical cohort of adults recently diagnosed with HIV.

INTERVENTIONS

Interferon-gamma release assays and tuberculin skin test.

MAIN OUTCOME MEASURE

Cost per quality-adjusted life year (QALY).

RESULTS

All strategies except T-SPOT.TB were cost-effective at identifying LTBI, with the QFT-GIT-negative followed by TST5mm strategy being the most costly and effective. Results indicated that there was little preference between strategies at a willingness-to-pay threshold of £20 000. At thresholds above £40 000 per QALY, there was a clear preference for the QFT-GIT-negative followed by TST5mm, with a probability of 0.41 of being cost-effective. Results showed that specificity for QFT-GIT and TST5mm were the main drivers of the economic model.

CONCLUSION

Screening for LTBI has important public health and clinical benefits. Most of the strategies are cost-effective. These results should be interpreted with caution because of the paucity of studies included in the meta-analysis of test accuracy studies. Additional high-quality primary studies are needed to have a definitive answer about, which strategy is the most effective.

Brief Report: Yield of Repeat Tuberculin Skin Testing for People Living With HIV in Brazil

OBJECTIVES

In Brazil, annual tuberculin skin tests (TSTs) are recommended for people living with HIV (PLWH) with CD4 >350, with tuberculosis preventive therapy provided on test conversion. We aimed to determine the yield of repeat TSTs for PLWH.

DESIGN

Secondary analysis of the stepped-wedge, cluster-randomized THRio trial for isoniazid preventive therapy (IPT) to prevent tuberculosis (TB).

METHODS

We analyzed data from newly registered PLWH with negative baseline TST results. We calculated the number of TST conversions after 1 and/or 2 years among patients eligible for follow-up TSTs, the proportion of converters initiating IPT, and incidence of TB/death.

RESULTS

Among 1770 PLWH with a negative baseline TST, 679 (38%) were female and median age was 36 years (IQR 29-43). Eighty-six (5%) developed TB or died within 1 year. Among 1684 eligible for a follow-up 1-year TST, 582 (35%) were tested and 53 (9%) were positive. Forty-nine converters (92%) started IPT. Of 529 patients with a negative 1-year TST, 7 (1%) developed TB or died over the following year. Of 522 patients eligible for a 2-year TST, 158 (30%) were tested and 13 (8%) were positive. Ten converters (77%) started IPT. Of 1102 patients who did not receive a 1-year TST, 33 (3%) developed TB or died. Of the 1069 patients eligible for a 2-year TST, 259 (24%) were tested and 34 (13%) were positive. Thirty converters (88%) started IPT.

CONCLUSIONS

In this cohort of PLWH in Brazil, TST conversion was high among those retested, but only 48% received a follow-up TST within 2 years.

Patterns of T and B cell responses to Mycobacterium tuberculosis membrane-associated antigens and their relationship with disease activity in rheumatoid arthritis patients with latent tuberculosis infection

This study was aimed at exploring whether latent tuberculosis infection (LTBI) contributes to the pathogenesis of immune-mediated inflammatory diseases in a TB endemic setting. We screened 198 rheumatoid arthritis (RA) patients with tuberculin skin test (TST) and studied 61 (median DAS28-ESR = 6.3) who were positive. Whole blood T cell proliferative responses to Mycobacterium tuberculosis (Mtb) membrane (MtM) antigens, including the latency-induced protein alpha crystallin (Acr), were determined by flow cytometry using Ki67 expression as the marker for nuclear proliferation. Serum antibody levels were determined by ELISA. Follow-up investigations (at 3–6, 9–12 and 15–18 months after baseline) were performed in 41 patients who were classified empirically as ‘high’ (HR-T/HR-B) or ‘low’ (LR-T/LR-B) responders based on their dynamic T cell or antibody responses. Significant correlations were seen between baseline T cell responses to MtM and Acr, and between IgG, IgA and IgM antibody responses to MtM. However, no correlation was seen between T and B cell responses. At all time points during the follow-up, T cell responses to both antigens (except for MtM at one point) were significantly higher in HR-T (n = 25) than LR-T (n = 16) patients. Levels of IgA and IgM (but not IgG) antibodies to MtM were also significantly higher in HR-B (n = 13) than LR-B (n = 28) at all time points. Importantly, HR-T patients exhibited significantly higher baseline and follow-up DAS28 scores than LR-T. Ten (of 61) patients had a history of TB and developed RA 6 years (median) after contracting TB. Three new TB cases (1 from TST-positive and 2 from TST-negative groups) emerged during the follow-up. Our results suggest that persistently elevated T cell responses to Mtb antigens may contribute to disease activity in RA.

The Magnitude of Interferon Gamma Release Assay Responses in Children With Household Tuberculosis Contact Is Associated With Tuberculosis Exposure and Disease Status

BACKGROUND

The clinical utility of the magnitude of interferon gamma (IFNγ) in response to mycobacterial antigens is unknown. We assessed the association between quantitative IFNγ response and degree of Mycobacterium tuberculosis exposure, infection and tuberculosis (TB) disease status in children.

METHODS

We completed cross-sectional analysis of children (≤15 years) exposed to an adult with bacteriologically confirmed TB, 2007-2012 in Cape Town, South Africa. IFNγ values were reported as concentrations and spot forming units for the QuantiFERON-TB Gold In-Tube (QFT-GIT) and T-SPOT.TB, respectively. Random-effects linear regression was used to investigate the relation between the M. tuberculosis contact score, clinical phenotype (TB diseased, infected, uninfected) and IFNγ▪response as outcome, adjusted for relevant covariates.

RESULTS

We analyzed data from 669 children (median age, 63 months; interquartile range, 33-108 months). A 1-unit increase in M. tuberculosis contact score was associated with an increase of IFNγ 0.60 international unit/mL (95% confidence interval [CI], 0.44-0.76 international unit/mL), and IFNγ spot forming unit 2 counts (95% CI, 1-3). IFNγ response was significantly lower among children with M. tuberculosis infection compared with children with TB disease (β = -1.42; 95% CI, -2.80 to -0.03) for the QFT-GIT, but not for the T-SPOT.TB. This association was strongest among children 2-5 years (β = -2.35 years; 95% CI, -4.28 to -0.42 years) and absent if <2 years.

CONCLUSIONS

The magnitude of IFNγ response correlated with the degree of recent M. tuberculosis exposure, measured by QFT-GIT and T-SPOT.TB, and was correlated with clinically relevant TB phenotypes using the QFT-GIT. IFNγ values are not only useful in estimating the risk of M. tuberculosis infection but may also support the diagnosis of TB disease in children.

DISCUSSION

The magnitude of IFNγ response correlated with the degree of recent M. tuberculosis exposure, measured by QFT-GIT and T-SPOT.TB, and was correlated with clinically relevant TB phenotypes using the QFT-GIT. IFNγ values are not only useful in estimating the risk of M. tuberculosis infection but may also support the diagnosis of TB disease in children.

Hemodialysis acutely altered interferon-gamma release assay test result and immune cell profile

Patients receiving hemodialysis (HD) are at risk of TB development. IGRA-positive patients showed significant decrease in quantitative IGRA result with alterations in CD3⁺CD4⁺CD45RO⁺, NK cell, and monocyte subsets immediately upon HD procedure. Our result suggested that the timing of IGRA testing is crucial in end-stage renal disease population.

Prevalence of Mycobacterium tuberculosis infection as measured by the QuantiFERON-TB Gold assay and ESAT-6 free IGRA among adolescents in Mwanza, Tanzania

Background

The prevalence of latent tuberculosis infection (LTBI) is vastly higher than that of tuberculosis (TB) disease and this enormous reservoir of individuals with LTBI impacts the global TB control strategy. Adolescents are at greatest risk of TB infection and are thus an ideal target population for a potential effective TB vaccine to be added to the current BCG programme as it could reduce the number of latent infections and consequently the number of adults with TB disease. However, LTBI rates are often unknown for this population. This study aims to estimate the magnitude of LTBI and to determine if Tanzanian adolescents would be a good population for a prevention of TB infection trial.

Methods

This was a descriptive cross-sectional study that recruited 193 adolescents aged 12 and 16 years from government schools and directly from the community in Mwanza Region, Tanzania. Socio-demographic characteristics were collected for all enrolled participants. Blood was drawn and tested using QuantiFERON-TB Gold In-Tube (QFT-GIT), and Early Secretory Antigenic Target-6–Free Interferon-gamma Release Assay (ESAT-6 free IGRA). Concordance between QFT-GIT and ESAT-6 free IGRA was evaluated using the McNemar’s test.

Results

Overall estimates of LTBI prevalence were 19.2% [95%CI, 14.1; 25.2] and 18.6% [95%CI, 13.6; 24.6] as measured by QFT-GIT IGRA and ESAT-6 free IGRA, respectively. The 16-year-old cohort had a higher LTBI prevalence (23.7% [95%CI, 16.1; 32.9]) as compared to 12-year-old cohort (14.6% [95%CI, 8.6; 22.7]) as measured by QFT-GIT IGRA. When measured by ESAT-6 Free IGRA, LTBI prevalence was 24.7% (95%CI, 16.9; 34.0) for the 16-year-old cohort and 12.5% (95%CI, 7.0; 20.3) among the 12-year-old cohort. According to both tests the prevalence of TB infection and the corresponding annual risk of tuberculosis infection (ARTI) and force of infection were high and increased with age. Of all enrolled participants, 97.4% had concordant results for QFT-GIT IGRA and ESAT-6 free IGRA (p = 0.65).

Conclusions

The prevalence of LTBI and the associated ARTI and force of infection among adolescents is high and increases with age in Mwanza Region. There was a high concordance between the QFT-GIT and the novel ESAT-6 free IGRA assays. These findings suggest Mwanza is a promising area to conduct novel TB vaccine research prevention of infection (POI) studies targeting adolescents.

QuantiFERON-TB and tuberculin skin test in patients with active tuberculosis: the experience of a single medium-sized Italian University Hospital

Interferon-γ releasing assays (IGRAs) are currently widely employed in the initial work up of Mycobacterium tuberculosis infection, as well as in suspected tuberculosis (TB). These assays are commonly utilized over the Tuberculin Skin Test (TST) in high resource and low TB burden settings, despite the unclear benefits shown in such contexts. The debate on the use of TST and IGRAs is of current interest also in Italy due to the increasing presence of immigrants from countries with a high incidence of TB and the rising attention of health care institutions to economic costs. The aim of this study was to compare QuantiFERON-TB (QFT) and TST results in active TB. We evaluated QFT results and TST reactions from 245 consecutive patients having both tests, registered among 411 patients admitted for TB at the Infectious Disease Clinic, Department of Medicine of the University of Perugia (Italy). We compared the rates of positive QFT and TST tests and noted no statistically significant differences overall or in relation to age, gender, HIV status and TB localization. Among foreign-born patients with confirmed TB, we observed a lower rate of positive TST results. The results of our study indicated that both QFT and TST can be used in the work up of TB having special attention when evaluating foreign-born patients.

Validation of Differentially Expressed Immune Biomarkers in Latent and Active Tuberculosis by Real-Time PCR

Tuberculosis (TB) remains a major global threat and diagnosis of active TB ((ATB) both extra-pulmonary (EPTB), pulmonary (PTB)) and latent TB (LTBI) infection remains challenging, particularly in high-burden countries which still rely heavily on conventional methods. Although molecular diagnostic methods are available, e.g., Cepheid GeneXpert, they are not universally available in all high TB burden countries. There is intense focus on immune biomarkers for use in TB diagnosis, which could provide alternative low-cost, rapid diagnostic solutions. In our previous gene expression studies, we identified peripheral blood leukocyte (PBL) mRNA biomarkers in a non-human primate TB aerosol-challenge model. Here, we describe a study to further validate select mRNA biomarkers from this prior study in new cohorts of patients and controls, as a prerequisite for further development. Whole blood mRNA was purified from ATB patients recruited in the UK and India, LTBI and two groups of controls from the UK (i) a low TB incidence region (CNTRLA) and (ii) individuals variably-domiciled in the UK and Asia ((CNTRLB), the latter TB high incidence regions). Seventy-two mRNA biomarker gene targets were analyzed by qPCR using the Roche Lightcycler 480 qPCR platform and data analyzed using GeneSpring™ 14.9 bioinformatics software. Differential expression of fifty-three biomarkers was confirmed between MTB infected, LTBI groups and controls, seventeen of which were significant using analysis of variance (ANOVA): CALCOCO2, CD52, GBP1, GBP2, GBP5, HLA-B, IFIT3, IFITM3, IRF1, LOC400759 (GBP1P1), NCF1C, PF4V1, SAMD9L, S100A11, TAF10, TAPBP, and TRIM25. These were analyzed using receiver operating characteristic (ROC) curve analysis. Single biomarkers and biomarker combinations were further assessed using simple arithmetic algorithms. Minimal combination biomarker panels were delineated for primary diagnosis of ATB (both PTB and EPTB), LTBI and identifying LTBI individuals at high risk of progression which showed good performance characteristics. These were assessed for suitability for progression against the standards for new TB diagnostic tests delineated in the published World Health Organization (WHO) technology product profiles (TPPs).

Phenotype Definition for "Resisters" to Mycobacterium tuberculosis Infection in the Literature-A Review and Recommendations

Tuberculosis (TB) remains a worldwide problem. Despite the high disease rate, not all who are infected with Mycobacterium Tuberculosis (Mtb) develop disease. Interferon-γ (IFN-γ) specific T cell immune assays such as Quantiferon and Elispot, as well as a skin hypersensitivity test, known as a tuberculin skin test, are widely used to infer infection. These assays measure immune conversion in response to Mtb. Some individuals measure persistently negative to immune conversion, despite high and prolonged exposure to Mtb. Increasing interest into this phenotype has led to multiple publications describing various aspects of these responses. However, there is a lack of a unified "resister" definition. A universal definition will improve cross study data comparisons and assist with future study design and planning. We review the current literature describing this phenotype and make recommendations for future studies.

Early Clearance of Mycobacterium tuberculosis: The INFECT Case Contact Cohort Study in Indonesia

BACKGROUND

Early clearance of Mycobacterium tuberculosis is the eradication of infection before an adaptive immune response develops. We aimed to identify host factors associated with early clearance.

METHODS

Indonesian household contacts patients with smear-positive tuberculosis (TB) had an interferon-γ release assay (IGRA) at baseline and 14 weeks later. Early clearance was defined as a persistently negative IGRA. Contact characteristics, exposure, and disease phenotype were assessed for association with a positive IGRA at each time point.

RESULTS

Of 1347 contacts of 462 TB cases, 780 (57.9%) were IGRA positive and 490 (36.3%) were IGRA negative. After 14 weeks, 116 of 445 (26.1%) initially negative contacts were IGRA converters; 317 (71.2%) remained persistently negative. BCG vaccination reduced the risk of a positive baseline IGRA (relative risk [RR], 0.89 [95% confidence interval {CI} .83-.97]; P = .01), and strongly reduced the risk of IGRA conversion (RR, 0.56 [95% CI, .40-.77]; P < .001). BCG protection decreased with increasing exposure (P = .05) and increasing age (P = .004). Risk of IGRA conversion was positively associated with hemoglobin concentration (P = .04).

CONCLUSIONS

A quarter of household TB case contacts were early clearers. Protection against M. tuberculosis infection was strongly associated with BCG vaccination. Lower protection from BCG with increasing M. tuberculosis exposure and age can inform vaccine development.

An observational study identifying highly tuberculosis-exposed, HIV-1-positive but persistently TB, tuberculin and IGRA negative persons with M. tuberculosis specific antibodies in Cape Town, South Africa

Background

Mycobacterium tuberculosis (Mtb) infection is inferred from positive results of T-cell immune conversion assays measuring Mtb-specific interferon gamma production or tuberculin skin test (TST) reactivity. Certain exposed individuals do not display T-cell immune conversion in these assays and do not develop TB. Here we report a hitherto unknown form of this phenotype: HIV-1-positive persistently TB, tuberculin and IGRA negative (HITTIN).

Methods

A community-based case-control design was used to systematically screen and identify adults living with HIV (HIV+), aged 35–60 years, who met stringent study criteria, and then longitudinally followed up for repeat IGRA and TST testing. Participants had no history of TB despite living in TB hyper-endemic environments in Cape Town, South Africa with a provincial incidence of 681/100,000. Mtb-specific antibodies were measured using ELISA and Luminex.

Findings

We identified 48/286 (17%) individuals who tested persistently negative for Mtb-specific T-cell immunoreactivity (three negative Quantiferon results and one TST = 0mm) over 206±154 days on average. Of these, 97·2% had documented CD4 counts<200 prior to antiretroviral therapy (ART). They had received ART for 7·0±3·0 years with a latest CD4 count of 505·8±191·4 cells/mm³. All HITTIN sent for further antibody testing (n=38) displayed  Mtb-specific antibody titres.

Interpretation

Immune reconstituted HIV+ persons can be persistently non-immunoreactive to TST and interferon-γ T-cell responses to Mtb, yet develop species-specific antibody responses. Exposure is evidenced by Mtb-specific antibody titres. Our identification of HIV+ individuals displaying a persisting lack of response to TST and IGRA T-cell immune conversion paves the way for future studies to investigate this phenotype in the context of HIV-infection that so far have received only scant attention.

Prevalence of LTBI among household contacts of sputum positive TB patients receiving DOTS chemotherapy

OBJECTIVES

1. To estimate the prevalence of latent tuberculosis infection among household contacts of sputum positive pulmonary tuberculosis patient receiving DOTS chemotherapy. 2. To evaluate the risk factors among household contacts of sputum positive pulmonary tuberculosis patient receiving DOTS chemotherapy. 3. To evaluate the degree of exposure among household contacts of sputum positive pulmonary tuberculosis patient receiving DOTS chemotherapy.

METHODS

This study was a cross sectional done among 220 household contacts of age 12 years and above (male and female) of the index sputum positive patients receiving DOTS. Mantoux skin test (Tuberculin Skin Test - TST) was administered by the principal investigator along with TST reading & final diagnosis. Chi-square test was done to find out the association.

RESULTS

Out of 220 household contacts tested, 43.6% (96) tested positive for latent TB (induration ≥10mm) with 95% CI ranging from 37% to 50%. The prevalence of latent TB among men and women are 35.6% and 49.2% respectively the difference between which is found to be statistically significant (p = 0.04). Odds Ratio of 5.5 was noted among study subjects who were diabetic (p = 0.018). Household contacts of index patients taking CAT II were at a higher risk than that of CAT I.

CONCLUSION

This study clearly shows the high prevalence of latent TB infection among household contacts of sputum positive patients receiving DOTS and so RNTCP should include them in IPT along with under 6 children. The household contacts who spend most time with the index case, who sleep close to them within 5 feet, female household contacts, students, diabetic household contacts are at a significantly higher risk than others.

Calvarial tuberculosis: two cases in children

Tuberculosis of the skull or calvarial tuberculosis (CTB) is rare. The literature until 2019 reported less than 60 cases of CTB in childhood. The authors describe two patients with CTB associated with other manifestations of TB, such as: spine and rib injuries, peripheral adenopathy, hepatic and splenic involvement who improved with chemotherapy. The patients were a four-year-old and an eight-year-old child, whose diagnoses were confirmed by histopathological, bacteriological or molecular investigation. Both were not infected with the human immunodeficiency virus (HIV) and did not need orthopedic treatment.

Tuberculosis infection in children visiting friends and relatives in countries with high incidence of tuberculosis: A study protocol

INTRODUCTION

Tuberculosis (TB) is a global infectious disease. In low-incidence countries, paediatric TB affects mostly immigrant children and children of immigrants. We hypothesize that these children are at risk of exposure to Mycobacterium tuberculosis when they travel to the country of origin of their parents to visit friends and relatives (VFR). In this study, we aim to estimate the incidence rate and risk factors associated to latent tuberculosis infection (LTBI) and TB in VFR children.

METHODS AND ANALYSIS

A prospective study will be carried out in collaboration with 21 primary health care centres (PCC) and 5 hospitals in Catalonia, Spain. The study participants are children under 15 years of age, either immigrant themselves or born to immigrant parents, who travel to countries with high incidence of TB (≥ 40 cases/100,000 inhabitants). A sample size of 492 children was calculated. Participants will be recruited before traveling, either during a visit to a travel clinic or to their PCC, where a questionnaire including sociodemographic, epidemiological and clinical data will be completed, and a tuberculin skin test (TST) will be performed and read after 48 to 72 hours; patients with a positive TST at baseline will be excluded. A visit will be scheduled eight to twelve-weeks after their return to perform a TST and a QuantiFERON-TB Gold Plus test. The incidence rate of LTBI will be estimated per individual/month and person/year per country visited, and also by age-group.

ETHICS AND DISSEMINATION

The study protocol was approved by the Clinical Research Ethics Committee of the Hospital Universitari Mútua Terrassa (code 02/16) and the Clinical Research Ethics Committee of the Fundació Institut Universitari per a la Recerca a l'Atenció Primària de Salut Jordi Gol i Gurina (code P16/094). Articles will be published in indexed scientific journals.

TRIAL REGISTRATION

Clinical-Trials.gov: NCT04236765.

Comparison of the change in QuantiFERON-TB Gold Plus and QuantiFERON-TB Gold In-Tube results after preventive therapy for latent tuberculosis infection

Background

We investigated changes in the interferon-γ levels before and after treatment of latent tuberculosis infection (LTBI) using QuantiFERON-TB Gold Plus (QFT-Plus) and QuantiFERON-TB Gold In-Tube (QFT-GIT) assays. The objective was to assess whether QFT-Plus could serve as a biomarker of LTBI treatment response.

Methods

We prospectively enrolled 44 individuals whose baseline QFT-GIT and QFT-Plus showed positive results at a tertiary referral center in South Korea between March 2017 and March 2018. The results of the QFT-Plus assay were defined as positive if either or both of the antigen tubes (TB1 and/or TB2) were positive. After LTBI treatment, both tests were repeated.

Results

The mean age of the participants was 47.6 years. The QFT-GIT and QFT-Plus assays revealed positive results in 42/44 (95.5%) and 41/44 (93.2%) participants after LTBI treatment, showing overall agreement of 93.2%, with a Cohen’s kappa value of 0.37 (fair agreement). The differences between pre- and post-LTBI treatment interferon-γ levels were measured using the QFT-GIT and QFT-Plus assays. No significant differences were noted among the 3 values: the median difference in interferon-γ value with QFT-GIT, QFT-Plus TB1, and QFT-Plus TB2 was 0.211 IU/mL (IQR, −0.337–3.347), 0.025 IU/mL (IQR, −0.338–1.368), and 0.180 IU/mL (IQR, −0.490–2.278), respectively (P = 0.401).

Conclusion

The change in interferon-γ levels before and after LTBI treatment measured using the QFT-Plus assay showed a similar trend to that of the QFT-GIT assay. Considering that the QFT-GIT assay is not a useful biomarker of LTBI treatment response, QFT-Plus also appears not to be useful for this purpose.