A comparison of interferon-γ and IP-10 for the diagnosis of tuberculosis

Interferon (IFN)-gamma (γ) inducible protein 10 (IP-10) in the diagnosis of latent and active tuberculosis in Bacille Calmette Guerin (BCG)-vaccinated pediatric population

BACKGROUND

Accurate diagnosis of tuberculosis (TB) in children continues to be challenging, primarily due to the low bacterial load characteristic of the disease and the obstacles in collecting sputum samples. Furthermore, detecting cases of latent Mycobacterium tuberculosis (M.tb) infection (LTBI) that have a high risk of progressing to active TB disease remains a significant diagnostic hurdle.

OBJECTIVE

The study explored the utility of interferon-gamma (IFN-γ) inducible protein 10 (IP-10) for diagnosing latent and active M.tb infections among children vaccinated with the Bacille Calmette-Guerin (BCG) vaccine. The research specifically assessed IP-10 levels in serum, urine, and QuantiFERON-TB Gold Plus (QFT) cultures stimulated with M.tb antigens to determine if IP-10 could be a useful diagnostic marker for pediatric tuberculosis, either alongside or as an alternative to IFN-γ.

RESULTS

Both urine and QFT cultures stimulated with M.tb antigens showed significantly higher IP-10 levels in individuals with active TB or latent TB infection (LTBI) when compared to those uninfected by M.tb but with nonmycobacterial pneumonia (NMP) and healthy controls (HC). Similarly, IFN-γ levels in M.tb-stimulated QFT cultures were significantly higher in the TB and LTBI groups compared to the NMP and HC groups. Notably, the study found a significant difference in IFN-γ levels between the TB and LTBI groups in the QFT cultures, a distinction not observed for IP-10 concentrations. Serum levels of IP-10 and IFN-γ did not significantly vary across the study cohorts.

CONCLUSIONS

IP-10 might be a viable alternative biomarker to IFN-γ for identifying M.tb infection in BCG-vaccinated children, although it cannot distinguish between latent and active TB cases. This highlights the potential of IP-10 in improving TB diagnosis among children, addressing the challenges posed by the paucibacillary nature of pediatric TB, but also underscores the need for further research to refine diagnostic approaches for distinguishing between latent and active TB infections.

Utility of interferon-gamma releasing assay for the diagnosis of active tuberculosis in children: A systematic review and meta-analysis

INTRODUCTION

The accurate diagnosis of tuberculosis (TB) in children is essential for its effective management and control. Reliable diagnostic tools that are currently available for identifying TB infection include the in vivo tuberculosis skin test (TST) and ex vivo interferon-gamma release assays (IGRAs). This systematic review and meta-analysis aimed to evaluate the diagnostic accuracy of IGRAs in children.

METHODS

Of the 768 screened studies, 47 met the eligibility criteria. Data from 9065 patients, including 1086 (12.0 %) with confirmed TB, were included in the analysis. The overall quality of the included studies, assessed using the Quality Assessment of Diagnostic Accuracy Studies-2 tool, was unclear.

RESULTS

The calculated pooled sensitivity and specificity of IGRAs in children were 0.85 (95 % confidence interval [CI]: 0.79-0.89) and 0.94 (95 % CI: 0.88-0.97), respectively. Subpopulation analysis revealed that the sensitivities and specificities were as follows: QuantiFERON tests: 0.83 (95 % CI: 0.74-0.89) and 0.93 (95 % CI: 0.87-0.96), T-SPOT: 0.87 (95 % CI: 0.79-0.91) and 0.99 (95 % CI: 0.85-1.00), IGRAs in children under 15 years: 0.77 (95 % CI: 0.43-0.94) and 0.96 (95 % CI: 0.84-0.97), and IGRAs in children under 5 years: 0.85 (95 % CI: 0.52-0.97) and 0.94 (95 % CI: 0.90-0.99), respectively.

CONCLUSIONS

This study demonstrated that the sensitivity and specificity of the IGRAs in children were moderate and high, respectively. Therefore, the IGRAs may be useful for detecting TB infection in children.

CLINICAL TRIAL REGISTRATION

The review protocol was prospectively registered with the University Hospital Medical Information Network Clinical Trials Registry (UMIN000046737).

IP-10 for the Diagnosis and Treatment Monitoring of Tuberculosis in Children

PURPOSE

To determine the utility of interferon-gamma-inducible protein 10 (IP-10) for identifying active tuberculosis (TB) and TB infection (TBI) in children in BCG-vaccinated populations, establish its diagnostic performance characteristics, and evaluate changes in IP-10 level during anti-TB chemotherapy.

METHODS

Concentrations of IP-10 and IFN-γ were measured in QuantiFERON-TB Gold (QFT) supernatants in children with suspected TB or due to recent TB contact. A total of 225 children were investigated: 33 with active TB, 48 with TBI, 83 TB contacts, 20 with suspected TB but other final diagnoses, and 41 controls. In 60 children, cytokine responses were evaluated at a follow-up visit after 2 months of anti-TB treatment.

RESULTS

IP-10 expression was significantly higher in infected children (active TB and TBI cases) than in uninfected individuals. IP-10 proved effective in identifying TB infection at its optimal cut-off (>1084.5 pg/mL) but was incapable of differentiating between children with active TB and TBI. Combining IP-10 and IFN-γ increased the QFT sensitivity. IP-10 but not IFN-γ decreased significantly during anti-TB treatment in children with active TB (p = 0.003).

CONCLUSION

IP-10 identifies TB infection and declines during anti-TB chemotherapy in children. Incorporating IP-10 into new immunodiagnostic assays could improve TB diagnosis and allow for treatment monitoring.

Diagnostic Value of IP-10 Level in Plasma and Bronchoalveolar Lavage Fluid in Children with Tuberculosis and Other Lung Diseases

Objectives: IP-10 has been proposed as a new diagnostic biomarker for Mycobacterium tuberculosis infection (MTBI). However, data on IP-10 concentration in bronchoalveolar lavage fluid (BALF) for pediatric tuberculosis are lacking. Aim: To determine IP-10 levels in unstimulated BALF and plasma in children with and without MTBI. Methods: IP-10 concentrations in BALF and plasma were measured in children hospitalized with suspected tuberculosis or other respiratory disease and scheduled for bronchoscopy. Thirty-five children were enrolled: 13 with suspected tuberculosis and 22 controls. The association between IP-10 and age was examined. Results: The IP-10 expression was increased in BALF compared to plasma (p = 0.008). We noticed higher BALF IP-10 levels in children with asthma, interstitial lung disease, and lung anomaly than in children with MTBI and other respiratory tract infections, but the differences were statistically insignificant. There was a moderate correlation between plasma and BALF IP-10 concentrations (rs = 0.46, p = 0.018). No correlation between IP-10 level and age was detected. Conclusions: IP-10 is detectable in unstimulated BALF in children with respiratory diseases, reaches higher concentrations in unstimulated BALF vs plasma, and does not correlate with age. However, it could not discriminate MTBI from other respiratory diseases.

Screening tests for active pulmonary tuberculosis in children

BACKGROUND

Globally, children under 15 years represent approximately 12% of new tuberculosis cases, but 16% of the estimated 1.4 million deaths. This higher share of mortality highlights the urgent need to develop strategies to improve case detection in this age group and identify children without tuberculosis disease who should be considered for tuberculosis preventive treatment. One such strategy is systematic screening for tuberculosis in high-risk groups.

OBJECTIVES

To estimate the sensitivity and specificity of the presence of one or more tuberculosis symptoms, or symptom combinations; chest radiography (CXR); Xpert MTB/RIF; Xpert Ultra; and combinations of these as screening tests for detecting active pulmonary childhood tuberculosis in the following groups. - Tuberculosis contacts, including household contacts, school contacts, and other close contacts of a person with infectious tuberculosis. - Children living with HIV. - Children with pneumonia. - Other risk groups (e.g. children with a history of previous tuberculosis, malnourished children). - Children in the general population in high tuberculosis burden settings.

SEARCH METHODS

We searched six databases, including the Cochrane Central Register of Controlled Trials, MEDLINE, and Embase, on 14 February 2020 without language restrictions and contacted researchers in the field.

SELECTION CRITERIA

Cross-sectional and cohort studies where at least 75% of children were aged under 15 years. Studies were eligible if conducted for screening rather than diagnosing tuberculosis. Reference standards were microbiological (MRS) and composite reference standard (CRS), which may incorporate symptoms and CXR.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed study quality using QUADAS-2. We consolidated symptom screens across included studies into groups that used similar combinations of symptoms as follows: one or more of cough, fever, or poor weight gain and one or more of cough, fever, or decreased playfulness. For combination of symptoms, a positive screen was the presence of one or more than one symptom. We used a bivariate model to estimate pooled sensitivity and specificity with 95% confidence intervals (CIs) and performed analyses separately by reference standard. We assessed certainty of evidence using GRADE.

MAIN RESULTS

Nineteen studies assessed the following screens: one symptom (15 studies, 10,097 participants); combinations of symptoms (12 studies, 29,889 participants); CXR (10 studies, 7146 participants); and Xpert MTB/RIF (2 studies, 787 participants). Several studies assessed more than one screening test. No studies assessed Xpert Ultra. For 16 studies (84%), risk of bias for the reference standard domain was unclear owing to concern about incorporation bias. Across other quality domains, risk of bias was generally low. Symptom screen (verified by CRS) One or more of cough, fever, or poor weight gain in tuberculosis contacts (4 studies, tuberculosis prevalence 2% to 13%): pooled sensitivity was 89% (95% CI 52% to 98%; 113 participants; low-certainty evidence) and pooled specificity was 69% (95% CI 51% to 83%; 2582 participants; low-certainty evidence). Of 1000 children where 50 have pulmonary tuberculosis, 339 would be screen-positive, of whom 294 (87%) would not have pulmonary tuberculosis (false positives); 661 would be screen-negative, of whom five (1%) would have pulmonary tuberculosis (false negatives). One or more of cough, fever, or decreased playfulness in children aged under five years, inpatient or outpatient (3 studies, tuberculosis prevalence 3% to 13%): sensitivity ranged from 64% to 76% (106 participants; moderate-certainty evidence) and specificity from 37% to 77% (2339 participants; low-certainty evidence). Of 1000 children where 50 have pulmonary tuberculosis, 251 to 636 would be screen-positive, of whom 219 to 598 (87% to 94%) would not have pulmonary tuberculosis; 364 to 749 would be screen-negative, of whom 12 to 18 (2% to 3%) would have pulmonary tuberculosis. One or more of cough, fever, poor weight gain, or tuberculosis close contact (World Health Organization four-symptom screen) in children living with HIV, outpatient (2 studies, tuberculosis prevalence 3% and 8%): pooled sensitivity was 61% (95% CI 58% to 64%; 1219 screens; moderate-certainty evidence) and pooled specificity was 94% (95% CI 86% to 98%; 201,916 screens; low-certainty evidence). Of 1000 symptom screens where 50 of the screens are on children with pulmonary tuberculosis, 88 would be screen-positive, of which 57 (65%) would be on children who do not have pulmonary tuberculosis; 912 would be screen-negative, of which 19 (2%) would be on children who have pulmonary tuberculosis. CXR (verified by CRS) CXR with any abnormality in tuberculosis contacts (8 studies, tuberculosis prevalence 2% to 25%): pooled sensitivity was 87% (95% CI 75% to 93%; 232 participants; low-certainty evidence) and pooled specificity was 99% (95% CI 68% to 100%; 3281 participants; low-certainty evidence). Of 1000 children, where 50 have pulmonary tuberculosis, 63 would be screen-positive, of whom 19 (30%) would not have pulmonary tuberculosis; 937 would be screen-negative, of whom 6 (1%) would have pulmonary tuberculosis. Xpert MTB/RIF (verified by MRS) Xpert MTB/RIF, inpatient or outpatient (2 studies, tuberculosis prevalence 1% and 4%): sensitivity was 43% and 100% (16 participants; very low-certainty evidence) and specificity was 99% and 100% (771 participants; moderate-certainty evidence). Of 1000 children, where 50 have pulmonary tuberculosis, 31 to 69 would be Xpert MTB/RIF-positive, of whom 9 to 19 (28% to 29%) would not have pulmonary tuberculosis; 969 to 931 would be Xpert MTB/RIF-negative, of whom 0 to 28 (0% to 3%) would have tuberculosis. Studies often assessed more symptoms than those included in the index test and symptom definitions varied. These differences complicated data aggregation and may have influenced accuracy estimates. Both symptoms and CXR formed part of the CRS (incorporation bias), which may have led to overestimation of sensitivity and specificity.

AUTHORS' CONCLUSIONS

We found that in children who are tuberculosis contacts or living with HIV, screening tests using symptoms or CXR may be useful, but our review is limited by design issues with the index test and incorporation bias in the reference standard. For Xpert MTB/RIF, we found insufficient evidence regarding screening accuracy. Prospective evaluations of screening tests for tuberculosis in children will help clarify their use. In the meantime, screening strategies need to be pragmatic to address the persistent gaps in prevention and case detection that exist in resource-limited settings.

Accumulate evidence for IP-10 in diagnosing pulmonary tuberculosis

BACKGROUNDS

Pulmonary tuberculosis (PTB) is a major health and economic burden. Accurate PTB detection is an important step to eliminating TB globally. Interferon gamma-induced protein 10 (IP-10) has been reported as a potential diagnostic marker for PTB since 2007. In this study, a meta-analysis approach was used to assess diagnostic value of IP-10 for PTB.

METHODS

Web of Science, PubMed, the Cochrane Library, and Embase databases were searched for studies published in English up to February 2019. The pooled sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR), the area under the curve (AUC) and hierarchical summary receiver operating characteristic (HSROC) curve were estimated by the HSROC model and random effect model.

RESULTS

Eighteen studies including 2836 total participants met our inclusion criteria. The pooled sensitivity, specificity, PLR, and NLR of IP-10 for PTB detection were 86, 88%, 7.00, and 0.16, respectively. The pooled DOR was 43.01, indicating a very powerful discriminatory ability of IP-10. The AUC was 0.93 (95% CI: 0.91-0.95), showed the accuracy of IP-10 was good. Meta-regression showed that there was no heterogeneity with respect to TB burden, study design type, age, IP-10 assay method, IP-10 condition and HIV-infection status.

CONCLUSIONS

Our results showed that IP-10 is a promising marker for differentiating PTB from non-TB.

Diagnostic accuracy of interferon-gamma-induced protein 10 for differentiating active tuberculosis from latent tuberculosis: A meta-analysis

Tuberculin skin test and interferon-gamma release assay are not good at differentiating active tuberculosis from latent tuberculosis. Interferon-gamma-induced protein 10 (IP-10) has been widely used to detect tuberculosis infection. However, its values of discriminating active and latent tuberculosis is unknown. To estimate the diagnostic potential of IP-10 for differentiating active tuberculosis from latent tuberculosis, we searched PubMed, Web of Science, Embase, the Cochrane Library, CNKI, Wanfang, VIP and CBM databases. Eleven studies, accounting for 706 participants (853 samples), were included. We used a bivariate diagnostic random-effects model to conduct the primary data. The overall pooled sensitivity, specificity, negative likelihood rate, positive likelihood rate, diagnostic odds ratio and area under the summary receiver operating characteristic curve were 0.72 (95% CI: 0.68-0.76), 0.83 (95% CI: 0.79-0.87), 0.32 (95% CI: 0.22-0.46), 4.63 (95% CI: 2.79-7.69), 17.86 (95% CI: 2.89-38.49) and 0.8638, respectively. This study shows that IP-10 is a potential biomarker for differentiating active tuberculosis from latent tuberculosis.

IP-10 for the diagnosis of tuberculosis in children: Protocol for a systematic review and meta-analysis

BACKGROUND

Tuberculosis (TB) is a highly contagious and chronic disease. The microbiological examination to confirm children TB disease are limited due to paucibacillary Mycobacterium, specimens and detecting facilities. Considering these limitations in diagnosing children TB, new and reliable methods that detect children TB should be developed. Recently, Interferon gamma-induced protein 10 (IP-10) has been identified as a sensitive parameter in detecting children TB. The present study aims to synthesis and analysis the diagnostic value of IP-10 for children TB.

METHODS

We will search PubMed, Embase, the Cochrane Library, Web of Science, Chinese National Knowledge Infrastructure, and Chinese Biological Medical Databases. We will search relevant citations up to May 2019. The quality of individual study will be assessed using the Quality Assessment of Diagnostic Accuracy Studies tool-2 (QUADAS-2). Stata 14.0 software will be used to calculate the pooled sensitivity, pooled specificity, pooled positive likelihood ratio (PLR), pooled negative likelihood ratio (NLR), pooled diagnostic odds ratio (DOR), pre-test probability, post-test probability and the hierarchical summary receiver operating characteristic (HSROC) curve.

RESULTS

The results of this study will be published in a peer-reviewed journal.

DISCUSSION

The evidence will indicate that IP-10 test is an alternative immunological test in detecting children TB. This is a protocol of systematic review and meta-analysis, so the ethical approval and patient consent are not required.

PROTOCOL REGISTRATION NUMBER

CRD42019129743.

Risk Factors for Indeterminate Interferon-Gamma Release Assay for the Diagnosis of Tuberculosis in Children-A Systematic Review and Meta-Analysis

Background: Interferon-gamma release assays (IGRA) are well-established immunodiagnostic tests for tuberculosis (TB) in adults. In children these tests are associated with higher rates of false-negative and indeterminate results. Age is presumed to be one factor influencing cytokine release and therefore test performance. The aim of this study was to systematically review factors associated with indeterminate IGRA results in pediatric patients. Methods: Systematic literature review guided by the preferred reporting items for systematic reviews and meta-analyses (PRISMA) searching PubMed, EMBASE, and Web of Science. Studies reporting results of at least one commercially available IGRA (QuantiFERON-TB, T-SPOT.TB) in pediatric patient groups were included. Random effects meta-analysis was used to assess proportions of indeterminate IGRA results. Heterogeneity was assessed using the I² value. Risk differences were calculated for studies comparing QuantiFERON-TB and T-SPOT.TB in the same study. Meta-regression was used to further explore the influence of study level variables on heterogeneity. Results: Of 1,293 articles screened, 133 studies were included in the final analysis. These assessed QuantiFERON-TB only in 77.4% (103/133), QuantiFERON-TB and T-SPOT.TB in 15.8% (21/133), and T-SPOT.TB only in 6.8% (9/133) resulting in 155 datasets including 107,418 participants. Overall 4% of IGRA results were indeterminate, and T-SPOT.TB (0.03, 95% CI 0.02-0.05) and QuantiFERON-TB assays (0.05, 95% CI 0.04-0.06) showed similar proportions of indeterminate results; pooled risk difference was-0.01 (95% CI -0.03 to 0.00). Significant differences with lower proportions of indeterminate assays with T-SPOT.TB compared to QuantiFERON-TB were only seen in subgroup analyses of studies performed in Africa and in non-HIV-infected immunocompromised patients. Meta-regression confirmed lower proportions of indeterminate results for T-SPOT.TB compared to QuantiFERON-TB only among studies that reported results from non-HIV-infected immunocompromised patients (p < 0.001). Conclusion: On average indeterminate IGRA results occur in 1 in 25 tests performed. Overall, there was no difference in the proportion of indeterminate results between both commercial assays. However, our findings suggest that in patients in Africa and/or patients with immunocompromising conditions other than HIV infection the T-SPOT.TB assay appears to produce fewer indeterminate results.

Performance of the QuantiFERON-TB Gold Assay Among HIV-infected Children With Active Tuberculosis in France

BACKGROUND

Data regarding the use of QuantiFERON to assist the diagnosis of active tuberculosis (TB) in HIV-infected children are limited, especially in countries with low incidence of TB/HIV coinfection.

METHODS

QuantiFERON results were analyzed in 63 HIV-infected children who presented to our hospital in Paris, France. Seventeen HIV-uninfected children with active TB (4 culture-confirmed) were included for comparison.

RESULTS

The 63 HIV-infected children (median age: 11 yr) had 113 QuantiFERON tests. Thirty-four (54%) were born in sub-Saharan Africa. Vertical HIV transmission was documented for 50 of 52 (96%) and stage III HIV-infection for 30 of 50 children (60%). Over the study period, active TB was diagnosed in 7 of 63 HIV-infected children (3 culture-confirmed). Additional ongoing or previous opportunistic infections were present in 4 of 7. QuantiFERON results were positive in 2 of 7 HIV-infected children with active TB (sensitivity: 29%) and 16 of 17 HIV-uninfected children with active TB (sensitivity: 94%). At initial QuantiFERON testing of the 63 HIV-infected children, 8 (13%) had positive results (1, active TB; 5, latent TB; 2, previous TB) and 51 (81%) had negative results. Of 33 children with repeat testing after an initially positive or negative result, the only change was one conversion from a negative to a positive result at the onset of active TB. The 4 children (6%) with indeterminate quantiFERON results had a concomitant opportunistic infection. Results of repeat testing after clinical stabilization were negative in all 4.

CONCLUSIONS

QuantiFERON testing performed poorly for active TB diagnosis in this series of children with advanced HIV infection.

Unique Chemokine Profiles of Lung Tissues Distinguish Post-chemotherapeutic Persistent and Chronic Tuberculosis in a Mouse Model

There is a substantial need for biomarkers to distinguish latent stage from active Mycobacterium tuberculosis infections, for predicting disease progression. To induce the reactivation of tuberculosis, we present a new experimental animal model modified based on the previous model established by our group. In the new model, the reactivation of tuberculosis is induced without administration of immunosuppressive agents, which might disturb immune responses. To identify the immunological status of the persistent and chronic stages, we analyzed immunological genes in lung tissues from mice infected with M. tuberculosis. Gene expression was screened using cDNA microarray analysis and confirmed by quantitative RT-PCR. Based on the cDNA microarray results, 11 candidate cytokines genes, which were obviously up-regulated during the chronic stage compared with those during the persistent stage, were selected and clustered into three groups: (1) chemokine genes, except those of monocyte chemoattractant proteins (MCPs; CXCL9, CXCL10, CXCL11, CCL5, CCL19); (2) MCP genes (CCL2, CCL7, CCL8, CCL12); and (3) TNF and IFN-γ genes. Results from the cDNA microarray and quantitative RT-PCR analyses revealed that the mRNA expression of the selected cytokine genes was significantly higher in lung tissues of the chronic stage than of the persistent stage. Three chemokines (CCL5, CCL19, and CXCL9) and three MCPs (CCL7, CCL2, and CCL12) were noticeably increased in the chronic stage compared with the persistent stage by cDNA microarray (p < 0.01, except CCL12) or RT-PCR (p < 0.01). Therefore, these six significantly increased cytokines in lung tissue from the mouse tuberculosis model might be candidates for biomarkers to distinguish the two disease stages. This information can be combined with already reported potential biomarkers to construct a network of more efficient tuberculosis markers.

Added Value of IP-10 as a Read-Out of Mycobacterium tuberculosis: Specific Immunity in Young Children

We have explored the added value of interferon-γ (IFNγ)-inducible protein 10 as a read-out of Mycobacterium tuberculosis-specific immunity in young Indian children, where the sensitivity of the IFNγ release assays for tuberculosis is poor. Reduced frequency of indeterminate results and an increased sensitivity for tuberculosis suggest a potential for fewer missed cases with a combined IFNγ/inducible protein 10 read-out in a 4th generation IFNγ release assays.

Tuberculosis in infants: a retrospective study in China

To describe the demographics, clinical characteristics and microbiologic findings of infant (≤2 years old) tuberculosis (TB) in a high TB burden country. Between Feb, 2007 and Jun, 2015, 115 TB infants who admitted to our hospital were enrolled in the study. Their clinicopathological characteristics were reviewed and analyzed. The mean age was 10.1 ± 7.4 (SD) months, and 84 of 115 infants (73.0 %) were males. 23 patients (20.0 %) had isolated pulmonary TB, 18 patients (15.7 %) had pulmonary and extrapulmonary TB (EPTB), the remaining 74 patients (64.4 %) had exclusively EPTB. The most common site of EPTB was lymph node (n = 61), 54 cases were left axillary lymph node involvement. 49 of 51 patients (96.1 %) were validated by pathological examination, 5 of 57 patients (8.8 %) were positive on acid fast bacilli smear, and 27 of 103 patients (26.2 %) were confirmed by mycobacterial culture. 29 of 59 patients (49.2 %) were PPD positive, 14 of 30 patients (46.7 %) were T-SPOT.TB positive. The most common complaints of patients were lymph node swelling (53.0 %), fever (36.5 %), cough (28.7 %) and dyspnea (10.4 %). There was significant difference in the time before hospital admission among different types of tuberculosis (P < 0.01), fever was also a factor influencing the time (P < 0.05). In infants, the sensitivities of routine TB tests were low and emphasize the need for improved diagnostics; EPTB was more common than pulmonary TB, tuberculous lymphadenitis constituted a high proportion of EPTB; there appears to be an association between the incidence of axillary lymph node TB and BCG vaccination among infants in China.

Mapping of Mycobacterium tuberculosis Complex Genetic Diversity Profiles in Tanzania and Other African Countries

The aim of this study was to assess and characterize Mycobacterium tuberculosis complex (MTBC) genotypic diversity in Tanzania, as well as in neighbouring East and other several African countries. We used spoligotyping to identify a total of 293 M. tuberculosis clinical isolates (one isolate per patient) collected in the Bunda, Dar es Salaam, Ngorongoro and Serengeti areas in Tanzania. The results were compared with results in the SITVIT2 international database of the Pasteur Institute of Guadeloupe. Genotyping and phylogeographical analyses highlighted the predominance of the CAS, T, EAI, and LAM MTBC lineages in Tanzania. The three most frequent Spoligotype International Types (SITs) were: SIT21/CAS1-Kili (n = 76; 25.94%), SIT59/LAM11-ZWE (n = 22; 7.51%), and SIT126/EAI5 tentatively reclassified as EAI3-TZA (n = 18; 6.14%). Furthermore, three SITs were newly created in this study (SIT4056/EAI5 n = 2, SIT4057/T1 n = 1, and SIT4058/EAI5 n = 1). We noted that the East-African-Indian (EAI) lineage was more predominant in Bunda, the Manu lineage was more common among strains isolated in Ngorongoro, and the Central-Asian (CAS) lineage was more predominant in Dar es Salaam (p-value<0.0001). No statistically significant differences were noted when comparing HIV status of patients vs. major lineages (p-value = 0.103). However, when grouping lineages as Principal Genetic Groups (PGG), we noticed that PGG2/3 group (Haarlem, LAM, S, T, and X) was more associated with HIV-positive patients as compared to PGG1 group (Beijing, CAS, EAI, and Manu) (p-value = 0.03). This study provided mapping of MTBC genetic diversity in Tanzania (containing information on isolates from different cities) and neighbouring East African and other several African countries highlighting differences as regards to MTBC genotypic distribution between Tanzania and other African countries. This work also allowed underlining of spoligotyping patterns tentatively grouped within the newly designated EAI3-TZA lineage (remarkable by absence of spacers 2 and 3, and represented by SIT126) which seems to be specific to Tanzania. However, further genotyping information would be needed to confirm this specificity.

The Use of Interferon Gamma Inducible Protein 10 as a Potential Biomarker in the Diagnosis of Latent Tuberculosis Infection in Uganda

Background

In the absence of a gold standard for the diagnosis of latent tuberculosis (TB) infection (LTBI), the current tests available for the diagnosis of LTBI are limited by their inability to differentiate between LTBI and active TB disease. We investigated IP-10 as a potential biomarker for LTBI among household contacts exposed to sputum positive active TB cases.

Methods

Active TB cases and contacts were recruited into a cohort with six months’ follow-up. Contacts were tested for LTBI using QuantiFERON^®-TB Gold In-Tube (QFN) assay and the tuberculin skin test (TST). Baseline supernatants from the QFN assay of 237 contacts and 102 active TB cases were analysed for Mycobacterium tuberculosis (MTB) specific and mitogen specific IP-10 responses.

Results

Contacts with LTBI (QFN⁺TST⁺) had the highest MTB specific IP-10 responses at baseline, compared to uninfected contacts (QFN^-TST^-) p<0.0001; and active cases, p = 0.01. Using a cut-off of 8,239 pg/ml, MTB specific IP-10 was able to diagnose LTBI with a sensitivity of 87.1% (95% CI, 76.2–94.3) and specificity of 90.9% (95% CI, 81.3–96.6). MTB specific to mitogen specific IP-10 ratio was higher in HIV negative active TB cases, compared to HIV negative latently infected contacts, p = 0.0004. Concentrations of MTB specific IP-10 were higher in contacts with TST conversion (negative at baseline, positive at 6-months) than in those that were persistently TST negative, p = 0.001.

Conclusion

IP-10 performed well in differentiating contacts with either latent or active TB from those who were uninfected but was not able to differentiate LTBI from active disease except when MTB specific to mitogen specific ratios were used in HIV negative adults. In addition, IP-10 had the potential to diagnose ‘recent TB infection’ in persons classified as having LTBI using the TST. Such individuals with strong IP-10 responses would likely benefit from chemoprophylaxis.

New Diagnostics for Childhood Tuberculosis

The challenge of diagnosing childhood tuberculosis (TB) results from its paucibacillary nature and the difficulties of sputum collection in children. Mycobacterial culture, the diagnostic gold standard, provides microbiological confirmation in only 30% to 40% of childhood pulmonary TB cases and takes up to 6 weeks to result. Conventional drug susceptibility testing requires an additional 2 to 4 weeks after culture confirmation. In response to the low sensitivity and long wait time of the traditional diagnostic approach, many new assays have been developed. These new tools have shortened time to result; however, none of them offer greater sensitivity than culture.

Validity of antibodies in lymphocyte supernatant in diagnosing tuberculosis in severely malnourished children presenting with pneumonia

Background

The diagnosis of tuberculosis (TB) in young children can be challenging, especially in severely malnourished children. There is a critical need for improved diagnostics for children. Thus, we sought to evaluate the performance of a technique that measures antibodies in lymphocyte supernatant (ALS) for the diagnosis of TB in severely malnourished children presenting with suspected pneumonia.

Methods

Children less than 5 years with severe acute malnutrition and radiological features of pneumonia admitted to the Dhaka Hospital of International Centre for Diarrhoeal Disease Research, Bangladesh, were enrolled consecutively following informed written consent. In addition to clinical and radiological assessment, samples taken for TB diagnosis included gastric lavage fluid and induced sputum for microbiological confirmation. ALS was measured from venous blood, and results were evaluated in children classified as “confirmed”, “non-confirmed TB” or “not TB”.

Results

Among 224 children who had ALS analysis, 12 (5.4%) children had microbiologically “confirmed TB”, a further 41 (18%) had clinically diagnosed “non-confirmed TB” and the remaining 168 (75%) were considered not to have TB. ALS was positive in 89 (40%) and negative in 85 (39%) of children, with a large number (47 or 21%) reported as “borderline”. These proportions were similar between the three diagnostic groups. The sensitivity and specificity of ALS when comparing “Confirmed TB” to “Not TB” was only 67% (95% CI: 31–91%) and 51% (95% CI: 42–60%), respectively.

Conclusions and Significance

Our data suggest that ALS is not sufficiently accurate to improve the diagnosis of TB in children with severe malnutrition.

What steps do we need to take to improve diagnosis of tuberculosis in children?

Tuberculosis still represents a big global public health challenge. The diagnosis of tuberculosis and the differentiation between active and latent tuberculosis remain difficult, particularly in childhood, because of the lack of a gold standard test for diagnosis. In the last decade, novel diagnostic assays have been developed. Among immunologic tests, new assays based on the measurement of different cytokines released by specific T cells in response to Mycobacterium tuberculosis antigens, other than INF-γ, have been investigated. Promising results rely on nucleic acid amplification techniques, also able to detect drugs resistance. Innovative research fields studied the modifications of CD27 expression in T cells as well as different host gene expression in response to M. tuberculosis. Further studies are needed to assess the diagnostic value and the accuracy of these new assays.