An Update on the Diagnosis of Tuberculosis Infection

Transcriptional profiling of human peripheral blood mononuclear cells in household contacts of pulmonary tuberculosis patients provides insights into mechanisms of Mycobacterium tuberculosis control and elimination

Household contacts (HHCs) of patients with active tuberculosis (ATB) are at higher risk of Mycobacterium tuberculosis (M. tuberculosis) infection. However, the immune factors responsible for different defense responses in HHCs are unknown. Hence, we aimed to evaluate transcriptome signatures in human peripheral blood mononuclear cells (PBMCs) of HHCs to aid risk stratification. We recruited 112 HHCs of ATB patients and followed them for 6 years. Among the HHCs, only 2 developed ATB, while the remaining HHCs were classified into three groups: (1) HHC-1 group (n = 23): HHCs with consistently positive T-SPOT.TB test, negative chest radiograph, and no clinical symptoms or evidence of ATB during the 6-year follow-up period; (2) HHC-2 group (n = 15): HHCs with an initial positive T-SPOT result that later became negative without evidence of ATB; (3) HHC-3 group (n = 14): HHCs with a consistently negative T-SPOT.TB test and no clinical or radiological evidence of ATB. HHC-2 and HHC-3 were combined as HHC-23 group for analysis. RNA sequencing (RNA-seq) in PBMCs, with and without purified protein derivative (PPD) stimulation, identified significant differences in gene signatures between HHC-1 and HHC-23. Gene ontology analysis revealed functions related to bacterial pathogens, leukocyte chemotaxis, and inflammatory and cytokine responses. Modules associated with clinical features in the HHC-23 group were linked to the IL-17 signaling pathway, ferroptosis, complement and coagulation cascades, and the TNF signaling pathway. Validation using real-time PCR confirmed key genes like ATG-7, CXCL-3, and TNFRSF1B associated with infection outcomes in HHCs. Our research enhances understanding of disease mechanisms in HHCs. HHCs with persistent latent tuberculosis infection (HHC-1) showed significantly different gene expression compared to HHCs with no M. tuberculosis infection (HHC-23). These findings can help identify HHCs at risk of developing ATB and guide targeted public health interventions.

Ocular manifestations and diagnosis of tuberculosis involving the uvea: a case series

BACKGROUND

Ocular tuberculosis (TB) affects 1-2% of patients with TB, with TB uveitis being the most common. This series aims to look at different manifestations of tuberculosis associated uveitis and the different tests used to make a presumptive or definitive diagnosis.

METHODS

Patients diagnosed with TB related uveitis in Hong Kong SAR between 2017 and 2020 were reviewed. Demographics, clinical features, investigations and treatments of patients were collected.

RESULTS

Fifteen eyes in 10 patients with a mean age 57.30 ± 10.17 years were included. The ocular manifestations on presentation included anterior uveitis (50%), posterior uveitis (40%) and panuveitis (10%), where 70% of them were unilateral and 30% were bilaterally infected; on subsequent visits the manifestations further developed into posterior uveitis (40%), panuveitis (40%) and anterior uveitis (20%), where 50% of them were unilateral and 50% bilateral infected. Tuberculosis tests were positive in 5 out of 7 Mantoux tests, 4 out of 4 T-SPOT TB tests, 3 out of 4 QuantiFERON-TB gold tests, 1 out of 1 lymph node biopsy, 0 out of 9 chest x-rays, and no aqueous fluid polymerase chain reaction (PCR) was tested. Vision impairing complications were seen in 6 patients where retinal vasculitis was most commonly seen. With anti-TB treatment prescribed in 9 patients, side effects occurred in 5 patients, including ocular hypertension, disc swelling, and hepatitis.

CONCLUSIONS

Ocular TB infections may manifest in various forms, and can involve different parts of the eye. Bilateral involvement of TB is commonly presented, and both eyes should be evaluated at every follow up. When TB is suspected in a patient, diagnostic confirmation requires multimodal investigations where a negative chest x-ray is not useful in ruling out ocular TB infections, especially in an endemic region like Hong Kong. In these patients, it is crucial to have a high index of suspicion for TB, even when they do not demonstrate classical respiratory signs and symptoms of TB.

Cytokine upsurge among drug-resistant tuberculosis endorse the signatures of hyper inflammation and disease severity

Tuberculosis (TB) elimination is possible with the discovery of accurate biomarkers that define the stages of infection. Drug-resistant TB impair the current treatment strategies and worsen the unfavourable outcomes. The knowledge on host immune responses between drug-sensitive and drug-resistant infection is inadequate to understand the pathophysiological differences and disease severity. The secreted proteins, cytokines display versatile behaviour upon infection with Mycobacterium tuberculosis (MTB) and their imbalances often tend to assist disease pathology than protection. Therefore, studying these soluble proteins across TB infection spectrum (drug-resistant TB, drug-sensitive TB, and latent TB) may unveil the disease mediated responses and unique stage specific cytokine signatures. Thus, we sought to determine the plasma cytokine levels from healthy, latently infected, drug-sensitive, and drug-resistant TB individuals. Our study revealed top 8 cytokines (IL-17, IL-1α, IL-2, IL-10, IL-5, IFN-γ, TNF-α and IL-6) and their biomarker abilities to discriminate different stages of infection.

Case Report: Multiple Ocular Manifestations Assisted the Diagnosis of Systemic Sarcoidosis

SIGNIFICANCE

Sarcoidosis is a variable, multisystem granulomatous disease which can affect many organs including the lungs, lymph nodes and eyes. It is difficult to differentiate sarcoidosis and tuberculosis due to their similar clinical and pathological features.

PURPOSE

To describe a sarcoidosis case with typical ocular and systemic manifestations combined with suspected tuberculosis infection.

CASE REPORT

A 30-year-old Chinese male, initially diagnosed with tuberculosis, presented with typical ocular sarcoidosis during anti-tuberculosis therapy. The ocular surface, anterior chamber, anterior chamber angle, ciliary body, vitreous, optic disc and lacrimal gland of the patient all exhibited manifestations of sarcoidosis, although optic disc involvement has rarely been reported. Typical ocular sarcoidosis manifestations and positive responses to corticosteroid therapy of the patient helped us reach the diagnosis of systemic sarcoidosis. The patient was followed up for 48 months and showed significant improvement of miliary nodules and lymph nodes in both lungs. However, the appearance of uveitis in the right eye persisted due to non-adherence with steroid treatment.

CONCLUSIONS

This case shows the importance of ophthalmic evaluation in the diagnosis and management of sarcoidosis, and supports a possible role of mycobacterium tuberculosis in the pathogenesis of sarcoidosis.

Elevated IP-10 at the Protein and Gene Level Associates With Pulmonary TB

There is an urgent need for accurate and sensitive diagnostic tools that can overcome the current challenge to distinguish individuals with latent tuberculosis infection (LTBI) from individuals with active tuberculosis (TB). Recent literature has suggested that a group of cytokines may serve as biomarkers of TB disease progression. Using a multiplex ELISA, we quantified 27 circulatory markers present within the unstimulated plasma of individuals in Durban, South Africa who were healthy (n=20), LTBI (n=13), or had active TB (n=30). RT-qPCR was performed to measure gene expression of the cytokines of interest, using RNA isolated from healthy (n=20), LTBI (n=20), or active TB (n=30). We found that at the protein level, IL-1RA, IL-6, and IP-10 were significantly more abundant in participants with active TB (p< 0.05) compared to those with LTBI individuals. IP-10 also showed the strongest association with active TB compared to healthy and LTBI at mRNA level. Our data shows that these proteins may serve as biomarkers of TB at both the protein and gene level.

Effect of adjusted cut-offs of interferon-γ release assays on diagnosis of tuberculosis in patients with fever of unknown origin

Background

Tuberculosis (TB) is a leading cause of fever of unknown origin (FUO). In recent years, interferon-γ release assays (IGRAs) have been widely utilized and the cut-off values given by the manufacturers are set in countries where rates of TB are not as high.

Methods

A prospective cohort study was conducted in a Chinese general hospital to evaluate the diagnostic performance of T-SPOT.TB (T-SPOT) and QuantiFERON-TB Gold (QFT) in detecting active TB (ATB) in a high TB endemic area. Test results were compared with the culture and clinically confirmed diagnosis. Further, we explored an alternative method of interpreting IGRAs by increasing the cut-off values.

Results

The sensitivity and specificity of T-SPOT in detecting ATB were 85.3% (95% CI 81.6–94.0%) and 71.8% (95% CI 67.3–76.0%), respectively. The sensitivity and specificity of QFT were 72.3% (95% CI 62.8–80.1%) and 77.0% (95% CI 72.7–80.8%), respectively. Receiver operating characteristic analysis was used for evaluation of different cut-off values. When the cut-off values were adjusted as 125 spot-forming cells (SFCs)/ 2.5*10⁵ cells for T-SPOT and 4.0 IU/ml for QFT, the specificity could be improved to > 90.0% (90.3% and 94.1%, respectively), and the sensitivity were 43.1% and 41.6%, respectively. The new adjusted cut-off values were validated in another independent validation cohort.

Conclusion

The adjusted cut-off values of the two assays considerably improved the diagnostic value when applied to FUO patients in clinical settings.

Blood transcriptomics reveal the evolution and resolution of the immune response in tuberculosis

Blood transcriptomics have revealed major characteristics of the immune response in active TB, but the signature early after infection is unknown. In a unique clinically and temporally well-defined cohort of household contacts of active TB patients that progressed to TB, we define minimal changes in gene expression in incipient TB increasing in subclinical and clinical TB. While increasing with time, changes in gene expression were highest at 30 d before diagnosis, with heterogeneity in the response in household TB contacts and in a published cohort of TB progressors as they progressed to TB, at a bulk cohort level and in individual progressors. Blood signatures from patients before and during anti-TB treatment robustly monitored the treatment response distinguishing early and late responders. Blood transcriptomics thus reveal the evolution and resolution of the immune response in TB, which may help in clinical management of the disease.

Frecuencia de positividad de la prueba de intradermorreacción a tuberculina en una cohorte de pacientes con artritis reumatoide

Introducción.

La artritis reumatoide es una enfermedad autoinmunitaria, crónica y deformante asociada con discapacidad. Quienes la padecen reciben inmunosupresores y tienen un gran riesgo de desarrollar tuberculosis. La prueba de intradermorreacción a la tuberculina se utiliza como tamización en quienes van a recibir terapia biológica.

Objetivo.

Evaluar la frecuencia de positividad en la prueba de intradermorreacción a la tuberculina en una cohorte de pacientes con artritis reumatoide.

Materiales y métodos.

Se hizo un estudio descriptivo de corte transversal de una cohorte de pacientes con artritis reumatoide a quienes se les practicó la prueba de tuberculina antes de iniciar la terapia biológica o en el momento del cambio de tratamiento. Los pacientes presentaban enfermedad moderada o grave y eran candidatos para iniciar o cambiar de terapia biológica. Se definió el valor de ≥6 mm como punto de corte para la positividad de la prueba y se hizo un análisis descriptivo de cada una de las variables.

Resultados.

Se incluyeron 261 pacientes con artritis reumatoide, 92 % de ellos eran mujeres, la edad promedio fue de 55 años (desviación estándar, DE=13,92) y el tiempo desde el diagnóstico era de 12,3 años (DE=8,54). La frecuencia de positividad de la prueba fue de 15,71 % (n=41). Nueve de los 41 pacientes positivos habían recibido la prueba previamente (entre 1 y 6 años antes), todos con resultado negativo; 18 (43,9 %) de ellos venían recibiendo tratamiento con glucocorticoides y todos los 41 (100 %) recibían metotrexate.

Conclusiones.

La frecuencia de positividad de la prueba de tuberculina en pacientes colombianos con artritis reumatoide fue de aproximadamente 16 %. Se recomienda optimizar las estrategias para detectar esta condición y darle un tratamiento oportuno y, así, disminuir el riesgo de reactivación de la tuberculosis.

Fabrication of an Electrochemical Aptasensor Composed of Multifunctional DNA Three-Way Junction on Au Microgap Electrode for Interferon Gamma Detection in Human Serum

Interferon gamma (IFN-γ) is an important cytokine with antiviral, antibacterial, and immunosuppressive properties. It has been used as a biomarker for the early detection of several diseases, including cancer, human immunodeficiency virus (HIV), tuberculosis, and paratuberculosis. In this study, we developed an electrochemical biosensor composed of multifunctional DNA 3WJ to detect IFN-γ level with high sensitivity. Each multifunctional triple-stranded aptamer (MF-3WJ) was designed to have an IFN-γ aptamer sequence, anchoring region (thiol group), and 4C-C (cytosine-cytosine) mismatch sequence (signal generation), which could introduce silver ions. To generate the electrochemical signal, four Ag⁺ ions were intercalated (3wj b-3wj c) in the 4C-C mismatch sequence. MF-3WJ was assembled through the annealing step, and the assembly of MF-3WJ was confirmed by 8% tris-boric-EDTA native polyacrylamide gel electrophoresis. The Au microgap electrode was manufactured to load sample volumes of 5 µL. The reliability of electrochemical biosensor measurement was established by enabling the measurement of seven samples from one Au microgap electrode. MF-3WJ was immobilized on the Au microgap electrode. Then, cyclic voltammetry and electrochemical impedance spectroscopy were performed to confirm the electrochemical properties of MF-3WJ. To test the electrochemical biosensor's ability to detect IFN-γ, the limit of detection (LOD) and selectivity tests were performed by square wave voltammetry. A linear region was observed in the concentration range of 1 pg/mL-10 ng/mL of IFN-γ. The LOD of the fabricated electrochemical biosensor was 0.67 pg/mL. In addition, for the clinical test, the LOD test was carried out for IFN-γ diluted in 10% human serum samples in the concentration range of 1 pg/mL-10 ng/mL, and the LOD was obtained at 0.42 pg/mL.

Human tuberculosis and Mycobacterium tuberculosis complex: A review on genetic diversity, pathogenesis and omics approaches in host biomarkers discovery

Mycobacterium tuberculosis complex (MTBC) refers to a group of mycobacteria encompassing nine members of closely related species that causes tuberculosis in animals and humans. Among the nine members, Mycobacterium tuberculosis (M. tuberculosis) remains the main causative agent for human tuberculosis that results in high mortality and morbidity globally. In general, MTBC species are low in diversity but exhibit distinctive biological differences and phenotypes among different MTBC lineages. MTBC species are likely to have evolved from a common ancestor through insertions/deletions processes resulting in species speciation with different degrees of pathogenicity. The pathogenesis of human tuberculosis is complex and remains poorly understood. It involves multi-interactions or evolutionary co-options between host factors and bacterial determinants for survival of the MTBC. Granuloma formation as a protection or survival mechanism in hosts by MTBC remains controversial. Additionally, MTBC species are capable of modulating host immune response and have adopted several mechanisms to evade from host immune attack in order to survive in humans. On the other hand, current diagnostic tools for human tuberculosis are inadequate and have several shortcomings. Numerous studies have suggested the potential of host biomarkers in early diagnosis of tuberculosis, in disease differentiation and in treatment monitoring. "Multi-omics" approaches provide holistic views to dissect the association of MTBC species with humans and offer great advantages in host biomarkers discovery. Thus, in this review, we seek to understand how the genetic variations in MTBC lead to species speciation with different pathogenicity. Furthermore, we also discuss how the host and bacterial players contribute to the pathogenesis of human tuberculosis. Lastly, we provide an overview of the journey of "omics" approaches in host biomarkers discovery in human tuberculosis and provide some interesting insights on the challenges and directions of "omics" approaches in host biomarkers innovation and clinical implementation.

Mycobacterium tuberculosis-specific cytokine biomarkers for the diagnosis of childhood TB in a TB-endemic setting

The tuberculin skin test and interferon-gamma release assays have limitations in diagnosing tuberculosis (TB), particularly in children. This study investigated the performance of candidate M. tuberculosis-specific cytokine biomarkers for TB in children in a TB-endemic setting. A total of 237 children with a household contact with smear-positive pulmonary TB were recruited. Importantly, a group of children with illnesses other than TB (sick controls) was included to assess specificity. Median IFN-ɣ, IL-1ra, IL-2, IL-13, IP-10, MIP-1β and TNF-α responses were significantly higher in children with active TB and latent TB infection (LTBI) than in both healthy and sick control children. Three of these cytokines - IL-2, IL-13 and IP-10 - showed better performance characteristics than IFN-ɣ, with IL-2 achieving positive and negative predictive values of 97.7% and 90.7%, respectively. Furthermore, IL-1ra and TNF-α responses differed significantly between active TB and LTBI cases, suggesting that they may be stage-specific biomarkers. Our data indicate that incorporating these biomarkers into future blood-based TB assays could result in substantial performance gains.

The Application of T.SPOT-TB Assay for Early Diagnosis of Active Tuberculosis in Chronic Kidney Disease Patients Receiving Immunosuppressive Treatment

Background: The current study investigated the clinical application of the T-SPOT.TB assay for detecting tuberculosis (TB) infection in chronic kidney disease patients treated with immunosuppressive therapy. Methods: Clinical data from 91 patients were retrospectively analyzed. The rate of positive T-SPOT.TB results and spot numbers were compared before and after treatment. Clinical characteristics that may affect the test results were also investigated. Results: Two active TB cases were observed after immunosuppressive treatment, and eight patients with negative T-SPOT.TB results at baseline had positive results after treatment. No significant changes in spot numbers were observed for patients who were positive at baseline. Compared with pretreatment baseline, patients who received medium/high doses of corticosteroids had a greater number of T-SPOT.TB positive results (p = 0.016) and CFP-10 spots (p = 0.041) after treatment. For patients who received combination therapy with medium/high doses of corticosteroids, the T-SPOT.TB positive rate (p = 0.046) and CFP-10 spot number (p = 0.041) were increased after treatment, with no significant changes in the total number of spots or ESAT-6 spots. For those who received combination therapy with low doses of corticosteroids and those who received single immunosuppressive medication, there were no significant differences in the T-SPOT.TB positive rate, total spot number, or numbers of ESAT-6 and CFP-10 spots. Conclusion: The increase in positive T-SPOT.TB results was mainly associated with medium/high doses of glucocorticoids. The active TB cases might represent new infections. Regular monitoring using the T-SPOT.TB assay will help in the early detection of active TB.

The Performance of Pleural Fluid T-SPOT.TB Assay for Diagnosing Tuberculous Pleurisy in China: A Two-Center Prospective Cohort Study

The performance of T-SPOT.TB (T-SPOT) assay in diagnosing pleural tuberculosis (plTB) is inconsistent. In this study, we compared the performance of peripheral blood (PB) and pleural fluid (PF) T-SPOT assay in diagnosing plTB. Between July 2017 and March 2018, 218 and 210 suspected plTB patients were prospectively enrolled from Wuhan (training) and Guangzhou (validation) cohort, respectively. PB T-SPOT, PF T-SPOT, and other conventional tests were simultaneously performed. Our data showed the performance of PB T-SPOT in diagnosing plTB was limited, especially with low sensitivity. However, the results of early secreted antigenic target 6 (ESAT-6) and culture filtrate protein 10 (CFP-10) in PF T-SPOT were significantly increased compared with those in PB T-SPOT in plTB patients. If using 76 as the cutoff value of MAX (the larger of ESAT-6 and CFP-10) in Wuhan cohort, the sensitivity and specificity of PF T-SPOT to diagnose plTB were 89.76 and 96.70%, respectively. The diagnostic accuracy of PF T-SPOT was better than other routine tests such as pathogen detection methods and biochemical markers. The diagnostic accuracy of PF T-SPOT in Guangzhou cohort was similar to that in Wuhan cohort, with a sensitivity and specificity of 91.07 and 94.90%, respectively. Furthermore, CD4⁺ T cells were more activated in PF compared with PB, and the frequency of mycobacterium tuberculosis-specific CD4⁺ T cells in PF was significantly higher than that in PB in plTB patients. In conclusion, the performance of PF T-SPOT is obviously better than PB T-SPOT or other laboratory tests, which suggests that PF T-SPOT assay has been of great value in the diagnosis of pleural tuberculosis.

Neutrophils: Innate Effectors of TB Resistance?

Certain individuals are able to resist Mycobacterium tuberculosis infection despite persistent and intense exposure. These persons do not exhibit adaptive immune priming as measured by tuberculin skin test (TST) and interferon-γ (IFN-γ) release assay (IGRA) responses, nor do they develop active tuberculosis (TB). Genetic investigation of individuals who are able to resist M. tuberculosis infection shows there are likely a combination of genetic variants that contribute to the phenotype. The contribution of the innate immune system and the exact cells involved in this phenotype remain incompletely elucidated. Neutrophils are prominent candidates for possible involvement as primers for microbial clearance. Significant variability is observed in neutrophil gene expression and DNA methylation. Furthermore, inter-individual variability is seen between the mycobactericidal capacities of donor neutrophils. Clearance of M. tuberculosis infection is favored by the mycobactericidal activity of neutrophils, apoptosis, effective clearance of cells by macrophages, and resolution of inflammation. In this review we will discuss the different mechanisms neutrophils utilize to clear M. tuberculosis infection. We discuss the duality between neutrophils' ability to clear infection and how increasing numbers of neutrophils contribute to active TB severity and mortality. Further investigation into the potential role of neutrophils in innate immune-mediated M. tuberculosis infection resistance is warranted since it may reveal clinically important activities for prevention as well as vaccine and treatment development.

Screening for latent tuberculosis infection in patients with inflammatory bowel disease: Can interferon-gamma release assays replace the tuberculin skin test?

BACKGROUND/AIMS

Screening for latent tuberculosis infection is mandatory before starting anti-tumor necrosis factor therapy. New assays based on interferon-γ (IFN-γ) release have recently become available and may be more accurate. The aim of this study was to compare QuantiFERON-TB and tuberculin skin test in screening for latent infection in patients with inflammatory bowel disease.

MATERIALS AND METHODS

We prospectively screened 138 patients with inflammatory bowel disease for latent tuberculosis infection with chest X-ray, tuberculin skin test, and a third-generation QuantiFERON-TB test. The association of the results in both tests with immunosuppression or inflammatory activity was determined by logistic regression.

RESULTS

The tuberculin skin test and QuantiFERON-TB were positive in 21.7% and 24.6% of the patients, respectively. Overall, 71% patients were receiving immunosuppressants. Concordance between the two tests was moderate (κ=0.59; 95% confidence interval (CI), 0.43-0.75) and was higher in immunosuppressant-naïve patients (κ=0.75; 95% CI, 0.52-0.97) than in immunosuppressed patients (κ=0.51; 95% CI, 0.30-0.72). In both the tests, disease activity and receiving immunosuppression were not associated with the test results. Nevertheless, QuantiFERON-TB was negatively influenced with two or more immunosuppressive drugs.

CONCLUSION

Concordance between the two tests was moderate, and it appears lower with immunosuppression. QuantiFERON-TB alone may be appropriate in immunosuppressant-naïve patients. Both tests should be considered in immunosuppressed patients.

QuantiFERON-TB Gold In-Tube test in active tuberculosis patients and healthy adults

Interferon-gamma (IFN-γ) release assays have improved latent tuberculosis (TB) detection and have been considered promising for the diagnosis of TB disease. However, diagnosis efficacy data is limited in high burden countries. The aim of this study was to determine the diagnostic potential of the QuantiFERON-TB Gold In-Tube (QFT-GIT) test for the diagnosis of active TB in an endemic setting for TB. A cross-sectional study was conducted in a group of 102 Thai patients with clinical symptoms and chest x-ray findings suggesting of active pulmonary TB and a group of 112 healthy adults. Testing was carried out using sputum microscopy, mycobacterial culture and QFT-GIT test. Of these patients, QFT-GIT was positive in 73 (71.57%), negative in 27 (26.47%), and undetermined in 2 (1.96%) cases. Among healthy controls, QFT-GIT was positive in 18 (16.07%), negative in 93 (83.04%), and undetermined in 1 (0.89%) person. Based on TB culture results, the sensitivity of QFTGIT for diagnosing active TB was 84.21% (95% confidence interval (CI); 72.13-92.52). The positive and negative predictive values were 65.75% (95% CI; 59.26-71.70) and 66.67% (95% CI; 49.94-80.04), respectively. The median IFN-γ level in culture-confirmed TB patients was 3.91 compared to 0.03 IU/mL of the healthy group. QFT-GIT appears to be a useful indirect test for TB diagnosis in Thailand and its use is recommended in association with clinical and radiological assessments for identifying active or latent TB.

Validation and comparison of ELISA kits to measure interferon gamma responses in QuantiFERON cultural supernatants for diagnosis of tuberculosis

Much effort has been made to reduce the cost of LTBI diagnosis with equivalent efficacy and efficiency of interferon-γ release assay (IGRA). This study showed that repeatability, intermediate precision, and accuracy of the Bionote-ELISA were comparable to QFT-ELISA. The Bionote-ELISA could provide the alternative method.

Peripheral kynurenine/tryptophan ratio is not a reliable marker of systemic indoleamine 2,3-dioxygenase: A lesson drawn from patients on hemodialysis

Indoleamine 2,3-dioxygenase (IDO) has emerged as a pivotal enzyme for mediating immune tolerance. Because IDO metabolizes tryptophan into kynurenine, the plasma kynurenine/tryptophan (Kyn/Trp) ratio has been widely used as a marker of systemic IDO. Here, we evaluated the clinical value of using the plasma Kyn/Trp ratio to estimate cell-mediated immune responses to tuberculin skin testing and risk of new bacterial infection. We also compared the Kyn/Trp ratio to a novel IDO marker, the IDO median fluorescence index (MFI) of peripheral blood mononuclear cells, which was determined by flow cytometry. In 228 patients from two hemodialysis centers, the two IDO markers were higher in patients than in healthy controls but were not correlated with each other. In vitro experiments demonstrated that peripheral blood mononuclear cells could not metabolize tryptophan into kynurenine, indicating that the increased Kyn/Trp ratio was IDO-independent. Skin induration diameters of tuberculin skin testing were correlated with the IDO MFI (negatively), but not the Kyn/Trp ratio. Further, in a 24-month prospective cohort, the Kyn/Trp ratio was not correlated with clinical infection. Alternatively, patients with a higher IDO MFI had a lower accumulative infection-free survival rate. Using a Cox proportional hazard model, it was also revealed that a higher IDO MFI was significantly associated with new bacterial infection. Taken together, these results indicate that the Kyn/Trp ratio is not a reliable circulating IDO marker in hemodialysis patients. However, the IDO MFI reflects an immunocompromised state and thus might be a potential clinical marker of bacterial infection.

Comparison of Interferon-γ Release Assays and the Tuberculin Skin Test for Diagnosis of Tuberculosis in Human Immunodeficiency Virus: A Systematic Review

Background

It remains uncertain if interferon-γ release assays (IGRAs) are superior to the tuberculin skin test (TST) for the diagnosis of active tuberculosis (TB) or latent tuberculosis infection (LTBI) in immunosuppressed populations including people with human immunodeficiency virus (HIV) infection. The purpose of this study was to systematically review the performance of IGRAs and the TST in people with HIV with active TB or LTBI in low and high prevalence TB countries.

Methods

We searched the MEDLINE database from 1966 through to January 2017 for studies that compared results of the TST with either the commercial QuantiFERON-TB Gold in Tube (QFTGT) assay or previous assay versions, the T-SPOT.TB assay or in-house IGRAs. Data were summarized by TB prevalence. Tests for concordance and differences in proportions were undertaken as appropriate. The variation in study methodology was appraised.

Results

Thirty-two studies including 4,856 HIV subjects met the search criteria. Fourteen studies compared the tests in subjects with LTBI in low TB prevalence settings. The QFTGT had a similar rate of reactivity to the TST, although the first-generation version of that assay was reactive more commonly. IGRAs were more frequently positive than the TST in HIV infected subjects with active TB. There was considerable study methodology and population heterogeneity, and generally low concordance between tests. Both the TST and IGRAs were affected by CD4 T-cell immunodeficiency.

Conclusion

Our review of comparative data does not provide robust evidence to support the assertion that the IGRAs are superior to the TST when used in HIV infected subjects to diagnose either active TB or LTBI.

IL-6 release of Rv0183 antigen-stimulated whole blood is a potential biomarker for active tuberculosis patients

OBJECTIVE

New tests for diagnosing active tuberculosis (aTB) are urgently needed, and TB antigen-specific cell-mediated immunity can be expected to develop new testing methods of aTB.

MATERIALS AND METHODS

Rv0183 protein, the only monoglyceride lipase identified in mycobacteria, was used to stimulate freshly heparin-treated whole blood. The Rv0183-specific cytokines/chemokines response associated with aTB was screened firstly with 4 aTB patients and 4 LTBIs, and further evaluated in 192 suspected aTB patients and 372 healthy individuals.

RESULTS

Out of 71 cytokines/chemokines, the response of IL-6 against Rv0183 protein was found to be associated with aTB. The Rv0183-specific IL-6 response was significantly higher in aTB patients (n = 128) than in those with non-TB lung disease (n = 64) and in healthy individuals (n = 327) (p < 0.0001), and not affected by latent TB infection. In IGRA+ suspected active TB patients, the sensitivity, specificity, PPV and NPV of IL-6 response (with cutoff of 235.2 pg/ml) were 85.7%, 100%, 100% and 51.5% for diagnosing aTB, respectively. While in IGRA- ones, they were 87.5%, 80.5%, 60.9% and 95.0% with 174.2 pg/ml IL-6 response as cutoff, respectively.

CONCLUSIONS

These results clearly show that the Rv0183 antigen-specific IL-6 response has the potential to be used as an immune-diagnosis test for active TB in clinical practice.

Multiplex analysis of plasma cytokines/chemokines showing different immune responses in active TB patients, latent TB infection and healthy participants

Interferon gamma release assays (IGRAs) have been widely used to diagnose Mycobacterium tuberculosis (MTB) infection. However, IGRAs cannot discriminate between active TB patients and latent TB infection (LTBI), and the sensitivity of IGRAs for MTB infection is suboptimal. Here, we analyzed cytokines/chemokines in MTB antigen-stimulated and -unstimulated plasma samples to identify host biomarkers that are associated with active TB and MTB infection. Active TB patients, subjects with LTBI and healthy participants were recruited. Seventy-one soluble cytokines and chemokines were tested using Luminex liquid array-based multiplexed immunoassays. For the 71 examined factors, our results indicated that the unstimulated levels of IL-8 _Nil, IP-10 _Nil, MIP-1a _Nil, and sIL-2Ra _Nil and the antigen stimulated levels of IL-8 _(Ag-Nil), VEGF _(Ag-Nil), and MCP-3 _(Ag-Nil) were potential biomarkers for differentiating between active TB and LTBI, with AUCs of 0.8, 0.86, 0.755, 0.845, 0.825, 0.812 and 0.75, respectively. The G-CSF _(Ag-Nil), GM-CSF _(Ag-Nil), IL-1a _(Ag-Nil), IL-2 _(Ag-Nil), IP-10 _(Ag-Nil), BCA-1 _(Ag-Nil) and Eotaxin-1 _(Ag-Nil) responses were significantly higher in patients with active TB and LTBI compared with healthy participants (p < 0.05), with AUCs of 0.922, 0.902, 0.908, 1.0, 0.937, 0.919 and 0.935, respectively. Our preliminary data suggest that unstimulated or stimulated levels of cytokines and chemokines could be used as host biomarkers for diagnosing active TB as well as additional biomarkers, except IFN-γ, for MTB infection.

IFN-γ and IL-2 Responses to Recombinant AlaDH against ESAT-6/CFP-10 Fusion Antigens in the Diagnosis of Latent versus Active Tuberculosis Infection

BACKGROUND

Discriminating latent tuberculosis infection (LTBI) from active TBI may be challenging. The objective of this study was to produce the recombinant L-alanine dehydrogenase (AlaDH) antigen and evaluate individuals with LTBI, those with active TBI, and uninfected individuals by enzyme-linked immunospot assay (ELISPOT) in order to distinguish LTBI from active TBI.

METHODS

This exploratory study was performed in the Iranian city of Shiraz from 2014 to 2015. The study population (N=99) was divided into 3 groups: individuals with newly diagnosed active TBI (n=33), their household contacts (n=33), and controls (n=33). AlaDH was produced through PCR and cloning methods. The diagnostic characteristics of AlaDH vs. ESAT-6/CFP-10 were evaluated in responses to interferon-γ (IFN-γ) and interleukin-2 (IL-2) with ELISPOT. Differences between the groups were assessed with the Kruskal-Wallis and Mann-Whitney tests for nonparametric data analysis. The statistical analyses were performed with SPSS, version 16.

RESULTS

IFN-γ responses to both ESAT-6/CFP-10 (P=0.81) and AlaDH (P=0.18) revealed that there were no significant differences between the individuals with LTBI and those with active TBI. The same results were determined for IL-2 responses to ESAT-6/CFP-10 between the 2 groups, while significantly higher IL-2 responses to AlaDH were observed in LTBI than in active TBI. According to the ROC curve analysis, a cutoff value of 275 SFC showed sensitivity of 75.8% and specificity of 78.8% for distinguishing LTBI from active TBI by IL-2 responses to AlaDH.

CONCLUSION

The current study suggests that it may be possible to discriminate LTBI from active TBI by IL-2 responses to AlaDH.

Evaluation of a New IFN-γ Release Assay for Rapid Diagnosis of Active Tuberculosis in a High-Incidence Setting

Blood-based interferon-gamma (IFN-γ) release assays (IGRAs) have been proven to be useful in the diagnosis of Mycobacterium tuberculosis (Mtb) infection. However, IGRAs have not been recommended for clinical practice in most low-income settings due to cost-intensive limitations and shortage of clinical data available. The established T-SPOT. TB assay containing Mtb-specific antigens ESAT-6 and CFP10 are widely used for immunodiagonsis of Mtb infection, but the high cost is one of the restricting factors against its clinical application in the developing countries. More recently, a cost-saving IGRA assay, TS-SPOT, was approved in China. This new assay contains an additional antigen Rv3615c. Rv3615c contains broadly recognized CD4⁺ and CD8⁺ epitopes, and T-cell responses to Rv3615c are as specific for Mtb infection as the responses to ESAT-6 and CFP10 in both Mtb-infected humans and M. bovis-infected cattle. Therefore, we assessed the likely effect of inclusion of Rv3615c as stimulus besides ESAT-6 and CFP10 in an IGRA assay and evaluated the performance of TS-SPOT for diagnosis of Mtb infection and active TB compared with T-SPOT.TB. We tested 155 active TB patients, 90 non-TB lung disease patients, and 55 healthy individuals. The results presented an improved positive rate for diagnosis of active TB and Mtb infection, that could be attributable to inclusion of Rv3615c in the mixture of stimulatory antigens. The diagnostic efficiency of TS-SPOT assay for active TB was as follows: sensitivity 80.00%, specificity 83.45%, positive predictive value (PPV) 83.78%, negative predictive value (NPV) 83.45%, positive likelihood ratio (LR+) 4.83, and negative likelihood ratio (LR−) 0.24. The results were similar to those of T-SPOT.TB, with an excellent agreement (κ = 0.91, 95% CI: 0.85–0.95) being observed between these two assays. The sensitivities of the TS-SPOT assay varied for patients with different forms of active TB, with the highest sensitivity for patients with culture-positive pulmonary TB (92.16%) and the lowest for those with tuberculosis meningitis (50.00%). Taken together, the current evidence indicates that this new TS-SPOT assay is a useful adjunct to the current tests for rapid diagnosis of active TB and Mtb infection in low-income and high-incidence settings due to its characteristics of cost-effectiveness and high-quality.

Unbiased Identification of Blood-based Biomarkers for Pulmonary Tuberculosis by Modeling and Mining Molecular Interaction Networks

Efficient diagnosis of tuberculosis (TB) is met with multiple challenges, calling for a shift of focus from pathogen-centric diagnostics towards identification of host-based multi-marker signatures. Transcriptomics offer a list of differentially expressed genes, but cannot by itself identify the most influential contributors to the disease phenotype. Here, we describe a computational pipeline that adopts an unbiased approach to identify a biomarker signature. Data from RNA sequencing from whole blood samples of TB patients were integrated with a curated genome-wide molecular interaction network, from which we obtain a comprehensive perspective of variations that occur in the host due to TB. We then implement a sensitive network mining method to shortlist gene candidates that are most central to the disease alterations. We then apply a series of filters that include applicability to multiple publicly available datasets as well as additional validation on independent patient samples, and identify a signature comprising 10 genes - FCGR1A, HK3, RAB13, RBBP8, IFI44L, TIMM10, BCL6, SMARCD3, CYP4F3 and SLPI, that can discriminate between TB and healthy controls as well as distinguish TB from latent tuberculosis and HIV in most cases. The signature has the potential to serve as a diagnostic marker of TB.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Impact of correcting the lymphocyte count to improve the sensitivity of TB antigen-specific peripheral blood-based quantitative T cell assays (T-SPOT.(®)TB and QFT-GIT)

BACKGROUND

The standardized blood-based TB antigen-specific T cell assay, T-SPOT.(®)TB, is ~10% more sensitive than QuantiFERON(®)-TB-GIT (QFT-GIT) in detecting presumed latent TB infection (LTBI). Whilst T-SPOT.(®)TB uses a fixed number of lymphocytes per well, QFT-GIT uses a fixed volume of blood (~1 mL). However, the person-to-person lymphocyte count can vary by 2 to 3 fold. We hypothesized that this variability could explain the reduced sensitivity of QFT-GIT. The findings could have potential implications for improving case detection.

METHODS

T-SPOT.(®)TB was compared to QFT-GIT readouts before and after normalization of lymphocyte count (by adjusting the blood volume or lymphocyte enrichment within a fixed 1 mL volume) to an arbitrary value of 2.5×10(6) cells/mL. Within-test variability was evaluated to meaningfully interpret results.

RESULTS

In patient-specific optimization experiments IFN-γ concentrations significantly increased when QFT-GIT positive samples were enriched with increasing concentrations of lymphocytes (1×10(6) vs. 2.5×10(6) cells/mL). However, for the group as a whole lymphocyte enrichment whilst maintaining a ~1 mL volume, compared to un-enriched samples, did not significantly increase IFN-γ [median (range): 0.03 (0-4.41) vs. 0.20 (0-2.40) IU/mL; P=0.64]. There was also no increase in IFN-γ readouts when QFT-GIT lymphocyte numbers were corrected (to 2.5×10(6) lymphocytes/mL) using volume adjustment. Interestingly, adjusted values were significantly lower than unadjusted ones [median (range): 0.02 (0-12.93) vs. 0.09 (0-14.23) IU/mL; P=0.008].

CONCLUSIONS

In QFT-GIT negative subjects lymphocyte enrichment did not increase QFT-GIT positivity rates. The reduced clinical sensitivity of the QFT-GIT assay, compared to T-SPOT.(®)TB, is likely to be due to factors other than lymphocyte count alone. Further studies are required to clarify these findings.

CELLULAR IMMUNITY ACTIVATION METHOD BY STIMULATING RD1 COMPLEX PROTEINS AS VIRULENCE MARKER ON Mycobacterium tuberculum TO ESTABLISH DIAGNOSIS ON TUBERCULOSIS AND LATENT TUBERCULOSIS INFECTION

This study was intended to invent a simpler and more affordable method to establish diagnosis on Tuberculosis (TB) and Latent Tuberculosis infection (LTBI). Similar to “Quantiferon TB Gold In Tube” (QFT-GIT) and T.SPOT.TB methods, the researchers also utilized “early secreted antigenic target 6kDa” (ESAT-6) and “cultur filtrate protein 10kDa” (CFP-10) proteins to be induced on the specimen. ESAT-6 and CFP-10 are commercial products used to induce interferon gamma (INF-γ) which were to be read using sophisticated and expensive equipment. This study was intended to conduct an analysis on effective cocktail protein modification, i.e. ESAT-6, CFP-10 and Ag85A/B/C, with high validity to detect cellular immunity activity through in vitro examination on peripheral blood monocyte cells of Tuberculosis-suspected patients or patients with latent tuberculosis infection. Peripheral Blood Monocyte Cells (PBMCs) activity on children tuberculosis patient or Latent Tuberculosis Infection (LTBI), adult tuberculosis patient or LTBI, which induced by cocktail protein modification and not induced, were analyzed microscopically. The activity of PBMCs on children and adult tuberculosis patient or LTBI induced by RD1 secretory proteins: ESAT-6, CFP-10, Ag85A/B/C was higher compared to PBMCs which had not been induced by the secretory proteins. Cellular debris and monocyte cells with abnormal shapes were found on PBMCs which had been induced by RD1 secretory proteins at 8 th day after culture.

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.

EVALUATION OF DIAGNOSTIC ACCURACY OF THE COMPARATIVE TUBERCULIN SKIN TEST IN REHABILITANT BORNEAN ORANGUTANS (PONGO PYGMAEUS)

The tuberculin skin test (TST) has been the mainstay of tuberculosis (TB) testing in primates for decades, but its interpretation in orangutans (Pongo spp.) is challenging, because many animals react strongly, without evidence of infection with Mycobacterium tuberculosis complex. One explanation is cross-reactivity with environmental nontuberculous mycobacteria (NTM). The use of a comparative TST (CTST), comparing reactivity to avian (representing NTM) and bovine (representing tuberculous mycobacteria) tuberculins aids in distinguishing cross-reactivity due to sensitization by NTM from shared antigens. The specificity of the TST can be increased with the use of CTST. We considered three interpretations of the TST in rehabilitant Bornean orangutans ( Pongo pygmaeus ) using avian purified protein derivative (APPD; 25,000 IU/ml) and two concentrations of bovine purified protein derivative (BPPD; 100,000 and 32,500 IU/ml). The tests were evaluated for their ability to identify accurately seven orangutans previously diagnosed with and treated for TB from a group of presumed negative individuals (n = 288 and n = 161 for the two respective BPPD concentrations). BPPD at 32,500 IU/ml had poor diagnostic capacity, whereas BPPD at 100,000 IU/ml performed better. The BPPD-only interpretation had moderate sensitivity (57%) and poor specificity (40%) and accuracy (41%). The comparative interpretation at 72 hr had similar sensitivity (57%) but improved specificity (95%) and accuracy (94%). However, best results were obtained by a comparative interpretation incorporating the 48- and 72-hr scores, which had good sensitivity (86%), specificity (95%) and accuracy (95%). These data reinforce recommendations that a CTST be used in orangutans and support the use of APPD at 25,000 IU/ml and BPPD at 100,000 IU/ml. The highest score at each site from the 48- and 72-hr checks should be considered the result for that tuberculin. If the bovine result is greater than the avian result, the animal should be considered a TB suspect.

A patient with urinary tract tuberculosis during treatment with etanercept

Patient: Female, 58

Final Diagnosis: —

Symptoms: —

Medication: —

Clinical Procedure: —

Specialty: —

Diagnostic value of T-SPOT.TB interferon-γ release assays for active tuberculosis

The aim of the present study was to evaluate the diagnostic value of interferon-γ release assays for the detection of active tuberculosis (ATB) in patients previously vaccinated with Bacillus Calmette-Guérin (BCG). In total, 540 patients underwent the T-SPOT.TB test, including 295 patients with active pulmonary TB (PTB), 52 patients with active extrapulmonary TB (EPTB), 11 individuals with inactive TB and 182 non-TB cases. Simultaneously, 186 patients with ATB, including PTB and EPTB cases, and 125 non-TB patients underwent tuberculin skin tests (TST). Associations between the sensitivity of the T-SPOT.TB assays and lung lesion severity, positive smear grade, disease site and the duration of anti-TB treatment were evaluated. The sensitivity and specificity values of the T-SPOT.TB assay for diagnosing ATB were 76.66 and 76.37%, respectively, and the positive rate in the inactive TB test results was significantly lower (23.63%; P<0.001). The diagnostic sensitivity was higher in the PTB cases when compared with the EPTB cases (P=0.01). Furthermore, the diagnostic sensitivity of the ATB cases undergoing anti-TB treatment was significantly lower when compared with the cases not undergoing treatment (P=0.002), and the sensitivity gradually decreased with the treatment duration (P=0.01). In addition, a statistically significant difference was identified in the specificity between the T-SPOT.TB assay and the TST (76.37 vs. 51.15%; P<0.001), whereas the sensitivity values did not differ significantly (76.66 vs. 75.56%). Therefore, the results indicated that the T-SPOT.TB assay is a promising diagnostic test for active PTB in a BCG-vaccinated population, and should replace the TST. As the administration of anti-TB treatment resulted in a lower sensitivity to the diagnostic test, the T-SPOT.TB assay may also be suitable for the assessment of treatment outcomes.

IFN-γ/TNF-α ratio in response to immuno proteomically identified human T-cell antigens of Mycobacterium tuberculosis - The most suitable surrogate biomarker for latent TB infection

The enormous reservoir of latent TB infection (LTBI) poses a major hurdle for global TB control. The existing Tuberculin skin test (TST) and IFN-γ release assays (IGRAs) are found to be suboptimal for LTBI diagnosis. Previously we had taken an immunoproteomic approach and identified 10 protein fractions (contains 16 proteins), which are solely recognized by LTBI. In a cohort of 40 pulmonary TB patients (PTB) and 35 healthy household contacts (HHC), IFN-γ and TNF-α response were measured against 16 antigens by using 1:10 diluted whole blood assay. Among all the antigens, IFN-γ response to Rv2626c has shown positivity of 88.57% in HHC and 7.5% in PTB group. IFN-γ response to combination of Rv2626c + Rv3716c has demonstrated 100% positivity in HHC and 17.5% positivity in PTB respectively. Compared to individual cytokines (i.e. IFN-γ and TNF-α), ratio of IFN-γ/TNF-α has shown promising results for diagnosis of LTBI. IFN-γ/TNF-α ratio against Rv3716c and TrxC has exhibited a positivity of 94.29% in HHC and 5% in PTB group. Accession of Rv2626c and Rv3716c may improve the diagnostic performance of existing QFT-GIT. Independent of QFT-GIT assay, ratio of IFN-γ/TNF-α in response to either Rv3716c or TrxC may acts as suitable surrogate biomarker for LTBI.

Diagnostic utility of interferon-gamma release assay in extrapulmonary tuberculosis

Early diagnosis of extrapulmonary tuberculosis (EP-TB) is essential. However, diagnosis of EP-TB is difficult. We evaluated the diagnostic utility of an interferon-gamma release assay (IGRA) in diagnosing active EP-TB among suspected patients in Korea. We retrospectively reviewed the clinical records of all patients with suspected EP-TB at Gangnam Severance Hospital in Seoul, Korea. Of the 418 patients with suspected EP-TB, 324 had active EP-TB. The tuberculosis (TB) group had a higher percentage of positive IGRAs (70.2%, 33/47) than the non-TB group (33.3%, 3/9) (P=0.034). The IGRA sensitivity and specificity were 70.2% (63.7-74.8%) and 66.7% (32.9-90.6%), respectively. The sensitivity and specificity of IGRAs in patients with TB lymphadenitis were 81.8% (61.4-90.4%) and 80.0% (35.1-98.9%), but 38.5% (31.2-45.7%) and 50.0% (2.7-97.3%) in patients with TB pleurisy. The diagnostic performance of IGRAs may vary depending on the site of EP-TB involvement. IGRA was potentially valuable for diagnosis of active EP-TB in TB lymphadenopathy.

Performance of an interferon-gamma release assay in the diagnosis of tuberculous meningitis in children / Performanţa testului bazat pe eliberarea interferonului gamma în diagnosticul meningitei tuberculoase la copil

The new immunodiagnostic tests based on the Mycobacterium tuberculosis specific antigen, early secretory antigenic target 6 (ESAT-6) and culture filtrate protein 10 (CFP-10), showed promising results in the diagnosis of tuberculosis infection. However, there are only few studies in the published literature on performance tests in cerebrospinal fluid. We investigated whether a rapid diagnosis of tuberculous meningitis (TBM) could be established by interferon-γ blood and cerebrospinal fluid (CSF) tests in children.

We used the QuantiFERON-TB Gold in Tube test (QFT-IT) on blood and the QuantiFERON-TB Gold test (QFT-G) on the CSF of 63 subjects with TBM (including 25 case of definite TBM and 38 cases of probable TBM) and 62 controls.

The CSF analyses indicated possible TBM in 63.4% of cases. The sensitivity of the CSF culture for Mycobacterium tuberculosis was only 39.6%. The sensitivity of the tuberculin skin test (TST) was 49.2% and the specificity was 88.6%. The estimated sensitivities of the QFT-G for the CSF and QFT-IT for the blood in culture confirmed TBM cases (gold standard) were 84% and 80%, respectively. The estimated specificities were 98.2% for the CSF and 87.9% for the blood. This study showed that the sensitivity of QFT for the CSF could be higher than TST and culture and slightly higher in CSF than in blood. The specificity of QFT-G for the CSF was higher those of the TST, but the specificity of QFT-IT is lower.

QFT-G of the CSF is a useful diagnostic marker of tuberculosis that may improve the management of TBM, but the test results must be correlated with clinical, radiological and characteristics of CSF. New researches are needed to investigate the performance of QFT-G in the CSF compared with ELISPOT and PCR

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

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

The tuberculin skin test in school going adolescents in South India: associations of socio-demographic and clinical characteristics with TST positivity and non-response

Background

India has generally used 1 TU purified protein derivative (PPD) as opposed to 2 TU PPD globally, limiting comparisons. It is important to assess latent TB infection in adolescents given that they may be a target group for new post-exposure TB vaccines.

The aim of this study is to describe the pattern and associations of tuberculin skin test (TST) responses (0.1 ml 2 TU) in adolescents in South India.

Methods

6643 school-going adolescents (11 to <18 years) underwent TST. Trained tuberculin reader made the reading visit between 48 and 96 hours after the skin test

Results

Of 6608 available TST results, 9% had 0 mm, and 12% ≥10 mm responses. The proportion of TST positive (≥10 mm) was higher among older children, boys, those with a history of TB contact and reported BCG immunization Those with no TST response (0 mm) included younger participants (<14 years), those whose mothers were illiterate and those with a recent history of weight loss. Those of a higher socio-economic status (houses with brick walls, LPG gas as cooking fuel) and those with a visible BCG scar were less likely to be non-responders.

Conclusion

Proportion of non-responders was lower than elsewhere in the world. Proportion of TST positivity was higher in those already exposed to TB and in children who had been BCG immunized, with a zero response more likely in younger adolescents and those with recent weight loss.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-014-0571-7) contains supplementary material, which is available to authorized users.

Human genetics of tuberculosis: a long and winding road

Only a small fraction of individuals exposed to Mycobacterium tuberculosis develop clinical tuberculosis (TB). Over the past century, epidemiological studies have shown that human genetic factors contribute significantly to this interindividual variability, and molecular progress has been made over the past decade for at least two of the three key TB-related phenotypes: (i) a major locus controlling resistance to infection with M. tuberculosis has been identified, and (ii) proof of principle that severe TB of childhood can result from single-gene inborn errors of interferon-γ immunity has been provided; genetic association studies with pulmonary TB in adulthood have met with more limited success. Future genetic studies of these three phenotypes could consider subgroups of subjects defined on the basis of individual (e.g. age at TB onset) or environmental (e.g. pathogen strain) factors. Progress may also be facilitated by further methodological advances in human genetics. Identification of the human genetic variants controlling the various stages and forms of TB is critical for understanding TB pathogenesis. These findings should have major implications for TB control, in the definition of improved prevention strategies, the optimization of vaccines and clinical trials and the development of novel treatments aiming to restore deficient immune responses.

Whole blood interferon-γ release assay is insufficient for the diagnosis of sputum smear negative pulmonary tuberculosis

PURPOSE

We investigated the value of an interferon-γ release assay (IGRA) for the diagnosis of active pulmonary tuberculosis (PTB) among sputum smear negative PTB suspects in an environment with intermediate burden of PTB and high Bacillus Calmette-Guerin (BCG) vaccination rate.

MATERIALS AND METHODS

We retrospectively reviewed IGRA, medical records, chest PA and CT scan of PTB suspects seen at Gangnam Severance Hospital, Seoul, Korea from Oct. 2007 to Apr. 2013. "Active PTB" was diagnosed when 1) M. tuberculosis culture positive, 2) confirmation by pathologic examination; or 3) clinical findings compatible with TB.

RESULTS

Of 224 sputum smear negative PTB suspects, 94 were confirmed as having active PTB. There were no statistically significant differences in the diagnostic yield of IGRA between immunocompromised and immunocompetent sputum smear negative PTB suspects. IGRA did show superior sensitivity [81.9%, 95% confidence interval (CI); 74.13-89.70%] in the diagnosis of sputum smear negative PTB when compared with chest high-resolution computed tomography (HRCT), tuberculin skin test (TST), and chest X-ray (p<0.001). Also, IGRA showed highest negative predictive value (82.7%, 95% CI; 75.16-90.15%) when compared with HRCT, TST and chest X-ray (p=0.023). However, combining the results of IGRA with those of HRCT, TST, or both did not increase any diagnostic parameters.

CONCLUSION

Failure to increase diagnostic yields by combination with other diagnostic modalities suggests that additional enforcement with IGRA may be insufficient to exclude other diagnoses in sputum smear negative PTB suspects and to screen active PTB in an environment with intermediate TB prevalence and a high BCG vaccination rate.

Tuberculosis: an overview

Tuberculosis (TB) is still a public health issue; it continues to reign as one of the world's deadliest diseases. One-third of the world's population has been infected with TB. Identified cases of mycobacterium must be notified in an attempt to reduce the public health impact of TB on the population. TB transmission occurs via inhalation of droplet nuclei. The most common site for the development of TB is the lungs. Treatment of TB depends on whether latent TB or active TB is treated.

Performance of QuantiFERON-TB Gold In-Tube test and Tuberculin Skin Test for diagnosis of latent tuberculosis infection in BCG vaccinated health care workers

Background

Tuberculin skin test (TST) has been used for years as an aid in diagnosing latent tuberculosis infection (LTBI) but it suffers from a number of well-documented performance and logistic problems. Quantiferon-TB Gold In Tube test (QFT-GIT) has been reported to have better sensitivity and specifity than TST. In this study, it was aimed to compare the performance of a commercial IFN-γ release assay (QFT-GIT) with TST in the diagnosis of HCWs at risk for latent TB infection in BCG vaccinated population.

Material/Methods

Hundred healthy volunteer health care workers were enrolled. All were subjected to TST and QFT-GIT. Results were compared among Health Care Workers (HCWs) groups in terms of profession, workplace, working duration.

Results

TST is affected by previous BCG vaccinations and number of cases with QFT-GIT positivity is increased in accordance with the TST induration diameter range. QFT-GIT result was negative in 17 of 32 TST positive (≥15 mm) cases and positive in 4 of 61 cases whose TST diameters are between 6–14 mm, that is attritutable to previous BCG vaccination(s). It was negative in all cases with TST diameters between 0–5 mm.

HCWs with positive QFT-GIT results were significantly older than the ones with negative results. Furthermore duration of work was significantly longer in QFT-GIT positive than in negative HCWs.

Conclusions

There was a moderate concordance between QFT-GIT and TST, when TST result was defined as positive with a ≥15 mm diameter of induration. We suggest that QFT-GIT can be used as an alternative to TST for detection of LTBI, especially in groups with high risk of LTBI and in population with routine BCG vaccination program.

Interferon-gamma treatment kinetics among patients with active pulmonary tuberculosis

Introduction:

Interferon-γ (IFN-γ) is essential for defence against Mycobacterium tuberculosis; however, levels in patients with active tuberculosis (TB) and changes during treatment have not been documented in our tuberculosis patients in Nigeria, hence this study has been carried out.

Objective:

To determine variations, treatment kinetics, and predictive value of IFN-γ levels during treatment of active tuberculosis.

Design:

Patients with pulmonary tuberculosis were recruited and subsequently followed up for 3 months during treatment with anti-TB. Peripheral blood was collected for IFN-γ assays, C-reactive protein and others followed by a Mantoux test. IFN-γ levels produced by stimulation with TB antigens were determined by ELISA and repeated measurement of IFN-γ were done at 1 and 3 months of anti-TB therapy. Chi Associations and correlations between IFN-γ were determined. Regression analysis was done to determine association between serial IFN-γ and treatment outcome.

Results:

We recruited 47 patients with active tuberculosis with a mean age of 34.8 ± 3.6 years and M:F ratio of 1.12:1. Six (11%) were HIV positive. The mean level of IFN-γ induced by TB antigens was 629 ± 114.1 pg/ml, higher for HIV-negative PTB patients compared with HIV-positive PTB patients, 609.78 ± 723.9 pg/ml and 87.88 ± 130.0 pg/ml, respectively, P-value = 0.000. The mean level of IFN-γ induced by TB antigen increased significantly from 629 ± 114.1 pg/ml to 1023.46 + 222.8 pg/ml, P-value = 0.03 and reduced to 272.3 ± 87.7 pg/ml by the third month on anti-TB drugs, P-value = 0.001. Negative correlation was observed between the mean of baseline and chest X-ray involvement, P = 0.03. There was no significant correlation between sputum smear grade with baseline and follow-up IFN-γ levels. Three-month IFN-γ level among cured patients were higher than those with treatment failure, regression analysis showed that it does not predict outcome.

Conclusion:

IFN-γ may be useful in early detection and monitoring response; however, large scale studies are needed.

A metabolic biosignature of early response to anti-tuberculosis treatment

Background

The successful treatment of tuberculosis (TB) requires long-term multidrug chemotherapy. Clinical trials to evaluate new drugs and regimens for TB treatment are protracted due to the slow clearance of Mycobacterium tuberculosis (Mtb) infection and the lack of early biomarkers to predict treatment outcome. Advancements in the field of metabolomics make it possible to identify metabolic profiles that correlate with disease states or successful chemotherapy. However, proof-of-concept of this approach has not been provided for a TB-early treatment response biosignature (TB-ETRB).

Methods

Urine samples collected at baseline and during treatment from 48 Ugandan and 39 South African HIV-seronegative adults with pulmonary TB were divided into discovery and qualification sets, normalized to creatinine concentration, and analyzed by liquid chromatography-mass spectrometry to identify small molecule molecular features (MFs) in individual patient samples. A biosignature that distinguished baseline and 1 month treatment samples was selected by pairwise t-test using data from two discovery sample sets. Hierarchical clustering and repeated measures analysis were applied to additional sample data to down select molecular features that behaved consistently between the two clinical sites and these were evaluated by logistic regression analysis.

Results

Analysis of discovery samples identified 45 MFs that significantly changed in abundance at one month of treatment. Down selection using an extended set of discovery samples and qualification samples confirmed 23 MFs that consistently changed in abundance between baseline and 1, 2 and 6 months of therapy, with 12 MFs achieving statistical significance (p < 0.05). Six MFs classified the baseline and 1 month samples with an error rate of 11.8%.

Conclusions

These results define a urine based TB-early treatment response biosignature (TB-ETRB) applicable to different parts of Africa, and provide proof-of-concept for further evaluation of this technology in monitoring clinical responses to TB therapy.