Rapid diagnosis of smear-negative tuberculosis by bronchoalveolar lavage enzyme-linked immunospot

Tuberculosis prevention: current strategies and future directions

BACKGROUND

An estimated one fourth of the world's population is infected with Mycobacterium tuberculosis, and 5-10% of those infected develop tuberculosis in their lifetime. Preventing tuberculosis is one of the most underutilized but essential components of curtailing the tuberculosis epidemic. Moreover, current evidence illustrates that tuberculosis manifestations occur along a dynamic spectrum from infection to disease rather than a binary state as historically conceptualized. Elucidating determinants of transition between these states is crucial to decreasing the tuberculosis burden and reaching the END-TB Strategy goals as defined by the WHO. Vaccination, detection of infection, and provision of preventive treatment are key elements of tuberculosis prevention.

OBJECTIVES

This review provides a comprehensive summary of recent evidence and state-of-the-art updates on advancements to prevent tuberculosis in various settings and high-risk populations.

SOURCES

We identified relevant studies in the literature and synthesized the findings to provide an overview of the current state of tuberculosis prevention strategies and latest research developments.

CONTENT

We present the current knowledge and recommendations regarding tuberculosis prevention, with a focus on M. bovis Bacille-Calmette-Guérin vaccination and novel vaccine candidates, tests for latent infection with M. tuberculosis, regimens available for tuberculosis preventive treatment and recommendations in low- and high-burden settings.

IMPLICATIONS

Effective tuberculosis prevention worldwide requires a multipronged approach that addresses social determinants, and improves access to tuberculosis detection and to new short tuberculosis preventive treatment regimens. Robust collaboration and innovative research are needed to reduce the global burden of tuberculosis and develop new detection tools, vaccines, and preventive treatments that serve all populations and ages.

Comparison of 3 diagnostic methods for pulmonary tuberculosis in suspected patients with negative sputum smear or no sputum

STUDY DESIGN

To explore the diagnostic value of 3 methods for sputum smear-negative and non-sputum patients with suspected pulmonary tuberculosis (TB).

METHODS

This prospective study enrolled sputum smear-negative and non-sputum patients with suspected TB admitted to Jiangxi Chest Hospital between January 2020 and December 2022. The 3 methods were bronchoalveolar lavage fluid (BALF)-acid-fast bacillus (AFB) smear, GeneXpert MTB/RIF, and gene chip for Mycobacterium strain identification. The diagnostic performance of the 3 tests was evaluated with BALF Mycobacterium culture + BALF-AFB smear + GeneXpert MTB/RIF + Gene chip as the gold standard.

RESULTS

A total of 456 samples were collected from 114 patients with suspected TB. Twenty-four patients were diagnosed with TB. The combination of GeneXpert MTB/RIF and gene chip for Mycobacterium strain identification yielded the highest area under the receiver operating characteristics curve (AUC) of 0.953 and had sensitivity of 90.57%, specificity of 100%, positive predictive value (PPV) of 100%, negative predictive value (NPV) of 92.42%, accuracy of 95.61%. GeneXpert MTB/RIF achieved AUC of 0.906, sensitivity of 81.13%, specificity of 100%, PPV of 100%, NPV of 85.92%, accuracy of 91.23%. BALF-AFB smear had AUC of 0.519, sensitivity of 3.77%, specificity of 100%, PPV of 100%, NPV of 54.46%, and accuracy of 55.26%. The combination of GeneXpert MTB/RIF and gene chip for Mycobacterium strain identification yielded the highest κ of 0.911, while BALF-AFB smear had the lowest κ value of 0.040.

CONCLUSION

For TB in sputum smear-negative and non-sputum patients using BALF Mycobacterium culture + BALF-AFB smear + GeneXpert MTB/RIF + Gene chip as the gold standard, BALF-AFB smear showed low diagnostic performance, while, though GeneXpert MTB/RIF and gene chip had good diagnostic performance, combining GeneXpert MTB/RIF and gene chip improved the diagnostic value to a great extent.

Rapid Diagnosis of Recurrent Paucibacillary Tuberculosis

Introduction

The rapid diagnosis of tuberculosis recurrence can be challenging due to persistently positive detection of Mycobacterium tuberculosis-specific DNA from sputum and bronchopulmonary samples in the absence of active disease.

Methods

We compared the diagnostic accuracy of the detection of M. tuberculosis-specific DNA by either Xpert (January 2010-June 2018) or Xpert Ultra (July 2018-June 2020) and M. tuberculosis-specific ELISPOT in bronchoalveolar lavage (BAL) samples with M. tuberculosis culture results from sputum or bronchopulmonary samples in patients with suspected recurrence of pulmonary tuberculosis.

Results

Among 44 individuals with previous tuberculosis and a presumptive diagnosis of recurrent pulmonary tuberculosis, 4/44 (9.1%) were diagnosed with recurrent tuberculosis by culture. DNA of M. tuberculosis was detected by Xpert in BAL fluid in 1/4 (25%) individuals with recurrent tuberculosis and in 2/40 (5%) cases with past tuberculosis without recurrence, while BAL-ELISPOT with a cut-off of >4,000 early secretory antigenic target-6-specific or culture filtrate protein-10-specific interferon-γ-producing lymphocytes per 1 million BAL-lymphocytes was positive in 4/4 (100%) individuals with recurrent tuberculosis and in 2/40 (5%) cases of past tuberculosis without recurrence.

Conclusion

M. tuberculosis-specific BAL-ELISPOT is more accurate than BAL-Xpert for the diagnosis of paucibacillary tuberculosis recurrence.

Loss of T cells expressing CD27 at the site of active tuberculosis - A prospective diagnostic study

The lack of a rapid and reliable diagnostic test for active tuberculosis is still a burden to the control of the infection. The accumulation of Mycobacterium tuberculosis (MTB)-specific CD4⁺ T cells at the site of infection and the increase of MTB-specific CD27^- cells seem to be characteristic for active tuberculosis. We evaluated CD27 expression of non-stimulated T cells at the site of infection compared to peripheral blood of seventy-two patients (n = 72) presenting with symptoms of active MTB-infection. Twenty patients (n = 20, 27.8%) were actually confirmed to have active tuberculosis. Overall, a significant increase of terminally differentiated CD27^- CD4⁺ T cells at the site of disease was noted when compared to peripheral blood (<0.001). However, the loss of CD27 at the site of disease was not restricted to active tuberculosis (p = 0.253). The CD27 expression profile of tuberculosis patients was only discriminative to patients with malignancy.

Elevated antigen-specific IFN-γ responses in bronchoalveolar lavage fluid impervious to clinical comorbidities improve the pulmonary tuberculosis diagnosis

The extremely slow growth rate of Mycobacterium tuberculosis (Mtb) challenges traditional methods for tuberculosis (TB) diagnosis. Here, we assessed the efficacy of a previously developed Mtb antigen-specific gamma interferon (IFN-γ) enzyme-linked immunospot (ELISPOT) performed on bronchoalveolar lavage fluid (BALF) from a cohort of 414 patients including 333 PTB patients (202/333 were sputum culture positive) for the diagnosis of PTB. We could confirm that antigen-specific IFN-γ-producing CD4⁺ T cells were concentrated significantly in BALF mononuclear cells (BALMC) compared with that in peripheral blood mononuclear cells (PBMC) assayed in parallel, but not those of CD8⁺ T cells both in sputum culture-negative and positive PTB. The magnitude of IFN-γ responses in the BALF was associated with bacterial load, and 9/202 of PTB with endobronchial TB (EBTB) were slightly reduced by the anti-TB treatment. Moreover, antigen-specific IFN-γ ELISPOT performed on BALMC showed higher sensitivity than PBMC ELISPOT. In addition, the differences of the BALMC ELISPOT between PTB and PTB with diabetes were not found, whereas PBMC IFN-γ responses were decreased in PTB with diabetes. Combined with the microbiological detection in BALF, such as microscopy and culture, the BALMC ELISPOT offers the opportunity for the more accurate diagnosis of PTB, especially those with clinical comorbidities.

Enhanced Mycobacterial Antigen-Induced Pro-Inflammatory Cytokine Production in Lymph Node Tuberculosis

Lymph node tuberculosis (LNTB) is characterized by the enhanced baseline and antigen-specific production of type 1/17 cytokines and reduced baseline and antigen-specific production of interleukin (IL)-1β and IL-18 at the site of infection when compared with peripheral blood. However, the cytokine profile in the lymph nodes (LNs) of Mycobacterium tuberculosis culture-positive LNTB (LNTB+) and negative LNTB (LNTB-) has not been examined. To address this, we have examined the baseline and mycobacterial antigen-stimulated cytokine levels of type 1 (interferon gamma [IFNγ], tumor necrosis factor alpha [TNFα], IL-2), type 2 (IL-4, IL-5, and IL-13), type 17 (IL-17A, IL-17F, and IL-22), pro-inflammatory (IL-1α, IL-1β, IL-18, and granulocyte macrophage colony-stimulating factor [GM-CSF]), and regulatory cytokines (IL-10, transforming growth factor beta [TGF-β]) cytokines in the LN culture supernatants of LNTB+ and LNTB- individuals. We have observed significantly enhanced baseline levels of IL-13 and IL-10 and significantly reduced baseline levels of IL-4 and GM-CSF in LNTB+ individuals compared with LNTB- individuals. By contrast, we have observed significantly enhanced levels of type 1 (IFNγ, TNFα, and IL-2), type 17 (IL-17F and IL-22), and pro-inflammatory (IL-1α and GM-CSF) cytokines and significantly reduced levels of TGFβ in response to purified protein derivative, early secreted antigen-6, and culture filtrate protein-10 antigens in LNTB+ compared with LNTB- individuals. On phorbol 12-myristate 13-acetate/ionomycin stimulation, no significant difference was observed for any of the cytokines examined. Thus, our study revealed several interesting differences in the cytokine profiles of mycobacterial antigen-stimulated LN cultures in LNTB+ and LNTB- individuals. Therefore, we suggest the presence of mycobacteria plays a significant role in driving the cytokine response at the site of infection in LNTB.

Prospective comparison of two enzyme-linked immunosorbent spot assays for the diagnosis of Lyme neuroborreliosis

Commercial cellular tests are used to diagnose Lyme borreliosis (LB), but studies on their clinical validation are lacking. This study evaluated the utility of an in‐house and a commercial enzyme‐linked immunosorbent spot (ELISpot) assay for the diagnosis of Lyme neuroborreliosis (LNB). Prospectively, peripheral blood mononuclear cells (PBMCs) were isolated from patients and controls and analysed using an in‐house Borrelia ELISpot assay and the commercial LymeSpot assay. B. burgdorferi B31 whole cell lysate and a mixture of outer surface proteins were used to stimulate the PBMCs and the numbers of interferon‐gamma‐secreting T cells were measured. Results were evaluated using receiver operating characteristic (ROC) curve analysis. Eighteen active and 12 treated LNB patients, 10 healthy individuals treated for an early (mostly cutaneous) manifestation of LB in the past and 47 untreated healthy individuals were included. Both assays showed a poor diagnostic performance with sensitivities, specificities, positive and negative predictive values ranging from 44.4–66.7%, 42.0–72.5%, 21.8–33.3% and 80.5–87.0%, respectively. The LymeSpot assay performed equally poorly when the calculation method of the manufacturer was used. Both the in‐house and the LymeSpot assay are unable to diagnose active LNB or to monitor antibiotic treatment success.

Tuberculosis: Diagnostic Challenges in Rural Africa

Tuberculosis (TB) remains among the top 10 infectious diseases with highest mortality globally since the 1990s despite effective chemotherapy. Among 10 million patients that fell ill with tuberculosis in the year 2017, 36 % were undiagnosed or detected and not reported; the number goes as high as 55 % in Tanzania, showing that the diagnosis of TB is a big challenge in the developing countries. There have been great advancements in TB diagnostics with introduction of the molecular tests such as Xpert MTB/RIF, loop-mediated isothermal amplification, lipoarabinomannan urine strip test, and molecular line-probe assays. However, most of the hospitals in Tanzania still rely on the TB score chart in children, the WHO screening questions in adults, acid-fast bacilli and chest x-ray for the diagnosis of TB. Xpert MTB/RIF has been rolled-out but remains a challenge in settings where the samples for testing must be transported over many kilometers. Imaging by sonography - nowadays widely available even in rural settings of Tanzania - has been shown to be a useful tool in the diagnosis of extrapulmonary tuberculosis. Despite all the efforts and new diagnostics, 30-50 % of patients in high-burden TB countries are still empirically treated for tuberculosis. More efforts need to be placed if we are to reduce the death toll by 90 % until 2030.

Mycobacterium Growth Inhibition Assay of Human Alveolar Macrophages as a Correlate of Immune Protection Following Mycobacterium bovis Bacille Calmette-Guérin Vaccination

Background

In order to eliminate tuberculosis (TB), an effective vaccine is urgently needed to prevent infection with Mycobacterium tuberculosis. A key obstacle for the development of novel TB vaccines is the lack of surrogate markers for immune protection against M. tuberculosis.

Methods

We investigated growth rates of M. tuberculosis in the mycobacterial growth inhibition assay (MGIA) as a marker for mycobacterial growth control of human bronchoalveolar lavage (BALC) and peripheral blood mononuclear cells (PBMC) before and after vaccination with Mycobacterium bovis Bacille Calmette–Guérin (BCG) of healthy adult volunteers.

Results

Vaccination induced a positive response (p < 0.001) to purified protein derivate (PPD) in 58.8% of the individuals in an interferon-γ release assay-ELISpot. Intraindividual evaluation of the MGIA growth rates before and after M. bovis BCG-vaccination revealed no significant difference in time to culture positivity before and after vaccination in BALC (p = 0.604) and PBMC (p = 0.199). The magnitude of the PPD-response induced by M. bovis BCG-vaccination did not correlate with growth control in BALC and PBMC (correlation = 0.468, 95% CI: −0.016 to 0.775).

Conclusion

In conclusion, M. bovis BCG-vaccination-induced mycobacterial-specific cytokine immune response does not result in functional immune control against M. tuberculosis in the MGIA.

Use of Interferon-γ release assay for the diagnosis of female genital tuberculosis in Northwest China

BACKGROUND

Female genital tuberculosis (FGTB) is one of the major causes of infertility. However, nonspecific manifestations and the lack of easy access to gold-standard diagnostic test render a diagnostic difficult for FGTB. The objective of this study was to determine T-SPOT.TB (an interferon-γ release assay, IGRA) performance in patients with FGTB.

METHODS

A total of 213 female patients with validated T-SPOT.TB results were recruited in this retrospective study. Among which, 103 were confirmed FGTB, and 110 were excluded from tuberculosis (control). Of the confirmed FGTB patients, 52 were confirmed by microbiologically/histopathologically examination, while the remaining 51 were clinically confirmed (successfully responsive to anti-tuberculosis treatment). T-SPOT.TB test was performed in both FGTB and control group during the diagnostic procedure.

RESULTS

The overall sensitivity and specificity of T-SPOT.TB were 86.41% and 75.45% respectively. Sensitivity of T-SPOT.TB was significantly higher when compared with conventional tuberculosis diagnostic tests. Moreover, T-SPOT.TB test using pelvic effusion (PE) showed higher sensitivity than using corresponding peripheral blood (PB) (94.44% vs 72.22%, P < 0.001). Mean value of spot forming cells (SFCs) of T-SPOT.TB using PE was significantly higher than that of PB in FGTB group (193 (IQR 105-280) SFCs/2.5 × 10⁵ PEMCs vs 71 (IQR 36-107) SFCs/2.5 × 10⁵ PBMCs, P = 0.01), while this was not detected in control group (11 (IQR 0-22) SFCs/2.5 × 10⁵ PEMCs vs 9 (IQR 0-18) SFCs/2.5 × 10⁵ PBMCs, P = 0.77).

CONCLUSION

These results demonstrated that T-SPOT.TB, especially PE T-SPOT.TB, is an useful adjunct in FGTB diagnosis.

Rapid diagnosis of pulmonary tuberculosis by combined molecular and immunological methods

Diagnosing pulmonary tuberculosis (TB) may be delayed until culture results become available.We ascertained the accuracy of a stepwise diagnostic algorithm for the rapid diagnosis of pulmonary TB by GeneXpert from sputum and/or bronchoalveolar lavage (BAL) followed by a Mycobacterium tuberculosis-specific BAL ELISPOT assay in patients with a suspected diagnosis of pulmonary TB at a clinical referral centre in Germany.Among 166 patients with a presumptive diagnosis of pulmonary TB, 81 cases were confirmed by M. tuberculosis culture from sputum and/or BAL. In 66 out of 81 (81.5%) cases, patients initially had M. tuberculosis detected by GeneXpert from sputum; in addition, six out of 81 (7.4%) cases were diagnosed by GeneXpert on BAL fluid (together 72 out of 81 (88.9%) patients). Out of the remaining nine patients with negative GeneXpert results from sputum and BAL, BAL ELISPOT identified eight patients with culture-confirmed TB correctly (median time to culture positivity 26 days). At a cut-off of >4000 early secretory antigenic target-6- or culture filtrate protein-10-specific interferon-γ-producing lymphocytes per 1 000 0000 lymphocytes, the specificity of the BAL ELISPOT for active TB was 97%.In low TB incidence countries, nearly all patients with active pulmonary TB can be identified within the first few days of clinical presentation using a stepwise strategy with GeneXpert and BAL ELISPOT.

Prospective Comparison of QFT-GIT and T-SPOT.TB Assays for Diagnosis of Active Tuberculosis

T-SPOT.TB and QuantiFERON-TB Gold In-Tube (QFT-GIT) tests, as two commercial blood assays for diagnosing active tuberculosis (ATB), are not yet fully validated. Especially, there are no reports on comparing the efficacy between the two tests in the same population in China. A multicenter, prospective comparison study was undertaken at four hospitals specializing in pulmonary diseases. A total of 746 suspected pulmonary TB were enrolled and categorized, including 185 confirmed TB, 298 probable TB and 263 non-TB. Of 32 patients with indeterminate test results (ITRs), age and underlying disease were associated with the rate of ITRs. Furthermore, the rate of ITRs determined by T-SPOT.TB was lower than QFT-GIT (0.4% vs. 4.3%, P < 0.01). When excluding ITRs, the sensitivities of T-SPOT.TB and QFT-GIT were 85.2% and 84.8%, and specificities of 63.4% and 60.5%, respectively in the diagnosis of ATB. The two assays have an overall agreement of 92.3%, but exhibited a poor linear correlation (r² = 0.086) between the levels of interferon-γ release detected by the different assays. Although having some heterogeneity in detecting interferon-γ release, both the QFT-GIT and T-SPOT.TB demonstrated high concordance in diagnosing ATB. However, neither of them showed suitability in the definitive diagnosis of the disease.

Evaluation of risk factors for false-negative results with an antigen-specific peripheral blood-based quantitative T cell assay (T-SPOT®. TB) in the diagnosis of active tuberculosis: A large-scale retrospective study in China

Objective To investigate the diagnostic efficacy of an interferon-γ release assay, T-SPOT^®. TB, for diagnosing active tuberculosis (TB) and to identify risk factors for false-negative results. Methods This retrospective study enrolled consecutive patients with active TB and with non-TB respiratory diseases to evaluate the risk factors for false-negative results when using the T-SPOT^®. TB assay for the diagnosis of active TB. Patients with active TB were categorized as having confirmed pulmonary TB, clinically diagnosed pulmonary TB or extrapulmonary TB (EPTB). Results This study analysed 4964 consecutive patients; 2425 with active TB and 2539 with non-TB respiratory diseases. Multivariate logistic regression analyses identified the following five factors that were all associated with an increased false-negative rate with the T-SPOT^®. TB assay: increased age (odds ratio [OR] 1.018; 95% confidence interval [CI] 1.013, 1.024); decreased CD8+ count (OR 0.307; 95% CI 0.117, 0.803); negative sputum acid-fast bacilli (AFB) smear staining (OR 1.821; 95% CI 1.338, 2.477); negative mycobacterial cultures (OR 1.379; 95% CI 1.043, 1.824); and absence of EPTB (OR 1.291; 95% CI 1.026, 1.623). Conclusions Increased age, decreased CD8+ count, negative sputum AFB smear results, negative sputum mycobacterial cultures and absence of EPTB might lead to an increased false-negative rate when using the T-SPOT^®. TB assay.

Evaluation of interferon-gamma release assays in extrasanguinous body fluids for diagnosing tuberculosis: A systematic review and meta-analysis

AIMS

In this study, we conducted a meta-analysis to systematically compare the diagnostic accuracy of IGRAs performed for extrasanguinous body fluids with that performed for blood in the diagnosis of TB.

MAIN METHODS

Multiple English and Chinese databases were searched up to November 2017. Studies that complied with the guidelines for the Quality Assessment of Diagnostic Accuracy Studies and used QuantiFERON-TB Gold In-Tube and/or T-SPOT.TB (ELISPOT) assays on both blood and extrasanguinous body fluids were included. Statistical analysis was performed using Stata 12.0 software. Since publication bias is a concern in the meta-analysis of diagnostic studies, we tested for this using Begg's funnel plots.

KEY FINDING

Among the 1332 articles searched from the databases, 24 articles met the inclusion criteria, which included 1040 samples in the patient group and 1044 samples in the control group. For extrasanguinous body fluids, the pooled sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR), and summary receiver operating characteristic (SROC) area under the curve (AUC) were 87% (95% CI: 0.81-0.91), 89% (95% CI: 0.84-0.93), 8.22 (95% CI 5.38-12.56), 0.15 (95% CI: 0.10-0.21), 44.92 (95% CI: 25.61-78.81), and 0.94 (95% CI: 0.92-0.96), respectively. For peripheral blood, these values were 83% (95% CI: 0.79-0.87), 74% (95% CI: 0.68-0.79), 3.17 (95% CI 2.63-3.84), 0.23 (95% CI: 0.19-0.29), 12.99 (95% CI: 10.19-16.57), and 0.86 (95% CI: 0.82-0.89), respectively.

SIGNIFICANCE

IGRAs performed on extrasanguinous body fluids exhibited a better diagnostic accuracy compared with IGRAs performed on peripheral blood for diagnosing TB.

Bronchoscopic techniques in the management of patients with tuberculosis

Tuberculosis (TB) is one of the leading causes of morbidity and mortality worldwide. Early diagnosis and treatment are key to prevent Mycobacterium tuberculosis transmission. Bronchoscopy can play a primary role in pulmonary TB diagnosis, particularly for suspected patients with scarce sputum or sputum smear negativity, and with endobronchial disease. Bronchoscopic needle aspiration techniques are accurate and safe means adopted to investigate hilar and mediastinal lymph nodes in cases of suspected TB lymphadenopathy. Tracheobronchial stenosis represents the worst complication of endobronchial tuberculosis. Bronchoscopic procedures are less invasive therapeutic strategies than conventional surgery to be adopted in the management of TB-related stenosis. We conducted a non-systematic review aimed at describing the scientific literature on the role of bronchoscopic techniques in the diagnosis and therapy of patients with TB. We focused on three main areas of interventions: bronchoscopic diagnosis of smear negative/sputum scarce TB patients, endobronchial TB diagnosis and treatment and needle aspiration techniques for intrathoracic TB lymphadenopathy. We described experiences on bronchoalveolar lavage, bronchial washing, and biopsy techniques for the diagnosis of patients with tracheobronchial and pulmonary TB; furthermore, we described the role played by conventional and ultrasound-guided transbronchial needle aspiration in the diagnosis of suspected hilar and mediastinal TB adenopathy. Finally, we assessed the role of the bronchoscopic therapy in the treatment of endobronchial TB and its complications, focusing on dilation techniques (such as balloon dilation and airway stenting) and ablative procedures (both heat and cold therapies).

Immunological diagnosis as an adjunctive tool for an early diagnosis of tuberculous meningitis of an immune competent child in a low tuberculosis endemic country: a case report

BACKGROUND

Pediatric tuberculous meningitis is a highly morbid, often fatal disease. Its prompt diagnosis and treatment saves lives, in fact delays in the initiation of therapy have been associated with high mortality rates.

CASE PRESENTATION

This is a case of an Italian child who was diagnosed with tuberculous meningitis after a history of a month of headache, fatigue and weight loss. Cerebrospinal fluid analysis revealed a lymphocytic pleocytosis with predominance and decreased glucose concentration. Microscopy and conventional diagnostic tests to identify Mycobacterium tuberculosis were negative, while a non classical method based on intracellular cytokine flow cytometry response of CD4 cells in cerebral spinal fluid helped us to address the diagnosis, that was subsequently confirmed by a nested polymerase chain reaction amplifying a 123 base pair fragment of the M. tuberculosis DNA.

CONCLUSIONS

We diagnosed tuberculous meningitis at an early stage through an innovative immunological approach, supported by a nested polymerase chain reaction for detection of M. tuberculosis DNA. An early diagnosis is required in order to promptly initiate a therapy and to increase the patient's survival.

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.

T cell recall response of two hypothetical proteins (Rv2251 and Rv2721c) from Mycobacterium tuberculosis in healthy household contacts of TB - Possible subunit vaccine candidates

The demonstrated variable efficacy of the only licensed TB vaccine Mycobacterium bovis bacillus Calmette-Guérin (M. bovis BCG) encourages the need for new vaccine candidates against TB. Antigen specific cellular immune response is often considered imperative during Mycobacterium tuberculosis (M. tuberculosis) infection and antigens that are strongly associated with the latent phase of infection are drawing increasing attention for anti-TB vaccine development. Here, we investigated the phenotypic and functional profiles of two novel mycobacterial antigens Rv2251 and Rv2721c during T cell recall response via multi-color flow cytometry. Healthy household contacts of TB (latent/HHC) and active pulmonary TB (PTB) patients were recruited to investigate the difference in antigen specific T cell recall response. These two antigens induced expansion of CD45RA^- CCR7⁺ central memory subtypes and CD45RA^- CCR7^- effector memory cells in latent population which suggests their possible association with HHC. Rv2251 and Rv2721c antigen specific IFN-γ, TNF-α and IL-2 response was also significantly high in HHC when compared to the PTB (p < 0.005, p < 0.05 and p < 0.05 respectively). The frequency of multifunctional T cells also was high in HHC compared to the PTB with statistical significance only for the antigen Rv2251. Often, the dominant Th1 immune response in HHC is correlated with the protection against the active TB disease. Collectively, we report the first insights into Rv2251 and Rv2721c antigen specific immune response in human donors of TB and provide the immunologic rationale for selecting them for vaccine development against TB.

Accuracy of the Bronchoalveolar Lavage Enzyme-Linked Immunospot Assay for the Diagnosis of Pulmonary Tuberculosis: A Meta-analysis

Assessing of local immune response may improve the accuracy of pulmonary tuberculosis (PTB) diagnosis. Many studies have investigated diagnosing PTB based on enzyme-linked immunospot (ELISPOT) assay of bronchoalveolar lavage (BAL) fluid, but the results have been inconclusive. We meta-analyzed the available evidences on overall diagnostic performance of ELISPOT assay of BAL fluid for diagnosing PTB.A systematic literature search was performed using PubMed, Embase, Wangfang, Weipu, and CNKI. Data were pooled on sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), and diagnostic odds ratio (DOR). Overall test performance was summarized using summary receiver operating characteristic curves and the area under the curve (AUC). Deeks test was used to test for potential publication bias.Seven publications with 814 subjects met our inclusion criteria and were included in this meta-analysis. The following pooled estimates for diagnostic parameters were obtained: sensitivity, 0.90 (95% CI: 0.85-0.94); specificity, 0.80 (95% CI: 0.77-0.84); PLR, 5.08 (95% CI: 2.70-9.57); NLR, 0.13 (95% CI: 0.06-0.28); DOR, 49.12 (95% CI: 12.97-186.00); and AUC, 0.96. No publication bias was identified.The available evidence suggests that ELISPOT assay of BAL fluid is a useful rapid diagnostic test for PTB. The results of this assay should be interpreted in parallel with clinical findings and the results of conventional tests.

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSION

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

Assessment of CD27 expression as a tool for active and latent tuberculosis diagnosis

There are still no reliable tests to distinguish active tuberculosis (TB) from latent TB infection (LTBI). Assessment of CD27 modulation on CD4⁺ T-cells has been suggested as a tool to diagnose different TB stages.

OBJECTIVES

To use several cytometric approaches to evaluate CD27 expression on Mycobacterium tuberculosis (Mtb)-specific CD4⁺ T-cells to differentiate TB stages.

METHODS

55 HIV-uninfected subjects were enrolled: 13 active TB; 12 cured TB; 30 LTBI. Whole blood was stimulated with RD1-proteins or Cytomegalovirus-lysate (CMV). Interferon (IFN)-γ response was evaluated by cytometry. The proportion of CD27(±) within the IFN-γ⁺ CD4⁺ T-cells or RATIO of the CD27-median fluorescence intensity (MFI) of CD4⁺ T-cells over the CD27 MFI of IFN-γ⁺ CD4⁺ T-cells was evaluated.

RESULTS

The greatest diagnostic accuracy in discriminating active TB vs. LTBI or cured TB was reached by evaluating the CD27(+) CD45RA(-) cells within the IFN-γ⁺ CD4⁺ T-cell subset (76.92 sensitivity for both, and 90% and 91.67% specificity, respectively), although the use of the CD27 MFI RATIO allows for stricter data analysis, independent of the operator.

CONCLUSIONS

the study of CD27 expression using different approaches, whether it involves evaluation of CD45RA expression or not, is a robust biomarker for discriminating TB stages.

Potential role of immunodiagnosis for pulmonary tuberculosis using induced sputum cells

PURPOSE

To evaluate the diagnostic utility and predictors for determinate results of an enzyme-linked immunospot assay using induced sputum cells (IS ELISPOT) for a rapid diagnosis of pulmonary tuberculosis (TB).

MATERIALS AND METHODS

Subjects suspected of pulmonary TB who had either sputum acid fast bacilli smear-negative or not producing sputum spontaneously were prospectively enrolled. ELISPOT assay was performed using cells from induced sputum.

RESULTS

A total of 43 subjects, including 25 with TB (TB group) and 18 with non-TB disease (non-TB group) were enrolled. Results of IS ELISPOT were determinate in only 17/43 (39%) subjects, but all of determinate results were consistent with the final diagnosis. Of the 43 sputum samples, 11 (26%) were inadequate to perform IS ELISPOT. Of 32 adequate sputum samples, the proportion of determinate results was significantly higher in the TB group (75%, 15/20) than in the non-TB group (17%, 2/12) (p=0.002). The status of active TB was a unique predictor but smear positivity was not a significant predictor for determinate results. In addition, sensitivity of IS ELISPOT (75%, 9/12) in smear negative TB was higher than that of TB-polymerase chain reaction (25%, 3/12).

CONCLUSION

IS ELISPOT showed relatively high diagnostic value and accuracy in the TB group, independent of smear positivity. IS ELISPOT may provide additional diagnostic yield for microbiological tools in the rapid diagnosis of smear-negative TB.

Performance of the QuantiFERON-TB gold interferon gamma release assay among HIV-infected children in Botswana

Interferon gamma release assays (IGRAs) are poorly studied in HIV-infected children. The authors prospectively evaluated QuantiFERON-TB Gold results and family-described tuberculosis (TB) risk factors in 100 HIV-infected children in Botswana. Median age was 10.2 years; 58 were girls, 92 had received the Bacillus Calmette-Guérin (BCG) vaccine, 98 were receiving antiretroviral therapy, and the median body mass index was 15.8 kg/m(2). Eighty-nine children had undetectable viral loads and the median CD4 count was 962 cells/mm(3). Eighteen children had been treated for TB in the last 3 years. In the last 3 years, 36 (including 9 with TB) had contact with persons with TB (26 within/15 outside the home and 5 had >1 contact). In all, 96 children had negative IGRAs, 3 were indeterminate, and 1 was positive. The positive IGRA was reported in a child treated for TB prior to 3 years. Interferon γ release assay positivity was rare in this pediatric cohort living in an area with a high prevalence of TB.

Interferon-gamma release assay performance of pleural fluid and peripheral blood in pleural tuberculosis

Background

The diagnosis of pleural tuberculosis (TB) remains to be difficult. Interferon-gamma release assay (IGRA) is a promising method for diagnosing TB in low TB burden countries. The release of interferon-gamma (IFN-γ) by T lymphocytes increases at a localized site of infection with Mycobacterium tuberculosis antigen. This study aimed to examine the clinical accuracy of T-SPOT.TB on pleural fluid and peripheral blood for the diagnosis of pleural TB in high TB burden country.

Methods

168 subjects with pleural effusion were enrolled prospectively and examined with T-SPOT.TB on pleural fluid and peripheral blood samples simultaneously.

Results

The receiver operating characteristic (ROC) curve and cut-off value of pleural fluid T-SPOT.TB was established according to spot forming cells (SFC) between culture/biopsy-confirmed pleural TB group and no pleural TB group. The sensitivity of pleural fluid T-SPOT.TB and peripheral blood T-SPOT.TB was similar (96.3% and 92.7%, respectively) (P= 0.691). In contrast, the specificity of pleural fluid T-SPOT.TB (94.5%) was significantly higher than that of peripheral blood T-SPOT.TB (76.1%) (P=0.002). 2% (2/98) of pleural fluid T-SPOT.TB results were indeterminate.

Conclusion

The diagnostic accuracy of peripheral blood T-SPOT.TB is low in high TB burden countries due to latent tuberculosis infection. Pleural fluid T-SPOT.TB is a relatively useful and supplementary test to explore pleural TB in high TB burden countries, but its diagnostic accuracy needs to be validated in further large scale research.

Mycobacterium tuberculosis PPE protein Rv0256c induces strong B cell response in tuberculosis patients

Tuberculosis (TB) is one of the most important diseases of humans and major public health problem worldwide. Early and accurate diagnosis of TB is necessary for the treatment, prevention, and control of TB. Therefore, it is important to identify suitable antigens that can differentiate active tuberculosis patients from BCG-vaccinated individuals. In the present study, we have used Rv0256c (PPE2) protein of Mycobacterium tuberculosis to screen the sera of infected patients belonging to different clinical TB presentations, and BCG-vaccinated clinically healthy individuals by enzyme immunoassay. Our results demonstrated that Rv0256c displayed stronger and specific immunoreactivity against the sera obtained from clinically active tuberculosis patients compared to PPD and ESAT-6 and could differentiate the TB-patients from the BCG-vaccinated controls. Importantly, Rv0256c was also found to detect even the extrapulmonary and smear-negative pulmonary cases which often are tedious and difficult to detect using conventional diagnostic methods. This study suggests that Rv0256c can be used as a potential marker for the serodiagnosis of tuberculosis patients.

Diagnostic value of ex vivo pleural fluid interferon-gamma versus adapted whole-blood quantiferon-TB gold in tube assays in tuberculous pleural effusion

BACKGROUND:

Noninvasive diagnosis of pleural tuberculosis (TB) remains a challenge due to the paucibacillary nature of the disease. As Mycobacterium tuberculosis (MTB)-specific T cells are recruited into pleural space in TB effusion; their indirect detection may provide useful clinical information.

OBJECTIVES:

Evaluation of pleural fluid interferon (INF)-γ levels vs Quantiferon–TB Gold In tube assay (QFT- IT) in blood and its adapted variants, using pleural fluid or isolated pleural fluid cells in the diagnosis of pleural TB.

METHODS:

Thirty-eight patients with pleural effusion of unknown etiology presented at Assiut University Hospital, Egypt, were recruited. Blood and pleural fluid were collected at presentation for INF-γ assays. Ex vivo pleural fluid INF-γ levels, QFT-IT in blood and its adapted variants were compared with final diagnosis as confirmed by other tools including blind and/or thoracoscopic pleural biopsy.

RESULTS:

The final clinical diagnosis was TB in 20 (53%), malignancy in 10 (26%), and effusion due to other causes in eight patients (21%). Ex vivo pleural fluid INF-γ levels accurately identified TB in all patients and were superior to the QFT-IT assays using blood or pleural fluid (70 and 78% sensitivity, with 60 and 83% specificity, respectively). QFT-IT assay applied to isolated pleural fluid cells had 100% sensitivity and 72% specificity. The optimal cut-off obtained with ROC analysis was 0.73 for TB Gold assay in blood assay, 0.82 IU/ml for the cultured pleural fluid assay, and 0.94 for isolated pleural cells assay.

CONCLUSION:

The ex vivo pleural fluid INF-γ level is an accurate marker for the diagnosis of pleural TB. QFT- IT assay in peripheral blood or its adapted versions of the assay using pleural fluid and/or washed pleural fluid cells had no diagnostic advantage over pleural fluid INF-γ in the diagnosis of pleural TB.

Dual analysis for mycobacteria and propionibacteria in sarcoidosis BAL

PURPOSE

Sarcoidosis is a non-caseating granulomatous disease for which a role for infectious antigens continues to strengthen. Recent studies have reported molecular evidence of mycobacteria or propionibacteria. We assessed for immune responses against mycobacterial and propionibacterial antigens in sarcoidosis bronchoalveolar lavage (BAL) using flow cytometry, and localized signals consistent with microbial antigens with sarcoidosis specimens, using matrix-assisted laser desorption ionization imaging mass spectrometry (MALDI-IMS).

METHODS

BAL cells from 27 sarcoidosis, 14 PPD- controls, and 9 subjects with nontuberculosis mycobacterial (NTM) infections were analyzed for production of IFN-γ after stimulation with mycobacterial ESAT-6 and Propionibacterium acnes proteins. To complement the immunological data, MALDI-IMS was performed to localize ESAT-6 and Propionibacterium acnes signals within sarcoidosis and control specimens.

RESULTS

CD4+ immunologic analysis for mycobacteria was positive in 17/27 sarcoidosis subjects, compared to 2/14 PPD- subjects, and 5/9 NTM subjects (p = 0.008 and p = 0.71 respectively, Fisher's exact test). There was no significant difference for recognition of P. acnes, which occurred only in sarcoidosis subjects that also recognized ESAT-6. Similar results were also observed for the CD8+ immunologic analysis. MALDI-IMS localized signals consistent with ESAT-6 only within sites of granulomatous inflammation, whereas P. acnes signals were distributed throughout the specimen.

CONCLUSIONS

MALDI-IMS localizes signals consistent with ESAT-6 to sarcoidosis granulomas, whereas no specific localization of P. acnes signals is detected. Immune responses against both mycobacterial and P. acnes are present within sarcoidosis BAL, but only mycobacterial signals are distinct from disease controls. These immunologic and molecular investigations support further investigation of the microbial community within sarcoidosis granulomas.

Clinical Utility of Two Interferon-gamma Release Assays on Pleural Fluid for the Diagnosis of Tuberculous Pleurisy

Background

The release of interferon-gamma (IFN-γ) by T lymphocytes increases after rechallenge with Mycobacterium tuberculosis antigen, especially, at a localized site of tuberculosis (TB) infection. We aimed to compare the clincial efficacy of two commercial IFN-γ release assays from pleural fluid for the diagnosis in tuberculous pleurisy.

Methods

We performed T-SPOT.TB and QuantiFERON-TB Gold tests simultaneously on pleural fluid and peripheral blood samples from patients with pleural effusion, in South Korea, an area with intermediate TB burden.

Results

Thirty-six patients were enrolled prospectively, and tuberculous pleurisy was found in 21 patients. Both the numbers of IFN-γ secreting T cells and the concentration of IFN-γ were greater in the pleural tuberculous group, comparing with the non-tuberculous group. Moreover, in the tuberculous group, there was a significant difference in IFN-γ producing spot-forming cells using the T-SPOT.TB method between pleural fluid and peripheral blood. The receiver operating characteristic (ROC) curve, was the greatest for pleural fluid T-SPOT.TB test, followed by peripheral blood T-SPOT.TB test, peripheral blood QuantiFERON-TB Gold test, and pleural fluid QuantiFERON-TB Gold test (area under the ROC curve of 0.956, 0.890, 0.743, and 0.721, respectively). The T-SPOT.TB assay produced less indeterminate results than did QuantiFERON-TB Gold assay in both pleural fluid and peripheral blood.

Conclusion

These findings suggest that the pleural fluid T-SPOT.TB test could be the most useful test among the IFN-γ release assays for diagnosing tuberculous pleurisy in an area with an intermediate prevalence of TB infection.

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

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

Bronchoalveolar lavage enzyme-linked immunospot for diagnosis of smear-negative tuberculosis in HIV-infected patients

Background

Peripheral blood interferon-gamma release assays (IGRAs) have sub-optimal sensitivity and specificity for diagnosis of active pulmonary tuberculosis (TB). However, assessment of local immune responses has been reported to improve the accuracy of TB diagnosis.

Methods

We enrolled HIV-infected adults with cough ≥2 weeks’ duration admitted to Mulago Hospital in Kampala, Uganda and referred for bronchoscopy following two negative sputum acid-fast bacillus smears. We performed an ELISPOT-based IGRA (T-SPOT.TB®, Oxford Immunotec, Oxford, UK) using peripheral blood and bronchoalveolar lavage (BAL) fluid mononuclear cells, and determined the accuracy of IGRAs using mycobacterial culture results as a reference standard.

Results

94 HIV-infected patients with paired peripheral blood and BAL IGRA results were included. The study population was young (median age 34 years [IQR 28–40 years]) and had advanced HIV/AIDS (median CD4+ T-lymphocyte count 60 cells/µl [IQR 22–200 cells/µl]). The proportion of indeterminate IGRA results was higher in BAL fluid than in peripheral blood specimens (34% vs. 14%, difference 20%, 95% CI 7–33%, p = 0.002). BAL IGRA had moderate sensitivity (73%, 95% CI 50–89%) but poor specificity (48%, 95% CI 32–64%) for TB diagnosis. Sensitivity was similar (75%, 95% CI 57–89%) and specificity was higher (78%, 95% CI 63–88%) when IGRA was performed on peripheral blood.

Conclusions

BAL IGRA performed poorly for the diagnosis of smear-negative TB in a high HIV/TB burden setting. Further studies are needed to examine reasons for the large proportion of indeterminate results and low specificity of BAL IGRA for active TB in high HIV/TB burden settings.

Immunodiagnosis of tuberculosis: a dynamic view of biomarker discovery

Infection with Mycobacterium tuberculosis causes a variety of clinical conditions ranging from life-long asymptomatic infection to overt disease with increasingly severe tissue damage and a heavy bacillary burden. Immune biomarkers should follow the evolution of infection and disease because the host immune response is at the core of protection against disease and tissue damage in M. tuberculosis infection. Moreover, levels of immune markers are often affected by the antigen load. We review how the clinical spectrum of M. tuberculosis infection correlates with the evolution of granulomatous lesions and how granuloma structural changes are reflected in the peripheral circulation. We also discuss how antigen-specific, peripheral immune responses change during infection and how these changes are associated with the physiology of the tubercle bacillus. We propose that a dynamic approach to immune biomarker research should overcome the challenges of identifying those asymptomatic and symptomatic stages of infection that require antituberculosis treatment. Implementation of such a view requires longitudinal studies and a systems immunology approach leading to multianalyte assays.

Added value of use of a purified protein derivative-based enzyme-linked immunosorbent spot assay for patients with Mycobacterium bovis BCG infection after intravesical BCG instillations

In this case series, we describe four cases in which the use of gamma interferon release assays with purified protein derivative (PPD) as a stimulating antigen was able to demonstrate PPD-specific immune activation. This may help to improve the adequate diagnosis of (systemic) Mycobacterium bovis BCG infections after intravesical BCG instillations for bladder carcinoma.

Local immune responses in human tuberculosis: learning from the site of infection

Host-pathogen interactions in tuberculosis should be studied at the disease site because Mycobacterium tuberculosis is predominately contained in local tissue lesions. Although M. tuberculosis infection involves different clinical forms of tuberculosis, such as pulmonary tuberculosis, pleural tuberculosis, and lymph node tuberculosis, most studies of human tuberculosis are performed using cells from the peripheral blood, which may not provide a proper reflection of the M. tuberculosis-specific immune responses induced at the local site of infection. A very low proportion of M. tuberculosis-specific effector T cells are found in the blood compared with the infected tissue, and thus there may be considerable differences in the cellular immune response and regulatory mechanisms induced in these diverse compartments. In this review, we discuss differences in the immune response at the local site of infection compared with the peripheral circulation. The cell types and immune reactions involved in granuloma formation and maintenance as well as the in situ technologies used to assess local tuberculosis pathogenesis are also described. We need to strengthen and improve the exploratory strategies used to dissect immunopathogenesis in human tuberculosis with the aim to accelerate the implementation of relevant research findings in clinical practice.

TB or not TB? Difficulties in the diagnosis of tuberculosis in HIV-negative immigrants to Germany

Background

Immigrants to Germany and their children are at particular risk for tuberculosis (TB).

Methods

35 Patients (10 male/25 female aged 2 - 59 years (median 33 years) originating mostly from high incidence countries in Asia (19 [54.3%]) in Africa (14 [40.0%] and East Europe (2 [5.7%]), attended at the Tropical Medicine unit were analysed.

Results

Primary clinical presentation was most frequently lymphadenitis (13 [37.1%]). other organs involved included bones (7 [20.0%]), central nervous system (5 [14.3%]), urogenital organs (3 [8.6%]), lung (3 [8.6%]), mediastinum, (2 [5.7%]) and abdomen (2 [5.7%]). ESR was abnormal in 21/28 (75.0%), CRP in 20/35 (57.1%), and protein electrophoresis in 22/26 (84.6%) cases. The tuberculin skin test was strongly positive in all 15 cases where the test had been performed. Tuberculosis interferon gamma release assay (TB-IGRA) was positive in all 35 cases (100%). PCR for nucleic acids of Mycobacterium (M.) tuberculosis complex was positive in only 7/20 (35.0%) cases. M. tuberculosis was identified in 32/35 (91.4%), M. bovis in 2 (5.7%) cases. 1 case was diagnosed clinically. All patients were negative for HIV. Typical histopathology was seen in the 29 cases, where biopsies had been taken. Chest-X-ray did not reveal specific pulmonary lesions in the majority of cases (22/35 [62.9%]). Diagnosis of TB was mostly delayed (4 to 299 weeks, [median 8]). The most frequent primary suspicion was a malignancy (17/35 [48.6%]) while TB was initially suspected in 5 cases only. Diagnosis of TB is impeded by its multifaceted presentation especially in immigrants.

Adjunctive tests for diagnosis of tuberculosis: serology, ELISPOT for site-specific lymphocytes, urinary lipoarabinomannan, string test, and fine needle aspiration

The diagnostic gold standard for active tuberculosis (TB) is the detection of Mycobacterium tuberculosis (MTB) by culture or molecular methods. However, despite its limited sensitivity, sputum smear microscopy is still the mainstay of TB diagnosis in resource-limited settings. Consequently, diagnosis of smear-negative pulmonary and extrapulmonary TB remains challenging in such settings. A number of novel or alternative techniques could provide adjunctive diagnostic use in the context of difficult-to-diagnose TB. These may be especially useful in certain patient groups such as persons infected with human immunodeficiency virus (HIV) and children, who are disproportionably affected by smear-negative and extrapulmonary disease and who are also most adversely affected by delays in TB diagnosis and treatment. We review a selection of these methods that are independent of nucleic acid amplification techniques and could largely be implemented in resource-limited settings in current or adapted versions. Specifically, we discuss the diagnostic use and potential of serologic tests based on detection of antibodies to MTB antigens; interferon gamma release assays using site-specific lymphocytes; detection of lipoarabinomannan, a glycolipid of MTB, in urine; the string test, a novel technique to retrieve lower respiratory tract samples; and fine needle aspiration biopsy of lymph nodes.

T-SPOT.TB assay usage in adults and children

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

Impact of a Mycobacterium tuberculosis-specific interferon-γ release assay in bronchoalveolar lavage fluid for a rapid diagnosis of tuberculosis

OBJECTIVES

Evaluation of different methods for an initial treatment decision in individuals with suspected pulmonary tuberculosis.

BACKGROUND

Recently, important advances regarding the diagnosis of pulmonary tuberculosis have been introduced, which influence the decision to initiate anti-tuberculosis treatment.

METHODS

To evaluate the impact of different methods for the presumed diagnosis of tuberculosis, individuals with suspected tuberculosis were prospectively enrolled following a specific algorithm including initial smear microscopy and Mycobacterium tuberculosis-specific nucleic acid amplification (NAAT) from sputum. In cases of negative initial test results, tuberculin skin testing, bronchoscopy with transbronchial biopsies and interferon-γ release assays (IGRAs) in peripheral blood and bronchoalveolar lavage (BAL) fluid were performed.

RESULTS

Amongst 135 individuals with suspected tuberculosis, 42 had tuberculosis, 10 had nontuberculous mycobacteria pulmonary infection/colonization (one had both tuberculosis and nontuberculous mycobacteria pulmonary infection/colonization) and 84 had an alternative final diagnosis. The sensitivity and specificity were 41% and 99% [positive likelihood ratio (LR+) = 40] for sputum microscopy and 31% and 98% (LR+) = 16) for BAL nucleic acid amplification, respectively. In patients with acid-fast bacilli smear-negative tuberculosis (25/42, 59.5%), M. tuberculosis-specific BAL fluid IGRA was 92% sensitive and 87% specific (LR+) = 7) for the diagnosis of tuberculosis.

CONCLUSION

None of the microbiological or immunological methods that aim to provide a rapid diagnosis of tuberculosis whilst waiting the confirmation of the M. tuberculosis culture results is on its own accurate enough to diagnose or exclude pulmonary tuberculosis. Negative sputum microscopy and M. tuberculosis-specific NAAT results should prompt bronchoscopy including BAL for M. tuberculosis-specific IGRA in individuals with suspected pulmonary tuberculosis.

Clinical evaluation of a homemade enzyme-linked immunospot assay for the diagnosis of active tuberculosis in China

The rapid diagnosis of smear-negative pulmonary tuberculosis (TB) and extrapulmonary TB is a significant problem in clinical practice. We evaluated the usefulness of a homemade enzyme-linked immunospot (ELISPOT) assay for the diagnosis of active TB in China. Seventy-eight healthy volunteers, 60 patients with active TB, and 32 patients with non-TB diseases were evaluated by tuberculin skin test (TST), an ELISPOT assay using a recombinant CFP-10/ESAT-6 fusion protein (rCFP-10/ESAT-6) as a stimulant, and T-SPOT-TB assay. The spot-forming cells (SFC) from 78 healthy subjects containing both PPD-positive and -negative persons was 3.7 ± 6.5. Among 31 diagnosed TB patients, the ELISPOT assay had a sensitivity of 67.7%, compared to a sensitivity of 77.4% for the T-SPOT-TB assay. The ELISPOT assay was more sensitive in smear-positive TB cases (76.9%) than in smear-negative TB cases (61.1%), while T-SPOT-TB had roughly similar sensitivities in smear-positive (76.9%) and smear-negative TB cases (77.8%). The specificity was 90.6% for ELISPOT and 78.1% for T-SPOT-TB among 32 subjects with non-TB diseases. The SFC of TB cases was significantly higher than that of non-TB disease cases, and the SFC of smear-positive TB cases was significantly higher than that of smear-negative TB cases (P < 0.01). We confirmed that the homemade ELISPOT assay appears more specific for the diagnosis of active TB than T-SPOT-TB. ELISPOT assay may be a useful method for the rapid diagnosis of active TB, especially for cases of smear-negative TB.

Role of the Quantiferon-TB Test in Ruling Out Pleural Tuberculosis: A Multi-Centre Study

Diagnosing pleural tuberculosis (plTB) might be difficult due to limited sensitivity of conventional microbiology tools. As M. tuberculosis (MTB)-specific T cells are recruited into pleural space in plTB, their detection may provide useful clinical information. To this aim, in addition to standard diagnostic tests, we used the QuantiFERON-TB Gold In-Tube (QFT-IT) test in blood and pleural effusion (PE) samples from 48 patients with clinical suspicion of plTB, 18 (37.5%) of whom had confirmed plTB. Four of them (22.2%) tested positive with a nucleic acid amplification test for MTB. The tuberculin skin test was positive in most confirmed plTB cases (88.9%). Positive QFT-IT tests were significantly more frequent in patients with confirmed plTB, as compared to patients with an alternative diagnosis, both in blood (77.7 vs 36.6%, p=0.006) and in PE samples (83.3% vs 46.6%, p=0.02). In addition, both blood and PE MTB-stimulated IFN-γ levels were significantly higher in plTB patients (p=0.03 and p=0.0049 vs non-plTB, respectively). In blood samples, QFT-IT had 77.8% sensitivity and 63.3% specificity, resulting in 56.0% positive (PPV) and 82.6% negative (NPV) predictive values. On PE, QFT-IT sensitivity was 83.3% and specificity 53.3% (PPV 51.7% and NPV 84.2%). The optimal AUC-derived cut-off for MTB-stimulated pleural IFN-γ level was 3.01 IU/mL (77.8% sensitivity, 80% specificity, PPV 68.4% and NPV 82.8%). These data suggest that QFT-IT might have a role in ruling out plTB in clinical practice.

Interferon-γ release assays for the diagnosis of latent Mycobacterium tuberculosis infection: a systematic review and meta-analysis

We conducted a systematic review and meta-analysis to compare the accuracy of the QuantiFERON-TB® Gold In-Tube (QFT-G-IT) and the T-SPOT®.TB assays with the tuberculin skin test (TST) for the diagnosis of latent Mycobacterium tuberculosis infection (LTBI). The Medline, Embase and Cochrane databases were explored for relevant articles in November 2009. Specificities, and negative (NPV) and positive (PPV) predictive values of interferon-γ release assays (IGRAs) and the TST, and the exposure gradient influences on test results among bacille Calmette-Guérin (BCG) vaccinees were evaluated. Specificity of IGRAs varied 98-100%. In immunocompetent adults, NPV for progression to tuberculosis within 2 yrs were 97.8% for T-SPOT®.TB and 99.8% for QFT-G-IT. When test performance of an immunodiagnostic test was not restricted to prior positivity of another test, progression rates to tuberculosis among IGRA-positive individuals followed for 19-24 months varied 8-15%, exceeding those reported for the TST (2-3%). In multivariate analyses, the odd ratios for TST positivity following BCG vaccination varied 3-25, whereas IGRA results remained uninfluenced and IGRA positivity was clearly associated with exposure to contagious tuberculosis cases. IGRAs may have a relative advantage over the TST in detecting LTBI and allow the exclusion of M. tuberculosis infection with higher reliability.

Rapid diagnosis of tuberculous pericarditis by ELISPOT assay

We describe a case in which the rapid diagnosis of tuberculous pericarditis was made using the Mycobacterium tuberculosis (MTB)-specific enzyme-linked immunospot (ELISPOT) assay on pericardial effusion mononuclear cells (PEMCs). The analysis of MTB-specific T-cells in PEMCs by ELISPOT may be useful for rapid decision-making in anti-tuberculous treatment.