David W. Connell

Utility of endobronchial ultrasound-guided transbronchial needle aspiration in patients with tuberculous intrathoracic lymphadenopathy: a multicentre study

Background Endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) has emerged as an important tool for the diagnosis and staging of lung cancer but its role in the diagnosis of tuberculous intrathoracic lymphadenopathy has not been established. The aim of this study was to describe the diagnostic utility of EBUS-TBNA in patients with intrathoracic lymphadenopathy due to tuberculosis (TB). Methods 156 consecutive patients with isolated intrathoracic TB lymphadenitis were studied across four centres over a 2-year period. Only patients with a confirmed diagnosis or unequivocal clinical and radiological response to antituberculous treatment during follow-up for a minimum of 6 months were included. All patients underwent routine clinical assessment and a CT scan prior to EBUS-TBNA. Demographic data, HIV status, pathological findings and microbiological results were recorded. Results EBUS-TBNA was diagnostic of TB in 146 patients (94%; 95% CI 88% to 97%). Pathological findings were consistent with TB in 134 patients (86%). Microbiological investigations yielded a positive culture of TB in 74 patients (47%) with a median time to positive culture of 16 days (range 3–84) and identified eight drug-resistant cases (5%). Ten patients (6%) did not have a specific diagnosis following EBUS; four underwent mediastinoscopy which confirmed the diagnosis of TB while six responded to empirical antituberculous therapy. There was one complication requiring an inpatient admission. Conclusions EBUS-TBNA is a safe and effective first-line investigation in patients with tuberculous intrathoracic lymphadenopathy.

IGRAs – The gateway to T cell based TB diagnosis

Development of Interferon-Gamma Release Assays (IGRAs) and implementation of their use in clinical practice almost 10 years ago has revolutionised diagnosis of latent tuberculosis (TB) infection (LTBI). The commercially available IGRAs, TSPOT.TB (Oxford Immunotech, Oxford, UK) and QuantiFERON Gold In-Tube (Cellestis, Victoria, Australia), allow detection of TB infection with greater specificity and sensitivity than the tuberculin skin test (TST) and are now recommended for diagnosis of LTBI. The TSPOT.TB assay is a simplified enzyme-linked immunospot assay (ELISpot) that enumerates TB-specific T lymphocytes (T cells) secreting interferon-gamma (IFNγ). In comparison, the QuantiFERON Gold In-Tube assay constitutes an enzyme-linked immunosorbent assay (ELISA) to quantify IFNγ released into blood plasma after incubation of whole blood with TB antigens. Release of IFNγ, as a result of antigen stimulation of TB-specific T cells within blood, is indicative of TB infection. Although IGRAs have significant advantages over the TST in diagnosis of latent TB, they have significant limitations. Discovery of new antigens and advances in methodology for measuring cellular immunity have recently paved the way for novel tests that overcome these limitations. By establishing for the first time technological platforms for T cell based diagnosis in diagnostic service laboratories, IGRAs provide a bridgehead to clinical application of T cell based diagnosis in routine practice.

Evaluation of screening methods for identification of patients with chronic rheumatological disease requiring tuberculosis chemoprophylaxis prior to commencement of TNF-α antagonist therapy

Background Patients undergoing tumour necrosis factor (TNF)-α antagonist therapy are at increased risk of latent tuberculosis infection (LTBI) reactivation. The aim of this study was to determine the optimum available screening strategy for identifying patients for tuberculosis (TB) chemoprophylaxis. Methods We conducted a prospective observational study of consecutive adults with chronic rheumatological disease referred for LTBI screening prior to commencement of TNF-α antagonist therapy. All patients included had calculation of TB risk according to age, ethnicity and year of UK entry, as described in the 2005 British Thoracic Society (BTS) guidelines and measurement of tuberculin skin test (TST) and T.Spot.TB. Results There were 187 patients included in the study, with 157 patients (84%) taking immunosuppressants. 137 patients would require further risk stratification according to the BTS algorithm, with 110 (80.3%) classified as being at low risk of having LTBI. There were 39 patients (35.5%) who were categorised as low risk but were either TST and/or T.Spot positive and would not have received chemoprophylaxis according to the BTS algorithm. Combination of all three methods (risk stratification and/or positive T.Spot and/or positive TST) identified 66 patients out of 137 who would potentially be offered chemoprophylaxis, which was greater than any single test or two-test combination. Conclusion Performing both a TST and T.Spot in patients on immunosuppressants prior to commencement of TNF-α antagonist therapy gives an additional yield of potential LTBI compared with use of risk stratification tables alone. Our results suggest that use of all three screening modalities gives the highest yield of patients potentially requiring chemoprophylaxis.

Performance of Xpert MTB/RIF in the Diagnosis of Tuberculous Mediastinal Lymphadenopathy by Endobronchial Ultrasound

RATIONALE The Xpert (GeneXpert) MTB/RIF, an integrated polymerase chain reaction assay, has not been systematically studied in extrapulmonary and in particular mediastinal tuberculosis (TB). OBJECTIVES To investigate the performance of Xpert MTB/RIF in the diagnosis of intrathoracic nodal TB in a large tertiary urban medical center in the UK. METHODS We collected clinical, cytological, and microbiological data from two cohorts: 116 consecutive patients referred with mediastinal lymphadenopathy with detailed diagnostic information obtained, and an immediately subsequent second cohort of 52 consecutive patients with microbiologically confirmed mediastinal TB lymphadenopathy. All data were derived between January 2010 and October 2012. All patients underwent endobronchial ultrasound and transbronchial needle aspiration (TBNA). The performance of a single Xpert MTB/RIF assay alongside standard investigations, cytology, and microscopy/culture was evaluated against culture-confirmed TB. MEASUREMENTS AND MAIN RESULTS Microbiologically confirmed TB mediastinal lymphadenopathy was diagnosed in a total of 88 patients from both cohorts. Three culture-negative cases with associated caseating granulomatous inflammation on TBNA were given a probable diagnosis. A single Xpert MTB/RIF assay demonstrated overall sensitivity for culture-positive TB of 72.6% (62.3-81.0%). Xpert specificity from cohort 1 was 96.3% (89.1-99.1%). The positive predictive value was 88.9% (69.7-97.1%), negative predictive value was 86.5% (76.9-92.1%), and odds ratio was 51.3 (24.0-98.0) for correctly identifying culture-positive disease. Xpert captured all microscopy-positive cases (14 of 14) and the majority of microscopy-negative cases (48 of 71, 67.6%). Among the cases that were culture positive by TBNA, Xpert identified two-thirds of the multiple drug-resistant TB cases, leading to immediate regimen change up to 5 weeks ahead of positive cultures. The use of Xpert combined with cytology increased the sensitivity to 96.6%. CONCLUSIONS Xpert MTB/RIF provides a rapid, useful, and accurate test to diagnose mediastinal nodal TB in intermediate-incidence settings. The additional use of TBNA cytology further enhances the sensitivity of Xpert. This combination can facilitate rapid risk assessment and prompt TB treatment.

Post-bronchoscopy sputum: Improving the diagnostic yield in smear negative pulmonary TB

INTRODUCTION Patients with suspected active Pulmonary Tuberculosis (PTB) who are Acid-Fast Bacilli (AFB) smear negative or non-productive of sputum may undergo bronchoalveolar lavage. However, post-bronchoscopy sputum (PBS) sampling is not routine. The aim of this study was to establish the potential diagnostic value of PBS sampling. METHODS A retrospective study of patients attending a London University hospital with microbiologically confirmed PTB between January 2004 and December 2010. Patients who were AFB smear negative or non-productive of sputum were eligible if sputum sampling was performed within 7 days of bronchoscopy. RESULTS Over the study period, 236 patients had microbiologically confirmed smear negative PTB of which 57 patients were eligible for the study. 15 patients (26.3%) were infected with HIV. 19 patients (33.3%) converted to AFB sputum smear positivity post-bronchoscopy and 5 patients (8.8%) were exclusively AFB sputum smear positive on PBS microscopy. Mycobacterium tuberculosis was cultured from the PBS of 43 patients (75.4%) and of these, 4 (7.0%) were exclusively PBS culture positive. CONCLUSION PBS analysis can provide a simple method of rapidly diagnosing pulmonary tuberculosis. In this cohort, M. tuberculosis culture yield was increased by 7% through PBS sampling. This study has important infection control implications with nearly one third of patients becoming more infectious after bronchoscopy.

Innate activation of human primary epithelial cells broadens the host response to Mycobacterium tuberculosis in the airways

Early events in the human airways determining whether exposure to Mycobacterium tuberculosis (Mtb) results in acquisition of infection are poorly understood. Epithelial cells are the dominant cell type in the lungs, but little is known about their role in tuberculosis. We hypothesised that human primary airway epithelial cells are part of the first line of defense against Mtb-infection and contribute to the protective host response in the human respiratory tract. We modelled these early airway-interactions with human primary bronchial epithelial cells (PBECs) and alveolar macrophages. By combining in vitro infection and transwell co-culture models with a global transcriptomic approach, we identified PBECs to be inert to direct Mtb-infection, yet to be potent responders within an Mtb-activated immune network, mediated by IL1β and type I interferon (IFN). Activation of PBECs by Mtb-infected alveolar macrophages and monocytes increased expression of known and novel antimycobacterial peptides, defensins and S100-family members and epithelial-myeloid interactions further shaped the immunological environment during Mtb-infection by promoting neutrophil influx. This is the first in depth analysis of the primary epithelial response to infection and offers new insights into their emerging role in tuberculosis through complementing and amplifying responses to Mtb.

Increased risk of Mycobacterium tuberculosis infection in household child contacts exposed to passive tobacco smoke.

Risk factors associated with Mycobacterium tuberculosis infection were investigated in a prospective cohort of household child tuberculosis contacts. A significantly increased risk of acquiring infection was associated with exposure to passive cigarette smoke, higher number of index cases, younger age and reduced household monthly income.

A presentation of Poncet's disease identified following immunosuppressive steroid therapy.

With many tuberculosis (TB) patients also human immunodefi ciency virus (HIV) infected, testing all TB patients for HIV is important so that HIV treatment can be initiated promptly. HIV testing in TB patients is one important route into combined HIV and TB treatment and care.1 We collected data as part of a multi-site crosss ectional study, Researching Equity in Access to Healthcare (REACH), to examine HIV testing coverage in TB patients, administering a structured questionnaire to 300 patients accessing TB treatment in fi ve primary health care clinics in Hlabisa subdistrict, KwaZulu-Natal, South Africa. These clinics operate within the Hlabisa HIV Treatment and Care Programme, with separate, vertically structured TB and HIV services devolved to the primary health care level.2 In 2009, the TB notifi cation rate in the area was approximately 928 per 100 000 population and HIV prevalence among adults in 2010 was 24%; the rate of co-infection was 76%.3 Fifty-three per cent of patients accessing TB care were female; the median age of the patients was 37 years. The majority (75%) were receiving care for a fi rst TB episode, mostly pulmonary TB. Although most patients were on DOTS, a substantial proportion (20%) did not take their medication under observation. Almost all patients (94%) reported that they had been offered HIV testing during their current TB treatment episode. The majority (97%) used the clinic closest to their homes; those who did were more likely to be offered HIV testing than those using a clinic further away (aOR 16.22, P < 0.01).* Among the 17 patients not offered HIV testing, 10 (59%) were female, and the median age was 33 years (18–75 years). There was no statistically signifi cant difference in age and sex between those offered and those not offered HIV testing, but the limited sample size would have reduced statistical power. We demonstrate high HIV testing rates among TB patients in a rural public programme in a high TB and HIV burden area, suggesting that TB-HIV coinfected patients can be managed appropriately for treatment of both infections.4 The decentralised programme appears largely successful in attaining universal HIV testing in TB patients5 in this resourcelimited setting. Our testing rate of 94% was slightly higher than the 88% seen previously in the area.3 However, there is scope for further improvement such as in DOTS delivery, a sustainable and e ffective way of ensuring good adherence to TB treatment. Patients mostly use the closest clinic for both TB treatment and HIV testing, suggesting a receding fear of stigma of HIV. However, the small number of patients not using the closest clinic are far less likely to undergo HIV testing, possibly indicating vulnerability expressed both in the location of seeking TB treatment and HIV testing uptake. Policy makers should encourage integration of services and cross-testing in HIVTB facilities.

Viral hepatitis prevalence in patients with active and latent tuberculosis.

AIM To assess the prevalence of hepatitis B virus (HBV) and hepatitis C virus (HCV) infection and association with drug induced liver injury (DILI) in patients undergoing anti-tuberculosis (TB) therapy. METHODS Four hundred and twenty nine patients with newly diagnosed TB - either active disease or latent infection - who were due to commence anti-TB therapy between September 2008 and May 2011 were included. These patients were prospectively tested for serological markers of HBV, HCV and human immunodeficiency virus (HIV) infections - hepatitis B core antigen (HBcAg), hepatitis B surface antigen (HBsAg), hepatitis B e antigen, IgG and IgM antibody to HBcAg (anti-HBc), HCV IgG antibody and HIV antibody using a combination of enzyme-linked immunosorbent assay, Western blot assay and polymerase chain reaction techniques. Patients were reviewed at least monthly during the TB treatment initiation phase. Liver function tests were measured prior to commencement of anti-TB therapy and 2-4 wk later. Liver function tests were also performed at any time the patient had significant nausea, vomiting, rash, or felt non-specifically unwell. Fishers exact test was used to measure significance in comparisons of proportions between groups. A P value of less than 0.05 was considered statistically significant. RESULTS Of the 429 patients, 270 (62.9%) had active TB disease and 159 (37.1%) had latent TB infection. 61 (14.2%) patients had isolated anti-HBc positivity, 11 (2.6%) were also HBsAg positive and 7 (1.6%) were HCV-antibody positive. 16/270 patients with active TB disease compared to 2/159 patients with latent TB infection had markers of chronic viral hepatitis (HBsAg or HCV antibody positive; P = 0.023). Similarly the proportion of HBsAg positive patients were significantly greater in the active vs latent TB infection group (10/43 vs 1/29, P = 0.04). The prevalence of chronic HBV or HCV was significantly higher than the estimated United Kingdom prevalence of 0.3% for each. We found no association between DILI and presence of serological markers of HBV or HCV. Three (5.3%) patients with serological markers of HBV or HCV infection had DILI compared to 25 (9.5%) patients without; P = 0.04. CONCLUSION Viral hepatitis screening should be considered in TB patients. DILI risk was not increased in patients with HBV/HCV.

Tuberculosis immunodiagnosis: delving below the surface

It is one hundred and thirty years since Franz Ziehl and Friedrich Neelsen developed the rapid stain for acid-fast bacilli;1 ,2 accurate point-of-care diagnosis of active tuberculosis (TB) remains a major unmet clinical need. With the sensitivity of the Ziehl–Neelsen stain in sputum less than 50% and more than 20% of TB cases negative on both acid-fast stain and culture for Mycobacterium tuberculosis , there has long been a yawning gap in the diagnostic toolkit for TB. New rapid molecular methods have recently improved detection of M tuberculosis nucleic acids in sputum providing diagnostic sensitivity that is much higher than sputum-smear microscopy but lower than culture.3 The longstanding diagnostic gap has stimulated decades of research into immunodiagnosis, mostly serological. Although serological tests for TB are point-of-care, they lack diagnostic accuracy and are devoid of clinical utility. After thorough review of the evidence, and on account of their continued widespread misuse in many high-burden countries, WHO recently tried to bury current commercial serological test kits with a negative endorsement warning against their use.4 Research into cellular immunodiagnosis has been more fruitful, delivering a tangible advance in clinical practice in the form of interferon-gamma release-assays (IGRA).5 IGRA detect M tuberculosis infection, providing a new standard-of-care for diagnosis of latent TB infection (LTBI), but they cannot distinguish active TB from LTBI. Hence, their potential role in evaluation of patients with suspected active TB is limited to that of a possible rule-out test of TB, yet currently available IGRA lack sufficient diagnostic sensitivity for this indication, as discussed elsewhere in this issue of Thorax .6 ,7 Are there immune responses that differ sufficiently between active TB and LTBI to enable development of an immunodiagnostic test that is specific for active TB? Quantifying genome-wide host gene-expression yielded a …