Tuberculosis control relies on the identification and preventive treatment of individuals who are latently infected with Mycobacterium tuberculosis. However, direct identification of latent tuberculosis infection is not possible. The diagnostic tests used to identify individuals latently infected with M. tuberculosis, the in vivo tuberculin skin test and the ex vivo interferon-c release assays (IGRAs), are designed to identify an adaptive immune response against, but not necessarily a latent infection with, M. tuberculosis. The proportion of individuals who truly remain infected with M. tuberculosis after tuberculin skin test or IGRA conversion is unknown. It is also uncertain how long adaptive immune responses towards mycobacterial antigens persist in the absence of live mycobacteria. Clinical management and public healthcare policies for preventive chemotherapy against tuberculosis could be improved, if we were to gain a better understanding on M. tuberculosis latency and reactivation. This statement by the TBNET summarises knowledge and limitations of the currently available tests used in adults and children for the diagnosis of latent tuberculosis infection.In summary, the main issue regarding testing is to restrict it to those who are known to be at higher risk of developing tuberculosis and who are willing to accept preventive chemotherapy.

Anti-tumour necrosis factor (TNF) monoclonal antibodies or soluble TNF receptors have become an invaluable treatment against chronic inflammatory diseases, such as rheumatoid arthritis, inflammatory bowel disease and psoriasis. Individuals who are treated with TNF antagonists are at an increased risk of reactivating latent infections, especially tuberculosis (TB).Following TNF antagonist therapy, the relative risk for TB is increased up to 25 times, depending on the clinical setting and the TNF antagonist used. Interferon-c release assays or, as an alternative in individuals without a history of bacille Calmette-Guérin vaccination, tuberculin skin testing is recommended to screen all adult candidates for TNF antagonist treatment for the presence of latent infection with Mycobacterium tuberculosis.Moreover, paediatric practice suggests concomitant use of both the tuberculin skin test and an interferon-c release assay, as there are insufficient data in children to recommend one test over the other. Consequently, targeted preventive chemotherapy is highly recommended for all individuals with persistent M. tuberculosis-specific immune responses undergoing TNF antagonist therapy as it significantly reduces the risk of progression to TB. This TBNET consensus statement summarises current knowledge and expert opinions and provides evidence-based recommendations to reduce the TB risk among candidates for TNF antagonist therapy.KEYWORDS: Interferon-c release assay, tuberculin skin test, tuberculosis, tumour necrosis factor T umour necrosis factor (TNF) and TNF receptors play a key role in mediating immune responses in acute and chronic inflammation [1][2][3]. Over the past decade, TNF antagonists in the form of anti-TNF monoclonal antibodies or TNF fusion protein have become an invaluable treatment against chronic inflammatory diseases, such as rheumatoid arthritis, psoriasis and psoriatic arthritis, ankylosing spondylitis, juvenile idiopathic arthritis and inflammatory bowel disease [4][5][6][7]. Tuberculosis (TB) is a granulomatous disease caused by infection with Mycobacterium tuberculosis.Most of the individuals who are thought to have become infected with M. tuberculosis will never develop TB due to the control exercised by the host immune system [8,9]. One of the key cytokines in the immune response against infection with M. tuberculosis is TNF, which is also critical for the integrity of the granuloma [10]. Individuals who are being treated with anti-TNF therapies are at increased risk of developing TB. Following TNF antagonist therapy, the relative risk for TB is increased 1.6-25.1 times, depending on the clinical setting and the TNF antagonist used [4,7,11,12]. The majority of cases of TB related to TNF antagonist therapies occur in close temporal proximity to

Interferon-γ release assays (IGRAs) are now established for the immunodiagnosis of latent infection with Mycobacterium tuberculosis in many countries. However, the role of IGRAs for the diagnosis of active tuberculosis (TB) remains unclear. Following preferred reporting items for systematic reviews and meta-analyses (PRISMA) and quality assessment of diagnostic accuracy studies (QUADAS) guidelines, we searched PubMed, EMBASE and Cochrane databases to identify studies published in January 2001-November 2009 that evaluated the evidence of using QuantiFERON-TB® Gold in-tube (QFT-G-IT) and T-SPOT.TB® directly on blood or extrasanguinous specimens for the diagnosis of active TB. The literature search yielded 844 studies and 27 met the inclusion criteria. In blood and extrasanguinous fluids, the pooled sensitivity for the diagnosis of active TB was 80% (95% CI 75-84%) and 48% (95% CI 39-58%) for QFT-G-IT, and 81% (95% CI 78-84%) and 88% (confirmed and unconfirmed cases) (95% CI 82-92%) for T-SPOT.TB®, respectively. In blood and extrasanguinous fluids, the pooled specificity was 79% (95% CI 75-82%) and 82% (95% CI 70-91%) for QFT-G-IT, and 59% (95% CI 56-62%) and 82% (95% CI 78-86%) for T-SPOT.TB®, respectively. Although the diagnostic sensitivities of both IGRAs were higher than that of tuberculin skin tests, it was still not high enough to use as a rule out test for TB. Positive evidence for the use of IGRAs in compartments other than blood will require more independent and carefully designed prospective studies.

Human T cell responses to ESAT-6 and eight synthetic overlapping peptides were investigated in tuberculosis (TB) patients and control subjects from regions of high and low endemicity for TB. ESAT-6 was recognized by 65% of all tuberculin purified protein derivative-responsive TB patients, whereas only 2 of 29 bacille Calmette-Guérin-vaccinated Danish healthy donors recognized this molecule. In Ethiopia, a high frequency (58%) of healthy contacts of TB patients recognized ESAT-6. All of the peptides were recognized by some donors, indicating that the molecule holds multiple epitopes. Danish and Ethiopian patients differed in the fine specificity of their peptide responses. Recognition of the C-terminal region (aa 72-95) was predominant in Danish patients, whereas recognition of aa 42-75 was predominant in Ethiopia. The relationship of these differences to the distribution of HLA types in the two populations is discussed. This study demonstrates that ESAT-6 is frequently recognized during early infection and holds potential as a component of a future TB-specific diagnostic reagent.