Position statement on interferon-γ release assays for the detection of latent tuberculosis infection.

Interferon-y release assays (IGRAs), such as the Quantiferon (QIFN) TB-Gold Plus assay (Qiagen, Hilden, Germany) and the T-SPOT.TB test (Oxford Immunotec Limited, Abingdon, United Kingdom), are marketed as a substitute for the tuberculin skin test (TST) for the detection of latent tuberculosis infection (LTBI). The relative merits of IGRAs and TST have been hotly debated over the last decade. The specificity of IGRAs has been optimised by using Mycobacterium tuberculosis-specific antigens. However, IGRAs are functional in vitro T-cell-based assays that may lack reproducibility due to specimen collection, transport, processing and kit manufacturing issues. Longitudinal studies comparing the ability of IGRAs and TST to predict the future development of active tuberculosis disease (TB) are the ultimate arbiters on the respective utility of these assays. Three meta-analyses addressing this comparison have now been published and clinical experience with IGRAs is accumulating. The systematic reviews show that IGRAs and TST have similar (but poor) ability to identify patients with LTBI at risk of developing active TB disease. The improved specificity of IGRAs however may reduce the number of patients requiring preventative therapy. Based on these meta-analyses, The National Tuberculosis Advisory Committee (NTAC) now recommends either TST or an IGRA for the investigation of LTBI in most circumstances. Both tests may be used in patients where the risk of progression to active TB disease is high and the disease sequelae potentially severe (eg. LTBI testing in immunocompromised patients or those commencing anti-tumour necrosis factor-ą (TNF) therapy). Neither test should be used in the investigation of active TB disease (though TST and/or IGRA may be used as supplementary tests in paediatric cases). The choice of test for serial testing in healthcare workers (HCWs) remains controversial. A preference remains for TST in this circumstance because IGRAs have been bedevilled by higher rates of reversions and conversions when used for serial testing. These recommendations supersede all previous NTAC IGRA statements. This work is copyright. You may download, display, print and reproduce the whole or part of this work in unaltered form for your own personal use or, if you are part of an organisation, for internal use within your organisation, but only if you or your organisation do not use the reproduction for any commercial purpose and retain this copyright notice and all disclaimer notices as part of that reproduction. Apart from rights to use as permitted by the Copyright Act 1968 or allowed by this copyright notice, all other rights are reserved and you are not allowed to reproduce the whole or any part of this work in any way (electronic or otherwise) without first being given the specific written permission from the Commonwealth to do so. Requests and inquiries concerning reproduction and rights are to be sent to the Online, Services and External Relations Branch, Department of Health, GPO Box 9848, Canberra ACT 2601, or by email to copyright@health.gov.au.