Do IFN-γ-release assays predict the risk of TB? New evidence from a study on patients with silicosis

Abstract

Evaluation of: Leung CC, Yam WC, Yew WW et al. T-SPOT.TB outperforms tuberculin skin test in predicting tuberculosis disease. Am. J. Respir. Crit. Care Med. DOI: 10.1164/rccm.200912-1875OC (2010) (Epub ahead of print).

IFN-γ-release assays (IGRAs) are new tools for the diagnosis of latent TB infection which, until recently, relied only on the use of the tuberculin skin test (TST). However, while the positive predictive value of a positive TST for active TB is well established, little evidence on this issue is available for IGRAs. In a study conducted on silicosis patients in Hong Kong, China, Leung et al. found that a positive response to an IGRA, the T-SPOT.TB, was associated with a larger than fourfold increase in the risk of developing TB compared with those who tested negative, while a smaller than twofold increase was observed for TST-positives compared with negatives. This study provides further support to the guidelines from public health agencies recommending the use of IGRAs in place of or in addition to TST. Several issues regarding their optimal use, however, remain open to debate.

Keywords::

• CFP-10
• ESAT-6
• IFN-γ-release assay
• isoniazid preventive therapy
• latent tuberculosis infection
• QuantiFERON TB-Gold In tube
• T-SPOT.TB
• tuberculin skin test
• tuberculosis

Financial & competing interests disclosure

The authors have a European patent on a T-cell assay based on selected RD1 peptides for the diagnosis of TB; they received support for the participation in a scientific meeting from the Italian dealer of the QuantiFERON TB-Gold In tube, and a research grant from the producer of TB-SPOT.TB. The authors are supported by the grants ‘Ricerca Corrente’ and ‘Ricerca Finalizzata’ 06.76.1 and 07.103 from the Italian Ministry of Health. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

No writing assistance was utilized in the production of this manuscript.