Diagnosis for Latent Tuberculosis Infection: New Alternatives

Abstract

Latent tuberculosis infection (LTBI) is a subclinical mycobacterial infection defined on the basis of cellular immune response to mycobacterial antigens. The tuberculin skin test (TST) and the interferon gamma release assay (IGRA) are currently used to establish the diagnosis of LTB. However, neither TST nor IGRA is useful to discriminate between active and latent tuberculosis. Moreover, these tests cannot be used to predict whether an individual with LTBI will develop active tuberculosis (TB) or whether therapy for LTBI could be effective to decrease the risk of developing active TB. Therefore, in this article, we review current approaches and some efforts to identify an immunological marker that could be useful in distinguishing LTBI from TB and in evaluating the effectiveness of treatment of LTB on the risk of progression to active TB.

Keywords: IGRA; LTBI; LTBI diagnosis; TST; latent tuberculosis infection.

Figure 1

Summary of the actual and potential tools for the diagnosis of latent tuberculosis infection (LTBI). At the center of the figure, there is the C-TB skin test, which combines the sensitivity of the in vivo tuberculin skin test (TST) and the specificity of early secretory antigenic target (ESAT-6) and the 10-kDa culture filtrate protein (CFP-10) antigens for M. tuberculosis on the left side of the figure are the current diagnostic tools (TST and IGRA). On right side of the figure are listed some of the potential biomarkers to detect LTBI.