Latent tuberculosis and immune-mediated inflammatory diseases: the performance of TST and IGRA

Immunobiological drugs, especially tumor necrosis factor inhibitors, are indicated to treat immune-mediated inflammatory diseases by promoting a significant improvement in the clinical condition. However, this approach increases the risk of infections, including reactivation of latent tuberculosis infection (LTBI). We aimed to compare the performance of the tuberculin skin test (TST) and interferon-gamma release assay (IGRA) LTBI detection in patients with immune-mediated inflammatory diseases. A cross-sectional study included patients from Pedro Ernesto University Hospital, Rio de Janeiro State University, Rio de Janeiro, Brazil. Patients underwent TST by intradermal injection of purified protein derivative (PPD), with reading after 72h, and IGRA (TB-Feron or QuantiFERON-Plus). 114 patients were included, of whom 42 (34,4%) have rheumatoid arthritis, 31 (25,4%) psoriasis, 17 (13,9%) systemic lupus erythematosus, among other diseases. The following combinations of results were analyzed: TST+/IGRA+ = 6; TST+/IGRA- = 7; TST-/IGRA- = 86; TST-/IGRA+ = 15. Thus, a prevalence of LTBI of 24.5% (28/114) was identified in the study population. Thirteen (11.4%) patients were positive by using TST, while 21 (18.4%) were positive by IGRA. We observed an agreement of 80.7% between these tests. All patients identified with LTBI were prophylactically treated. In conclusion, our data highlighted the relevance of a better understanding of the novel LTBI tests and, especially their disagreements. Finally, IGRA seems to be a useful LTBI test among immune-mediated disease, since that IGRA alone allowed the identification of two cases not detected by TST.