THU0360 Interferon-gamma release assays in rheumatic patients: Baseline study and in the course of anti-tumor necrosis factor-alpha agents

Background IFN-γ release assays are useful methods for diagnosing LTBI (latent tuberculosis infection). It allow us to detect: a) false negative TST in anergic subjects, b) false positives in BCG-vaccinated patients and c) NTM (non-tuberculous mycobacterias) previously sensitized individuals. All in all, these tests contribute to detect additional cases of LTBI. Objectives To establish the usefulness of blood interferon-γ (IFN-γ) release assays in patients with inflammatory rheumatic diseases scheduled for anti-TNF-α treatment and at the follow up. Methods Prospective study including rheumatic patients starting an anti-TNF-α agent. All patients underwent TST (two step), a chest radiograph, QuantiFERON GOLD in tube (QFN-G-IT), and T-SPOT.TB. Both tests were repeated after a year of anti-TNF treatment in 21 patients. As control group, 35 adult individuals were included. Concordance were analyzed by Cohen’s kappa test. Results We included 53 patients (18 male/35 female) candidates for anti-TNF-α (18 rheumatoid arthritis, 13 ankylosing spondylitis, 9 psoriatic arthritis and 13 miscellanea). Mean age was 49±13 years and mean disease evolution was 8.8±8 years. Twenty-four out of 53 patients (45.3%) were receiving systemic steroids, mean daily dose 9.1±11.9 mg/day. BCG vaccination status was documented in 3 patients, 2 referred history suggestive of TB disease and other 3 patients had contact with a confirmed TB case in the past. The results of our study are summarized in Table 1. The differences in the results between the IFN-γ tests were not significant (p=0.675). Interestingly enough, neither T-SPOT.TB nor QFN-G-IT were significant in comparison to TST results (p=0.344 and p=0.727, respectively). Overall agreement between TST and T-SPOT.TB and QFN-G-IT was 77.35% (k=0.33; and k=0.40, respectively), and between both in vitro tests was 83.01% (k=0.57) was observed. Three patients with positive TST and negative T-SPOT.TB and QFN-G-IT, was positive on ELISPOT after stimulation with NTM sensitins. Positive TST, T-SPOT.TB and QFN-G-IT results were not affected by the immunosuppressive therapies. We found 4 conversions (1 patient convert T-SPOT and QFN, and 3 patients convert only T-POT) out of 21 cases evaluated after a year under anti-TNF-α agents. We also observed 2 reversions, one in a patient who had undergone prophylactic treatment for tuberculosis. Diagnostic testAll rheumatic patientsRheumatoid arthritis patientsAll 1 year after treatment with anti-TNF-α n=53