Background Mexico is a high burden tuberculosis (Tb) country. Inflammatory rheumatic diseases such as rheumatoid arthritis have an increased risk of Tb associated with both RA activity itself and treatment requirement, particularly TNF inhibitors (iTNF). According biological therapy (BT) guidelines, before the BT, a screening with tuberculin skin test (TST) must be performed to define Tb chemoprophylaxis therapy. Few studies describe the effect of BT on TST reactivity, and the benefit of treatment of latent Tb in spite of the low sensitivity of TST, as well as the necessity of receiving chemoprophylaxis in case of conversion of PPD when BT is maintained.

Objectives To determinate dermo-conversion of TST (latent tuberculosis) in patients under biological therapy with a previous negative basal screening test.

Methods TST were made basal and each year in adult patients with aggressive rheumatoid arthritis who required biological therapy. Basal evaluation in all patients included a normal chest X-ray and negative TST without active tuberculosis history. Most of them (85%) had been vaccinated with BCG during pediatric age and only 5% had probable familiar history of active tuberculosis. All of patients were asymptomatic and denied recent relationship with an active tuberculosis patient. In case of a positive TST, additionally to complete clinical evaluation we performed laboratory tests and chest X-ray to discard active Tb.

Results We included 155 patients treated with biologic therapy with screening test negatives to latent tuberculosis; 75 received abatacept (ABA), 19 rituximab (RTX), 33 tocilizumab (TCZ) y 28 others different to iTNF biologic therapies. TST changed to positive in 23 patients, 8 with ABA, 3 RTX and 12 TCZ, with average time of treatment of 6.5, 3.7 and 5 years, respectively. Interestingly despite to have received chemoprophylaxis only 2 patients (1 ABA, 1 TCZ), none of them had evidence of active tuberculosis with subsequent following of 3.3 years under biologic therapy.

Conclusions PPD + in patients with biologic therapy do not seem “per se” to indicate necessity of chemoprophylaxis in spite of a higher prevalence of tuberculosis in our country. BT could not modify the immune response, specifically to TST.

Disclosure of Interest None Declared