Estimation of the prevalence of latent tuberculosis infection in patients with moderate to severe plaque psoriasis in Spain: The Latent study.

Background And Objective: Anti-tumor necrosis factor therapy for moderate to severe psoriasis can increase the risk of active tuberculosis in patients who have latent tuberculosis infection (LTBI). The main objective of this study was to estimate the prevalence of LTBI in patients with moderate to severe plaque psoriasis being treated in dermatology clinics in Spain.

Material And Method: Non-interventional, cross-sectional, national epidemiological study conducted in Spain in 2011-2012. Patients with moderate to severe plaque psoriasis were included if they had undergone at least one tuberculin skin test (TST) and/or been evaluated with an interferon-γ release assay (IGRA) based on enzyme-linked immunosorbent assay (QuantiFERON(®) TB Gold In-Tube) in the 2 years preceding the study.

Results: Data for 440 patients were valid for analysis. In total, 97.7% of the patients had undergone a TST, with a positive result in 23%. Of the 238 patients in whom the initial result was negative, 5% converted to positive on re-testing for a booster effect. IGRA results were available for 16.8%, 20.5% of them positive. Two of the patients with positive IGRA results had a negative TST. The prevalence of LTBI in the whole sample was 26.6%. The degree of concordance between the TST and the IGRA was moderate (κ=0.516; P<.001).

Conclusions: The prevalence of LTBI in this study was similar to previous estimates for Spain.