Clinical applicability of Quantiferon-TB-Gold testing in psoriasis patients during long-term anti-TNF-alpha treatment: a prospective, observational study

Background Psoriasis patients who are treated with tumour necrosis factor (TNF)‐alpha antagonists are at increased risk of reactivation of latent tuberculosis infection (LTBI) and should be adequately screened and monitored during active treatment. Objectives To evaluate in a prospective study, the performance of Quantiferon‐TB‐Gold in tube (QFT) in vitro assay compared to the conventional tuberculin skin test (TST) in detecting LTBI among a cohort of non‐BCG‐vaccinated patients with moderate‐to‐severe psoriasis during long‐term treatment (12 months) with TNF‐alpha antagonists. Methods A total of 50 patients underwent QFT and TST testing at baseline and after 6 and 12 months of continuous anti‐TNF‐alpha treatment. Diagnosis of LTBI was made on the basis of a positive QFT result and negative chest‐radiographic and microbiological assays. Patients with LTBI were subjected to standard isoniazid chemoprophylaxis and after 1 month, they resumed anti‐TNF‐alpha treatment with subsequent QFT and TST testing after 6 months. In all the cases, a follow‐up period of 12 months was observed. Results During the 12‐month‐study period, 14% of patients presented a QFT conversion. During active anti‐TNF‐alpha treatment, a QFT conversion was observed in 10% of patients (five cases). Agreement between QFT and TST was moderate (κ = 0.408) at screening, good (κ = 0.734) after 6 months and fair (κ = 0.328) after 12 months of treatment. A total of 18% of patients presented a positive, discordant TST during the study period. Conclusions A single‐test QFT‐based screening strategy for LTBI in psoriasis patients receiving long‐term anti‐TNF‐alpha treatment could reduce the incidence of false‐positive LTBI cases, preventing unnecessary TB chemoprophylaxis.