The 'either test positive' strategy for latent tuberculous infection before anti-tumour necrosis factor treatment

SETTING: A tertiary referral centre in South Korea. OBJECTIVES: The `either test positive' strategy, incorporating both the tuberculin skin test (TST) and the TSPOT (R).TB (T-SPOT) assay, was evaluated as a novel method for diagnosing latent tuberculous infection (LTBI) before treatment with anti-tumour necrosis factor (TNF) in patients with immune-mediated inflammatory diseases. DESIGN: From June 2008 to April 2012, 430 patients received anti-TNF treatment at our institution. TST and T-SPOT were performed simultaneously at baseline. LTBI was defined as a positive TST or a positive T-SPOT result. RESULTS: The positivity rates for the TST and T-SPOT assays were respectively 19.1% (82/430) and 44.2% (190/430), yielding an LTBI-positive rate of 48.6% (209/430). LTBI treatment was initiated in 46.0% (198/ 430) of patients and was completed by 89.4% (177/ 198). During follow-up (median 884 days), 0.9% (4/ 430) of the patients developed active tuberculosis (TB). All four TB patients were TST-negative at baseline, although two received LTBI treatment based on the baseline positive T-SPOT assay results. CONCLUSIONS: The either test positive strategy is a valid method for diagnosing LTBI before anti-TNF treatment, although it is not clear whether it is superior to other strategies.