Objective: To compare the performance of two interferon γ release assays (IGRAs) and conventional screening tests in patients with inflammatory arthritis undergoing screening for latent tuberculosis infection (LTBI) before treatment with anti-tumour necrosis factor α (anti-TNFα) compounds.
Methods: Successive patients were subjected to conventional LTBI screening, including a tuberculin skin test (TST). The T-SPOT.TB test was performed on all patients and the QuantiFERON-TB Gold test was performed on a large subset. The results of the IGRAs were compared with the results of conventional screening tests.
Results: A total 150 patients were evaluated. The majority (57.9%) had rheumatoid arthritis. Previous vaccination with Bacille Calmette–Guerin was confirmed in 82% of patients. No patient had received prior anti-TB treatment. A total of 57 patients (38.0%) had at least one positive conventional risk factor. In contrast, an unequivocally positive T-SPOT.TB test was seen in only 14/143 (9.8%). There was 98.2% agreement between the two IGRAs. Statistically significant associations were found between each of the IGRAs and both TST and risk history, but not chest x-ray (CXR). A positive IGRA result was significantly associated with increased age. TB was not reactivated in any patient during the follow-up period.
Interpretation: This study suggests that IGRAs may be useful when screening for LTBI before anti-TNFα therapy in patients with immune-mediated inflammatory diseases. The observations reported here also highlight the inadequate performance of CXR as a marker of LTBI.
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▸ Additional data are published online only at http://ard.bmj.com/content/vol69/issue1
Funding This research was supported by unconditional grants from Abbott Immunology, Wyeth Pharmaceuticals and Schering Plough.
Competing interests None.
Contributors: JM, DV, OF and BB participated in the study design, patient recruitment, data collection and analysis and preparation of the manuscript. CW and UF established the interferon γ release assays and assisted with data analysis and preparation of the manuscript. AG participated in patient recruitment and data collection. TM and JK participated in the study design, data analysis and preparation of the manuscript. JD advised on interpretation of the chest radiographs. MBC assisted in the statistical analysis of the data.