OBJECTIVE: To compare the performance of two interferon gamma 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 alpha (anti-TNFalpha) 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-TNFalpha therapy in patients with immune-mediated inflammatory 
diseases. The observations reported here also highlight the inadequate 
performance of CXR as a marker of LTBI.