Background Tumor Necrosis Factor-α (TNF-α) inhibitors have increased risk of reactivation of latent tuberculosis infection (LTBI). Screening for LTBI before initiating anti-TNF therapy is recommended.(1) Tuberculin skin test (TST) and in vitro interferon-γ (IFN-γ) assays; Quantiferon-TB Gold In-Tube test (QTF-IT) are used for screening LTBI.(2) In patients refractory to standart therapies in Behçet’s disease (BD) and Takayasu’s arteritis (TA), TNF-α inhibitors are new therapy options.(3)
Objectives To screen for LTBI in BD and TA patients with TST and QTF-IT and to find out the agreement between two tests.
Methods Forty patients with BD who fulfilled the 1990 International Study Group Criteria and 40 TA patients who fulfilled the 1990 American College of Rheumatology Classification Criteria were included in this study. As the control groups, 80 healthy subjects, age and sex-matched with patients were also included. Along with healthy controls, both BD and TA cases were evaluated for LTBI by using TST and QTF-IT tests.
Results The percentage of TST positivity was significantly higher in patients group than healthy controls. TST positivity was 80% in TA patients, 65% in BD patients and 35% in healthy controls. There were no differences between BD and TA patients in TST positivity. In contrast, there were no differences between QTF-IT positivity in patients and healthy controls. QTF-IT positivity was 35% in TA patients, 25% in BD patients and 21.3% in healthy controls. There were also no differences between BD and TA patients in QTF-IT positivity. The total agreement between QTF-IT and TST was observed to be 53.33% in the whole group, 60% in BD, 50% in TA and 65.71% in healthy controls. Their level of agreement was low in all groups (κ=0.25, 0.30, 0.15, 0.23). This discordance was thought to be related to the false positive TST values according to prior BCG vaccination.
Conclusions In a country with a high incidence of TB and BCG vaccination, the QTF-IT test might help to differentiate false positive TST results from LTBI. Because there is no gold standart screening test for LTBI; patients should also be evaluated with clinics and radiographic findings. Further studies are needed for patients with vasculitis.
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Karadag O, Aksu K et al. Assessment of latent tuberculosis infection in Takayasu arteritis with tuberculin skin test and Quantiferon-TB Gold test. Rheumatol Int 2010;30:1483-87.
Disclosure of Interest None Declared