Screening potential of tuberculin skin and interferon gamma release tests for latent tuberculosis prior to anti-tumor necrosis factor (TNF)-α therapy in patients with rheumatoid arthritis and spondyloarthritis

Aim of the work: To compare between tuberculin skin test (TST) and interferon-gamma release test (IGRT) for latent tuberculosis infection (LTBI) screening before anti-tumor necrosis factor (TNF)-α therapy in patients with rheumatoid arthritis (RA) and spondyloarthritis (SpA) including radiographic (r)-axialSpA and psoriatic arthritis (PsA). Patients and methods: The study included 55 RA patients and 133 SpA: 93 radiographic r-axSpA (2 with PsA) and 40 PsA without axial involvement, receiving anti-TNF-α. TST and IGRT results were obtained before starting anti-TNF-α treatment. Results: The mean age for RA and SpA patients was 55.9 ± 10.7 and 46.3 ± 10.6 years, and disease duration was 9.1 ± 7.7 and 3.7 ± 2.9 years, respectively. The mean age (p < 0.001) and disease duration (p < 0.001) were significantly higher in RA patients, whereas male gender (p < 0.001) and smoking (p < 0.001) were more prominent in SpA patients. TST positivity, IGRT positivity and prophylactic antibiotic use were comparable between RA and SpA patients. Only prophylactic antibiotic use was significantly higher in r-axSpA patients (RA 18.2 %, r-axSpA 35.5 % and PsA 17.5 %, p = 0.024). The agreement between TST and IGRT was low for RA (κ = 0.34 and p = 0.003) and PsA patients (κ = 0.39 and p = 0.002) and moderate for r-axSpA (κ = 0.6 and p < 0.001). Non-smoking (p = 0.01), presence of Bacillus Calmette-Guerin vaccination (p = 0.005) and non-use of disease modifying anti-rheumatic drugs (DMARDs) (p = 0.04) were significant predictors for TST positivity, whereas non-use of DMARDs (p = 0.007) was the only significant predictor for IGRT positivity. Conclusion: The agreement between TST and IGRT was poor for RA and PsA and moderate for r-axSpA. IGRT may be more reliable in those receiving immunosuppressives.