Serial QuantiFERON TB-Gold in-tube testing during LTBI therapy in candidates for TNFi treatment

Objectives: To evaluate the T-cell interferon (IFN)-γ response to Mycobacterium tuberculosis-specific antigens during latent tuberculosis infection (LTBI) therapy in candidates for tumor necrosis factor-α inhibitors (TNFi). Methods: 1490 Patients were screened for LTBI. One-hundred and sixty-six of them were treated for LTBI and followed-up with QuantiFERON-TB Gold (QFT-IT) testing at baseline (T0) and therapy completion (T1); 92 subjects were also tested 3-6 months after therapy completion (T2). Results: At T1 the QFT-IT reversion and conversion rates were 24% (27/111) and 18% (10/55), respectively. By multivariate analysis, the likelihood of reversion significantly decreased with older age (>50-60), larger TST size (>15 mm) and higher IFN-γ value at T0 (>1 IU/ml); the likelihood of conversion increased with higher IFN-γ levels at T0 (1 IU/ml) and in female patients. Quantitative data among those who scored QFT-IT-positive at T0 showed a decreasing trend of IFN-γ levels between T0 and T1 that reached statistical significance when T0 was compared to T2, and T1 to T2. Conclusions: The data confirm the difficulty of interpreting the modulation of IFN-γ levels during LTBI therapy. Currently, there is no evidence to support the use of QFT-IT in the clinical practice of monitoring LTBI treatment in candidates for TNFi.