Performance of LTBI Screening in Patients with Rheumatic Diseases Using Two Different Interferon-Gamma Releasing Assays

Abstract

Background: To evaluate the concordance between QuantiFERON-TB Gold in-tube test (QFT-GIT) and T-SPOT.TB test (T-SPOT) for the screening of latent tuberculosis infection (LTBI) in patients with rheumatic diseases (RDs). Methods: Patients diagnosed as rheumatic diseases (RDs) with clinical indications for test of interferon gamma release test (IGRA) were prospectively recruited from 2019 to 2020. The consistency of QFT-GIT and T-SPOT was assessed by Kappa analysis and the factors associated with the indeterminate results were explored by multivariable logistic analysis. Results: A total of 108 patients with RDs were enrolled, including 64 patients with systemic lupus erythematosus (SLE) and 44 with inflammatory arthritis (26 with rheumatoid arthritis (RA) and 18 with ankylosing spondylitis (AS)). Poor concordance was confirmed between QFT-GIT and T-SPOT results in patients with SLE (K = 0.175, 95% confidence interval [95% CI] [-0.06, 0.40], p < 0.001), whereas concordance was moderate in patients with inflammatory arthritis (K = 0.539, 95% CI [0.11, 0.88], p < 0.001). Among SLE patients, the ratio of indeterminate results in detecting LTBI was significantly higher by QFT-GIT than by T-SPOT (18.8% vs. 4.7%, p = 0.013), while the statistical difference was not achieved in patients with inflammatory arthritis. The multivariable logistic analysis identified that the presence of lower lymphocyte counts (odds ratio [OR] = 0.81, 95% CI [0.68, 0.97], p = 0.020) was the independent predictor of an indeterminate result of the QFT-GIT in SLE patients. Conclusions: In patients with RDs, the result of screening of LTBI was more definitive by T-SPOT test than QFT, and the concordance was poor especially in the setting of SLE.

PD-1/PD-L1 governed cross-talk of exhausted CD8+T and memory B cells in systemic lupus erythematosus

“…It is noteworthy that indeterminate QFT 4 result are prevalent among patients with SLE in juxtaposition with other rheumatic musculoskeletal diseases (RMDs), 5 which is largely attributed to suboptimal readouts of the positive control according to our preliminary observations. In other words, peripheral blood mononuclear cells (PBMCs) from patients with SLE have shown an insufficient interferon-γ response (IIR) to phytohaemagglutinin (PHA), which might lead to this interesting laboratory finding, that is, indeterminate QFT results.…”