Comparative evaluation of QuantiFERON-TB Gold Plus for diagnosis of latent tuberculosis infection during solid organ transplantation

BACKGROUND: The diagnosis of latent tuberculosis infection (LTBI) in solid organ transplantation (SOT) patients under lifelong immunosuppression has profound effects on preoperative and postoperative management. Interferon-gamma release assay (IGRA) is widely used to screen LTBI before or after transplantation. METHODS: We evaluated the effect of posttransplantation immunosuppression on IGRA and influencing factors by measuring interval change of QuantiFERON-TB Gold Plus (QFT-Plus) between pretransplantation (pre-QFT-Plus) and posttransplantation (post-QFT-Plus) state in 20 patients who previously had reactive IGRA but not taken LTBI treatment. RESULTS: Eleven (55%) out of 20 pre-QFT-Plus reactive patients became nonreactive state in repeated QFT-Plus (post-QFT-Plus) at 194–413 days (median, 257 days) after transplantation (discordant group). Even in persistently reactive group (concordant group), interferon-gamma (IFN-γ) levels after transplantation were decreased about 34% and 36% of their pretransplantation levels for TB1 and TB2, respectively. The only significant factors that affect interval change of QFT-Plus between pre- and post-SOT status were the concentrations of IFN-γ in pre-QFT-Plus (6.93 vs. 0.44 IU/mL in TB1 and 7.33 vs. 0.71 IU/mL in TB2). CONCLUSIONS: The reactivity of QFT-Plus is significantly compromised by immunosuppressive therapy, which increase the risk of false negative, particularly in patients with low level of IGRA reactivity. Therefore, interpretation of IGRA under immunosuppressive treatment require a caution and eventually, more sensitive tuberculosis-specific cytokine markers might be needed.