Comparative evaluation of quantiFERON-TB gold in-tube and quantiFERON-TB gold plus in diagnosis of latent tuberculosis infection in immunocompromised patients

Abstract

QuantiFERON-TB Gold Plus (QFT-Plus) is a new-generation QuantiFERON-TBGold In-Tube (QFT-GIT) assay which has two antigen-coated tubes called TB1, whichcontains long peptides derived from ESAT-6 and CFP-10, and TB2, which containsthe same components as TB1 and additional short peptides which potentially stimulate CD8 T cells through the presentation of major histocompatibility complex classI. This is the first study to compare QFT-Plus and QFT-GIT for use in the diagnosis oflatent tuberculosis infection (LTBI) among immunocompromised patients in the Republic of Korea. Among 317 consecutive patients who underwent screening for LTBIbefore solid organ or hematopoietic stem cell transplantation and tumor necrosisfactor alpha inhibitor treatment, LTBI was identified in 92 (29.0%) and 88 (27.8%) patients by QFT-GIT and QFT-Plus, respectively. The rate of concordance between QFTGIT and QFT-Plus was 93.7% (value, 0.860), and the indeterminate rate (3.2%) wassimilar between QFT-GIT and QFT-Plus. Of 20 (6.3%) samples with discordant results,11 (55.0%) and 7 (35.0%) were positive by QFT-GIT alone and QFT-Plus alone, respectively, and 2 (15.0%) were indeterminate by each assay. The interferon gammalevel in samples with discordant results ranged from 0.39 to 1.10 IU/ml, except forone sample, in which the gamma interferon level was 2.97 IU/ml only in TB2. Conclusively, there was a high degree of agreement between the results of QFT-GITand QFT-Plus for the screening of immunocompromised patients for LTBI. The reactivity in TB2 contributed substantially to the difference between QFT-GIT andQFT-Plus, particularly in solid organ transplant candidates. The significance of thediscrete responses in TB1 and TB2 of QFT-Plus needs to be explored further bymeans of an immunological and clinical approach in different patient groups andclinical settings.