Evaluation of the performance of QuantiFERON®-TB Gold plus test in active tuberculosis patients

The aim was to evaluate the sensitivity and the possible factors affecting the sensitivity of the QuantiFERON®-TB Gold Plus (QFT-Plus) assay in culture-positive active TB (Tuberculosis) patients, to investigate the possible causes of negative and indeterminate results in active TB patients, and to compare the QFT-Plus results of active TB patients and latent tuberculosis infection (LTBI) cases. The QFT-Plus assay was performed in 46 active TB patients and 64 LTBI. The sensitivity of the test was found as 79.5% in all culture-positive patients, 72.7% in the immunocompromised patients, and 86.4% in the non-immunocompromised patients. Compared to active TB, individuals with LTBI had a lower T-cell response and lower IFN-ɣ concentrations. It was determined that the immunocompromisation reduced the sensitivity of the test and the secreted IFN-ɣ concentrations and increased the indeterminate results in patients with active TB. There was no difference in secreted IFN-ɣ concentrations between M. tuberculosis clones, but higher IFN-ɣ concentrations in patients infected with M. tuberculosis strains compared to patients infected with zoonotic strains. Compared with active TB, response to "only to TB2" was significantly higher in LTBI. In conclusion, it was concluded that TB2 tube increased sensitivity in LTBI but may not contribute to sensitivity in active TB.