Figure 1.

QFT and TST analyses. (a) IFN-γ levels as measured by QFT. The levels of IFN-γ were assayed in whole blood from CC and HW QFT positive individuals and TB patients participating in the study by using the QFT kit. IFN-γ levels are expressed as IU/mL (IU_IFN-γ/mL = IU_IFN-γ/mL detected in TB1 or TB2 antigen tube – IU_IFN-γ/mL measured in Nil tube). (b) Diameter of induration as measured by the Tuberculin Skin Test (TST). Purified protein derivative (PPD) was administered and 48–72 h after the injection, the skin test reaction was measured as mm of the induration. Mean ± SEM for each group of subjects is shown. **P < 0.01. P-values were calculated by Kruskal-Wallis test and Dunn’s multiple comparisons post-test for unpaired samples. Each symbol represents an individual. (c) Scatter plot of IFN-γ levels (as measured by QFT) and diameter of induration (as measured by TST). IFN-γ levels were assayed in whole blood using the QFT kit and were expressed as IU/mL. The skin test reaction was measured as mm of the induration after 48–72 h of PPD injection. The vertical dotted line represents the TST cut-off (10 mm); the horizontal dotted line indicates the QFT cut-off (0.35 IU_IFN-γ/mL). Percent Concordant = 78%; Percent Discordant = 22%. Kappa = 0.530. SE of kappa = 0.067. Moderate agreement.