Scatter plot of TST measurement and QFT-GIT assay (IU/ml) results. Tuberculin skin test (TST) was performed by injecting 0.1 ml Tuberculin PPD RT 23 intradermally on the ventral aspect of the left forearm. After 48-72 hours, the transverse diameter of the skin induration was measured using a plastic ruler graduated in millimeters. A positive TST result was defined as an induration of ≥10mm. QuantiFERON®-TB Gold In-Tube (QFT-GIT) assay was performed according to the manufacturer’s instructions. The QFT-GIT (IU/ml) raw data was analyzed by using QuantiFERON®-TB Gold IT Analysis Software and reported as Negative, Positive and Indeterminate. In this figure, the correlation between the two latent tuberculosis infection (LTBI) test results, TST in mm and QFT-GIT in IU/ml, was assessed by spearman correlation; Spearman correlation coefficient = 0.81, p<0.05.