Comparison of QuantiFERON-TB Gold Plus vs tuberculin skin test in a healthy population in Mexico

<b>Introduction:</b> One third of the world9s population is infected with latent tuberculosis (LTBI) (Getahun H, et al, N Engl J Med 2015;372(22):2127-2135), 34% cases of contacts have been reported using Tuberculin Skin Test (TST) and 41% with QuantiFERON-TB Gold Plus (QFT-Plus) (Serrano-Escobedo CJ, et al, Arch Med Res. 2013;44(3):242-248), however, there are no studies for comparison of the two in population without risk factors. <b>Objective:</b> To compare reactivity to QFT-Plus vs TST in a healthy population in the northeast of Mexico. <b>Methods:</b> Cross-sectional study conducted in healthy patients over 18 years old. Patients with a history of tuberculosis or risk factors&nbsp;for acquiring it were excluded. TST and QFT-Plus were performed&nbsp;simultaneously after informed consent process. Patients who did not attend the TST measurement at 72 hours were eliminated. A TST ≥ 10 mm and/or QFT-Plus ≥ 0.35 IU/ml were considered as positive. <b>Results:</b> A total of 151 subjects, 27 (71.1%) women&nbsp;and 11 (28.9%) men with a media age of 43±12, were included. Positivity to either test was: 38 (25%) by TST and 47 (31%) by QFT-Plus. 69 (45.7%) subjects had a positive result for either one of the tests. BCG vaccination was identified in&nbsp;36 (86.8%) of those with a positive TST, and in&nbsp;39 (83%) with a positive QFT-Plus. Agreement between tests&nbsp;was assessed with&nbsp;Kappa (0.169), Table 1. <b>Conclusions:</b> An elevated percentage of subjects had positive result for either test. QFT-Plus performed better than TST, and there was a poor agreement between the two. BCG vaccination&nbsp;didn9t seem to interfere with either test.