Once the best threshold value for the ELISpot IL-2 result was set for each specific antigen to discriminate between subjects with active TB and subjects with LTBI, the correlation between ELISpot and TST, that is still the standard test for MTB infection diagnosis, was assessed for every antigen by computing The Cohen's Kappa coefficient and interpreting the data as described above. The gene discussed is IL2; the disease is tuberculosis.