Further, to identify HHCs for whom treatment could safely be withheld due to likely natural TB immunity, we compared QFT consistent negatives with Household contacts with Mtb infection and identified a 4-protein signature (bFGF, GCSF, IFNγ, and IL1RA) that correctly classified QFT consistent negatives with an AUC of 0.81 and a disappointing specificity of 62.5%. The gene discussed is CSF3; the disease is tuberculosis.