PCR: polymerase chain reaction, PPD: purified protein derivative, RPR: rapid plasma regain, VDRL: Venereal Disease Research Laboratory, HIV: human immunodeficiency virus, TB: tuberculosis, CMV: cytomegalovirus, EBV: Epstein-Barr virus, IGRAs: interferon-gamma release assays. The gene discussed is IFNG; the disease is tuberculosis.