An induration of 5 mm or more is considered positive in high-risk individuals with the following risk factors: HIV infection, recent contact with an active TB case within the past 2 years; fibronodular changes on chest X-ray consistent with healed TB (but not previously treated); immune suppression (e.g., from organ transplantation, TNF-α inhibitors, corticosteroids, etc.); or end-stage kidney disease requiring dialysis. This evidence concerns the gene TNF and tuberculosis.