Targeted tuberculin testing is a strategic component of tuberculosis (TB) control that identifies persons at high risk for developing TB who would benefit by treatment of TB, if detected. The appearance of an indurated area of 5mm or more 48 to 72 hours after administration of purified protein derivative (PPD) is considered a positive reaction in persons who have recently had close contact with an individual with active tuberculosis, in persons with radiographic findings consistent with a past history of tuberculosis or in persons with known or suspected human immunodeficiency virus infection. Ten or more millimeters of induration is considered a positive reaction in persons at increased risk of tuberculosis. Induration of 15mm or more is considered a positive result in all other persons. Ten percent to 25% of people with active tuberculosis have false‐negative test results, especially early in treatment. Some people who are not infected have a reaction due to infection with other mycobacterial species or to bacilli Calmette‐Guerin vaccine BCG).