Does having more than one TST placed in 1 year pose any risk?
No risk exists for having TSTs placed multiple times per year. • Can repeated TSTs, by themselves, cause the TST result to convert from negative to positive? No, the TST itself does not cause false-positive results. Exposure to other mycobacteria or BCG vaccination can cause false-positive TST results. • What defines a negative TST result? A TST result of 0 mm or a measurement below the defined cut point for each criteria category is considered a negative TST result (Box 2). • What defines a positive TST result? A TST result of any millimeter reading above or at the defined cut point for each criteria category is considered a positive TST result (Box 2). The cut point (5 mm, 10 mm, and 15 mm) varies according to the purpose of the test (e.g., infectioncontrol surveillance or medical and diagnostic evaluation, or contact investigation versus baseline testing). • What defines a false-negative result? A false-negative TST or QFTG result is one that is interpreted as negative for a particu
