Distribution of Mantoux test results by mm induration among 155 exposed health care workers and 48 healthy controls. Left columns: percent of total number of exposed health care workers (HCWs). Right columns: percent of total number of healthy controls. HCWs with a previous positive TST (by Mantoux test ≥ 10 mm increase or ≥ 15 mm if previously unknown) where not retested, but were counted as ≥ 15 mm. The distribution of T-SPOT.TB positives is indicated by white circles; all of these 5 HCWs had ≥ 15 mm induration or were vesicular.