Tuberculin skin tests among medical students with prior bacille-Calmette Guérin vaccination in a setting with a high prevalence of tuberculosis.

Presence of a bacille Calmette-Guérin vaccination scar in medical students was an independent factor associated with initial tuberculin skin test reactions of 10-19 mm (P=.03) and booster effects of 6-9 mm (P=.02). These findings suggest that an initial tuberculin skin test reaction of at least 20 mm or a booster effect of at least 10 mm will reveal tuberculosis among students with prior bacille Calmette-Guérin vaccination.