The effect of open heart surgery on tuberculin skin test reactivity

To examine whether treatment with cardiopulmonary bypass (CPB), which causes transient cellular immunity depression, influences tuberculin skin testing (TST) interpretation. The study was also aimed to assess the degree of cellular immunity depression following open heart surgery. Fifteen children from developing countries with latent tuberculosis (TST ≥10 mm), undergoing open heart surgery had their TST repeated within 48-72 h following surgery. We compared the size of skin test induration before and after surgery and the relation of postsurgery skin induration to time on CPB (pump time). There was no significant difference in the size of induration before and after surgery (mean: 14.7 mm versus 13 mm, respectively). Pump time ranged from 38 to 204 min (mean: 110 min). Two of the children had pump time over 3 h. The TST of both of them turned negative after surgery, as opposed to all other children (P = 0.01). Most patients retained skin test reactivity. Only patients with pump time longer than 3 h had a negative TST.