The effect of topical calcipotriol or zinc on tuberculin skin tests in hospitalised South African children

BACKGROUND: The tuberculin skin test (TST) is used to help diagnose tuberculosis (TB) in acutely ill hospitalised children. OBJECTIVE: To investigate the potential augmentative effect of topical calcipotriol (a vitamin D analogue) or zinc on TST induration. METHODS: Three TSTs were performed among 64 hospitalised children; each site was covered with topical aqueous cream (control), calcipotriol or zinc and assessed 24 and 48 h later by investigators blinded to all topical applications. RESULTS: TSTs were reactive in 15 (23.4%) children, of whom 13 (20.3%) were TST-positive. Topical calcipotriol and zinc induced TST positivity in two children with reactive but negative control TSTs. These treatments, however, did not significantly increase TST positivity rates. In children with reactive TSTs, the median 48 h induration diameter was not significantly different between the control, calcipotriol- or zinc-treated groups, which were respectively 12.0 (25%-75% IQR 5.0-18.0), 14.0 (25%-75% IQR 10.0-15.0) and 12.0 (25%-75% IQR 8.0-15.0) mm. Topical treatments did not induce TST reactivity or TST positivity in children with culture-confirmed TB disease (n = 4), human immunodeficiency virus infection (n = 18) or kwashiorkor (n = 9). CONCLUSIONS: Topical calcipotriol or zinc does not induce TST reactivity or significantly increase TST positivity rates in acutely ill hospitalised children. However, further studies are required to assess the effects of topical treatments on TST positivity in severely malnourished children.