Use of lidocaine-prilocaine patch for the mantoux test: Influence on pain and reading.

A formulation of a eutectic mixture of lidocaine-prilocaine (EMLA) changes basal skin perfusion. Its use for alleviating pain associated with the Mantoux test may modify the recruitment of sensitised lymphocytes and then the response to tuberculin test. Twenty-four healthy BCG-vaccinated volunteers (26.7+/-4.1 years) received on each forearm an intradermal injection of 10IU tuberculin, one of the forearms being randomly pre-treated for 1h with EMLA-patch 5%. Pain associated with the Mantoux test was evaluated using a visual analogue scale. The transversal diameter of the induration was read at 72h. Subjects with 6mm difference between diameters (i.e. twice the usual variation for a Mantoux test) were recorded. Results were compared using a paired t-test. When using lidocaine-prilocaine prior to the test, a three-fold decrease in pain was noted (p<0.0001). Reading of the test were not affected by the lidocaine-prilocaine application (p=0.26). Four subjects had 6mm or more difference between their two tests, two of them having an induration greater than 15mm with lidocaine-prilocaine. Lidocaine-prilocaine reduces significantly pain associated with the Mantoux test but does not normally affect the test reading. However, when the induration is more than 15mm, a control without lidocaine-prilocaine has to be considered.