[The value of prick tests in the detection of anaphylaxis caused by muscle relaxants].

Intradermal tests (IDR) are a sure diagnostic procedure for confirming the IgE origin of anaphylactoid accidents due to muscle relaxant drugs. Because carrying these out and interpreting them correctly is difficult, epidermal prick-tests (PT) could be used if they proved as sure as IDR. To ascertain this, IDR and PT were carried out in 38 patients who had a shock after being given a muscle relaxant 6 months to 5 years previously; for these tests, increasing concentrations of five muscle relaxants were used (suxamethonium, gallamine, alcuronium, pancuronium and vecuronium). The PT were also carried out with the five same pure and diluted muscle relaxants in a group of 147 volunteer controls. For the 38 patients, PT and IDR were always positive for the same drugs, but at different concentrations, the epiderm seeming less sensitive than the derm (with a ratio of 1 to 100). In the control group, all the tests were negative, even with the pure drug. PT with muscle relaxants were sensitive, specific of anaphylaxis, and permanent. Easy to carry out, easily interpreted, they could be useful as tests for predicting latent sensitisation in risk patients requiring muscle relaxants. But all muscle relaxants must be tested, and not just the one the anaesthetist is likely to use.