Evaluation of systemic provocation tests in patients with suspected allergic and pseudoallergic drug reactions.

In order to examine the diagnostic value of systemic provocation tests, we studied 56 inpatients hospitalized for identification of the agent eliciting previous severe allergic or pseudoallergic reactions to non-steroidal anti-inflammatory drugs, local anaesthetics or antibiotics. Skin tests were positive in only 4 patients reacting to antibiotics and propyphenazone and were always negative for local anaesthetics (n = 32). Only 4 of 26 patients reacted to oral or subcutaneous provocation, 3 times to penicillin and once each to mepivacain, propyphenazone and cyanocobalamine when the suspected drug was tested. In the remaining 30 patients, who for safety reasons were tested only with alternative drugs, none had positive reactions, but 11 patients reported non-specific symptoms, as did 9 of 21 patients given placebo. Systemic provocation tests for drug allergy thus gave few positive results. However, these tests should always be done together with placebo testing for validation of results, and they remain indispensable for identification of alternative, well-tolerated drugs.