Work up of patients with history of beta-lactam hypersensitivity.

INTRODUCTION Beta-lactam antibiotics are the most frequent cause of antibiotic hypersensitivity reactions. The study of all cases of suspected beta-lactam hypersensitivity is highly important, to avoid the use of less efficient or more expensive alternatives, for fear of a reaction. MATERIALS AND METHODS Sixty-seven consecutive patients with suspected beta-lactam hypersensitivity reactions were studied. Skin prick tests (SPT), intradermal tests (IDT) and specific IgE determination were performed. In non-immediate reactions, epicutaneous testing was also done. If all were negative, a drug challenge was performed. RESULTS Sixty-seven patients (54 female symbol), with a mean age + or - SD of 36.6 + or -19.3 years (4-78 years) were studied. The self-reported antibiotics were amoxicillin and amoxicillin/clavulanic acid in 30 (45%), penicillin in 24 (36%), cephalosporins in 11 (16%) and flucloxacillin in 2 (3%). SPT and IDT were positive in 6 patients (9%) and specific IgE in 11 (16%). Only one patient had both positive specific IgE and skin tests. Of the remaining 51 cases, 33 underwent a drug challenge with the culprit antibiotic, with a positive reaction in 2 (6%). In all positive cases and when a drug challenge with the suspected antibiotic was not indicated, a challenge with an alternative drug was done, all with negative results. CONCLUSIONS Of the 67 studied cases with history of beta-lactam hypersensitivity reactions, 18 (27%) were confirmed after testing. A combination of skin testing, specific IgE determination and drug challenge is necessary since none has sufficient sensitivity to be used alone.