A comparison of the performance of two penicillin reagent kits in the diagnosis of beta-lactam hypersensitivity

Background: Skin testing with penicilloyl polylysine (PPL) and minor determinant mixture (MDM) represents the first-line method for diagnosing beta-lactam hypersensitivity. However, in 2004, Allergopharma and Hollister-Stier announced their decision to stop the production of penicillin reagents (Allergopen((R)) and PrePen((R)), respectively) within 1 year. Therefore, we decided to compare PPL and MDM from Allergopharma (Allergopen) with those from Diater (DAP((R))). Methods: We skin-tested 195 subjects with both Allergopen and DAP reagents, as well as with other beta-lactams; 74 (group A) had had immediate reactions to beta-lactams and 74 (group B) nonimmediate reactions, while 47 (group C) underwent prophylactic tests. Results: One hundred two patients (52.3%) had positive skin tests; 29 (14.9%) were positive to PPL and/or MDM. Of the 102 skin-test-positive patients, 44 belonged to group A, 57 to B and 1 to C; the last was positive only to Allergopen PPL (PPL-A) and tolerated the benzylpenicillin challenge. Minor determinant mixture reagents produced identical results in the 148 patients of groups A and B, 22 (14.9%) of which were positive. Both PPL reagents produced negative results in 139 of these 148 patients and positive ones in 5; one subject was positive to DAP PPL (PPL-D) and negative to PPL-A, while three patients were positive to PPL-A and negative to PPL-D; two of the latter tolerated benzylpenicillin challenges. Conclusions: Minor determinant mixture reagents produced identical results in all 195 patients. Results of skin testing with PPL reagents were concordant in 190 (97.4%) of them. Therefore, DAP reagents are a reliable alternative to Allergopen ones.