Italian cases assessed by NGS
A total of 24 Italian cases with T-cell-mediated hypersensitivity to penicillins and 20 with immediate hypersensitivity were studied by NGS-based HLA genotyping. The participants were recruited in the allergy units of the Columbus Hospital, Rome, Italy and Oasi Research Institute-IRCCS, Troina, Italy between January 2000 and June 2016. Participants were evaluated by skin tests and patch tests with penicillin reagents, as previously described.16,17Skin tests and patch tests with five cephalosporins were also performed. The inclusion criterion of the 24 cases was a reported delayed reaction to penicillin and a positive patch test and/or delayed-reading skin test result to at least one penicillin reagent. The 20 cases with immediate hypersensitivity had typical clinical presentations and positive prick and/or intradermal reactions. The cases with negative cephalosporin allergy tests underwent controlled administrations of therapeutic doses of the cephalosporins concerned (Supplemental Table 1 ), as previously described.16 The 24 subjects were classified into three groups according to the results of skin testing: group A, positive to ampicillin and amoxicillin; group B, positive to benzylpenicillin, ampicillin, and amoxicillin; and group C, positive to all three penicillins and aminocephalosporins.