Betalactams (BL) are the main elicitor of antibiotic hypersensitivity reactions (HRs). We describe our experience in diagnostic methods used to get a confirmed diagnosis.
Between 2015 and 2017, 80 subjects were confirmed as BL allergic. To achieve diagnosis, in vivo (skin prick and intradermal tests) and in vitro tests (basophil activation test (BAT) and RAST) were performed and gold standard drug provocation test (DPT) if necessary.
RESULTS: A total of 66% referred amoxicillin-clavulanic acid (AX-CLV) as trigger HRs, followed by AX (21%), penicillin (6%) and cephalosporins (5%). Almost 80% of HRs were immediate (<60 minutes). Positivity of skin tests was observed in 65% subjects, of BAT in 61% and of RAST in 68%. Finally, in 67% of subjects DPT was performed to define diagnosis. Immediate HRs patients reacted to a median dose of 20mg (5-500mg) of penicillin and 287mg (5-500mg) of AX whereas non-immediate HRs patients reacted after a full therapeutic dose during a home treatment course. Finally, 44% subjects were diagnosed as selective allergic to AX, 32% as selective to CLV, 22% allergic to all BL and 2% selective allergic to cephalosporins.
Increase of selective allergic patients to AX and CLV is evident due to their widely utilization, while hypersensitivity to all BL is decreasing. Therefore, performance of combination of in vivo and in vitro test followed by DPT in patients referring HRs due to AX-CLV and AX is transcendent in terms of determining an accurate diagnosis and safety performance of DPT.