D3.90 - Outcomes of Beta-Lactam Allergy Evaluation in Patients with Suspected Hypersensitivity: One-Year Experience

Beta-lactam (BL) allergy is one of the most frequently reported drug hypersensitivities, although it is confirmed after diagnostic evaluation in only a minority of cases. Incorrect labeling may lead to the use of suboptimal antibiotic alternatives, contribute to antimicrobial resistance, and increase healthcare costs. The aim of this study was to assess the prevalence of confirmed BL allergy and to determine the proportion of patients with an inaccurate allergy label among those referred with suspected BL hypersensitivity over a one-year period.

A retrospective observational study was performed including all adult patients (≥18 years) evaluated for suspected BL allergy in our allergy unit during 2024. Demographic data and clinical characteristics of the index reaction were collected, including the implicated BL antibiotic, indication for prescription, route of administration, latency to symptom onset, clinical manifestations, and time since the reaction. All patients underwent skin testing with prick and intradermal tests, and total and specific serum immunoglobulin E levels were measured when clinically indicated. Drug provocation tests were performed to confirm or exclude BL allergy. Diagnostic outcomes were analyzed.

A total of 242 patients were included (61.2% female), with a mean age of 51.7 years (range 18–86 years). The most frequently implicated antibiotics were penicillin (33.1%), amoxicillin–clavulanate (28.9%), and amoxicillin (27.7%), with aminopenicillins accounting for 91.3% of cases. Reactions occurring within the previous year represented 28.5% of the total. The most common clinical manifestations were cutaneous reactions (57.8%) and anaphylaxis (11.2%), followed by gastrointestinal symptoms (4.5%).  BL allergy was ruled out in 168 patients (69.4%). Drug allergy was diagnosed in 67 patients (27.6%), most frequently involving aminopenicillins (13.6%) and clavulanic acid (4.9%) in the overall cohort. 

BL allergy was excluded in more than two-thirds of patients referred with suspected hypersensitivity.  Accurate diagnostic evaluation enabled safe delabeling and facilitated the identification of alternative antibiotics in patients with confirmed allergy, representing a simple and effective intervention to optimize antibiotic use and improve clinical management.