D3.63 - 5 Year Follow Up: Unveiling True Beta-Lactam Immediate Hypersensitivity in the University of Chile Clinical Hospital

Hypersensitivity to beta-lactam antibiotics (BL) can cause serious consequences at an individual and public health level, forcing us to use second-line treatments that can be less effective and more expensive. Despite its importance, the prevalence of allergy to beta-lactams has not yet been established in our country. 

Objective

Determine the prevalence of beta-lactam allergy in patients with suspected immediate hypersensitivity reaction (IHR).

We conducted a retrospective descriptive study by analyzing clinical records and results of skin tests and drug provocation tests (DPT) in patients evaluated for suspected allergy to BL at the allergy center of the Clinical Hospital of the University of Chile from January 2020 to December 2024. We evaluated the subcohort of patients with suspicion of IHR based on the clinical history.

We included 101 patients with IHR out of 170 patients with suspicion of allergy to BL. 74% were female with an average age of 44 years and 13.8% were underage. The main manifestation was anaphylaxis (56%), while the remaining had urticaria and/or angioedema (UA/AE). The most implicated drugs were amoxicillin and cefazolin accounting for over 80% of cases. 

Out of all patients, the positivity was: 2.9% in skin prick test (SPT), 28.7% in intradermal reaction (IDR) and 5.9% in both. 60 patients underwent DPT, with a 5% positivity. The remaining 41 patients had another culprit agent or did not complete protocol. 

Finally, allergy status was defined as: confirmed with positive SPT or IDR and a compatible history (35.6%); ruled out with a negative complete protocol (SPT, IDR and DPT) or with another culprit agent identified (39.6%). The remaining 24.8% could not be categorized. When we analyze the subfractions of patients that had anaphylaxis and UA/AE, the confirmation of allergy varies to 52.6% and 13.64% respectively.

Allergy to BL in Chile appears to be higher than reported internationally, standing out that over half of patients with anaphylaxis were confirmed allergic. Allergy diagnosis was based on compatible history plus a positive skin test on the basis of a high specificity of skin tests to BL reported in the literature and the local infrastructure and lack of personnel that hinders the realization of DPT. It is also worth mentioning that almost a quarter of patients could not be clearly categorized as allergic or non-allergic, mainly due to lack of DPT after negative skin tests, which poses the challenge to implement standardized local health strategies.