D3.62 - Beta-Lactam Hypersensitivity: 5-year characterization of patients evaluated at the University of Chile Clinical Hospital

Beta-lactam antibiotics are the first-line treatment for many bacterial infections and at the same time one of the leading causes of drug-induced anaphylaxis worldwide. Last year we conducted the first study in our country to determine the prevalence of sensitization to beta-lactams in patients with suspected allergies and determined that 28.7% of the patients had a beta-lactams sensitization. Based on this background we decided to continue this line of work and expand the follow up time. 

Objectives 

Clinically characterize the chilean population with suspected beta-lactam hypersensitivity and their sensitization profile, tested the last 5 years in the University of Chile Clinical Hospital. 

A descriptive study was conducted with a retrospective analysis of variables where we analyzed clinical records and the results of skin tests and drug provocation tests in patients evaluated for suspected hypersensitivity to beta-lactams at the allergy center of the University of Chile Clinical Hospital from January 2020 to December 2024.

The study included 170 patients, predominantly females in 71% of the cases, with an average age of 40.2 years (ages 1 to 80 years). The main clinical manifestation was anaphylaxis in 35% of cases, followed by urticaria and exanthema (27% of cases each). 

Over 40% of patients were studied within the first year after the reaction, ascending to 55% in case of anaphylaxis. The most implicated drugs were amoxicillin and cefazolin; highlighting that 81.4% of patients with suspected cefazolin hypersensitivity have had anaphylaxis. In 47% of the cases, beta-lactams were not the only suspicious drug responsible for the reaction.

Skin tests and drug provocation tests were conducted in 85% and 59% of patients respectively, 15% only underwent provocation testing.  Overall, we found sensitization in skin tests to beta-lactams in 26.5% of the studied population.

Once again the obtained sensitization is higher than reported in the literature, revealing a particular phenomenon that is worth continuing investigating and remarks the importance of knowing our local population, considering the massive use of beta- lactams in our country. The high prevalence obtained raises the question whether these findings correspond only to sensitization or true allergy, which will be addressed separately.