OP3-Evaluation of patients with a reported beta-lactam allergy for de-labelling

Abstract

Introduction

Beta-lactams are the most common cause of drug hypersensitivity reactions and are self-reported by at least 10% of patients. A label of β-lactam allergy alters treatment decisions, resulting in suboptimal therapy, increased costs, and the emergence of antibiotic resistance. When evaluated and tested, 90% of patients can be successfully de-labelled

Objectives

This study explored the clinical characteristics and risk profiles of patients with reported β-lactam allergy and evaluated them for de-labeling using skin prick tests (SPT), intradermal tests (IDT), and graded challenges (GC).

Design, setting, and methods

A descriptive cross-sectional study was conducted from November 2023 to February 2024 at the Faculty of Medicine, University of Kelaniya. Adult patients (≥18 years) with self-reported or documented β-lactam allergy were consecutively enrolled from the outpatient department of North Colombo Teaching Hospital and the Medical Research Institute. An interviewer-administered questionnaire was used to assess patients clinically.  SPT, IDT, and GC were performed according to standard procedures for de-labelling.

Results

Among the 158 patients assessed, 68% were female, and the mean age was 45 years. The majority (61%, n = 96) reported a single allergy episode, while 39% (n = 61) experienced multiple episodes. While 11% of the allergies were self-reported, 89% had been diagnosed by a doctor.

Amoxicillin was the most common allergen (66%, n = 105), followed by co-amoxiclav (20%), penicillin (15%), cephalexin (6%), cefuroxime (1%), and ceftriaxone (1%). Concurrent allergy to NSAIDs was reported by 30% (n=46).

According to clinical presentations, the risk categories for allergy evaluation included 13% (n=20) low-risk and 87% (n=138) high-risk.

Allergy testing was performed in 115 out of 158 patients using SPT, IDT, and GC. A total of 75 patients (65%) were de-labelled. De-labeling rates were 61% (n = 61) for high-risk patients and 93% (n = 14) for low-risk patients, which were statistically significant (p = 0.0286). De-labeling rates were similar between patients with single allergy episodes (69.1%) and multiple allergy episodes (58.7%) (p=0.253).

Conclusion

A detailed clinical evaluation, skin testing, and graded challenges identified that 65% of patients with a reported β -lactam allergy could be de-labeled, allowing for subsequent safe β-lactam use. This highlights the importance of formal allergy evaluation to reduce the misdiagnosis of β-lactam allergy.