Prevalence of beta-lactam allergies & factors predicting genuine allergies in Hong Kong

Abstract

Introduction: Beta-lactams (BL) are the most widely used class of antibiotics and most frequently reported cause of drug allergy. However, the vast majority of patients are found not to be genuinely allergic after allergy evaluation. Despite devastating consequences of incorrect allergy labelling, few studies have investigated the predictors of genuine BL allergies and the local epidemiology in Hong Kong is unknown. Methods: Demographic and allergic data from patients admitted to the acute medical wards of Queen Mary Hospital over a period of 6 months were analysed to identify the prevalence and factors associated with the presence of BL allergy labels in Hong Kong. A combined cohort of patients having completed allergy investigation for suspected BL allergies in the United Kingdom and Hong Kong were analysed. Association analysis comparing the clinical characteristics of confirmed BL allergic and non-allergic patients was performed to identify predictors of genuine allergy. Results: The local prevalence of BL allergy labels was 5% in Hong Kong, which was associated with female sex and concomitant non-BL antibiotic allergy labels. After completing allergy testing, the rate of genuine BL allergy was only 14%. History of anaphylaxis and duration of <1 year since the index reaction were independent clinical predictors of genuine BL allergy. The negative predictive value of penicillin skin testing was 90%. There was an alarmingly high rate of confirmed piperacillin-tazobactam allergy. Discussion: The estimated true prevalence of genuine BL allergy in Hong Kong is around 0.5%. This high rate of BL mislabelling highlights the need for comprehensive allergy evaluation and screening. Physicians should be reminded to ascertain history of anaphylaxis and duration since the index reaction as clinical predictors of genuine BL allergy. Piperacillin-tazobactam allergy may pose a unique challenge to our locality with high prevalence of suspected allergies, surging antibiotic resistance and lack of testing available.