Authors (including presenting author) :
Li PH, Lau CS.
Affiliation :
Division of Rheumatology and Clinical Immunology, Department of Medicine, Queen Mary Hospital, University of Hong Kong, Hong Kong
Introduction :
Allergy to β-lactam (BL) antibiotics is one of the most frequently reported drug reactions, and the prevalence of penicillin allergy in western populations has been estimated at approximately 10%. However, many patients mistakenly self-report non–immune-mediated adverse drug reactions as allergy, and up to 90% of these patients are found not to be genuinely allergic after evaluation. Misreported BL antibiotic allergies are associated with obligatory use of less effective antibiotics and a multitude of adverse clinical consequences.
Epidemiological data are crucial for guiding urgently needed BL antibiotic allergy testing, especially against the growing pandemic of antimicrobial resistance. Our previous pilot study conducted in Queen Mary Hospital (QMH) found a 5% prevalence of misreported BL allergy in a cohort of hospitalized patients. However, epidemiological data of incorrect BL allergy labels in the general Hong Kong/Chinese populations are lacking.
Evaluation of reactions suggestive of BL antibiotic allergy includes history taking, skin tests (including skin prick and intradermal), and drug provocation tests. Ethnic- and region-specific data on sensitization patterns are needed to determine optimal local antibiotic skin test strategies, but studies from Chinese cohorts have not yet been performed. Furthermore, few studies have looked into the incidence rather than just prevalence of reported BL antibiotic allergy; that is, how many new reports of BL antibiotic allergy are being generated over time. Such data would be of immense advantage in further delineating the rate of the rapidly increasing need for BL antibiotic allergy testing.
Objectives :
To identify the prevalence, incidence and sensitization patterns of reported BL antibiotic allergy in patients in Hong Kong.
Methodology :
To study the prevalence and incidence of reported BL allergy, we retrieved anonymized data regarding physician-reported drug allergies from the Hospital Authority Clinical Management Systems in Hong Kong (study period: between 2018-2019).
To study the sensitization pattern of patients with BL antibiotic allergy, we analyzed a subgroup of patients who were referred to QMH for BL antibiotic allergy testing during the study period. All results and outcomes of allergological workup were reviewed and analyzed.
Result & Outcome :
Complete records of a total of 7 184 271 unique patients were analyzed, representing more than 95% of the total estimated population of Hong Kong (7 524 100 in 2019), with a men to women ratio of 1:1.2 and with a median age of 44 years. Of the 7 184 271 patients, 511 492 (7.1%) had physician-reported drug allergies, of which 143 483 (28.1%) were BL antibiotic allergies. The point prevalence of BL antibiotic allergy labels was therefore 2.0% (95% CI, 1.99%-2.01%). The cumulative incidence was 107 per 100 000 population, with 8032 new BL antibiotic allergies reported in 2018 alone.
Skin tests were performed between 2018 to 2019 for a subgroup of 355 patients (referred to QMH) with reactions suggestive of BL antibiotic allergies. However, only 14% had positive skin test results. Among those who completed full BL allergy testing (including a drug provocation test), only 14% of all suspected BL allergies were confirmed to be genuine (86% of incorrect BL allergy labels were removed).
In conclusion, we performed the largest epidemiological study of BL antibiotic allergies ever reported, and the first among Chinese patients. In Hong Kong, the near-absolute prevalence of physician-reported BL antibiotic allergies was 2.0% of the 7.1 million patient records we examined. The cumulative incidence was 107 per 100 000 population, with more than 8000 new BL antibiotic allergies reported in 2018 alone. However, after complete allergological workup, only 14% of these reported BL allergies were found to be genuine (i.e. 86% of patients were mislabelled and patients could reintroduce BL without problems).
This overwhelming prevalence, incidence of BL allergy (but also high rate of mislabeling) highlights the urgent need and demand for Immunology & Allergy services in Hong Kong.
