Characteristics, risk factors and clinical impact of penicillin and other antibiotic allergies in adults in the UK General Practice: a population-based cohort study.

Objective: To assess the characteristics, risk factors and clinical impact of penicillin and other antibiotic allergies labels in general practice in the UK.

Design: Population-based cohort study.

Setting: Primary care in the UK, 2000-2018.

Participants: Adults aged 18-100 years who were registered with their general practice for at least 12 months between 01-Jan-2000 and 31-Dec-2018 and followed until 25-Sep-2019.

Main Outcome Measures: The main outcomes include the annual prevalence and incidence of penicillin and other antibiotic allergies labels. Multinominal logistic regression was used to examine the characteristics associated with receiving an allergy label to different antibiotics. Cox regression modelling was used to compare the risk of resistant infections (methicillin resistant Staphylococcus aureus [MRSA] and vancomycin resistant enterococci) as well as Clostridioides difficile (C.difficile) infection between patients with and without allergy labels. The monthly proportion of patients who had a penicillin allergy test, either before their allergy label was recorded or within one year, was calculated to assess any impact of NICE penicillin allergy assessment recommendations (Clinical guideline [CG183]) in September 2014.

Results: Both the prevalence and incidence of penicillin allergy label showed a pattern of initial growth followed by a decline. The prevalence reached a maximum of 8.25% in 2011, and the incidence peaked at 0.46% in 2004. Older age, being female, living in less deprived areas, belonging to a larger general practice, and having co-morbidities were associated with a higher chance of receiving a penicillin or other antibiotic allergy label. Patients with antibiotic allergy labels were more likely to receive alternative broad-spectrum antibiotics and had a higher risk of MRSA and C.difficile infections. The introduction of NICE drug allergy guideline did not alter the proportion of patients undergoing penicillin allergy assessment.

Conclusion: Penicillin and other antibiotic allergy labels are common and lead to radical change in the antibiotic prescribing practices and are associated with resistant and healthcare associated infections.