Epidemiology of penicillin allergy labels in a general Swedish population

Penicillin allergy prevalence is reported in up to 10% of patients and is linked to broad-spectrum antibiotic overuse, extended hospitalizations, and higher mortality. Its prevalence has not previously been evaluated in Sweden.

The aim of this study was to investigate the prevalence and characteristics of penicillin allergy labels (PALs) in the electronic medical records of 3 Swedish regions (1,088,000 inhabitants).

A retrospective analysis of PALs in the electronic medical records in the Southeast Healthcare Region of Sweden and estimation of point prevalence were performed. Two nonoverlapping cohorts were defined by label complexity: a simple cohort with pre-2017, nonstandardized labels identified by keywords (n = 7,514), and a complex cohort (n = 22,736) with post-2017, standardized labels identified using Anatomical Therapeutic Chemical codes.

Point prevalence of PALs was 2.8% across all regions (69.6% female). Differences were noted across the 3 regions for the different phenotypes. The regional prevalences of skin symptoms were 15.9-32.2% for urticaria and angioedema, 2.4-23.8% for maculopapular or undefined rash, and 4.9-7.6% for flushing. Severe reactions were rare (3.0-6.9%). Mild nonallergic symptoms appeared in 1.9-2.0%, with unclear symptoms in 24.4-64.7%. The most prevalent culprits were narrow-spectrum penicillins (32.9-48.1%). Multidrug-resistant bacteria were significantly more prevalent in all regions among patients with a PAL (Östergötland, P = .03, Jönköping, P < .001 and Kalmar, P = .049).

Overall, 2.8% of the study population carried a PAL. Labels need to be better documented: Up to two thirds lacked sufficient information to determine the phenotype and other characteristics of the reactions. Moreover, antimicrobial resistance was more prevalent among patients with a PAL.