D3.339 - Severe β-lactam hypersensitivity phenotypes in routine care: anaphylaxis frequency in a 22-centre outpatient survey in China

Beta-lactam allergy labels are common, but severe phenotypes documented in routine care are less well characterised. We assessed anaphylaxis frequency and documentation patterns among self-reported penicillin and cephalosporin allergy labels in China.

We conducted a multicentre cross-sectional outpatient survey across 22 institutions (n=6,070). Evidence supporting each label in routine care was classified as prior skin-test record, chart-documented clinical reaction, or uncertain. Severe phenotype was defined as anaphylaxis attributed to penicillin or cephalosporins in the record/survey. Prespecified subgroup analyses by age, sex were conducted. Proportions were compared using Fisher’s exact test; odds ratios (ORs) are reported.

Self-reported penicillin allergy was 21.9% (1,331/6,070) and cephalosporin allergy 4.5% (273/6,070). For penicillin labels, 82.5% (1,098/1,331) cited prior skin testing and 17.5% (233/1,331) reported a clinical reaction; anaphylaxis accounted for 15.9% (37/233) of penicillin reactions (0.61% of all respondents). For cephalosporin labels, 28.9% (79/273) had a skin-test record, 44.7% (122/273) reported reactions, and 26.4% (72/273) were uncertain; anaphylaxis accounted for 2.5% (3/122) of cephalosporin reactions (0.05% overall). Anaphylaxis was more frequent in penicillin than cephalosporin reactions (OR 7.49, 95% CI 2.26–24.82; p<0.001). 

In this routine-care survey, population-level beta-lactam anaphylaxis was uncommon, but severe reactions represented a sizeable subset of reported penicillin reactions. Severity phenotyping, alongside standardised verification pathways, may support risk-based triage for delabelling and more rational first-line beta-lactam use.