Urticaria: The 1-1-1 Criterion for Optimized Risk Stratification in β-Lactam Allergy Delabeling

Background A spurious label of β-lactam allergy compromises antibiotic stewardship. Delabeling protocols based on direct challenges (ie, not preceded by allergy tests) can be applied in low-risk patients. Objective This study aims at determining the significance of the characteristics of urticaria in the risk stratification for delabeling. Methods The characteristics of urticarial eruptions that had occurred during therapeutic courses with a β-lactam, namely the time interval between the exposure and onset, the dose (first or subsequent) after which urticaria appeared, and the duration of the eruption, were correlated to the results of a systematic allergy workup (skin tests, specific IgE measurements, and challenges). Data from 410 patients enrolled in 3 allergy centers (Rome and Troina, Italy, and Antwerp, Belgium) were analyzed. A multivariable logistic regression was performed, which included appearance within 1 hour after the first dose and regression within 1 day: a model that can be summarized as the “1-1-1” urticaria criterion. Results An urticarial eruption that had appeared within 1 hour after the first dose and had regressed within 1 day was more frequently reported in the group with a positive allergy workup, with odds ratios of 17 (95% confidence interval [CI]: 9-31), 11 (95% CI: 6-20), and 48 (95% CI: 14-157), respectively (P Conclusion Patients with urticaria meeting the 1-1-1 criterion should be considered at high risk and referred for an allergy workup with skin testing and specific IgE measurement before challenging.