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

BACKGROUND: A spurious label of beta-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 beta-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 < .005). The 1-1-1 criterion displayed a sensitivity and specificity of 85%, and a negative predictive value and a positive predictive value of 80% and 90%, respectively. 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. (C) 2021 American Academy of Allergy, Asthma & Immunology

Automated summary

This study focused on the importance of urticaria characteristics in risk stratification for delabeling patients with a spurious beta-lactam allergy. The results showed that patients with urticaria appearing within 1 hour after the first dose and regressing within 1 day were more likely to have a positive allergy workup. The 1-1-1 urticaria criterion demonstrated high sensitivity, specificity, negative predictive value, and positive predictive value for identifying patients at high risk.