Development and validation of the Food Allergy Severity Score

Montserrat Fernández-Rivas, Ismael Gómez García, Alejandro Gonzalo-Fernández, Manuel Fuentes Ferrer, Sabine Dölle-Bierke, Guadalupe Marco-Martín, Barbara K. Ballmer-Weber, Riccardo Asero, Simona Belohlavkova, Kirsten Beyer, Frédéric de Blay, Michael Clausen, Mareen R. Datema, Ruta Dubakiene, Kate E. C. Grimshaw, Karin Hoffmann-Sommergruber, Jonathan O. B. Hourihane, Monika Jedrzejczak-Czechowicz, André C. Knulst, Tanya KralimarkovaThuy-My le, Nikolaos G. Papadopoulos, Todor A. Popov, Lars K. Poulsen, Ashok Purohit, Suranjith L. Seneviratne, Angela Simpson, Atanasios Sinaniotis, Mirjana Turkalji, Sonia Vázquez-Cortés, Rosialzira N. Vera-Berrios, Antonella Muraro, Margitta Worm, Graham Roberts, Ronald van Ree, Cristina Fernández-Pérez, Paul J. Turner, Elizabeth N. Clare Mills

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24 Citations (Scopus)


Background: The heterogeneity and lack of validation of existing severity scores for food allergic reactions limit standardization of case management and research advances. We aimed to develop and validate a severity score for food allergic reactions. Methods: Following a multidisciplinary experts consensus, it was decided to develop a food allergy severity score (FASS) with ordinal (oFASS) and numerical (nFASS) formats. oFASS with 3 and 5 grades were generated through expert consensus, and nFASS by mathematical modeling. Evaluation was performed in the EuroPrevall outpatient clinic cohort (8232 food reactions) by logistic regression with request of emergency care and medications used as outcomes. Discrimination, classification, and calibration were calculated. Bootstrapping internal validation was followed by external validation (logistic regression) in 5 cohorts (3622 food reactions). Correlation of nFASS with the severity classification done by expert allergy clinicians by Best-Worst Scaling of 32 food reactions was calculated. Results: oFASS and nFASS map consistently, with nFASS having greater granularity. With the outcomes emergency care, adrenaline and critical medical treatment, oFASS and nFASS had a good discrimination (receiver operating characteristic area under the curve [ROC-AUC]>0.80), classification (sensitivity 0.87–0.92, specificity 0.73–0.78), and calibration. Bootstrapping over ROC-AUC showed negligible biases (1.0 × 10−6–1.23 × 10−3). In external validation, nFASS performed best with higher ROC-AUC. nFASS was strongly correlated (R 0.89) to best-worst scoring of 334 expert clinicians. Conclusion: FASS is a validated and reliable method to measure severity of food allergic reactions. The ordinal and numerical versions that map onto each other are suitable for use by different stakeholders in different settings.
Original languageEnglish
JournalAllergy: European Journal of Allergy and Clinical Immunology
Early online date2021
Publication statusE-pub ahead of print - 2021


  • allergic reactions
  • anaphylaxis
  • food allergy
  • score
  • severity

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