Clinical-haematological changes and predictors of severity in acute food protein-induced enterocolitis syndrome reactions at oral food challenge: a multicentre observational study.

Background Oral food challenge (OFC) is the gold standard for diagnosis of acute Food Protein-Induced Enterocolitis Syndrome (FPIES). No diagnostic/prognostic biomarkers are available, and OFC assessment criteria are not validated. Objective. To assess clinical-haematological changes and predictors of severity of FPIES reactions at OFC. Methods Observational multicentre prospective study. Children aged 0-18 years diagnosed with acute FPIES were recruited at follow-up OFC in 12 tertiary centres in Spain and Italy. OFC Outcomes (as positive/negative/inconclusive and mild/moderate/severe) were assessed based on published ‘2017 FPIES Consensus’ criteria. Clinical characteristics were recorded, and full blood count was done at baseline, reaction onset and 4 hours later. Regression analysis was performed to assess predictors of severe reactions at OFC. Results 81 children had positive OFC (mild in 11% (9/81), moderate in 61% (49/81), severe in 28% (23/81)). Increase in neutrophils and reduction in eosinophils, basophils and lymphocytes was observed (P-value<0.05). OFC was inconclusive in 19 cases despite objective signs or neutrophilia. Regression analysis showed a 2-day OFC protocol where only 25% of an age-appropriate portion is given on day 1 (not gender, age, culprit food, cumulative dose and previous reaction severity) was associated with reduced odds of severe reaction compared to giving multiple doses in a single day. Conclusion Distinct haematological changes may help support FPIES diagnosis. Current OFC assessment criteria may not capture the broad spectrum of acute FPIES presentations. This 2-day protocol may associate a reduced risk of severe reactions. Future work should aim to develop safer OFC and non-OFC diagnostics for FPIES.