No abstract

RATIONALE: Ovomucoid-specific IgE (OVM-sIgE) levels and OVM-sIgE/total IgE ratio are reportedly predict IgE-mediated egg allergy among children with positive serum OVM-sIgE. Affinity of sIgE was known to critically regulate basophil/mast cell degranulation in vitro, however little is known whether avidity of sIgE is involved in IgE-mediated heated egg allergy in young children in vivo. METHODS: This cross-sectional case-control study enrolled 59 children (2 to 3 yo) with low levels of OVM-sIgE (0.7 to 17.5 UA/mL) as measured by ImmunoCAP who underwent an oral food challenge test (OFC) at the National Center for Child Health and Development in Tokyo between November 2013 and January 2019. The avidity of OVM-sIgE (IC 50-OVM-sIgE (nM)) was measured by competitive binding inhibition assay using densely carboxylated protein (DCP)-chip (Immun Inflamm Dis 2019, 7:74-85). RESULTS: The avidity of OVM-sIgE was significantly higher in children who were allergic to, than in those who were tolerant of heated egg. Receiver operating characteristic analysis showed that a combination of the serum OVM-sIgE level and the avidity of OVM-sIgE ratio (OVM-sIgE/IC 50-OVM-sIgE) had a larger AUC (0.913; 95%CI 0.842-0.983) than OVM-sIgE level or OVM-sIgE/total IgE ratio alone (0.777; 95%CI 0.623-0.931, 0.763; 95%CI 0.63-0.897, respectively) in predicting heated egg allergy. CONCLUSIONS: Our findings suggested that not only the quantity of sIgE but also the quality of sIgE is involved in heated egg allergy, and a combination of these two factors may help more accurate diagnosis of egg allergy.