Clinical and laboratory factors associated with follow-up oral food challenge outcomes in cow's milk allergy

Background: Reliable predictors that link first oral food challenge (OFC) responses to the outcomes of follow-up OFCs in children with food allergies are still lacking. Objective: To identify clinical and laboratory factors associated with follow-up OFC outcomes in preschool children with cow’s milk allergy after a positive first challenge result. Methods: This retrospective study included 85 preschool children with cow's milk allergy who had a positive first OFC outcome and subsequently underwent follow-up OFCs. Demographic, clinical, and laboratory data were analyzed to identify factors associated with positive follow-up OFC outcomes. Results: Older age at the first OFC, anaphylaxis during the first OFC, pre‐first OFC casein immunoglobulin E (IgE) level ≥ 3.71 kUA/L, pre‐first OFC cow’s milk IgE level ≥ 14 kUA/L, and larger cow’s milk skin-prick test (SPT) results were associated with positive follow-up OFC outcomes. A pre-first OFC casein specific IgE (sIgE) level ≥ 3.71 kUA/L remained independently associated with follow-up OFC positivity after multivariable adjustment. In univariable analyses, reactions that occurred after completion of the full-dose protocol during the first OFC were associated with lower follow-up OFC positivity. The combination of a pre‐first OFC casein IgE level < 3.71 kUA/L and a reaction after completion of the full-dose protocol during the first OFC was associated with a 92.9% negative predictive value for follow-up OFC outcomes. Conclusion: Clinical and laboratory markers during the first OFC may be related to follow-up OFC outcomes in children with cow’s milk allergy. Higher pre‐first OFC casein and cow’s milk IgE levels and anaphylaxis during the first OFC were associated with follow-up OFC positivity. Lower pre‐first OFC casein IgE levels, with reactions after completing the full-dose protocol, were linked to lower follow-up OFC positivity rates.