Low-dose oral cow's milk challenge outcome for patients on complete avoidance: A multicenter study in Japan.

Background: Few studies have reported significant risk factors for allergic symptoms during low-dose (1-3 mL) cow's milk (CM) oral food challenges (OFCs). We investigated patients from multiple centers in Japan to identify high-risk, low-dose CM OFCs and conducted these tests at allergy-specialized facilities.

Methods: We retrospectively collected the results of the first low-dose CM OFCs performed at 10 hospitals in Japan between January and December 2019. All patients completely eliminated CM and underwent low-dose CM OFCs. The risk factors for positive OFC and anaphylaxis were analyzed using logistic regression analyses.

Results: We included 244 patients (median age: 2.5 years). The median level of CM-specific immunoglobulin E (sIgE) was 13.1 (interquartile range: 3.7-45.6) kU/L. The rates of positive and anaphylaxis among positive for CM OFCs were 44% and 19%, respectively. Multivariate analyses that separately analyzed each sIgE identified high CM sIgE and casein sIgE levels as significant risk factors for OFC positivity (both p < .001). The optimal cut-off values for CM and casein sIgE levels to predict positive CM OFCs from receiver operating characteristic curves were 5.4 and 7.3 kU/L, respectively. When CM sIgE or casein sIgE levels were ≥10.9 kU/L or ≥ 11.5 kU/L, they corresponded to 5% predicted probabilities of anaphylaxis. Furthermore, when their levels are ≥100 kU/L, the predicted probabilities increase to 20%.

Conclusion: CM and casein sIgE levels should be considered when predicting low-dose CM OFC outcomes.