Casein sIgE as the most accurate predictor for heated milk tolerance in Finnish children.

Background: Up to 83% of children with cow's milk allergy (CMA) tolerate baked milk, but research on heated milk (HM) tolerance and allergen-specific IgE (sIgE) cutoff values predicting oral food challenge (OFC) outcomes are lacking. We hypothesized that casein sIgE is the best predictor for HM tolerance.

Methods: Finnish children suspected of having IgE-mediated CMA were recruited. sIgE levels to milk, casein, alpha-lactalbumin, beta-lactoglobulin, and bovine serum albumin were measured alongside skin prick tests (SPT) to fresh milk (FM) and HM. The diagnosis was confirmed with an FM OFC. IgE-sensitized children with a positive FM OFC underwent an HM OFC with extensively heated milk in rice porridge. Cutoff values to predict HM OFC outcome were determined, reaction severity analyzed, and effect of age investigated.

Results: Of the 158 children (median age: 2.59 years) undergoing FM OFC, 127 proceeded to an HM OFC. Of these, 77 (61%) demonstrated HM tolerance. Casein sIgE emerged as the best predictor for the HM OFC outcome (AUC 0.786), with a 95% sensitivity cutoff value of <0.54 kU/L and a 95% specificity cutoff value of >14.1 kU/L. Most HM OFC reactions were mild (66%), but reaction severity was unpredictable. Casein sIgE, milk sIgE, and HM SPT showed greater accuracy in ≤3-year-old children.

Conclusion: Casein sIgE cutoffs <0.54 and >14.1 kU/L can help identify children with a high or low likelihood of HM tolerance. This approach may reduce unnecessary OFCs in high-risk patients and guide safe dietary advancement on a milk ladder in low-risk cases.