Low efficacy of atopy patch test in predicting tolerance development in non-IgE-mediated cow's milk allergy

Background: The food atopy patch (APT) test has been used in previous studies to help the diagnosis of non-IgE mediated food allergies (FA). The aim of this study was to evaluate the efficacy of different cow's milk APT preparations to predict oral tolerance in children with previous non-IgE-mediated cow's milk allergy (CMA) diagnosis.

Methods: Thirty-two patients non-IgE-mediated CMA diagnosed by oral food challenge (OFC) were enrolled to perform APT with three different cow's milk preparations (fresh, 2% in saline solution, 2% in petrolatum) and comparing with a new OFC after at least three months of diet exclusion.

Results: Only six (18.7%) subjects presented positive OFC to cow's milk. No differences in gender, onset symptoms age, OFC age, Z-score, and exclusion period were found between positive and negative OFC patients. Preparations using fresh milk and powdered milk in petrolatum presented sensitivity equal to zero and specificity 92.3% and 96.1%. The preparation using powdered milk in saline solution showed sensitivity and specificity of 33.3% and 96.1%. Two patients presented typical IgE symptoms after OFC.

Conclusion: Cow's milk APT presented a low efficacy to predict tolerance in patients with previous non-IgE-mediated CMA and should not be used in clinical routine. The presence of typical IgE reactions after OFC hallmark the necessity of previous IgE-mediated investigation for this patient group.