Results from an Italian study show that atopy patch tests (APTs) could predict oral tolerance in children with gastrointestinal symptoms related to non-IgE-mediated cow's milk allergy.
Cow's milk allergy is the most common food allergy in childhood, explain Roberto Canani (University of Naples) and co-investigators. Oral food challenge (OFC) is traditionally used to confirm a diagnosis of cow's milk allergy, but the possible use of APTs for predicting the occurrence of oral tolerance is unknown.
The researchers therefore investigated the benefit of APTs in predicting oral tolerance in 172 children with a confirmed diagnosis of non-IgE-mediated cow's milk allergy and gastrointestinal symptoms. The APTs and OFCs were performed at diagnosis and after 12 months on an exclusion diet.
For the APT, a 20 µl drop of fresh cow's milk was placed on filter paper and applied with adhesive tape to the unaffected skin of each child's back. After 48 hours, the filter paper was removed and, after 20 minutes and again at 24 hours, the results were read. Reactions were judged to be either positive or negative.
As reported in Allergy, 65.7% of children had positive APTs to cow's milk proteins at diagnosis.
After 12 months on the exclusion diet, the APT results significantly correlated with OFC outcomes. The APT predicted the results of OFC after 12 months with a sensitivity of 67.95% and a specificity of 88.30%.
"Our results demonstrate that APTs could be a valuable tool in the follow-up of pediatric patients with gastrointestinal symptoms related to non-IgE-mediated cow's milk allergy by contributing to determining whether an OFC can safely be undertaken," say the researchers.
"Negative APTs would incite the clinician to plan a challenge, whereas a persistent positivity of APTs should lead to greater caution," they write. "We therefore believe that the amount of unnecessary, costly, and potentially dangerous positive challenge could be avoided adding these simple and cheap tests."
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