Negative atopy patch test and negative skin prick test reduce the need for oral food challenge in children with atopic dermatitis

Atopic dermatitis (AD) is commonly associated with food allergy. Oral food challenge is the gold standard in the diagnosis of food allergy, but still has some troubles. The aim of this study was to evaluate whether a single test among skin prick test (SPT), measurement of specific immunoglobulin E (IgE), and atopy patch test (APT) or a combination of them could make food challenges unnecessary in patients with AD. Twenty patients affected by AD, under 6 years of age, were evaluated. Every child was investigated for cow's milk and hen's egg allergy using SPT, measurement of serum IgE (sIgE), APT, diagnostic elimination diet for 4 weeks, and open food challenges for milk and egg. The diagnosis of food allergy was established according to the results of the food challenge. We compared the results of all the tests with those of the open food challenge and calculated for each test the following parameters: sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). Eight of 40 open food challenges were assessed as positive. None of the diagnostic tools showed a sufficient accuracy to be able to replace the food challenge. However, SPT, APT, and the measurement of sIgE as single parameters showed an NPV of 90%, and the combination of SPT and APT showed an NPV of 92%. Food challenge remains the gold standard for food allergy diagnosis in young children with AD, but the combination of SPT and APT is useful when both tests are negative, because this result provides a guidance in excluding an allergy to the investigated food and could make the food challenge superfluous in this case.