Evaluation of the utility of atopy patch testing, skin prick testing, and total and specific IgE assays in the diagnosis of cow's milk allergy

Background Information on the utility of atopy patch testing (APT) in the diagnosis of food allergy is derived from studies of children with atopic dermatitis. Objective To evaluate the usefulness of APT in the diagnosis of cow's milk allergy (CMA) and to determine interleukin 4 and interferon-γ production by peripheral blood mononuclear cells. Methods Thirty-seven children (median age, 11 months) with suspected CMA who had a variety of symptoms that involved many organ systems were evaluated using double-blind placebo-controlled food challenges (DBPCFCs), and the performances of milk specific IgE, skin prick testing (SPT), and APT were determined. To search for a possible relationship between the diagnostic tests and the T H 1/T H 2 immune response, we measured interferon-γ and interleukin 4 levels in the supernatants of peripheral blood mononuclear cell cultures. Results Seventeen children with positive DBPCFC results and 6 with a history of anaphylaxis were diagnosed as having CMA. The combined use of APT and SPT had a sensitivity of 100% and a negative predictive value of 100% but a specificity of 50% and a positive predictive value of 76%. The addition of milk specific IgE assays to APT and SPT did not improve these values. Pattern of cytokine secretion was not associated with APT positivity or a specific response to DBPCFC. Conclusions Atopy patch testing may be a useful adjunct to SPT in excluding CMA in children who have allergic manifestations other than atopic dermatitis. However, DBPCFCs are still necessary in the presence of positive test results.