Food-antigen–specific immunoglobulin E (sIgE) levels were not clinically useful for predicting food allergy development in a study of infants with atopic dermatitis (AD).
The dual-phase study included 1,087 patients aged 3-18 months who had been diagnosed with AD for no more than 3 months prior to enrollment in the study and had at least mild disease activity. During the first phase of the study, which was a 36-month, randomized, double-blind, vehicle-controlled phase, half of patients were treated with placebo cream and the other half were treated with 1% pimecrolimus cream. In the second phase of the study, which was open-label, all patients received 1% pimecrolimus cream for up to 33 months or the patient’s 6th birthday, whichever occurred sooner. Patients were excluded if they received treatment with topical or systemic agents within 7 days before the first application of cream in the study.
The researchers followed food allergy development during both phases of the study. Other data collected by the researchers included sIgE levels for various foods at baseline and at the end of both phases of the study, with sIgE decision points having been assigned to each food.
By the end of the second phase of the trial, 15.9% of patients had developed a food allergy, with 292 days having been the median period of time that passed before the initial diagnosis of a food allergy was made. The most common food allergies were to peanuts, cow’s milk, and egg whites, occurring in 7%, 4%, and 4% of patients respectively. The percentage of patients with any allergy to food other than fish decreased over time. Higher levels of AD severity were predictive for the development of food allergy, with the percentage of patients who developed one or more food allergies by the end of the study having increased with increasing AD severity at baseline.
Total serum immunoglobulin E (IgE) and sIgE for milk, eggs, and peanuts measured at the end of the second phase also were increased in patients with increasing AD severity. Despite these findings, the positive predictive values for sIgE decision points for the foods tested were low (less than 0.6 for all values tested).
“SIgE decision points, both published values and the novel decision points used in this study, had high [negative predictive values], in particular for peanut[s], egg white[s], and cow’s milk. Thus, patients with mild AD with sIgE levels below these cutoffs would be unlikely to have or develop these specific allergies and would not benefit from food challenges or elimination diets. Similarly, elevated sIgE, as defined by the decision points tested, had very low [positive predictive values] for food allergy, both for sIgE values at baseline and at the end of the [first phase of the study] ... Thus, despite an increased likelihood of allergy development with increasing sIgE shown for cow’s milk, egg[s], and peanut[s], our data do not support the use of sIgE testing for the diagnosis of food allergy in subjects without a history of reaction to that food,” said Dr. Jonathan M. Spergelof the Children’s Hospital of Philadelphia and his colleagues.
Read the full study in Pediatrics (doi: 10.1542/peds.2015-1444).