Diagnostic accuracy of the atopy patch test in children with food allergy-related gastrointestinal symptoms

Background: Little is known about the diagnostic accuracy of atopy patch tests (APT) in the clinical practice of pediatric gastroenterology. Moreover, APTs containing purified food extracts have recently become available, but their diagnostic accuracy is largely undefined. Patients and methods: We evaluated the diagnostic accuracy of food challenge, skin prick test (SPT), serum specific IgE determination, and APT using fresh food and commercial food extracts in parallel in children referred for suspected food allergy-related gastrointestinal symptoms. Results: Eighty-nine food challenges were performed in 60 patients (38 boys, median age 23 months, range 3-48 months): 31 tested positive for cow's milk (CM), 19 for hen's egg (HE), and two for wheat. Specific immunoglobulin E (IgE) determination, and SPT, respectively, were positive in 7/31 and 14/31 of patients with cow's milk allergy (CMA), and in 7/19 and 7/19 with HE allergy. The results of APT with fresh food vs a commercial assay were (1) CM: sensitivity: 64.5% vs 6.4%, specificity 95.8% vs 95.6%, positive predictive value (PPV) 95.2% vs 66.6% and negative predictive value (NPV) 67.6% vs 43.1 %; (2) HE: sensitivity 84.2% vs 5.2%, specificity 100% vs 100%, PPV 100% vs 100% and NPV 75.0% vs 33.3%. Conclusions: Atopy patch test is a useful toot in the diagnostic work up of children with food-allergy-related gastrointestinal symptoms. The diagnostic accuracy of ATP was higher with fresh food than with commercial food extracts.