Cut-Off Values of Specific IgE and Skin Prick Test to Predict Oral Food Challenge Positivity in Children with Cow's Milk Allergy

Objective: The cut-off values for the skin prick test diameters and cow's milk-specific IgE measurements are used to predict the result of the oral food challenge test for the diagnosis of cow's milk allergy. This study aimed to determine the diagnostic values of skin prick test and cow's milk-specific IgE according to age groups and compare the diagnostic powers of these 2 methods. Materials and Methods: In total, 153 children who had a preliminary diagnosis of cow's milk allergy were evaluated. Group A (n = 90) consisted of cow's milk allergy patients whose diagnosis was confirmed by a positive oral food challenge or a history of anaphylaxis. Group B (n = 63) was composed of patients with a negative oral food challenge. The demographic, clinical, and laboratory findings of 2 groups were compared. Results: The cut-off points for cow's milk-specific IgE and cow's milk-skin prick test were determined as >2.12 kUA/L and >5 mm, respectively. The area under the curve was 0.844 for cow's milk-skin prick test (sensitivity 73%, specificity 84%) and 0.745 for cow's milk-specific IgE (sensitivity 67%, specificity 86%). The diagnostic power of skin prick test was determined to be higher when compared to cow's milk-specific IgE (P=.02). According to the predicted probability curves, decision points for cow's milk-specific IgE and cow's milk-skin prick test with 95% probability were determined as follows, respectively: for <= 24 months: 22 kUA/L, 11.3 mm; for >24 months: 44.1 kUA/, 15.1 mm. The lowest cut-off value with a positive predictive value of 95% and a specificity of 96% was found in patients <1-year-old (>3.3 kUA/L) Conclusion: The use of high probability diagnostic values of communities for specific IgE and skin prick test along with a significant clinical history may provide accurate and rapid diagnosis of cow's milk allergy and facilitate patient follow-up.