PURPOSE OF THE STUDY.
To prospectively analyze the value of peanut and hazelnut component-specific immunoglobulin (Ig)E testing in the diagnosis of peanut and hazelnut allergies.
Infants and children who were clinically suspected to have allergy to peanut or hazelnut in various hospitals in Germany. Two hundred and ten patients underwent oral food challenge with peanut and 143 with hazelnut.
Oral food challenges were done with roasted peanuts or raw hazelnuts with a cumulative dose of 4443 mg of protein. Specific IgE to peanut, hazelnut, and their components (Ara h 1, Ara h 2, Ara h 3, and Ara h 8; Cor a 1, Cor a 8, Cor a 9, and Cor a 14) were measured by ImmunoCAP. Results were analyzed using logistic regression, and the probability for a positive challenge outcome was calculated to estimate positive and negative predictive values, sensitivity, and specificity for each test.
Forty-three percent of the 210 peanut challenges and 31% of the 143 hazelnut challenges were considered positive. Peanut- and hazelnut-specific IgE levels were higher in allergic compared with tolerant children, although there was some overlap. The overlap was less for Ara h 2–specific IgE for peanut and Cor a 14–specific IgE for hazelnut. The logistic models demonstrated an area under the curve of 0.92 for Ara h 2 and 0.89 for Cor a 14, both of which were superior to total peanut- or hazelnut-specific IgE levels. The sensitivity and specificity of Ara h 2 was 86% at a level of 0.35 kU/L, and for Cor a 14, a level of 0.35 kU/L corresponded to a sensitivity of 85% and a specificity of 81%. A 90% probability for a positive challenge was predicted for Ara h 2 at 14.4 kU/L and for Cor a 14 at 47.8 kU/L.
Component testing for peanut and hazelnut allergy, specifically to Ara h 2– and Cor a 14–specific IgE, is superior in predicting clinical reactivity compared with peanut- or hazelnut-specific IgE alone.
Diagnostic testing for food allergy is complicated by the fact that many children can safely eat a food to which they test positive. Oral food challenges remain the gold standard for diagnosis but do carry inherent risks. Therefore, better tests that would eliminate unnecessary food challenges are highly desirable. This study highlights the potential utility of component testing for both peanut and hazelnut allergy, specifically using Ara h 2 and Cor a 14. However, it is important to recognize that even component testing has significant limitations and must be used and interpreted in the context of each individual patient. Age, other allergic sensitivities, and many other factors should be considered. In addition, as this field evolves, it is apparent that there are significant regional differences, especially for peanut, so that the data from this German study may not be directly applicable to children in North America where considerably lower cutoff values for Ara h 2 have been proposed. For example, a 90% positive predictive value for Ara h 2 was 14.4 kU/L in this study, whereas in our clinic, we consider the same cutoff to be closer to a level of 2 kU/L. Additional studies are therefore needed to clarify this picture.
- Copyright © 2015 by the American Academy of Pediatrics