Usability of Fag e 2 ImmunoCAP in the diagnosis of buckwheat allergy.

Currently, the detection of crude buckwheat extract-specific IgE by ImmunoCAP (f11) (Phadia AB, Uppsala, Sweden) is widely used to diagnose buckwheat allergy. However, the results of this test do not always correlate with the development of allergic symptoms. This study aimed to evaluate the diagnostic usefulness of specific IgE antibody titers for the major buckwheat allergens Fag e 1 and Fag e 2. Specific IgE antibodies were determined using the ImmunoCAP method for native Fag e 1 and Fag e 2, recombinant Fag e 1 and Fag e 2, and crude buckwheat extract (f11) in 10 buckwheat allergy patients, 14 atopic dermatitis patients, and 15 healthy subjects. All buckwheat allergy patients showed positive results for native Fag e 1- and Fag e 2-specific IgE tests and for ImmunoCAP (f11). In contrast, the rates of atopic dermatitis patients with positive results for native Fag e 1- and Fag e 2-specific IgE tests were 64.2% (9/14) and 57.1% (8/14), respectively. The sensitivities of the test using recombinant proteins were lower than those of the test using native proteins. The area under the curve (AUC) as determined by receiver operating characteristic (ROC) curve analysis was the largest for the native Fag e 2-specific IgE test (0.967), with a sensitivity of 90% and a specificity of 89.6% (cut-off: 2.74 kUa/L). Thus, the native Fag e 2-specific IgE antibody titer obtained using the ImmunoCAP method is more reliable than the buckwheat ImmunoCAP (f11) value for predicting buckwheat allergy.