Published Online: January 5, 2016
Buckwheat is abundantly consumed in Asia and is now becoming increasingly popular in America and Europe. Allergy to buckwheat has been reported in Asia, Europe and America. Although the prevalence of buckwheat allergy in Japanese and Korean schoolchildren is low (0.1–0.2%), buckwheat is one of the leading causes of food anaphylaxis in these countries. If buckwheat allergy is suspected, food avoidance is often initiated without performing the oral food challenge (OFC) owing to the risk of anaphylaxis. Therefore, improved laboratory tests to diagnose buckwheat allergy would be extremely useful. Testing for specific IgE (sIgE) against specific proteins (components) in foods is one approach that may increase diagnostic accuracy.
In a recent publication in The Journal of Allergy Clinical Immunology: In Practice, Maruyama et al. prepared buckwheat components as recombinant allergens and assessed their value in the diagnosis of buckwheat allergy by using (sIgE analysis. Sixty-five children (median age 6 years, 73% male) with suspected buckwheat allergy were divided into symptomatic and asymptomatic groups according to their clinical reactivity to buckwheat on the basis of challenge outcome and/or clinical history. Diagnostic values of measurement of sIgE antibody against Fag e 1 (13S globulin), Fag e 2 (2S albumin), Fag e 3 (vicilin), Fag e 10 kD (2S albumin), and Fag e TI-2c (trypsin inhibitor) were investigated using fluorescent enzyme-linked immunosorbent assay (ELISA). Maruyama et al. found that Fag e 3 had the best clinical performance among the components.
In additional studies, the clinical utility of Fag e 3 was evaluated using a commercial platform, ImmunoCAP. There was no significant difference between the results of the commercially available buckwheat ImmunoCAP and Fag e 3 experimental ImmunoCAP assay for the symptomatic group. However, the levels of sIgE against Fag e 3 were significantly lower than those by buckwheat ImmunoCAP in the asymptomatic group. Receiver operating characteristic analysis showed that the experimental Fag e 3 ImmunoCAP test yielded a larger area under curve (0.714; 95% confidence interval [CI], 0.574–0.854) than the buckwheat ImmunoCAP test (0.565; 95% CI, 0.418–0.711), although the CIs overlapped. Clinical sensitivity and specificity of 61% and 92%, respectively, were obtained for Fag e 3 by using the statistically optimal cut-off, whereas the commercially available buckwheat ImmunoCAP test had lower clinical specificity (65%), although the clinical sensitivity was almost the same (57%) as that for Fag e 3.
This is the largest study published on children with suspected buckwheat allergy to evaluate sIgE antibodies against buckwheat allergen components. The commercially available buckwheat ImmunoCAP test gave many false-positive results in the asymptomatic group. In contrast, the experimental Fag e 3 ImmunoCAP test showed better diagnostic accuracy owing to higher clinical specificity than the buckwheat ImmunoCAP test. At present, no test for sIgE against buckwheat components is commercially available for clinicians; therefore, further studies are needed to confirm the findings.
The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.