Utility of the immunoglobulin E crosslinking-induced luciferase expression assay in buckwheat allergy diagnosis

Background: Buckwheat allergy carries a high risk of anaphylaxis. Although the oral food challenge (OFC) is the diagnostic gold standard, it can provoke severe reactions, leading many patients to adopt elimination diets. Conventional markers, including buckwheat-specific IgE (Bw-sIgE) and skin prick testing, have limited accuracy. The IgE crosslinking-induced luciferase expression (EXiLE) assay is a serum-based in vitro cell-activation test that has shown high accuracy for other food allergies. We evaluated its utility for buckwheat allergy. Methods: This multicenter observational study in Japan enrolled participants with buckwheat-specific IgE ≥ 0.35 U_A/mL (n = 25), categorized as buckwheat allergy (BwA) or non-buckwheat allergy (non-BwA) based on OFC results. The EXiLE assay used crude buckwheat antigen at 0.1–1000 ng/mL. Diagnostic performance was compared using receiver operating characteristic (ROC) curves for EXiLE, Bw-sIgE, and the Bw-sIgE/total IgE ratio. Results: Among 25 participants, the EXiLE assay demonstrated superior diagnostic performance compared to Bw-sIgE and the Bw-sIgE/total IgE ratio. The area under the ROC curve (AUC) was 0.96 at 10 ng/mL (1 ng/mL, 0.94), exceeding Bw-sIgE (0.68) and the Bw-sIgE/total IgE ratio (0.72). At optimal cutoffs, EXiLE achieved sensitivity 0.92, specificity 0.92, and LR+ 11.1 (versus LR+ 3.2 for Bw-sIgE and 2.5 for the IgE ratio), indicating fewer false positives and better overall accuracy. Conclusion: The EXiLE assay provides high diagnostic accuracy for IgE-mediated buckwheat allergy and, as a serum-based in vitro assay, may reduce reliance on OFC and help avoid unnecessary elimination diets.