杉田 晃

BACKGROUND: Walnut (Juglans regia) frequently triggers nut allergies in the United Kingdom and in the United States, with increasing cases in Japan. While oral food challenges (OFCs) are the definitive method for diagnosing these allergies, they pose the risk of symptom provocation, necessitating safer alternative tests. Our aim here was to evaluate the diagnostic utility of IgE (immunoglobulin E) crosslinking-induced luciferase expression (EXiLE) for walnut allergy compared with the walnut-specific IgE (sIgE) test, Jug r 1-sIgE test, and skin prick test (SPT). METHODS: This retrospective study analyzed 55 patients tested for walnut allergy (WA) at Fujita Health University Bantane Hospital from January 2021 to December 2023. Among them, 38 had allergic reactions to walnuts based on history or OFCs and 17 did not. We evaluated the sensitivity, specificity, positive predictive value, negative predictive value, and the area under the curve (AUC) of the receiver operating characteristic curve. RESULTS: The EXiLE method (AUC = 0.938) exhibited superior diagnostic accuracy compared to the walnut-sIgE and comparable performance to Jug r 1-sIgE and SPT. The optimal cutoff value of 1.26-fold change demonstrated high sensitivity (0.92), specificity (0.88), positive predictive value (0.92), and negative predictive value (0.82). The EXiLE method yielded positive results in all three cases with negative Jug r 1-sIgE (< 0.35 UA/mL). CONCLUSION: The EXiLE method showed high sensitivity and specificity for diagnosing WA, indicating its potential clinical utility. Furthermore, the combination of Jug r 1-sIgE and EXiLE may enhance diagnostic accuracy. Future large-scale studies are warranted to confirm these findings and establish comprehensive diagnostic protocols.

Herein, we report the case of a 7-year-old girl with a history of atopic dermatitis because of infancy. Her grandfather grew Egoma (Perilla frutescens), and her family frequently consumed food items prepared using Egoma; however, she never consumed them because she did not enjoy these food items; she experienced vomiting, facial swelling, and oral discomfort upon ingesting Egoma during school lunch for the first time. Her food oral challenge test was positive, as well as a skin-prick test with sesame powder. Egoma antigen protein was extracted and reacted with patient serum by immunoblotting, which detected a positive band of approximately 26kDa. She was brought up in an environment with high exposure to Egoma; hence, she most likely developed an allergy to Egoma because of percutaneous sensitization. This is the first time an Egoma allergen analysis has been conducted in Japan, and we consider it to be a valuable case.