Specific IgE for Fag e 3 Predicts Oral Buckwheat Food Challenge Test Results and Anaphylaxis: A Pilot Study.

BACKGROUND: Buckwheat (BW) is the source of a life-threatening allergen. Fag e 3-specific serum IgE (sIgE) is more useful than BW-sIgE for diagnosis; however, it is unknown whether Fag e 3-sIgE can predict oral food challenge (OFC) results and anaphylaxis. This study aimed to clarify the efficacy of Fag e 3-sIgE in predicting OFC results and anaphylaxis. METHODS: We conducted a retrospective review of BW- and Fag e 3-sIgE data obtained using the ImmunoCAP® assay system and fluorescent enzyme-linked immunosorbent assay from children who underwent OFC using 3,072 mg of BW protein between July 2006 and March 2014 at Sagamihara National Hospital, Kanagawa, Japan. RESULTS: We analyzed 60 patients aged 1.9-13.4 years (median 6.0 years); 20 (33%) showed objective symptoms upon BW OFC. The patients without symptoms had significantly lower Fag e 3-sIgE than those with non-anaphylactic (p < 0.001) and anaphylactic reactions to BW (p = 0.004). Fag e 3-sIgE was the only tested factor that significantly predicted positive OFC results (odds ratio 8.93, 95% confidence interval 3.10-25.73, p < 0.001) and OFC-induced anaphylaxis (2.67, 1.12-6.35, p = 0.027). We suggest that a threshold Fag e 3-sIgE level of 18.0 kUE/L has 95% probability of provoking a positive reaction to BW. CONCLUSIONS: Fag e 3-sIgE predicted OFC results and OFC-induced anaphylaxis. We further emphasize paying careful attention to the risk of BW OFC-induced anaphylaxis.

Skin prick test is more useful than specific IgE for diagnosis of buckwheat allergy: A retrospective cross-sectional study.

BACKGROUND: Buckwheat (BW) is a potentially life-threatening allergen. Usefulness of BW-specific immunoglobulin-E (BW-sIgE) level for diagnosis of BW allergy is controversial, while the skin prick test (SPT) is widely used because of its less invasive procedure and immediate results. However, there are no data comparing usefulness of the SPT and BW-sIgE level. Therefore, our study aimed to clarify efficacy of the SPT for diagnosis of BW allergy. METHODS: This retrospective cross-sectional study evaluated patients who underwent an oral food challenge (OFC) for diagnosis or confirmation of acquired tolerance using 3072 mg of BW protein between July 2006 and April 2014. We then compared the diagnostic performance of BW sIgE and SPT to predict positive OFC results. RESULTS: We analyzed 126 patients aged 2-16 years (median, 7.7 years), 18 (14%) of whom showed positive OFC results. Between patients with positive and negative OFC results, there was no significant difference in BW-sIgE level. However, patients with positive OFC results had a larger SPT wheal diameter. Area under the curve for positive OFC results for BW-sIgE level and SPT wheal diameter were 0.583 and 0.791, respectively. The 5%, 10%, 50%, and 90% positive predictive values of SPT wheal diameter were 2.0 mm, 5.2 mm, 14.7 mm, and 24.1 mm, respectively. CONCLUSIONS: Our study revealed that the SPT was more useful than BW-sIgE level for diagnosis of BW allergy. Thus, an OFC may be avoided if the patient's SPT wheal diameter is at least 24.1 mm.

Reactions of Buckwheat-Hypersensitive Patients during Oral Food Challenge Are Rare, but Often Anaphylactic.

BACKGROUND: Buckwheat (BW) is a common cause of life-threatening allergy in Asia. Few have examined oral food challenges (OFCs) using BW. We here describe the OFC outcomes for the diagnosis or confirmation of tolerance acquisition and clarify risk factors for positive OFCs. METHODS: Between July 2005 and March 2014, we retrospectively reviewed data from children who underwent OFCs using 3,072 mg of BW protein at Sagamihara National Hospital. Children were suspected of having BW allergy because of positive results for BW-specific IgE or because they had been previously diagnosed with BW allergy owing to immediate reactions to BW. RESULTS: Of 476 such patients, we analyzed 419 aged 1-17 years (median age 6.7 years). Forty-four (10.5%) reacted to the BW OFC and 24 (54.5%) experienced anaphylaxis. Among patients with suspected BW allergies (n = 369), 30 (8.1%) reacted to OFC. However, among patients with definitive BW allergies (n = 50) who underwent OFCs a median of 7.0 years after their last immediate reaction, 14 (28.0%) reacted to OFC. Among 12 patients with past anaphylactic reactions to BW, 8 exhibited tolerance to BW. A history of immediate reaction to BW and high BW-specific IgE levels were significant risk factors for a positive OFC. CONCLUSIONS: BW allergies are rare among children suspected of having BW allergies due to positivity for BW-specific IgE. Most children with definitive BW allergies can tolerate BW, even after anaphylactic reactions. Nevertheless, careful observation is needed when performing BW OFCs, considering the high incidence of anaphylactic reactions.