Macadamia nut-specific IgE levels for predicting anaphylaxis.

Background: Despite the high risk of anaphylaxis in patients with a macadamia nut allergy (MdA), little is known about the significance of macadamia nut-specific immunoglobulin E (Md-sIgE). Thus, this study aimed to investigate the utility of Md-sIgE for predicting anaphylaxis.

Methods: Children with suspected MdA who visited our hospital were included. MdA was defined as either failing the 3-g macadamia nut (Md) oral food challenge (OFC) or confirming obvious immediate symptoms following Md ingestion. Non-MdA was defined as passing the 3-g Md OFC.

Results: A total of 41 children (29 [71%] males) with a median age of 7.7 years were included. The median Md-sIgE level was 2.23 kU /L. Among the 21 children diagnosed with MdA, eight and 13 children did (An group) and did not (non-An group) develop anaphylaxis. Twenty children were included in the non-MdA group. The Md-sIgE level was significantly higher in the An group relative to the others (7.97 vs. 1.92 kU /L, p < .001). Furthermore, the Md-sIgE level was significantly higher in the An group than in the non-An group (7.97 vs. 1.92 kU /L, p = .02). However, there was no significant difference in the Md-sIgE between the non-An and non-MdA groups (1.92 vs. 1.90 kU /L, p > .99). The area under the curve for predicting anaphylaxis in Md-sIgE was 0.92 (95% CI: 0.83-1.00), and the optimal cut-off value was 3.76 kU /L.

Conclusion: Md-sIgE levels were useful in predicting anaphylaxis. Above the cut-off value, we emphasize paying careful attention to the risk of anaphylaxis.