Specific IgE levels may predict anaphylaxis in children with macadamia nut allergy

Levels of macadamia nut-specific IgE were useful in predicting anaphylaxis among children with macadamia nut allergy, according to a study published in Pediatric Allergy and Immunology.

These levels also may be useful in diagnosing allergy to macadamia nuts, although clinicians need to remain mindful of risks of performing oral food challenges at high risk for anaphylaxis, Kei Kubota, of the department of pediatrics, National Hospital Organization, Sagamihara National Hospital in Sagamihara, Japan, and colleagues wrote.

The study involved 41 children (71% boys; median age, 7.7 years) with suspected macadamia nut allergy who visited the hospital between April 2012 and July 2021. Patient interviews and a three-level stepwise OFC found that 21 of these children had an allergy and 20 did not.

Eight of the allergic children (38%) had experienced anaphylaxis. Symptoms included generalized urticaria, cough, wheezing, throat pruritis, abdominal pain, lip swelling and recurrent emesis. Among the other 13 allergic children (62%) who did not experience anaphylaxis, symptoms included face swelling, localized or generalized urticaria, intermittent cough, lip swelling and throat pruritis. None of the allergic children experienced mild subjective symptoms that were localized to the oral cavity.

The researchers also collected blood samples from all patients within 12 months of the OFC or the allergic reaction to macadamia nut.

The median level of macadamia nut-specific IgE (Md-sIgE) for the full cohort was 2.23 kU_A/L.

The children with allergy and anaphylaxis had higher Md-sIgE levels (median, 7.97 kU_A/L; interquartile range [IQR], 5.08-23.3) than the children with allergy who did not have anaphylaxis (median, 1.92 kU_A/L; IQR, 0.83-6.04; P = .02) and those who did not have allergy (median, 1.9 kU_A/L; IQR, 0.56-2.78; P < .001). The difference between the latter two groups did not reach significance.

Based on receiver operating characteristic analysis for predicting anaphylaxis using Md-sIgE levels, the researchers found that the area under the curve of Md-sIgE was 0.92 (95% CI, 0.83-1) with an optimal cutoff value of 3.76 kU_A/L. Eight of the 16 children (50%) with Md-sIgE levels over this level and none of the children with levels under that benchmark developed anaphylaxis.

Also, positive predictive values for anaphylaxis included 5% for 1.8 kU_A/L, 10% for 2.75 kU_A/L, 20% for 4.36 kU_A/L, 80% for 21.06 kU_A/L, 90% for 33.38 kU_A/L and 95% for 51.04 kU_A/L, with a maximum value of 38.3 kU_A/L.

Clinicians should be cautious in providing OFC due to the risk for anaphylaxis experienced by the children in this study, the researchers wrote, but these probabilities based on Md-sIgE could help them assess these risks before beginning these challenges.

For example, about one-third of the children with sIgE values under 3.76 kU_A/L had a macadamia nut allergy with no anaphylaxis, the researchers wrote, indicating that OFC could be safe for them.

As the researchers considered children above the 3.76 kU_A/L threshold to be at high risk for macadamia nut-induced anaphylaxis, they recommended careful clinical management for these children.