Individual tree nuts yield different oral food challenge outcomes

Data from oral food challenges show almond and hazelnut can be challenged more aggressively, whereas cashew and walnuts should be challenged more conservatively, according to study results.

Previous studies have explored the severity of tree nut allergies. However, there are few studies that characterize different tree nut allergies and their diagnostic decision point thresholds.

“While oral food challenges (OFCs) remain as the gold standard for food allergy diagnosis, there are various obstacles such as time, resources and risk [for] severe reaction. Thus, it is important to develop a clearer idea of the diagnostic utility and accuracy of skin prick tests and serum allergen-specific IgE (sIgE) tests to help guide clinical decisions,” Cynhia Hsu, BS, clinical research coordinator at Ann and Robert H. Lurie Children’s Hospital of Chicago, and colleagues wrote in their study, published in The Journal of Allergy and Clinical Immunology: In Practice. “This study reviewed tree nut oral food challenges performed for standard clinical care. Therefore, oral challenges were performed to confirm or refute a diagnosis of food allergy, or to determine the development of natural tolerance.”

Hsu and colleagues conducted a retrospective chart review of patients (aged 0-20 years; mean age at OFC, 7.77 years; 57.5% male) who completed a total of 531 unblinded OFCs to any tree nut from 2007 to 2019 at Lurie Children’s Hospital of Chicago.

Researchers compared differences among tree nut challenges for almond, cashew, hazelnut and walnut, and they used probability curves to estimate positive predictive values (PPV) and sIgE at OFC.

Approximately 74% of children with tree nut allergies passed their OFCs, and almost all patients passed OFC to almond (97.3%) and hazelnut (87.9%). OFC pass rates were lower for cashew (65.3%) and walnut (57%; P < .0001). No demographic characteristics correlated with the pass or fail rates.

In a comparison between patients who passed or failed the tree nut OFC, researchers observed an association between sIgE at OFC for almond (P = .029), cashew (P = .011) and walnut (P = .0007). They also observed an association between skin prick test at diagnosis and OFC outcomes for almond (P = .012), cashew (P = .0076) and walnut (P < .0001); however, they did not find an association between diagnostic test results and outcomes for hazelnut challenges.

The odds of failing a challenge were 0.83 times lower for children who avoided tree nuts based on sIgE sensitivity compared with those who avoided due to a reaction after ingestion (P = .0025), suggesting that “those children preventatively avoiding tree nuts due to another nut allergy (including peanut or other tree nut) pass tree nut challenges at higher sIgE levels,” the researchers wrote.

Based on their findings, the researchers established PPVs at the 50th percentile of 3.35 kU/L for cashew, 2.84 kU/L for walnut and 92.8 kU/L for almond, the latter of which reflected the low fail rate, according to the researchers. They were unable to calculate a PPV for hazelnut.

“Our study provides a real-world examination of people who get offered an oral food challenge. Due to current clinical recommendations, challenges are only offered to patients who have a high likelihood of passing, meaning that sIgE at OFC and SPT are likely to be lower in our study population than if we had offered OFCs to all patients presenting with tree nut allergy,” Hsu and colleagues wrote.

“While further work is needed on hazelnut and almond challenges to determine more clinically relevant PPVs, our data suggests that almond and hazelnut can be challenged more aggressively, and cashew and walnut challenged more conservatively,” they added.