Tree nut allergy diagnosis poses challenges

HOUSTON — Data presented here at the American College of Allergy, Asthma and Immunology Annual Scientific Meeting indicate that tree nut allergies are responsible for up to 40% of anaphylaxis reactions. Also, when combined with peanuts, tree nut allergies account for up to 90% of anaphylactic fatalities.

Healio has previously reported that despite exhibiting skin or blood test sensitivity to peanuts and tree nuts, more than 50% of patients with a documented allergy to an individual nut passed oral food challenges consisting of additional nuts.

That data, coupled with a discussion held by Maria Crain, APRN, CPNP-PC, AE-C, a pediatric nurse practitioner at the Food Allergy Center within Children’s Health in Dallas, and Jodi Shroba, MSN, APRN, CPNP, of the division of allergy and immunology at Children’s Mercy Hospital in Kansas City, Missouri, suggest tree nut allergy diagnosis is not always cut and dry.

One diagnostic test mentioned, Component Resolved Diagnostic Testing, “may give you a better understanding of what a patient’s IgE levels are and can differentiate between reactivity and actual food allergy,” Shroba told attendees.

 

A discussion held at the annual meeting of the American College of Allergy, Asthma and Immunology suggests that tree nut allergy diagnosis is not always cut and dry.

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But she added that other researchers have found weaknesses of the Component Resolved Diagnostic Test, including patient selection bias, study design, questionable reference standards, derivation of optimal cutoff levels and inability to infer reaction severity.

Another test with pros and cons was Skin Prick Testing, in which the size of a wheal determines allergy. While Skin Prick Testing can be used for cashews, hazelnuts and walnuts, there is no wheal size that can determine allergy to almond, brazil nut, pistachio or pecan, according to Shroba.

In addition, “skin prick tests can remain positive even in those who have achieved tolerance. Therefore, don’t always use skin tests as your only determining factor. Patient history also has to come into play. You may want consider the IgE tests as well,” Shroba continued.

Another test discussed, the double-blind placebo control food challenge, is the “gold standard” when it comes to diagnosing tree nut allergy. But it too, has its pros and cons, according to Crain.

“The double-blind placebo control food challenge is very hard to do,” Crain told attendees. “While it does eliminate bias and the diagnosis is clear, it is time consuming, it can be expensive, and it can be burdensome to both the provider and the patient.”

A fourth test described with strengths and weaknesses, the Single Tree Nut Challenge, involves administering one serving size of one nut over an hour in divided doses, then observing the patient for up to 2 hours after ingestion. If the patient does not experience any adverse reactions, that particular tree nut can be added to the patient’s diet on a regular basis. Though Crain said she has found the Single Tree Nut Challenge helpful, she added that like some of the others, the test can be very time-consuming.

In addition, “we have a lot of teenaged patients who avoid food allergy tests [for as long as possible],” Crain said. “This can cause anxiety, which can cause difficulties determining if it is anxiety or the food causing the allergy symptoms. And with infants and young children, it may be harder to get them to eat the amount that you need them to.” - by Janel Miller

References:

Crain M. A tough nut to crack: The complexity of tree nut allergy management in the office and at home.

Shroba J. A tough nut to crack: The complexity of tree nut allergy management.

Both presented at: American College of Allergy, Asthma and Immunology Annual Scientific Meeting; Nov. 7-11, 2019; Houston.

Disclosures: Healio Primary Care was unable to determine Crain and Shroba’s relevant financial disclosures prior to publication.