Ara h 6 found relevant for peanut allergy testing in children

PHOENIX — Researchers identified Ara h 6 as a relevant component for diagnosing peanut allergy among children in the U.S., according to a study presented at the American Academy of Allergy, Asthma & Immunology Annual Meeting.

“This has not been studied in the U.S. yet, especially in a pediatric population,” Jessica M. Palmieri, DO, a second-year allergy and immunology fellow at Baylor College of Medicine, told Healio.

Although Ara h 6 has been studied as an indicator of peanut allergy in Europe, it is not usually evaluated in the U.S., Palmieri said. Ara h 2 usually is the most elevated and most significant component in individuals with peanut allergies, she continued.

However, Ara h 2 and 6 share 60% of their sequence identity and multiple epitopes, the researchers said. Also, the researchers noted reports of patients with peanut allergies who have tested positive in Ara h 6 mono-sensitized oral food challenges.

The study involved 46 patients (age range, 6 months to 18 years; male, n = 30; Black, n = 14) who were being evaluated for peanut allergy. Standard testing included skin prick testing, specific IgE and components Ara h 1, 2, 3, 6, 8 and 9.

Patients were divided into allergic (n = 31), indeterminate (n = 3) or nonallergic (n = 12) cohorts based on test results. The patients in the indeterminate cohort participated in food challenges, with all negative results.

Ara h 2 was the dominant component in 48% of the cases, which Palmieri said was expected for a test involving patients with peanut allergies, followed by Ara h 6 at 23%. Ara h 1 had 19% dominance, while Ara h 3, 8 and 9 all had 0% of the dominant components.

“In sensitivity and specificity, Ara h 2 was perfect, at 1.0 for both,” Palmieri said.

Ara h 6 was close behind in sensitivity at 0.97, Palmieri said, although it had a 1 specificity.

Additionally, Ara h 6 had the greatest correlation with Ara h 2 (0.96; P < .0001), although the researchers also found a strong correlation with Ara h 1 (0.82; P < .0001) and 3 (0.86; P < .0001), with a moderate correlation between Ara h 6 and 9 (0.59; P < .0001).

Palmieri also said she was surprised by the Ara h 6 mono-sensitization that the researchers encountered.

“Sometimes, you have kids or people in general who have a specific IgE, and you have seen testing where they’re fully appropriate to challenge, where you have a less than 50% chance of them reacting,” she said. “But then they react, and you ask why they reacted. You just don’t know.”

Ara h 2 is more sensitive than Ara h 6 for diagnosing peanut allergies, the researchers concluded, but Ara h 6 is still relevant in the pediatric population in the U.S.

Noting that some doctors only use specific IgE or SPT to diagnose peanut allergy, Palmieri likes using components because they provide additional information.

“If you have a patient who has skin prick testing that is positive, but they’re only sensitized to Ara h 8, there’s a 5% to 10% chance they’re going to have a systemic reaction. But most likely, they are going to be fine and can eat peanuts, and they’re not going to react. That’s a reason to challenge them and get them to eat peanuts,” she said.

The use of Ara h 6, however, can help doctors with indeterminate cases decide whether they want to perform an oral food challenge.

“Food challenge is always a risk. There’s always a risk you’re going to have anaphylaxis,” Palmieri said. “So, this may be a guiding post for whether you want to challenge some of those indeterminate patients.”

Additional clarity in testing decisions provides peace of mind for patients and their families, and for practitioners as well, Palmieri added.

“Oral food challenges are long. They’re time consuming. They’re expensive. And there’s always a risk,” she said. “If I’m very sure that you’re going to react, I probably will be less likely to bring you in.”