Patient history drives lab options in food allergy diagnostics

Key takeaways:

• Jodi Shroba, MSN, APRN, CPNP, tackled varied topics at a conference Q&A.
• Outreach may teach pediatricians to order fewer panels.
• Exhaust skin care management before food allergy testing in atopic dermatitis.

SAN ANTONIO — How good are home allergy tests? Should patients pause biologic treatment before oral food challenges? Is it possible to stop pediatricians from ordering so many food panels? Is skin prick testing needed before OFCs?

Jodi Shroba, MSN, APRN, CPNP, a pediatric nurse practitioner, addressed these queries and more during a robust question and answer period at the 16th Annual Allergy, Asthma & Immunology CME Conference.

The Q&A followed her presentation on food allergy diagnostics, where she discussed the importance of using patient history to drive laboratory testing decisions as well as how broad panel testing can lead to misdiagnosis, anxiety and overly restrictive diets.

Shroba also discussed current testing modalities, such as specific IgE and component resolved diagnostic testing; newer options including basophil and mast cell activation tests and epitope assays; and unproven tests such as applied kinesiology, IgG testing and patch testing.

Home allergy tests

First, one of the attendees asked how home kits for food allergy testing work.

“Most of them are IgG testing,” said Shroba, noting that these tests are for food sensitivities and not true IgE-mediated allergy.

Specifically, Shroba said that IgG4 is not useful in clinical diagnosis of a food allergy, although it is still used in clinical trials as a marker to see if the investigational product has induced immunological changes. IgG4 will increase when an immune response has occurred, but this is not considered diagnostic.

Another attendee asked about hair analysis, and Shroba explained that this falls under unproven testing and should not be used for diagnosis of an immune-mediated allergy. These types of testing can lead to misdiagnosis, she continued.

“That’s a problem,” she said.

Biologics before challenges

When another attendee asked Shroba if patients with food allergy should continue treatment with omalizumab (Xolair; Genentech/Novartis) before OFCs, Shroba asked Maria Crain, APRN, CPNP-PC, AE-C, how she would handle the situation.

“We don’t stop it,” said Crain, a pediatric nurse practitioner, University of Texas Southwestern Medical Center Food Allergy Center. Crain also was another presenter at the conference, where she discussed tips and tricks for successful food challenges.

“We actually have several patients on Xolair now for food allergy. I just challenged a teenager last week who had really high levels prior to starting Xolair,” Crain continued.

Maria Crain

Crain tested the patient for different tree nuts such as almonds and walnuts, and she reported that he did well. She also said that she and her team instruct patients that they need to keep consuming the allergen regularly while they are using omalizumab. Further, she tells patients that if they do decide to discontinue omalizumab, they will need to be rechallenged.

Although Crain said that she did not know if this patient would stop using omalizumab, she said that they were not planning to stop it to perform OFCs.

“We just let them know that once they do stop Xolair, they may still be allergic to it, and we may need to repeat the challenge once they’re off of it,” she said, due to the possibility that the patient may become resensitized.

Shroba said that she would tell patients who are using dupilumab (Dupixent; Regeneron, Sanofi) the same thing and that she would not pause the biologic to perform any challenges.

“But we did tell them, ‘There is a good chance you’re going to do better in this food challenge because you are on dupilumab. If you stop dupilumab in the future, then we may need to rechallenge you,’” she said.

Shroba emphasized that there is no indication for dupilumab for food allergies, but some patients do have negative food challenges while they are on it.

Food allergy panels

Another attendee asked how Shroba discourages local pediatricians from performing food panels for “every little complaint.”

“We appreciate the referrals to the allergy clinic, but it’s doing a ton of harm when primary care providers are performing panel testing,” Shroba said.

Shroba said that she and her colleagues have lectured to pediatricians at a hospital-sponsored conference where they worked and wrote an article for a newsletter distributed to local private practice pediatricians discussing the importance of narrowing the complaint down to a few selected foods instead of large panel test.

Also, she observed that the younger physicians were getting a little bit better about not doingpanel tests compared with older colleagues.

“So, I feel like somewhere along the line, we were doing something right,” she said.

Shroba also suspected that students still do not get enough education about food allergy diagnosis and management in medical school.

“It is important that we provide that education to them in residency/fellowships or early in their careers,” she said.

Shroba encouraged allergy providers to reach out to local pediatricians via newsletters or even in person.

“If there is an office that you feel is frequently ordering tests incorrectly, reach out and ask, ‘Can we do a lunch and learn for you and your staff?’” she said.

Skin prick testing

One attendee asked Shroba for recommendations about using fresh food commercial serum in SPT.

“I always liked doing fresh skin pricks with fruits and vegetables, but I stuck with commercial product for really everything else,” Shroba said. “Even if they didn’t bring in fresh fruit, there still are extracts to a lot of these foods now. But yes, if they bring it in, I think it’s fun to use fresh fruit and vegetables.”

Another attendee asked Shroba if she would conduct any SPT before OFCs for baked egg or baked milk.

“I never did for baked challenges,” she said. “I would skin prick at diagnosis, and I usually never skin pricked again. I just didn’t find a lot of utility in skin prick testing beyond the diagnostic feature.”

Shroba conceded that other providers may have a different answer.

“A food challenge is the gold standard for a reason. I’m not going to change my answer because of the skin prick test on the day of the challenge,” she said. “If you felt like their history and prior testing made them eligible for a food challenge, then perform the food challenge.”

Testing in atopic dermatitis

Finally, an attendee asked Shroba for her thoughts on food testing when patients have severe atopic dermatitis.

“This is a tough one,” she said.

When parents came in with infants with severe atopic dermatitis and no other history with inhestion and they wanted to know what food was causing it, Shroba said that she typically did not test them. Instead, she focused on skin management first.

“What products are they putting on the skin? What are they using for soap, shampoo, lotion and laundry detergent? Then look at what they are using for their topical steroid,” she said.

If these infants still failed aggressive skincare management, Shroba said she would test for some foods.

“But then you also have to look at what food is in their diet,” she said. “If they’re only on a milk-based formula, and not on any food yet, then maybe I would test milk.”

When patients have severe atopic dermatitis and recurrent episodes of vomiting around their feedings, Shroba suggested performing a diet inventory.

“Again, if they are only on milk-based formula, then you do need to look at their formula,” she said.

Shroba said that she is a “huge fan of wet wraps,” adding that even though they are difficult to do and very time consuming, they have a place in skin management. If skin clears up with wet wraps, she said, then there is no need to test any foods unless there is something in the patient’s history besides “really bad skin.”

Overall lessons

Education was a running theme in Shroba’s responses to these and other questions.

“The positive and negative of our job as allergy providers is educating patients and families about necessary testing and the correct time to perform said testing,” Shroba said.

“Some families will be happy with this education and the opportunity to forgo unnecessary testing, while others will still want testing,” she continued. “It can make for some good and not so good visits.”

Shroba acknowledged that it can be difficult to tell families that the testing and treatment they were hoping to get is not appropriate based on history and symptom development.

“But if you know in your heart of hearts, just doing more harm than good, then you know it’s worth saying, ‘This is just not clinically needed at this time,’” she said.

“The most important element of a clinic visit is that we provide correct options regarding testing and do not do additional harm to a child’s growth and development based on inappropriate testing,” she said.