Poorly-Conceived Allergy Testing Can Lead to Unnecessary Diet Restrictions and Complications

As noted in previous blog posts (see below), allergy testing can lead to unnecessary food restrictions which can in turn lead to numerous subsequent problems. Case in point: YV Virkud et al (NEJM 2020; 383: 2462-2470) report on A 29-Month-Old Boy with Seizure and Hypocalcemia

This boy presented with severe hypocalcemia, rickets, and seizures one year after allergy testing led to additional dietary restrictions. Also, his mother was a vegetarian. At time of allergy testing, IgE testing suggested allergies to milk, cashews, pistachios, egg whites, almonds, soybeans, chickpeas, green peas, lentils, peanuts, and sesame seeds. Many of these foods caused no symptoms with food challenges.

Besides working through the potential reasons for hypocalcemia, the authors make several key points:

  • Nutritional rickets is NOT a historical relic. Vitamin D deficiency appears to be increasing in high-income countries despite food-fortification strategies.
  • There are frequent misdiagnosis of food allergies. “Clinical and laboratory testing is severely limited by poor specificity…approximately 20 to 25% of children have positive IgE blood tests to specific food allergens, even though the true prevalence of IgE-mediated food allergy is likely closer to 6 to 8%.”
  • Avoid indiscriminate use of IgE blood testing. Allergen panels are “particularly problematic, because they often uncover false positives and lead to unnecessary food avoidance.” Individual IgE testing can be used to help confirm a diagnosis after an allergic reaction to a food trigger.
  • The most accurate diagnostic tool is an oral food challenge.
  • In children with food allergies, supplements are often needed to avoid micronutrient deficiencies and a low threshold is needed for involvement of dieticians.
  • Early introduction of foods can reduce incidence of allergies and periodic reassessment is needed to determine if a child has outgrown an allergy.
Xrays show generalized demineralization. The metaphyses show flaring (dashed arrow) and cupping (arrowbead). The physes are radiolucent and widened (asterisks).

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Disclaimer: This blog, gutsandgrowth, assumes no responsibility for any use or operation of any method, product, instruction, concept or idea contained in the material herein or for any injury or damage to persons or property (whether products liability, negligence or otherwise) resulting from such use or operation. These blog posts are for educational purposes only. Specific dosing of medications (along with potential adverse effects) should be confirmed by prescribing physician.  Because of rapid advances in the medical sciences, the gutsandgrowth blog cautions that independent verification should be made of diagnosis and drug dosages. The reader is solely responsible for the conduct of any suggested test or procedure.  This content is not a substitute for medical advice, diagnosis or treatment provided by a qualified healthcare provider. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a condition

“The Truth About Allergies and Food Sensitivity Tests”

This is a link to a 20 minute video regarding “The Truth About Allergies and Food Sensitivity Tests” with Dr. Dave Stutkus and Dr. Mike Varshavski. (If trouble with link, then can find with quick search on YouTube.)

A couple of clarifications:

The video (~at the 3 minute mark) does not provide much nuance on “non-celiac gluten sensitivity” (see related blog posts below)

Some other points:

  • Don’t perform Food IgG testing -this is a memory antibody and does not reflect food allergy or sensitivity
  • So-called food sensitivity IgG tests do not have standardized normal values
  • Don’t perform broad-based IgE testing; there are many false-positives and false negative

Dr. Stutkus decided to undergone ‘food sensitivity’ tests and was reportedly sensitive to nearly 80 foods.

Related blog posts:

Disclaimer: This blog, gutsandgrowth, assumes no responsibility for any use or operation of any method, product, instruction, concept or idea contained in the material herein or for any injury or damage to persons or property (whether products liability, negligence or otherwise) resulting from such use or operation. These blog posts are for educational purposes only. Specific dosing of medications (along with potential adverse effects) should be confirmed by prescribing physician.  Because of rapid advances in the medical sciences, the gutsandgrowth blog cautions that independent verification should be made of diagnosis and drug dosages. The reader is solely responsible for the conduct of any suggested test or procedure.  This content is not a substitute for medical advice, diagnosis or treatment provided by a qualified healthcare provider. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a condition

What’s Wrong with “I Want My Kid Tested For Food Allergies”

Most parents, and many physicians, do not understand the limitations of food allergy testing.  As I am sure is common among physicians, I frequently receive requests for food allergy testing; parents do not realize that the strategy for food allergy testing is not straight-forward and has not advanced significantly for decades.  This information is detailed in a recent study and associated editorial (J Pediatr 2015; 166: 97-100, editorial 8-10: “Pitfalls in Food Allergy”).

The study was a retrospective review of all new patients seen at a pediatric food allergy center (2011-2012).  This involved a review of 797 new patients.

Key findings:

  • Of 284 patients who had received a food allergy panel, only 90 (32.8%) had a history warranting evaluation for food allergy.
  • Among 126 individuals who had food restrictions imposed based on food allergy panel testing, 112 (88.9%) were able to re-introduce at least 1 food into their diet.
  • The positive predictive value of food allergy testing was 2.2%.

So what can we learn from this study and editorial?

Misdiagnosis often relates to a lack of understanding regarding serum IgE-based testing.  First of all, many children with atopic dermatitis (and other atopic conditions) have elevated total IgE which results in more false positives.  In addition, a positive IgE test for a specific food indicates sensitization but not necessarily an allergy.

Strategy for testing (recommended by editorial):

  • “The key to the diagnosis of food allergy cannot be overstated; it begins with a detailed clinical history”
  • Testing should be “limited in general to the food(s) in question.”
  • When there is uncertainty, oral food challenges can be performed by specialists.
  • “If a patient is consuming a food without clinical symptoms of allergy, allergy testing should not be done to that food.”

Bottomline (from authors’ conclusion): “Food allergy panel testing often results in misdiagnosis of food allergy, overly restrictive dietary avoidance, and an unnecessary economic burden on the health system.”

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