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).

Related blog posts:

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