Dr. Dave Stutkus shared some slides (on twitter) recently based on a lecture at Nationwide Children’s. Since I see children everyday who are undergoing poorly-conceived allergy testing, I wanted to share some of them.
Excluding foods from diet based on allergy testing without concurrent symptoms can lead to allergies rather than tolerance:
Newer antihistamines are safer
Most individuals with penicillin allergy are not truly penicillin allergic. Also, there is a low rate of cross-reactivity with most cephalosporins.
Proper allergy testing relies on the basic understanding that sensitization is not equivalent to being allergic. In addition, allergy testing has a high rate of false positives; therefore, testing needs to be limited (avoid broad panels).
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
A recent study (DR Stutkus et al.PediatricsDecember 2016, VOLUME 138 / ISSUE 6) suggests that primary care providers could used more education on utilizing allergy testing more effectively. The main problem with food allergy testing is its very low positive predictive value. In a previous study of food allergy testing, the positive predictive value of food allergy testing was 2.2%!
Thanks to Kipp Ellsworth for this reference.
BACKGROUND AND OBJECTIVE: Immunoglobullin E (IgE)-mediated food allergies affect 5% to 8% of children. Serum IgE levels assist in diagnosing food allergies but have low positive predictive value. This can lead to misinterpretation, overdiagnosis, and unnecessary dietary elimination. Use of IgE food allergen panels has been associated with increased cost and burden. The scale of use of these panels has not been reported in the medical literature.
METHODS: We conducted a retrospective review of a commercial laboratory database associated with a tertiary care pediatric academic medical center for food IgE tests ordered by all provider types during 2013.
RESULTS: A total of 10 794 single-food IgE tests and 3065 allergen panels were ordered. Allergists ordered the majority of single-food IgE tests (58.2%) whereas 78.8% of food allergen panels were ordered by primary care providers (PCPs) (P < .001). Of all IgE tests ordered by PCPs, 45.1% were panels compared with 1.2% of orders placed by allergists (P < .001). PCPs in practice for >15 years ordered a higher number of food allergen panels (P < .05) compared with PCPs with less experience. Compared with allergists, PCPs ordered more tests for unlikely causes of food allergies (P < .001). Total cost of IgE testing and cost per patient were higher for PCPs compared with allergists.
CONCLUSIONS: Review of food allergen IgE testing through a high volume outpatient laboratory revealed PCPs order significantly more food allergen panels, tests for uncommon causes of food allergy, and generate higher cost per patient compared with allergists. These results suggest a need for increased education of PCPs regarding proper use of food IgE tests.
A recent review article (Clin Gastroenterol Hepatol 2014; 12: 1216-23) summarizes the potential role of allergy testing for eosinophilic esophagitis (EoE).
The article summarizes the potential ways to use various allergy testing and reviews the literature on its effectiveness. The article notes a couple of key points:
Overall, using skin prick testing (SPT) and atopy patch testing (APT), allergy testing has not proved more reliable then empirically administering a 6-food elimination diet. Thus, “the issue remains whether food allergy testing provides a useful tool in EoE.” However, targeted testing-based diets (especially in children) may require elimination of fewer foods.
“Serum IgE food-specific IgE panels should not be used for EoE.” “Testing for foods, especially IgE testing, leads to recognition of food sensitizations that may not be clinically relevant and that on elimination, could result in the loss of tolerance to the food.”
Testing for milk allergy is noted have a high false negative rate.
IgG based testing is not recommended. In fact, IgG immunoglobulins are “associated with tolerance rather than allergy.”
“Only 8% of children will become tolerant to all foods that cause their EoE.”
Bottomline: While foods commonly triggers EoE, the tests to identify these foods are far from perfect. I find that families are quite uninformed about the frequent lack of correlation between allergy testing and true EoE triggers.