And what about the following... am I reading this right? My take is that with my son's .48 result to arah 2 he has a 70 to 90% chance of reacting to the ingestion of peanut? Why on the world would his allergist be recommending a food challenge if this is correct???
Info from the ask the expert section of American Academy of Allergy, Asthma and Immunology- found at:
http://www.aaaai.org/ask-the-expert/component-testing-peanut.aspxSignificance of component testing to peanutQuestion:
10/21/2013
I would like some help interpreting component testing for peanut. I have a 32 yr-old male with a 20 yr history of immediate vomiting and angioedema of the throat when he ate a peanut cookie. Since then he has avoided peanut altogether and he wished to find out if he was still allergic. His skin test was a 4+ with a wheal of 14 mm greater than negative control, histamine was 5 mm wheal. His component tests for Ara h1 and 3 were <0.10 (ref range from Quest Diagnostics) and Ara h2 was 0.31, Ara h9 was 0.90 and Ara h8 was 9.97. Based on these results and the history should he continue to avoid peanut despite being 20 years ago or based on his tests his Ara h8 reveals that he may have developed tolerance.
Answer:
Thank you for your inquiry.
Based upon the results you have supplied, your patient has a high likelihood of reacting to the ingestion of peanuts. An Ara h2 level of about 0.3 has a 70 to 90% predictive value of a reaction upon the ingestion of peanuts (1-3). This would not of course preclude an oral challenge, but the decision to do so would be based upon your own assessment of the risk/benefit ratio and a discussion of risk/benefit with your patient. If you decided to do a challenge, I would suggest doing it outside of the tree pollen season (wintertime) to minimize the chance of an oral allergy syndrome reaction secondary to the Ara h8 sensitization.
Finally, it should always be noted that component testing gives one statistical risks, but not definitive information. Anaphylaxis can occur to any component including those such as Ara h8 which are more classically associated with oral allergy syndrome. In this regard, for your convenience, I have copied below an entry regarding a similar question that was posted to our website 6/26/2013.
Thank you again for your inquiry and we hope this response is helpful to you.
References:
1. Klemans et al: Ara h 2 Is the Best Predictor for Peanut Allergy in Adults, Journal of Allergy and Clinical Immunology: In Practice 11 October 2013.
2. Lieberman J et al:The Utility of Peanut Components in the Diagnosis of IgE-Mediated Peanut Allergy Among Distinct Populations Journal of Allergy and Clinical Immunology: In Practice Vol. 1, Issue 1, Pages 75-82, 2013.
3. Keet et al: Evaluation of Ara h2 IgE thresholds in the diagnosis of peanut allergy in a clinical population. Journal of Allergy and Clinical Immunology: In Practice Vol. 1, Issue 1, Pages 101-103.
Previous posting to Ask the Expert website:
The value of component testing in predicting a systemic reaction to peanut
Question:
6/26/2013
Seven-year-old boy with significant seasonal allergic rhinitis (very allergic to oak, and Birch) and no history of food allergies ate honey roasted peanuts . Within 5 minutes he started with a barky, croupy cough and then developed very significant skin pruritus. He was itching very hard over his chest and neck. Then the cough got worse and he sounded wheezy. He was given a dose of Benadryl, and fortunately he did not have any further complications. The results of my evaluation are: Skin test to Peanut 2+/4+. sIgE to peanut 1.02 kU/L. Ara H 1,2,3,9 <0.1. Ara H 8 24.1 kU/l. According to the review, he should be at low risk for anaphylaxis but the initial reaction is definitely much more than oral allergy syndrome. What would you advise?
Answer:
Thank you for your inquiry.
Your interpretation of the literature is correct in that “classically” the pattern of specific IgE to peanut components seen in your patient would be more likely to predict that only oral symptoms, and not a systemic reaction, would occur upon ingestion of peanuts. However, it is important to understand that this classical interpretation is based only on statistical probabilities. By this I mean that children demonstrating only specific IgE to Ara h 8 are less likely to exhibit a systemic reaction than children exhibiting specific IgE to Ara h 2, for example. Nonetheless, systemic reactions can occur with isolated sensitivity to Ara h 8.
As you can see from the abstract (Asarnoj, et al.) copied below, systemic reactions can occur in children with isolated Ara h 8 sensitivity. This is seen clearly in Figure 3 of this article.
The most reliable test to discern whether a child will exhibit a systemic reaction to peanut is an actual oral challenge. In essence, the reaction exhibited by the child described in your inquiry should be taken at “face value,” and the child, at least for the present, should be considered allergic to peanuts. It is clear that patients who have negative skin tests as well as serum specific IgE to foods may still exhibit allergic reactions upon oral food challenge (see Journal of Allergy and Clinical Immunology reference copied below).
Thus, in summary, the results of serum specific IgE testing both in testing to “whole” and component testing, simply serve as guidelines, pointing out the relative risks of a reaction upon ingestion. They are not intended to confer 100 percent predictability as to whether or not a patient will react to the ingestion of the food in question.
Thank you again for your inquiry and we hope this response is helpful to you.
Allergy. 2010 Sep;65(9):1189-95. doi: 10.1111/j.1398-9995.2010.02334.x. Epub 2010 Feb 8.
IgE to peanut allergen components: relation to peanut symptoms and pollen sensitization in 8-year-olds.
Asarnoj A, Movérare R, Ostblom E, Poorafshar M, Lilja G, Hedlin G, van Hage M, Ahlstedt S, Wickman M.
Source
National Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
Abstract
Background: Allergen-specific IgE testing is often performed with crude peanut extract, but the results may be difficult to interpret because of cross-reactions between peanut and other plant allergens. The aim was to investigate IgE reactivity to peanut allergen components in children from a birch-rich region in relation to pollen sensitization and peanut symptoms.
Methods: From a birth cohort, clinical parameters were obtained through questionnaires and IgE antibody levels to peanut and birch pollen were measured. Different peanut/birch sensitization phenotypes were defined among 200 selected children. IgE reactivity to peanut and pollen allergen components was analysed using microarray technique.
Results: Peanut symptoms were reported in 87% of the children with IgE reactivity to any of the peanut allergens Ara h 1, 2 or 3 but not to Ara h 8 (n = 46) vs 17% of children with IgE reactivity to Ara h 8 but not to Ara h 1, 2 or 3 (n = 23), P < 0.001. Furthermore, symptoms were more severe in children with Ara h 1, 2 or 3 reactivity. Children with IgE reactivity both to Ara h 2 and to Ara h 1 or 3 more often reported peanut symptoms than children with IgE only to Ara h 2 (97%vs 70%, P = 0.016), particularly respiratory symptoms (50%vs 9%, P = 0.002).
Conclusions: IgE analysis to peanut allergen components may be used to distinguish between peanut-sensitized individuals at risk of severe symptoms and those likely to have milder or no symptoms to peanut if sensitized to pollen allergens and their peanut homologue allergens.
J Allergy Clin Immunol. Author manuscript; available in PMC 2012 November 1.
Published in final edited form as:
J Allergy Clin Immunol. 2011 November; 128(5): 1120–1122.
Published online 2011 August 11. doi: 10.1016/j.jaci.2011.07.012
PMCID: PMC3205298
NIHMSID: NIHMS319256
Outcomes of office-based, open food challenges in the management of food allergy
Jay A Lieberman, MD, Amanda L Cox, MD, Michelle Vitale, RN, and Hugh A Sampson, MD
Sincerely,
Phil Lieberman, M.D.
