Component resolved diagnostics for food allergy - Twitter summary from 2014 #ACAAI meeting

Dr. Robert Wood discussed component resolved diagnostics for food allergy.

Component resolved diagnostics helps to differentiate true allergy from positive tests due to cross-reacting antibodies. Dr Wood is not impressed that component testing can predict severity. Component testing is most helpful in guiding decisions about who should undergo oral food challenges. Component testing shouldn't be used routinely in all patients, but rather in selected cases where diagnosis is less clear.

Luengo and Cardone Clin Trans Allergy 2014 - a great article breaking down allergen families in food and pollens.

Egg

Ovomucoid = Gal d 1, is a stable against heat and digestion, possibly thus more predictive of failure of oral challenge to baked egg. Ovomucoid spIgE tracks well with total egg white IgE. Dr Wood isn't convinced it adds much extra to prediction of OFC results.

Milk

Casein specific IgE cut off of 0.94 gives a NPV of 96%; Total cow's milk IgE cut off of 1.21 give a NPV of 94%. Undetectable spIgE to casein is very reassuring that an oral challenge to baked milk would be successful.



8 foods cause 90% of food allergies (click to enlarge the image). The likelihood of a negative oral food challenge is shown in relation to the respective values of skin prick test (SPT) and serum IgE (sIgE).

Soy

Soy-allergenic components include Gly m 4 - associated with Bet v1 (i.e birch) cross reactivity and thus it implies only OAS, not true worrisome allergy. Gly m 5 and Gly m 6 are associated with true soy allergy.

Peanut

Ara h 2 seems to have the best correlation with clinical reactivity and systemic reactions whereas Ara h 8 is simply related to OAS.

Nicolaou 2011 - Ara h 2 cut off of 0.35 was associated with good chance of failing an oral challenge to peanut. If you take the cut off of 3.5 for Ara h 2 the LR is infinity! So don't challenge those people! Optimal sensitivity and specificity for Ara h 2 is in the range of 0.1 to 0.5.

Geography matters - in Spain Ara h 8 is not as common due to less birch sensitization, whereas Ara h 9 more common.

If the history of clinical reactivity to peanut is dramatic and convincing, specific IgE and component testing is not necessary. It's those patients with vague history of peanut induced mouth itch or no history at all, who are birch allergic where this will help.

This is a Twitter summary from 2014 #ACAAI meeting. The post is a part of series. See the rest here: http://allergynotes.blogspot.com/search/label/ACAAI

The Twitter summary was made possible by @DrAnneEllis and @MatthewBowdish

Several allergists did a great job posting updates from the 2014 meeting of the #ACAAI. I used the website “All My Tweets” to review the tweets. For comparison, here are the tweets from previous #ACAAI meetings (scroll down the page for the past years): http://allergynotes.blogspot.com/search/label/ACAAI

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