Peanut Allergy Misdiagnosed in 2 out of 3 Cases ?

 
Attacking Peanut Allergy

 

Peanut Allergy Misdiagnosed in 2 out of 3 Cases  

This title from Medical News Today April 13, 2010 caught my attention.  It has always been a mystery as to why peanut allergy has increased dramatically over the years. This publication may shed some light on that mystery.   

There are a number of factors in the peanut allergy equation  and a recalculation may be necessary. First we need to be careful in discerning peanut allergy from peanut sensitization. Peanut allergic children would be those who have symptoms with exposure and evidence of a positive allergy test (skin prick test or specific IgE to peanut determined by a blood test). The sensitizated child is one with a positive test and no clinical correlate.   

Secondly, the use of allergy tests has become more frequent and is being done by many other specialties. The manufacturers of blood tests for allergy market to primary caretakers an array of food allergen diagnostic panels that contain peanut along with many other foods. If the history was hives occurring after eating egg, a panel would include egg but would also have a number of additional foods. Sometimes these add-on foods return as positives (despite no history of a problem with ingestion) and the diagnosis of allergy is made.  

Thirdly, this news report indicates that the diagnosis of peanut allergy was wrong in 66% of the patients.   

A reworking of the prevalence of peanut allergy has a potential confounding variable; faulty diagnostic tools.   

This news article began with a poignant comment- peanut allergy has always been associated with a deep anxiety, especially in the parents of peanut allergic children. I have many patients who will attest to that.  

“Many people are being told that they are allergic to peanut, that they must avoid them and all foods that contain them at all costs, are actually not allergic to the nut at all” says Professor Wickman (Stockholm, Sweden). Dr. Wickman reported that 2/3 who are considered allergic to peanuts experience mild symptoms or none at all. A cross-reactive protein from birch tree pollen was thought responsible for the peanut reaction.   

This report included the shortcomings of the materials used for allergen skin testing and those used for testing the blood for allergy.   

To address this issue, a new diagnostic test was used on 4000 children to determine the specific proteins that are cross-reactive. It is known that specific peanut proteins are responsible for allergic reactions to peanut. The new test looks at antibody (IgE) production to the allergy-causing proteins. This allergy component test was used to show that 2/3 children who were diagnosed with peanut allergy were not allergic. Their positive test to peanut was due to some other protein that cross-reacted.  

Now this was a news report and not a peer-reviewed article and I know how reporters can get things wrong or misquote. In regards to the report, remember peanut is a legume, not a nut.   

In the report a statement is made that…” up to 7.5% of children seemed to be allergic to peanut at age 8 based on routine tests”. This made me wonder if they were truly allergic (symptoms by history) or they were declared allergic because a test was positive (done routinely for allergy?).   

Now for a few critical comments- both positive and negative;  

1. The capability of sorting out reactivity to the important proteins is applauded. We may be able to go back and de-diagnose a seemingly large proportion of peanut allergic people. The peanut-free tables at the schools are still essential but will be smaller by 2/3.  

2. How would this been all different if the diagnostics, both skin prick tests and specific IgE would have been done only in those who had a history of exposure and reactivity with exposure? If the patient’s history directed our choice of individual tests, would we have so many peanut sensitive/allergic people? Avoid doing food allergen panels. Pick out the pertintent allergens- it will be less confusing and it will save money (one example from a local sendout laboratory -$300 for the panel and $25 for the individual allergen).   

3. Look at the consequences of marketing panels or doing standard groupings of skin tests or blood tests- in 66% diagnosed perhaps falsely the families have an emotional burden, a nutritional burden, an isolation burden, and a financial burden. The peanut allergic person needs to have self-injected epinephrine available.  

4. We always have to be careful in applying the findings from one area to another. This report on the 4000 children was from Sweden. There may be significant differences in our population. I would relish the opportunity to sort out our population of peanut sensitive children.  

I am an advisor to the Southside Indianapolis Food Allergy Support Group. In March when I presented an update on food allergy, I promised that I would look at our peanut positive population. This has been quite a task.  I am creating a database to characterize the population in the hopes of being able to participate in a peanut study. We have 360 positive skin tests for peanut from January 1, 2009 through March 31, 2010-15 months of clinic visits. The spreadsheet has a number of epidemiologic parameters including the age and type of reaction to peanut. Many of the children were diagnosed based on a panel that was performed because of atopic eczema or due to blood test panels and referred by primary caretakers for further evaluation. A few had anaphylaxis.This project is fascinating and I think will be very informative. It hopefully will catch the eye of those in the allergen diagnostic community or someone looking for a large population to enroll in a peanut immunotherapy study. These families are highly motivated to make a difference and to help others with this problem.  

The new technology may help to address a historical and continuing over-enthusiastic and unfocused use of allergy tests, both skin prick test and blood test for peanut allergy. The tests we have now only tell us that antibody (IgE) is being made. The significance of that antibody is left to the clinician and must be based on the history and exposure to the allergen making sure that the clinical condition fits the template of IgE-mediated reactions. I for one eagerly await the arrival of more definitive diagnostic tools. 

  

FEL  

April 25, 2010 · fleickly · 4 Comments
Tags: , , , ,  · Posted in: Allergies, Allergy Testing, Food Allergies, Peanut Allergy, Phadia Allergy Tests

4 Responses

  1. Abbie Hunt - May 25, 2010

    Most allergies can be treated by corticosteroids and also some antihistamine blockers.;”~

  2. Hayden Bennett - July 10, 2010

    to treat my allergies, i just take in some antihistamines like claritin”-.

  3. fleickly - July 11, 2010

    Antihistamines may work but it does depend on the condition. Histamine against which an ‘anti-histamine’ acts is just one of more than 100 mediators that are released in an allergic reaction. Many will get relief with an antihistamine when the condition is nasal allergy or hives, however when the allergy is anaphylactic shock, a flare of atopic dermatitis, or asthma additional medicines would be required.
    Thanks for the comment.
    FEL

  4. Justin Campbell - October 7, 2010

    i hate may allergies coz they turn my skin red and i sneeze a lot~*-