Usually when I review an article I go directly to that part of the introduction that deals with the purpose of the study. However, the background information provided in the introduction I thought was very helpful in understanding food allergy, noting the concerns regarding food allergy, and sharing how experts in the field of food allergy handle it (especially as they see a significant number of food allergic children in their referral center).

Identified problems with food allergy;

1.  Availability of serum IgE tests for foods
2.  Use of allergy tests to direct avoidance diets
3.  Consequences of avoidance diets
   • Poor weight gain
   •  Malnutrition
4.  Idea that food allergy is the exclusive cause of atopic dermatitis
5.  Food allergy focus leads to neglect of skin care

The allergy test result, whether by skin prick test or by serum IgE (formerly known as RAST) antibody levels, predict the chance of having a reaction with exposure to that food (they also demonstrate the presence of IgE directed against that food). These probabilities have been established for just a few foods; cow’s milk, hen’s egg, fish, peanut, and tree nuts. For all the other foods the levels that predict the chance of the child having a positive reaction have not been established.

Another significant issue that clouds the picture is that both allergic skin testing and serum specific IgE levels obtained from a blood test frequently detect sensitization that is not associated with any symptoms when the food is ingested. The false positive rate- when the test is positive and the story is that there were no problems with ingestion – is 50%! The gold standard for a food allergy is the double-blind placebo-controlled challenge. In other words, the best indicator is the history- what happens when the food is ingested.

The Purpose of the Study- was to raise awareness about the overreliance on serum immunoglobulin results as the primary indicator for establishing a food elimination diet in children (with atopic dermatitis).

Methods-This was a retrospective chart review of children who were seen for atopic dermatitis and food allergy. The number evaluated was 125.

Results

The median age of the children was 4 years. Most of had atopic dermatitis (96%). The severity of the atopic dermatitis varied- 30% were mild, 24% were moderate, and 42% were severe.

There were 364 oral food challenges performed on foods that were avoided at the time of the evaluation. That is almost 3 food challenges per child. Most of these challenges were negative- 325/364 (89%). Of note that during these food challenges, if there was a reaction, it occurred within a 2-hour observation period. Also, there were no documented flares of the skin condition.

Those 364 food challenges occurred in three different groups of children; 111 in whom foods were avoided due to a positive allergy test, 122 in whom a food was avoided due to a previous reaction to a food, and the last grouping was 131 children in whom a food was avoided for other reasons (not a history of a reaction or a positive allergy test). This last group included those who avoided a food because of lack of prior exposure, another family member with an allergy to that food, parental fear, refusal to eat the food, worsening of atopic dermatitis was uncertain with exposure, being too young for the food, and uncertain reasons.

In the group who avoided a food due to a positive allergy test (n=44 children) – with wheat being an exception (at 77% negative), 80% or more of the food challenges were negative. When there was a positive food challenge, the foods involved included egg, banana, peanut, soy, and wheat.

There were 122 food challenges done in a group of children (n=67 children) who had a history of a reaction to the food. When peanut and oats are excluded, more than 75% of the food challenges were negative. The positive food challenges were to; egg, chicken, milk, oat, peanut, soy, pea, wheat, beans, and pork & beans. This group of children had an array of food reactions by history; anaphylaxis (5%), gastrointestinal reactions (17%), lower respiratory tract reactions (8%), upper respiratory tract reactions (10%), and skin reactions (76%).

In the last group, those who avoided a food for other reasons, (n=131) more than 90% of the challenges were negative. There were 11 positive food challenges. The positive foods included egg, fruits (strawberry), meats (beef, chicken), milk, shellfish (shrimp), soy, barley, and Alimentum.

The levels of specific IgE antibody to the food were used to divide those who were challenged versus those who were not challenged. The following table shows the serum IgE level, the offering of a food challenge, and the result of the food challenge. When the serum IgE levels were elevated, no challenges were offered. For these three foods everyone who was below the critical cut-off point passed the food challenge. The decision levels for doing a food challenge were as follows- egg:< 2years of age -2 kU/L and >2 years of age 7 kU/l, Milk:< 2 years of age -5 kU/L and > 2 years of age a5 kU/l, peanut: 14 kU/L.

84-93% of foods that were avoided for a variety of reasons were returned to the child’s diet after a successful food challenge.

Conclusions- the authors concluded that in the absence of a history of anaphylaxis, the primary reliance on serum food-specific IgE testing to establish the need for a food elimination diet is not sufficient, especially within the population of children with atopic dermatitis. Oral food challenges are indicated to confirm the presence of a food allergy.

Many of the children seen were on overly restrictive diets that were inclusive of foods they never had exposure to or foods that were eaten without a problem. This restriction was based on food blood test results. The successful food challenge demonstrated that specific food restriction was not necessary in most instances. A food challenge discerns sensitization from true allergy.

The authors point out that it is important to optimize skin care and clearing to accurately sort out the impact of a food on the condition. It is also stated that there is a significant overreliance on allergy test results in making the diagnosis of food allergy especially in the children with atopic dermatitis. Allergy test results, if not supported by a food challenge, can lead to unnecessary food restrictions. To quote the authors, ‘misinterpretation of food allergy immunoassays, for which there is no correlation between the level and the probability of reacting to a food, is leading       unnecessary dietary restrictions that could result in nutritional deficiencies.’

Reviewer’s Comments- After my first read of the article, I felt that this was a very strongly worded statement against the indiscriminate use of serum IgE testing.  After numerous reads, that opinion of the article has not changed. This work is a strong statement against serum IgE testing for allergy.

It is important to point out that the vast majority of children who were in the study had atopic dermatitis (aka eczema). This clinical condition is notorious for having many false positive food allergy tests. During the 1980’ there were many studies that linked food allergy with atopic dermatitis. During my fellowship at Duke we watched children with severe atopic dermatitis react during the double-blind placebo-controlled food challenges. These studies led to the observation that there were 6 foods commonly associated with the condition; egg, milk, wheat, soy, peanut, and fish. Subsequently, many children with a range of presentations of atopic dermatitis have undergone allergy testing both by the skin prick method and by serum testing.  That has led to the concerns presented in this article.

The current ‘state of the art’ noted in the NHLBI Guidelines for the Diagnosis and Management of Food Allergy  suggests that food allergy considerations should include egg and any other food that the family feels is causative to the skin condition.

The authors point out that the availability of immunoassay food allergy panels to identify possible food allergy has added to the ongoing potential for misinterpretation of the results.

We also have that issue that continuously plagues us- sensitization vs. allergy. The laboratory test tells us that IgE is being made. The significance of that IgE has to be determined by the clinician. Taking a history is one way to begin establishing significance. The food challenge would be the bottom line for establishing relevance and significance of a positive IgE test for a food.

There are many messages within this study. The concerns regarding restrictive diets and avidly pursing food allergy diagnostics can lead to;

1. Failure to thrive due to food restrictions
2. Parental perceptions about unclear messages about which foods must be avoided
3. Attempts to treat atopic dermatitis by diet alone and not proper skin care
4. Pressure from parents to get these blood tests for food allergy
5. Incomplete understanding about the class designations
6. Applying the well-established food specific IgE values to foods that have not been rigorously evaluated

These concerns are seen with parents, primary caretakers, and yes, even allergists.

 When an allergy test for a food is positive yet the food is eaten without any clinical reaction, the test was a false positive. We should not let the laboratory result dictate the care of the child. Specific food allergy testing can be done for the food of interest. Select the test based on the story that supports it.

I think the role of the allergist in the near future will be to clear many of these positive tests. Here at Riley hospital we have an extensive experience in doing food challenges. Most of the time we perform a food challenge to demonstrate that a food allergy has been outgrown. We offer them in a controlled clinical environment. Everything is in place to take care of a reaction. In the near future I am sure we will be doing more food challenges to demonstrate the irrelevance of positive allergy test results.

The serum tests for IgE to food have helped with the decision to offer a food challenge for some foods. I look to the serum tests for food to decide the chance of a reaction and whether or not an oral food challenge should be scheduled. It is always perplexing to have a child present who has had a panel performed. All too often we struggle with results deemed high due to the ‘H’ notation after the specific concentration. We struggle with positive results from foods that the child has never ingested. We very frequently struggle with results on foods that the child has eaten with impunity and never had a problem. The food challenge helps to sort the well from the worried well.

Many times I have witnessed the joy of having the yoke (not yolk) of a food allergy removed by doing the food challenge.

FEL

The July issue of Pediatrics has an article entitled, ‘The Prevalence, Severity, and Distribution of Childhood Food Allergy in the United States’ by R S Gupta, E E Springston, M R Warrier, B Smith, R Kumar, J Pongracic, and J L Holl. The bottom line from this work is that the prevalence and severity of food allergy is greater than previous reports would indicate and this was a fairly large nationwide survey designed to address the question of prevalence. The authors also conclude that disparities exist with the clinical diagnosis of the condition.

Purpose of the paper- to determine the prevalence, severity, and distribution of food allergy in children.

Methods-The authors created a survey that was population-based and cross-sectional. It was administered to a representative sample of the United States population between June 2009 and February 2010. This survey was carefully developed and evaluated prior to its use. It was not a previously used, standardized tool.

Recruiting and survey administration was performed by a survey research company. Internet access was required to participate.

Completion of 40,000 surveys would give the study significant power (0.9) at a significance level of 0.5 to detect overall and allergen-specific food allergy prevalence (between 1-9%) and prevalence variability from 1-7% in groups as small as 1% of the sample.

Outcome Measures

The primary outcomes were food allergy prevalence and severity.

Food allergy was defined as a report of a confirmed or a convincing story of an allergy.

A convincing food allergy was based on at least one of the following;

1. Anaphylaxis- defined as a severe reaction that could lead to death
2. Angioedema (swelling) of the lips, eyes, or face
3. Other Angioedema
4. Coughing
5. Other oropharnygeal symptoms
6. Eczema
7. Flushing
8. Hives
9. Low blood pressure
10. Pruritis (itching)
11. Trouble breathing
12. Vomiting
13. Wheezing

A confirmed food allergy had the above criteria and included a report of a physician-diagnosis with serum-specific IgE, skin prick test results, or the result of an oral food challenge.

The severity of a food reaction was based on the nature of the symptoms;

Mild-moderate food allergy symptoms were limited to;

1. Angioedema of the lips, eyes, or face
2. Other angioedema
3. Coughing
4. Other oropharyngeal symptoms
5. Eczema
6. Flushing
7. Hives
8. Pruritis
9. Vomiting

Severe food allergy symptoms were;

1. Any report of anaphylaxis
2. Low blood pressure
3. Trouble breathing
4. Wheezing
5. Vomiting and angioedema, and coughing in combination

Results

The final sample size was 38,480 children.

The prevalence of food allergy in children was 8%. Multiple food allergies were reported in 2.4% (approximately 1/3 children of those with food allergy had more than one food to report).

Allergen prevalence was as follows;

Peanut- 767/3339 (23% of the reports) 52% had severe reactions, 48% had mild-moderate reactions

Milk- 702/3339 (21% of the reports) 31% had severe reactions, 69% had mild-moderate reactions

Shellfish- 509/3339 (15% of the reports) 47% had severe reactions, 53% had mild-moderate reactions

There was an age variation reported (the highest percentage reporting a specific food allergy);

Peanut- 30% in the 3-5 years of age group

Milk- 32% in the 0-2 years of age group

Shellfish- 24% in the > 14 year old age group

Tree nuts- 15% in the 11-13 year old age group

Egg – 16% in the 0-2 year old age group

Fish (fin) – 7% in the >14 year old age group

Strawberry- 8% in the 0-2 year old age group

Wheat- 8% in the 11-13 year old age group

Soy- 7% in the 11-13 year old age group

Severity of the Food Reactions

The prevalence of a severe reaction to a food was 3.1% of the surveyed population. This translates to 38.7% of the food allergy population. These severe reactions were reported more frequently in the children who had peanut or tree nut allergy. From the note above- 52% of the peanut and 53% of the tree nut allergic group had severe reactions.

When it happens to you or your child- it is 100%. The reassurance factor- just over 1/3 have serious reactions, most do not. Serious reactions are seen just over half the time with peanuts and tree nuts.

Food Allergy Associations- Odd/Risk Factors

The odds of having a food allergy were-

1. Higher in Asian and black children as compared to white children.
2. Higher in all age groups compared to children aged 0-2 years.
3. Higher in geographic areas outside the Midwest.
4. Lower with household incomes <$50,000.
5. Gender did not make a difference
6. Higher for a confirmed food allergy compared to a convincing food allergy history in those children with multiple food allergies.
7. Lower for confirmed food allergy in Asian, black, and Hispanic as compared to white children.
8. Lower for confirmed food allergy in households with incomes <$50,000.
9. Higher for a severe reaction among children in all age groups compared to children 0-2 years of age,  boys compared to girls, and those with compared to those without multiple food allergies.

Conclusions

Eight percent of children have food allergy with 38.7% having a severe reaction and 30.4% having multiple food allergies.

The disparity regarding food allergy diagnosis was seen with race, age, and income.

Reviewer’s Comments

Prevalence refers to the proportion of individuals with the clinical condition in a population at a specific moment in time. It provides an estimate of the risk or probability that an individual will have the condition. This would be the number of cases divided by the total population at a given moment.

When looking over the information there are a few points that need to be stressed. First was the sample truly representative?

The study was not performed on the entire pediatric population of the United States. The population was recruited from 6100 participants through a Web-enabled panel and an additional 33,900 came from on online sample of households with children; they all had access to the internet. This specific population is reported to be representative of U.S. households with children. So the first concern has been answered. However, a question arises as to selection bias. Do families who have children with food allergy have more computer access? Did the lack of computer (internet access) lead to non-selection for the study?

The second point was the definition of a food allergy. This was by the family’s report of a reaction or a confirmed food allergy. This was not a medical record review nor was this a bone-fide food challenge. The authors do point out that another bias; recall bias may be at work.

This was the largest study conducted looking at food allergy prevalence- a uniqueness to the work.

The article points out a number of helpful ‘between the lines’ points. About half of the children with a peanut allergy had a severe reaction. You can have mild-moderate reactions to peanut. The same relationship was seen with shellfish allergy.

The authors used multiple logistic regression models to establish odds. This statistical tool looks at the degree of association between having the condition after adjusting for factors that may be confounding. When the odds equal 1, then there is no increased/decreased relationship. When confidence interval include the number one, then there is no strong statistical difference. There seems to be a tendency for disparity, however I would be cautious due to the stated confidence intervals. The disparities that look clear are

Race- Asian, Black for having food allergy

Less confirmed vs. convincing cases with Asians

Age-compared to two year olds, more food allergy in all other ages

Age- compared to two year olds, more severe food allergy in all other age groups

Income- household income lower than $50,000 was protective for having food allergy, for having fewer confirmed vs. convincing histories, and having less severe food allergy. (In these instances the odds was less than one)

Geographic regions- compared to the Midwest, there was more food allergy in the Northeast, South, and West.

As for summarizing discrepancies in a few sentences- if the child was Asian or Black there was a higher chance of having food allergy, and less of a chance that it was confirmed if the child was Asian. Children over the age of two years have more reported food allergies and they tend to be more severe in the older age groups. If your family made less than $50,000, there was less of a chance that there would be a food allergy (poverty protects?). Lastly, there is less food allergy in the Midwest that in other regions of the country.

I enjoyed reading and reviewing this article. As with many good studies it stimulates more questions.

Respectfully submitted,
FEL

Now she also has nasal allergy that is very well controlled on an antihistamine. She ate almonds with impunity, but had one experience with cashew that caused the same symptoms.

We tested her for cashew and peanut- they were positive. We also tested her for birch and alder tree pollen, hazelnut, celery, apple, peach, and carrot. Birch and hazelnut (food) were also positive. I felt very sure that she had peanut- induced oral allergy syndrome. She was given injectable epinephrine, information regarding the Food Allergy and Anaphylaxis Network, and information on medical alert bracelets.

I only wished that I could have ordered a few additional blood tests to help provide some guidance regarding the seriousness of her peanut reaction.

We are currently working with a large group of children who have been seen at Riley Hospital for Children with peanut positive skin prick tests. This group of 76 children (from the 350 we have seen over the past year who have had a positive skin test to peanut) had wide variety of clinical presentations for their peanut allergy. Phadia has performed their microarray assay on these children. Now I am eagerly working on the information looking for associations, frequencies, odds ratios, and predictive values. This project and what I read in the literature, indicates that reactions to specific peanut proteins may help predict who will have a serious reaction to peanut. What we see is that the skin test for peanut and even the blood test for peanut tend to be rather crude tests and may measure antibody responses to a wide variety of proteins in peanut, not all of which are important in causing serious reactions. Positive peanut test results may be due to proteins in peanut that are shared with other members of the plant kingdom. So a child may have a positive screening test, by skin prick or by blood, but not show reactivity to the proteins associated with serious reactions and may show possible cross-reactivity to birch or alder tree pollen or the foods celery, carrot, apple, peach, or hazelnut.

My guess is that this young lady has the oral allergy syndrome due to peanut. I await her ImmunoCap specific IgE to peanut- her value may be low enough, below the critical cut-off point, to allow her to undergo a safe peanut challenge. However, I would have relished the opportunity to evaluate her responses via the Phadia microarray. This may help with my diagnosis and guidance. Knowing the specifics of her response may help with the family’s fear of a more serious peanut reaction, it may help with her socialization at school, and it may obviate the need for having injectable epinephrine.

Just another day in clinic!

FEL

Our Indianapolis Star posted a story from Shari Roan. Ms Roan is reporter for the Los Angeles Times. The title of the article in the Star was ‘You may be allergic to a food . . . or not’ . The original article by Ms. Roan had a slightly different title.

The article coincided with the announcement of the publications of the ‘New Guidelines for the Diagnosis and Management of Food Allergy’. This document represented the efforts of a group of food allergy experts working with the National Institute of Allergy and Infectious Diseases. In one of my earlier posts I commented on a draft of this document. The final product is now available.

What struck me after reading the article was the need for us to undo what has been done. There are  many children out there who have had extensive food allergy testing performed and struggle with numerous positive food allergy test results. Are they all truly allergic to all those foods? Are they being deprived of adequate nutrition? Can we help them and their families?

‘A lot of physicians order large numbers of blood tests of various foods, and when they find small amounts of antibody present, they indicate to the patient  that they are allergic to this food and should not ingest it,’ according to Dr. Hugh Sampson- an internationally recognized expert in food allergy. The article goes to state that many children are placed on highly restricted diets that are probably not necessary.

It is also important to point out that the same consequence can be seen with the results of skin testing.

The New Guidelines state that oral food challenges will be needed to sort out the relevance of the positive food allergy test. The oral food challenge is required to make an accurate diagnosis. These guidelines point out that a positive test result only shows sensitization. The test result must be used together with a history for a correct diagnosis of food allergy.

Stated a bit more firmly, these New Guidelines advise against making the diagnosis of food allergy solely based on the results of skin prick tests or blood tests.

 I foresee pediatric allergy practices becoming more involved with doing food challenges. A child presents with an array of positive food allergy tests, restrictive dietary advice, and accompanied by scared and frustrated parents. All too often many of the foods they have been told to avoid had been eaten with impunity- there was absolutely no observed reactions with ingestion, but there was a positive allergy test. This is very confusing.

In  pediatric allergy we sort through the history of exposure and the appearance of reactions that are IgE-mediated (the antibody detected by food allergy testing). We look for that constancy of cause/effective relationships with the food. We also need a sense of the timing between exposure and reaction. From that history, the proper selection of food allergy tests is then made.

So now we need to verify clinical reactivity to food allergy test results that revealed sensitization. For some foods we have been given guidance regarding the chance of having a reaction. For many other foods we do not have that information. Many of these challenges will be adventures in uncharted waters. In our practice we have done many challenges for milk, egg, soy, wheat, and peanut. We have also challenged to beef.  For the other foods we can put together a protocol for the safe introduction of a ‘challenge’ food.

Take a look at these New Guidelines for the Diagnosis and Management of Food Allergy.

FEL

The title was ‘A Practical Approach to Food Allergy’. Slide copy can be found by clicking on the link which will take you to Google Documents. References for the talk can be found by clicking the link.

FEL

When the presentations were finished, we had a panel discussion and took questions from the audience. This 20 minute Q & A went close to 45 minutes.

I have linked to Google Documents this presentation. It is entitled ‘Allergy Testing and Referral to the Allergist’.  This presentation was completed in April. You will notice slides with red titles. It has been a rule for speakers, especially in Continuing Medical Education (CME) offerings to not make changes. An article in JAMA was published the week prior to this presentation. In an attempt to provide the 50 learners at the seminar with the most up-to-date information, I quickly added these slides.

The reference list for the presentation (Food Allergy Testing Reference List)  is also available via a link to google documents.

FEL

Last week I was interviewed by a reporter from the Wall Street Journal. The topic was food allergy. The reporter came across this website and thought that I be a good resource for her article. We had a delightful talk that went on for 45 minutes. Questions were asked about the increase in food allergy; is it real or is it possibly due to the over use of diagnostics (allergy testing).

Needless to say I was excited about the prospect of being quoted in the Journal.

My hopes were dashed. The reporter had to cutback on material. My name did not appear in the article. The article was very well done and did quote a number of outstanding leaders in the field of food allergy (Drs. Hugh Sampson and Robert Wood).

I do encourage you to read the article written by Melinda Beck.

FEL

N. Nicolaou, M Poorafshar, C Murray,  A Simpson, H Winell, G Kerry, A Woodcock, S Ahlstadt, and A Custovic.  Journal of Allergy and Clinical Immunology(JACI) 2010;125:191-7.

This article appeared in the most recent JACI. Almost as soon as I read the article, I began to put together this review (I am excited about the approach and ideas in this work). This paper states very clearly the problem of positive allergy tests for peanut (sensitization) and demonstrating clinical relevance- that is allergy to peanut. It addresses this problem using a new test for determining sensitization, component-resolved diagnostics.

Background:

          A few very important facts are noted about peanuts;

            1. Peanut is a nutritious and inexpensive food

            2. Peanut is one of the most common food allergies

            3. The prevalence of peanut allergy is increasing

            4. Peanut allergy is usually life-long

            5. Peanut avoidance is the current management of this allergy

            6. Accidental peanut exposure is common

            7. Peanut exposure in the allergic child can be life-threatening

Peanut allergy diagnosis issues:

            1. An accurate diagnosis is very important- sensitized or truly allergic?

            2. The gold standard for the diagnosis of peanut allergy is the

               ‘double-blind placebo-controlled food challenge (DBPCFC)

            3. DBPCFC are costly, time consuming, and dangerous

            4. The diagnosis is made with a suggestive history of what happens after exposure,

                supported by a skin prick test or by the determination of specific IgE in the blood

            5. These tests detect the presence of antibody (sensitization)

            6. Positive allergy tests does not equate to the presence of allergic symptoms after exposure-

                known as clinical allergy

            7. Current tests –both skin prick tests (SPT) and specific IgE tests (sIgE-blood) use crude peanut

                 extracts and contain a mix of the allergic proteins and non-allergic proteins that may

               cross-react with other allergens.

            8. Bottom line- peanut sensitization may not equal peanut allergy

Solving this problem:

            1. A new blood test to detect antibody production by the child to the important proteins in peanut that cause

                allergic symptoms has been developed

            2. This is called component-resolved diagnostics (CRD) – developed by Phadia

            3. This may be a more accurate tool to assess food allergy (vs. sensitization)

The purpose of the paper was to look at the CRD to correctly identify children with peanut allergy.

Methods:

A birth cohort of children enrolled in the Manchester Asthma and Allergy Study (Manchester, England) was evaluated. Information on exposure and reactivity to peanut was collected.  Peanut sensitization was measured by skin prick testing and by Phadia specific IgE.

There were 110 children (cohort contained 1085) who were sensitized and were asked to undergo a more extensive evaluation of their reactivity to peanut. This included more extensive history, skin testing, specific IgE, a DBPCFC, and the CRD.

The definition of peanut allergy included two very specific sets of criteria.

                        1. Sensitization and a positive oral challenge or

                        2. A convincing history and specific peanut IgE >15 kU/L and/ or a skin prick test that was greater than

                           an 8 mm wheal (this group did not have an oral challenge).

Results:

The cohort included 1085 children, 1029 were evaluated at age 8 years. There were 17 (1.6%) who had a history of peanut allergy.

Skin-testing was performed in 919 of the children with 47 (5.1%) having a positive SPT. Sensitization to grass pollen was noted in 59.6% of the children.

Blood studies were performed on 582 children with 71 (12.2%) having a detectable level of specific IgE to peanut. Grass sensitization was found in 67 (94.4%).

Overall, of the 933 children who had either a SPT or sIgE 110 or 11.8% were considered to be sensitized to peanut.

From this group of 110, 108 agreed to participate in the program. Seventeen did not consent to a food challenge. From the remaining 91 children, 12 had convincing histories and SPT/sIgE criteria to fit the definition of peanut allergy. Food challenges were performed in 79.

In the 79 oral food challenges to peanut, 66 had no symptoms with the exposure. Of the 13 who developed symptoms, 7 had two or more signs/symptoms and were declared peanut allergic. The breakdown on these number was- 66 were peanut tolerant and 19 were had peanut allergy (12 not challenged plus the 7 with a positive challenge).

The proportion of children with peanut allergy among those sensitized was 22.4%.

Peanut allergic and peanut tolerant children were compared.

            1. Asthma, eczema, and food allergies were more common in the peanut allergy group.

            2. Allergic rhinitis was more common in the peanut tolerant group.

            3. Peanut tolerant children had lower peanut sIgE and higher grass sIgE.

The CRD results differentiated the peanut allergic from the peanut tolerant group. The peanut allergic group had higher values to the major peanut proteins Ara h 1-3. The peanut tolerant group had higher reaction values to grass components. The response to the peanut protein Ara h 2 was the best discriminator.

A model was developed to discriminate between children with peanut allergy and peanut sensitization. The model misclassified only 2 (6.9%) with peanut allergy and 4 (7.7%) peanut tolerant children.

Conclusions:

The majority of children who have peanut sensitization based on SPT or sIgE do not have peanut allergy. The CRD may help the diagnosis of peanut allergy.

Reviewers Comments:

This is exciting work. In the practice of allergy we struggle with positive tests and their clinical relevance. The authors very clearly point out the differences between sensitization and allergy. The test makes no one allergic. The test only tells us that specific IgE is being made. The history and/or a food challenge help define that clinical relevance in making the diagnosis of food allergy.

Phadia has developed a very specific assay which will help in making the diagnosis of peanut allergy. I am excited about the prospects for CRD. Phadia’s science is at the cutting edge of food allergy and I look forward to using this assay for the large number of children we see in our practice with a positive test for peanut antibody. I have always had the greatest respect for Phadia’s science; it is the marketing part that I have issues with (topic of a few of my posts).

The authors point out the strengths of this study. They performed a very extensive evaluation and used the DBPCFC for verification.

The small number of children reported is a recognized weakness. The authors encourage replication of their work.

The study looked at 8 year old children. I wonder about why that age and from the paper my guess is that this was the most recent year of evaluation on their cohort. This birth cohort attended the clinic at ages 1, 3, 5, and 8 years. In our clinic we use age 5 as our cut-off for peanut challenges. At this age, most children are able to communicate with us regarding the subtle aspects of allergic reactions.

Look at the rate of positive tests for peanut. The testing of a population of children revealed that almost 12% will have a positive test for peanut.

The last paragraph in the paper goes as follows; “The majority of children within the general population with positive skin test or measurable serum IgE to peanut do not have clinical peanut allergy.

Authors: Amy Branum and Susan Lukacs

Reference: Pediatrics Volume 124 (6) December 2009

This title caught my eye. The impression in clinical practice is that more and more children have food allergy. This article looks at the prevalence of food allergy in children. I wanted to get this review posted this week. I am off to Santa Fe to moderate an AAP Practical Pediatrics Course. This AAP meeting is similar to the one I reported on earlier on this home page (Rhode Island). This meeting has an excellent cast of presenters. I plan to take notes and post a few updates upon my return.

Purpose of the article: To describe trends in the prevalence of food allergy and food allergy-related health care utilization in children in the United States.

Methods (how was this study conducted?): Data from a number of national health surveys were reviewed.

• Food allergy prevalence was evaluated in children 0-17 years of age from surveys conducted over the years 1997-2007. The question asked about food allergy was “During the past 12 months has the child had any kind of food or digestive allergy?”
• Blood tests for IgE antibodies to foods were taken from the National Health and Nutrition Examination Survey (NHANES) 2005-2006. Specific IgE antibodies to peanut, egg, and milk were measured using the Pharmacia ImmunoCap 1000 System. Specific IgE to shrimp was measured only in children over the age of 6 years. The range of specific IgE values was 0.35 to 1000 kU/L.
• Information regarding food allergy-related visits to physician offices and hospital facilities was taken from two additional surveys.
• The results were analyzed using rather sophisticated statistical tools that included weighing the data for the analysis of trends.

Results (what the study found):

• The prevalence of reports of food allergy in children has increased from 3.3% in 1997 to 3.9% in 2007.
• Peanut IgE antibodies were found in 9.3%, egg IgE antibodies were found in 6.7%, milk IgE antibodies in 12.2%, and shrimp specific IgE was found in 5.2% of children.
• Ambulatory care visits for food allergies tripled between 1993 and 2006. Between the years 2003 and 2006 there were 317,000 visits/years to emergency departments and outpatient offices. Hospitalizations with a recorded diagnosis related to food allergy increased from 2600 to 9500 discharges/year.

Conclusions:

                These national surveys show that food allergy prevalence and/or food allergy awareness has increased in recent years.

Commentary:

                The authors point out a number of limitations in the study, however the major contribution here is reporting on what these surveys reveal about the parent’s report regarding food allergy. Food allergy may be rising however it is possible that the results may be due to increased food allergy awareness which is also a very good thing. This is a report of prevalence and does not go into the possible reasons for the increases.

                It is important to note that this was a survey. A simple question was asked. These were not absolutely proven cases of food allergy. The question included digestive allergy which has the potential to include a number of clinical conditions that are more common and may or may not be allergy; lactose intolerance, eosinophilic esophagitis, and celiac disease for example. This was a report on what a parent thought about food allergy in their child.

                The report has a few ‘between the lines’ issues as well. The conclusion is that food allergy and digestive tract allergy has a prevalence of 3.9%. The study also included a survey in which a blood test for allergy was performed. Using the blood test the prevalence of peanut, egg, milk, and shrimp ‘allergy’ exceeds the overall food allergy prevalence. The authors do point out this difference and are very careful about what is allergy and what sensitization to food is.  “Although serum IgE measurements cannot be used alone to determine the prevalence of food-specific allergies or to predict reactions to certain foods, they give an indication of increased atopy and risk for allergic reactions to food.” I define allergy and atopy on my allergy testing page.

                We also need to be a bit careful on the hospital data. The information on health care utilization included children who had a diagnosis of a food allergy. This did not necessarily mean that they were in the health care facility for a food allergy issue. There is a tendency in coding encounters to include as many codes as possible and to include codes that will help with health care utilization reimbursements.

                The statistical analyses on papers like this always fascinate me. During my MPH training I had a number of biostatistics courses. The weighing of the data is frequently done and when it is done, differences can be found. Sometimes it is interesting to see what the results were before any weighing. I have also wondered what went into the ‘weighing’ of the data. What elements of the data were assigned a ‘weight’ to make them work into the analysis?

                This was a nicely done paper and does answer some questions however as many quality studies also do it has us asking many more questions about food allergy in children.

Fred Leickly

I should be receiving my copy of the journal soon. I am concerned about how food allergy will be defined in the paper: will the diagnosis of food allergy be based on a history of exposure confirmed with appropriate allergy testing or will this be based on only laboratory results and no history?

As soon as I have this in hand I will post a commentary.

Fred Leickly