Statistics or Symptoms?

This is one of a series of several posts discussing issues that complicate the diagnosis of allergies. The summary and index of the series can be found here.

Problem: Even though current allergy testing is unreliable, many practitioners take a negative allergy test as conclusive or near-conclusive proof that the patient is not allergic to the substance.

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Unfortunately, too many doctors and allergists believe the hype about allergy testing. Far too many interact with their patients based on statistics rather than on that person's individual history, and assume that if something is rare then it must not be present in their patient.

When confronted with a patient who has an anaphylactic reaction or consistent allergic symptoms when consuming a particular food, but has a negative result to the allergy-testing, too many doctors will tell the patient that they don't truly have an allergy and don't really need to avoid the food.

This kind of advice could land a patient in the emergency room or the morgue.

I know of someone who "forgets to breathe" when she is exposed to popcorn fumes, along with other symptoms of anaphylaxis, had huge welts on the skin prick test, and yet still has trouble getting doctors to take her allergies seriously.

She says, "Think about this. I have the highest weal scores possible, confirmed reaction to at least one corn product (popcorn) through an ER visit, and yet, I cannot get the majority of the medical community to take me seriously. Is it any wonder others have issues?"

The attitude from doctors that allergic reactions aren't real because they are rare, don't fit into a certain tightly-defined set of symptoms (usually limited to athsma, hives and airway restriction), or are unverified by a particular test is all too common.

I've experienced this attitude personally.

My allergist believes that because it's rare for a child to have more than 4 food allergies, some of Baby E's positive skin tests confirmed by clinical observations "must be false positives", because she can't possibly really be allergic to that many foods.

Our allergist insists that many of my daughter's and my own adverse reactions to specific foods must be "coincidence" and refuses to consider even the possibility of an intolerance, much less an allergy. Those reactions include swelling and itching of the mouth and throat, all-over body itching, eczema, rashes (but not the magical giant hives), severe immediate vomiting and/or diarrhea, and other reactions happening consistently after the food is consumed.

This board-certified pediatric allergist believes that because Baby E's positive skin test welts were "not that big" that she obviously "isn't very allergic" to any of the foods she tested positive to. He says that despite the clinical evidence of a severe, immediate reaction (sometimes bordering on anaphylaxis) to the smallest trace of any corn or soy derivative. He has encouraged me to go ahead and give my child things with corn and soy derivatives in them, and was not willing to try to find an allergy medicine that doesn't contain corn or soy for her.

He must not be aware of the research and clinical evidence indicating that the size of the wheal is not directly correlated to the severity of the reaction, and that allergic reactions can take place even with a completely negative skin test. A person can have a very small wheal with a severe anaphylactic reaction to that food.

Also, it is common knowledge that "the wheal size induced by both positive control solutions and allergen-induced prick tests tend to be smaller in infants than adults." Young children are also known to have a higher number of false negatives than adults.

As we have already established, current allergy tests are not all that accurate or specific. Commonly-cited statistics attribute about 50% to 90% accuracy to skin prick testing. Most sources agree that the other methods of testing are even less accurate.

Yet what are the remaining 10% to 50% or more of patients to do when their doctor believes that such testing is the only accurate way to diagnose allergy?

They find themselves in situations like my recent experience: I had an anaphylactic reaction to a food, but (possibly because I had recently tested "negative" to that food) my allergist did not believe me or take the reaction seriously.

He would not even see me or talk to me personally about it, instead communicating through a nurse that he didn't think I needed any treatment or precautions. He said that if I wished, we could do a skin test in a few weeks to see if I was really allergic to the food.

On another occasion, this same allergist told me that my daughter's facial swelling and rash after receiving a gas anesthetic was not any kind of allergic reaction "because if it was an anaphylactic reaction, she would have most likely had trouble breathing."

Like many others, he seems to have little frame of reference for an allergic reaction that falls somewhere in the spectrum between nothing and respiratory arrest--at least if systemic hives or athsma are not involved.

A different board-certified pediatric allergist refused to include rice in the panel of grains she was testing my daughter for, even though Baby E was having symptoms after consuming rice.

Her reasoning? "Nobody is ever allergic to rice," she said. "In all my 30 years of practice I've never had a patient who tested positive to rice, so I just took it off the panel. I don't even test for it."

Of course, people can be and are allergic to rice . . . the prevalence varies in different studies from less than 1% in groups of adults with generalized allergies to 69% in Finnish children allergic to wheat. The prevalence is about 10% or more in areas where rice is frequently consumed, such as in Japan.

Rice is most commonly cross-reactive with other grasses and grains. Rice allergy is much more common in patients who are also allergic to wheat, corn, soy or oats. Studies have indicated that 50% of patients with corn allergy, 65% with soy allergy, and 35% with oat allergy were also allergic to rice.

Baby E is allergic to corn, soy and oats, and we suspected allergies to wheat, rye and barley as well. The allergist ran tests for just about every grain under the sun except for rice. Baby E was definitely a case where testing for hypersensitivity to rice (an allergen not included in routine panels) would have been wise. Leaving it off her panel made no sense.

Like too many doctors, this allergist looked at overall statistics about prevalence of rice allergy in the general population instead of considering my child's specific risk factors and symptoms.

Wouldn't it be far better to treat the patient as an individual instead of a statistic?