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An Allergy Breakthrough

Blood test to allow primary-care doctors to confirm allergies

SUNDAY, June 10, 2001 (HealthDayNews) -- A new blood test is expected to eliminate much of the guesswork for primary-care physicians trying to diagnose allergies.

The guesswork typically occurs because primary-care doctors usually don't offer the method of allergy testing used by most allergists -- skin-prick testing. As a result, many patients who complain of allergic symptoms are often offered allergy medicine by their primary-care physicians and sent on their way, without any confirmation of their allergies, health experts say.

The consequence: Only about 35 percent of Americans who take such medications actually have allergies, according to recent studies.

"Usually, the paradigm for diagnosing and treating patients is to take a patient's history, do a physical, run objective testing and then make a diagnosis and treatment," says Dr. Leonard Fromer, an allergist, family physician and assistant professor at the University of California at Los Angeles.

"But with allergies, everyone always tends to skip the objective-testing part," he says. "They'll take the history, examine the patient and come to a conclusion. Even when that's done in the hands of a specialist, it's only about 60 percent accurate. In the hands of a family doctor, it's a little worse."

But the new blood test can be administered even in the offices of primary-care physicians.

It's called ImmunoCap, developed by the drug company Pharmacia. And a study appearing in a recent issue of Annals of Allergy, Asthma, and Immunology indicates that, compared to other most popular blood tests that were accurate about 50 percent of the time, ImmunoCap was accurate in detecting allergies 98 percent of the time.

The findings are significant because many doctors have tended to shy away from blood tests for allergy diagnoses, because they were notoriously inaccurate only a few decades ago.

"The early tests were very inaccurate, so those generations of doctors got used to just not trusting the blood tests," Fromer says.

The new test, however, could make a big difference in getting more accurate diagnoses at the primary-care level, he adds.

The ImmunoCap test "would help immensely to get a better diagnosis in whether a patient is allergic and what they're allergic to," Fromer says. "It's probably about half the price as the skin-prick test, depending on what part of the country you're in. And it can be conducted by the primary-care doctors without even having to refer a patient to a specialist."

While the ImmunoCap test can be used to detect most allergies, its real potential may lie in diagnosing food allergies, for which the skin-prick test is unreliable, experts say.

"The standard tests err on the side of giving false positives, and even more so with foods than other allergens," says Dr. Wesley Burks, a professor of pediatrics at the University of Arkansas for Medical Sciences.

"So the utility of ImmunoCap is that, if you do have a positive skin test to a food like peanuts, then you could do the ImmunoCap and find out the likelihood of a person being allergic or not." Some food allergies, like peanut allergies, can be fatal.

Experts with the American Academy of Allergy, Asthma and Immunology say about 20 percent of Americans suffer from nasal allergies, and 2 to 6 percent have food allergies.

What to Do: Read more about allergies in these HealthDay stories. And visit the Food Allergy and Anaphylaxis Network for more on food allergies.

SOURCES: Interviews with Wesley Burks, M.D., professor of pediatrics, Arkansas Children's Hospital and University of Arkansas for Medical Sciences, Little Rock, Ark.; Leonard Fromer, M.D., assistant professor, UCLA; April 2000 Annals of Allergy, Asthma, and Immunology
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