62 percent of frequent antihistamine users did not test positive for allergies

Jun 28 2004

A new study in the current issue of Journal of Managed Care Pharmacy concludes that 62 percent of frequent antihistamine users did not test positive for allergies.

The authors recommend that objective diagnosis with an allergen-specific IgE test might yield more appropriate clinical management, reduce office visits and improve patients' quality of life.

"A specific-IgE test for allergy is an essential diagnostic tool for managed care providers and should be a first step for effective treatment of allergic disease," said Sheryl Szeinbach, Ph.D., Professor, Division of Pharmacy Practice and Administration, Ohio State University, the study's lead author. "From a practical standpoint, it could be economically wasteful and medically inappropriate for patients without allergies to take prescription antihistamines frequently."

A total of 246 managed care patients who were diagnosed with allergies and prescribed low-sedating antihistamines consented to an allergy blood test. Results revealed no relation between antihistamine use and evidence of allergy though low-sedating antihistamines are indicated primarily for the treatment of allergy-related symptoms.

Among all 246 patients, 159 of them, or 64.6 percent, tested negative for allergy. Even among the 163 patients who were classified as frequent antihistamine users (three or more prescriptions in one year), 101, or 62 percent, tested negative. "Simply put, about two of three patients may not be receiving appropriate treatment," Szeinbach said.

Americans spend about 8.4 billion dollars per year on low-sedating antihistamines such as cetirizine (Zyrtec(R)), fexofenadine (Allegra(R)) and loratadine (Claritin(R)). While these drugs can be effective when used as indicated, their use for non-allergic patients is clinically and economically questionable.

About 50 percent of Americans have allergy-like symptoms associated with upper respiratory disease, such as a runny or stuffy nose, sneezing or watery eyes. Generally, they believe they're allergic, but most of the time they are not. About 35 percent of them have allergic rhinitis (allergy), about 35 percent have non-allergic rhinitis, and about 30 percent have sinusitis. Though these conditions have similar symptoms, their treatments differ greatly, and they are so difficult to diagnose accurately that even physicians can do so only about 50 percent of the time unless they test patients to obtain objective evidence.

The researchers used the ImmunoCAP(R) Allergy blood test in the study, an advanced allergy testing method that measures patients' sensitivity to common inhalant allergens such as animal dander, pollen and mold. In response to each allergen, the immune system produces a specific form of immunoglobulin E (IgE) that can trigger allergic reactions. By quantifying specific IgE, ImmunoCAP not only determines whether a person is allergic and (if so) to what, but also suggests how severe each allergy is.

An unrestricted grant from Pharmacia Diagnostics, the manufacturer of the ImmunoCAP test, supported the research.

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