Identification of allergic disease among users of antihistamines.

Objective: Patients exhibit a multitude of symptoms that may or may not be allergy related. In this study, we examined the consistency between results obtained by a multiallergen-specific immunoglobulin E (IgE) test and frequent use (3 months or more) of prescribed antihistamines.

Methods: A retrospective examination of 1-year prescription claims records from January 1, 2000, through December 31, 2000, for 4,643 patients enrolled in a 115,000-member managed care organization who received 1 or more prescriptions for an oral antihistamine (loratadine, fexofenadine, or cetirizine).

Results: A total of 1,343 health plan enrollees who received an oral antihistamine prescription were continuously enrolled during the year 2000 and diagnosed with allergic rhinitis. Of these patients, 246 (18%) consented to a multiallergen- specific IgE test, and 159 patients (64.6%) had a negative IgE test result. A total of 163 patients were classified as frequent antihistamine users (3 or more antihistamine prescriptions), and 101 (62.0%) of these patients had negative test results. Our study demonstrated no relation between prescribed antihistamine use and patient sensitization status.

Conclusions: Only 35.4% of the patients who used an oral antihistamine and were diagnosed with an allergy tested positive to the multiallergen-specific IgE test, and only 38% of the patients with records of frequent antihistamine use and who were diagnosed as allergic tested positive to the multiallergen-specific IgE test. Apparently, there are patients taking medications prescribed for allergic rhinitis who are, in fact, not allergic, which is both wasteful economically and not indicated medically. Additional evaluation may be advisable to support the clinical diagnosis of allergy for patients presenting with allergy-like symptoms who use antihistamines frequently.