WASHINGTON — Allergen-specific immunoglobulin E testing is an effective tool for accurately diagnosing atopic triggers in patients with asthma, but it is underused in the United States, Dr. Leonard Fromer said at the annual meeting of the American Academy of Family Physicians.
Only 1 in 20 (5%) asthmatics in the U.S. is tested for triggers, he added.
Primary care physicians manage the majority of patients with mild to moderate asthma. In about 70%–90% of children and 60% of adults with asthma, the disease is atopic. But too often, the emphasis is on what medications to prescribe and not on identifying allergen exposures, said Dr. Fromer, professor of family medicine at the University of California, Los Angeles.
The shortcomings of skin-prick testing do not apply to blood-based IgE testing, because the test is looking only for the presence of the IgE antibody. Newer generation IgE tests such as Phadia's ImmunoCAP system allow for accurate testing in children as young as 6 months old, he said.
Some study findings have shown IgE testing to have sensitivity and specificity similar to that of skin-prick testing (J. Allergy Clin. Immunol. 1999;103:773–9). Moreover, there is a significant degree of variability in the way skin tests are performed, interpreted, and documented (Ann. Allergy Asthma Immunol. 2006;96:19–23), Dr. Fromer said.
There are more than 300 available reagents when ordering an IgE test. The respiratory panel is most important in young children and adults because by 3 years of age, respiratory allergens start to dominate, Dr. Fromer said.
The United States is divided into 19 regions, depending on the climate and prominent triggers, and these divisions are used by reference laboratories to create region-specific respiratory panels with the most common molds, dust mites, and pollens in the area where your patient lives or works.
Testing requires 2 mL of blood for children and 4 mL for adults, with results typically available in 48 hours. Negative results can occur even when symptoms suggest an allergic response. When this occurs, one should go with the patient history, Dr. Fromer said, emphasizing the importance of clinical history in driving the diagnosis.
Evidence also suggests that knowing a patient's psychosocial situation could help primary care physicians treat patients with asthma (Intl. Prim. Care Respir. J. 2006;15:278–85).
Too often, the emphasis is on what medications to prescribe and not on identifying allergen exposures. DR. FROMER