A chat with the good doctor: how can the lab support the physician in the allergy march?

Medical Laboratory Observer, Sept, 2004 by Ed Susman

Allergy testing is also performed to identify allergens for immunotherapy treatment--injections of small amounts of the substance to which the patient is allergic, typically given once or twice weekly for six months. Maintenance treatment can last years. Exposure to the injected allergen generates an antibody response that blocks its effects on the body. Often, allergy shots can provide long-term relief from allergic symptoms. Usually, immunotherapy is considered when avoidance or antihistamines have failed. Immunotherapy is usually initiated after blood tests, such as the new third-generation RAST (radioallergosorbent test), or skin-sensitivity tests to determine exactly which allergens are causing the patient's reaction.

If the clinician is going to treat the patient symptomatically, it makes no sense to identify the sensitivities. If the physician is considering immunotherapy, then the antigens provoking the responses must be identified to be included in the injections.

Another form of allergy testing is required for new--and expensive--anti-IgE medications. The physician must establish that the patient's total IgE is elevated; if it is not, there is no reason to administer a drug that is going to react with IgE. In that situation, knowing the total IgE protein level is more useful than identifying individual IgE antibodies. The development of anti-IgE pharmacotherapy gives those with allergic disease a new treatment option, especially for persistent allergic asthma and lifestyle-altering disorders, such as peanut allergies. Anti-IgE drugs disrupt the cascade of events, including the blocking of the release of inflammatory mediators that results from exposure to allergens. In clinical studies, patients undergoing anti-IgE therapy have reduced rates of allergic attacks. These patients may also be able to reduce their intake of other drugs, such as corticosteroids.

Doctors must depend on the laboratory to determine allergic patient's IgE levels.

For example, that a patient has allergic disease to perennial aeroallergens and an elevated baseline level of serum IgE protein (30 IU/mL to 700 IU/mL) must be documented. Nonallergist specialists typically evaluate patients for such therapy and either refer the patient for skin testing with aeroallergens or order tests for IgE antibodies prior to treatment.

By knowing which tests are most appropriate, laboratory scientists provide clinicians with information on better treatments for patients with allergic disease. In the future, the laboratory will have to perform tests that provide better understanding of allergies to foods, medicines, and allergens in the workplace.

Clearly, allergen avoidance will help people who have sensitivities, but to help people avoid allergens, we have to know what they are allergic to. Newer, more specific tests are required for this. Tests under development will more specifically determine the level of atopy; others will differentiate the chemical structure of allergens. There will also be more tests to identify IgE antibodies--such as those that cause peanut allergies. In addition to finding food-sensitivity levels, new tests may also help in critical situations involving medication allergies. We now have only a limited repertoire of tests to determine if a patient is allergic to prescribed medications. Other breakthroughs will involve the integration of testing with new biotechnology drugs.