Am Fam Physician. 2004;70(10):1988-1989
Rhinitis, defined as nasal membrane inflammation accompanied by nasal discharge, sneezing, and congestion, is considered allergic when it is caused by an IgE-initiated immunologic reaction. Allergens bind to the IgE, which binds to mast cells and basophils, causing local release of inflammatory mediators. Empiric treatment is common, but some patients benefit from specific allergen testing.
Gendo and Larson reviewed diagnostic strategies for evaluating patients with suspected allergic rhinitis using studies that compared various techniques of allergen testing. A personal and/or family history of allergies and symptoms help identify patients with allergic rhinitis, especially that caused by animal and pollen triggers. If atypical symptoms such as pain, bleeding, fever, purulent discharge, headache, or dyspnea are present, other diagnoses should be considered. Physical examination findings usually are not helpful.
Puncture skin tests use 15 to 25 potential allergens that are compared with a positive control histamine solution and a negative control saline solution. The preparations are introduced into the epidermis or intradermally by a needle. The allergen reacts with any specific IgE present, causing release of histamine from the mast cells, resulting in a wheal with surrounding erythema. In vitro tests looking for specific IgE (i.e., Phadebas RAST and enzyme-linked allergosorbent tests) have been updated using specfic immunoassay reagents and automation. Accuracy of these direct tests can vary between laboratories.
Management of allergic rhinitis offers the choice of testing, empiric treatment, or watchful waiting. Testing is indicated if the results would affect the decision to treat. The latter includes patients whose diagnosis is unclear, but not those in whom the probability of allergic rhinitis is high. Watchful waiting is appropriate in patients with a low likelihood of allergic rhinitis when testing would not change the management plan.
The authors conclude that diagnostic allergy testing is useful if the result will affect the decision to treat. Because the tests are highly accurate, the results will most likely affect treatment when the diagnostic suspicion of allergic rhinitis is relatively low and not when it is high. When patients require immunotherapy because of failure to improve with treatment, allergy testing is important. Skin tests are more useful for identifying specific components involved in an allergic reaction.
editor’s note: Rhinitis may be allergic or nonallergic. Patients with the most common type of nonallergic rhinitis, vasomotor rhinitis, can have symptoms similar to those in the allergic group. Allergic rhinitis is most commonly identified by the history, including the timing or seasonal periodicity of symptoms. Nonallergic rhinitis can present with less prominent nasal itching and conjunctival irritation. Other distinguishing features of allergic rhinitis include increased eosinophils in blood or nasal-probe smears, and increased IgE levels.—r.s.