Investigations
1st investigations to order
therapeutic trial of antihistamine or intranasal corticosteroid
Test
Oral or intranasal antihistamine can be used. In moderate or severe AR, a trial of an intranasal corticosteroid should be considered a preferred first choice, especially if nasal obstruction is an issue. Re-assess after a 1- or 2-week trial.
Amelioration of symptoms and improvement in quality-of-life parameters such as sleep quantity and quality, activities of daily living, and ability to pursue hobbies, sports, and social activities without limitation should guide the clinician in determining whether a specific treatment regimen represents a failure. Validated quality of life questionnaires specific for AR can be used to assess therapy response (e.g., Rhinoconjunctivitis Quality of Life Questionnaire [RQLQ] and Rhinitis Control Assessment Test [RCAT]).[50][51][52]
Result
clinical improvement
Investigations to consider
allergen skin-prick testing
Test
Provides superior sensitivity and specificity compared with in vitro specific IgE determination testing, as long as the test is performed by a properly trained individual.
Also offers rapid results and lower costs, especially if the number of individual skin tests performed is limited.
However, it is not suitable for patients with severe eczema affecting the testing area, those with significant dermatographism, or those unwilling or unable to stop their antihistamines or medications with antihistamine properties (e.g., tricyclic antidepressants).
Most medical laboratories offer a variety of allergen panels that should incorporate the most important perennial allergens such as animal danders and dust mites as well as geographically important local pollens such as grasses, weeds, and trees. Tests should be ordered judiciously in the context of the patient's symptoms and exposures.
Interpretation of results can be challenging. Individuals with very high IgE levels may have multiple positives that may or may not be clinically relevant.
Clinical correlation with symptoms by an individual highly trained in the interpretation of allergy testing is recommended.
Size of individual wheal and flare responses do not necessarily correlate with clinical reactivity to that particular allergen.
Result
wheal and flare reaction after specific allergen is introduced into the skin is 3 mm larger than negative (saline) control
in vitro specific IgE determination
Test
Sandwich-type assay that utilises the patient's serum to bind to specific allergens present on a solid phase/chip.
Tends to be more expensive than skin-prick testing, and results are not immediately available. However, can be employed in patients with severe eczema, significant dermatographism, or those unwilling or unable to stop their antihistamines (because antihistamine use may cause false-negative results in skin-prick tests).
Interpretation can be challenging and should be performed by an individual trained in the interpretation of specific IgE testing in the clinical context.
IgE levels do not necessarily correlate with clinical reactivity to that particular allergen.
RAST results, and to a lesser degree skin tests, can be difficult to interpret in individuals with very high IgE levels, as they often have non-specific reactivity that may or may not be clinically relevant.
Result
specific allergen response
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