From the Guidelines
RAST testing for airborne allergens should include common inhalant allergens such as tree pollens, grass pollens, weed pollens, dust mites, animal danders, molds, and cockroach allergens, as these are the most relevant allergens to test for, according to the most recent evidence 1. When considering RAST testing, it is essential to prioritize the patient's clinical history, regional allergen prevalence, and seasonal symptoms to guide the testing process.
Key Allergens to Test
- Tree pollens (oak, birch, maple)
- Grass pollens (timothy, bermuda)
- Weed pollens (ragweed, mugwort)
- Dust mites (Dermatophagoides pteronyssinus and Dermatophagoides farinae)
- Animal danders (cat, dog)
- Molds (Alternaria, Aspergillus, Cladosporium)
- Cockroach allergens These tests measure specific IgE antibodies in the blood that the immune system produces in response to these allergens.
Modern RAST Testing
Modern versions of RAST testing, such as ImmunoCAP, ELISA, and multiplex array technology, offer improved sensitivity and specificity 1.
Advantages of RAST Testing
RAST testing is particularly useful when skin prick testing is contraindicated due to widespread dermatitis, use of antihistamines that cannot be discontinued, or risk of anaphylaxis. The results are typically reported in classes (0-6) or kU/L units, with higher numbers indicating stronger allergic sensitivity. While RAST testing is less sensitive than skin prick testing, it offers the advantage of being unaffected by medications and provides objective quantification of allergic sensitivity 1.
Clinical Decision-Making
The decision to perform RAST testing should be guided by the patient's clinical presentation and the need to confirm a diagnosis of allergic rhinitis or to identify specific allergens that may be contributing to their symptoms 1.
From the Research
RAST Tests for Airborne Allergens
The following airborne allergens can be tested using RAST:
- Dermatophagoides farinae (D. farinae) 2, 3, 4, 5, 6
- Dermatophagoides pteronyssinus (D. pteronyssinus) 2, 3, 4, 5, 6
- Cockroach 2
- Cat epithelium 2
- Dog epidermal 2
Sensitivity and Specificity of RAST Tests
The sensitivity and specificity of RAST tests may vary by type of causative allergen and type of allergic manifestation 2.
- For D. farinae, the concordance between RAST and skin prick test (SPT) results was high (84%) 3.
- For cat epithelium and dog epidermal, skin testing (ST) was superior to RAST in detecting sensitization 2.
Correlation between RAST and Skin Prick Test (SPT) Results
The scores of RAST and SPT showed weak to moderate correlation (r = 0.24 to 0.54) 2.