Lab
RAST
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RAST
, RadioAllergoSorbent Test, ImmunoCAP, Allergen Specific IgE Antibody Measurement
See Also
Allergy Test
Patch Testing
Regional Allergy Screening
Mechanism
Assays
RadioAllergoSorbent Test (RAST)
Older methodology
ImmunoCAP has largely replaced the older RAST methodology
Enzyme-linked Immunosorbent Assay (
ELISA
, most common)
Fluorescent Enzyme Immunoassay (FIA)
Chemiluminescent Immunoassay
Efficacy
Highly specific for allergens
Lower
Test Sensitivity
than allergy
Skin Testing
Indications
Not recommended for food, venom, or drug allergies unless high risk for
Anaphylaxis
Alternative to
Skin Testing
in certain cases
Skin Testing
contraindicated
Interfering medications (e.g.
Antihistamine
s)
Age <3 years
Allergy Test
ing for common allergens
Pet dander
Dust mite
s
Pollen
Mold spores
Approach
Screen Contents
June Grass and cross reacting grasses
Rye
Sweet Vernal
Timothy
Brome
Oak Tree
Short ragweed
Alternaria mold
Dust mite
Cat
Technique
Allergen coupled to a paper disc
Patient's serum is added to paper disc
Antigen
-
Antibody
forms in the case of allergy
Radioactive anti-IgE added and complexes with above
Gamma counter scores binding
Interpretation
RAST Scoring
Class 0: 200-750 (No significant allergy)
Class 1: 750-1600 (Mild allergy)
Class 2: 1600-3600 (Moderate allergy)
Class 3: 3601-8000
Class 4: 8001-18000
Class 5: 18001-40000 (Most allergic)
References
Chang (2018) Am Fam Physician 98(1): 34-9 [PubMed]
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