Lab

RAST

search

RAST, RadioAllergoSorbent Test, ImmunoCAP, Allergen Specific IgE Antibody Measurement

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