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IgE Antibody level, Allergy Blood testing, Radioallergosorbent Test (RAST)

IgE Antibody level, Allergy Blood testing, Radioallergosorbent Test (RAST)
September 21, 2020Immune systemLab Tests

Sample

  1. A venous blood sample is needed to get the serum.
  2. A random sample can be used.
  3. Analyze a fresh sample or store at 4 °C for less than 72 hours.
  4. Avoid lipemic or hemolyzed samples.

Purpose of the test (Indications)

  1. It is done to diagnose an allergy.
  2. This is a blood test and different than the skin test.
  3. It is indicated in patients where skin test is contraindicated.

Contraindication

  1. If the patient has a reaction to the skin test for allergy.
  2. If patients have multiple sources of allergens.

Pathophysiology

  1. This is a type 1 hypersensitivity reaction where there is the role of IgE type of antibody.
  2. Where allergen (Antigen) produces IgE type of antibody.
  3. Mast cells and Basophils have a receptor for the Fc portion of IgE.
Fc Receptor on Mast cell and Basophil

Fc Receptor on Mast cell and Basophil

  1. When IgE molecules form a bond over the surface of the mast cell or basophils, it leads to the release of histamine and histamine-like substances.
Histamine and Histamine like substances secreted by Mast cell

Histamine and Histamine like substances secreted by Mast cell

Type 1 Hypersensitivity reaction and mediators

Type 1 Hypersensitivity reaction and mediators

Stimulant for Type 1 Hypersensitivity reaction:

Various substances can give rise to this Type 1 reaction like :

    1. Animal dandruff.
    2. Foods.
    3. Pollens.
    4. Dust.
    5. Molds.
    6. Insect venoms.
    7. Drugs.
    8. Environmental pollution.
  • The total level of raised IgE is the diagnostic of an allergic reaction.
  • This can be used to diagnose allergen because of the preparation of liquid allergen preparations available.
IgE antibody can persists for 6 months on Mast cell

IgE antibody can persist for 6 months on Mast cell

Normal IgE Level

Source 1

Age IU/mL
Cord blood At term ∼ 1% of the maternal value
Child
0 to 4 days <1,5
5 days to 12 months <15
1 to 5 years <60
6 to 9 years <90
10 to 16 years <200
>16 years <100
Adult  3 to 423
Median level 39
  • To convert into SI unit x 1.0 = kIU/L
Source 2
Child
  • 0 to 23 months = 0 to 13 IU /mL.
  • 2 to 5 years = 0 to 56 IU/mL (<60 IU/mL)
  • 6 to 10 years = 0 to 85 IU/mL (<90 IU/mL)

Adult = 0 to 100 IU/mL (<100 IU/mL)

 RAST rating with specific IgE level: 
RAST Rating IgE level Comments
0 < 0.35 Absent or undetectable allergen-specific IgE
1 0.35 – 0.69 Low-level allergen-specific IgE
2 0.70 – 3.49 Moderate level of allergen-specific IgE
3 3.50 – 17.49 High level of allergen-specific IgE
4 17.50 – 49.99 High level of allergen-specific IgE
5 50.00 – 100.00 Very high level of allergen-specific IgE
6 > 100.00 Extremely high level of allergen-specific IgE

Significant raised level will be seen in allergic diseases:

  1. Asthma.
  2. Dermatitis.
  3. Food allergy.
  4. Drug allergy.
  5. Occupational allergy.
  6. Latex allergy.
  7. Angioedema.
  8. allergic rhinitis.

False Results may be seen in:

  1. If patients have a disease where there is an elevated level of IgE.
  2. Corticosteroids increase the level of IgE.

Possible References Used
Go Back to Immune system

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