Allergen-Specific IgE (RAST), Serum
A blood test that measures IgE antibodies to selected allergens. It may help identify triggers related to allergy symptoms.
["This test can help determine whether specific allergens are likely triggers of your allergy symptoms."]
Key facts at a glance
- LOINC
- 102136-9
- Short code
- A alternata IgE RAST
- Synonyms
- A alternata IgE RAST
- Category
- liver
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 7
- Ref high
- 56
- Critical range
- — – 500 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- rast
- CPT
- 84484
- SNOMED
- 302773008
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
What is this test?
This test, also called the radioallergosorbent test (RAST), measures allergen-specific IgE antibodies in a blood sample. IgE is an immune-system protein that can react with particular substances such as pollen, foods, dust mites, or animal dander.
Why might I need this test?
Your clinician may order this test to help evaluate allergy symptoms such as sneezing, wheezing, hives, or swelling. The results can help identify possible triggers and guide further allergy evaluation or treatment.
How is the test performed?
A blood sample is collected and tested in a laboratory for antibodies against selected allergens. The report usually identifies the allergens tested and gives a result for each one.
How do I prepare for the test?
Fasting is generally not required. Tell your clinician about all medicines and supplements you take because antihistamines and certain other treatments may affect test results; do not stop prescribed medication without medical advice.
Reference range
Adult males: 7-56 U/L; Adult females: 7-43 U/LN/A
No special preparation required. Avoid fatty meals before the test if possible.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
A detectable allergen-specific IgE result indicates that your immune system has produced antibodies against that allergen, but it does not by itself prove that the allergen causes your symptoms. Results can also be positive without current allergy symptoms, so they should be interpreted alongside your medical history and examination. Your clinician may recommend additional allergy testing when needed.
Short name
Allergen-Specific IgE (RAST)
Frequently asked questions
Does a positive result mean I am allergic to that substance?
Can this test identify every possible allergen?
Should I stop taking allergy medicine before the test?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 17, 2026. · Read our editorial policy