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Allergen-Specific IgE, Serum — Radioallergosorbent (RAST) Method

Published: August 9, 2026Updated: August 17, 2026

A blood test that measures IgE antibodies directed against specific allergens, helping evaluate possible allergic sensitization.

Quick summary

["Detected allergen-specific IgE can support the diagnosis of an allergy, but results must be interpreted with your symptoms and medical history."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
102674-9
Short code
A alternata IgG RAST
Synonyms
A alternata IgG 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 measures allergen-specific IgE antibodies in blood. RAST stands for radioallergosorbent test, although some laboratories may use a non-radioactive immunoassay method.

Why might I need this test?

It may be ordered to help identify allergic sensitization to foods, environmental allergens, insect venoms, or certain medications. Your clinician will interpret the results alongside your exposure history and symptoms.

How is the test performed?

A blood sample is collected and separated to obtain serum. The laboratory then tests the serum for IgE antibodies against the specific allergens included in the ordered panel.

How do I prepare for the test?

No special preparation is usually required. Antihistamines can sometimes reduce results, so tell your clinician about all medicines and supplements; do not stop any medication unless instructed.

Reference range

Adult males: 7-56 U/L; Adult females: 7-43 U/LN/A

Specimen: serum

No special preparation required. Avoid fatty meals before the test if possible.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Allergen-Specific IgE (RAST)

Frequently asked questions

Does a positive result mean I am allergic?
It indicates allergic sensitization, but your clinician must interpret it with your symptoms and history. Some people have positive test results without noticeable allergy symptoms.
What happens if the test is negative?
A negative result means that IgE to the tested allergen was not detected. Your clinician may still consider non-IgE reactions, allergies not included in the panel, or another cause of your symptoms.
Can I take allergy medicines before this test?
Some antihistamines can affect the results. Ask your clinician whether to pause them and for how long; do not stop prescribed medication without medical advice.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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