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Peanut Ara h 2-Specific IgE by Radioallergosorbent Test (RAST), Qualitative (Deprecated)

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

A legacy blood test that detects IgE antibodies directed against the peanut protein Ara h 2. A positive result supports peanut sensitization but requires clinical interpretation.

Quick summary

["This test looks for peanut-specific IgE antibodies that may indicate an immune reaction to peanuts."]

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

Key facts at a glance

LOINC
81991-2
Short code
Deprecated Peanut (rAra h) 2 IgE RAST Ql
Synonyms
Deprecated Peanut (rAra h) 2 IgE RAST Ql
Category
liver
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
10
Ref high
40
Critical range
— – 500 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
84484
SNOMED
302774002
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 qualitative blood test looks for IgE antibodies directed against Ara h 2, a peanut protein. It is a legacy RAST test and may no longer be offered because newer peanut allergy testing methods are available.

Why might I need this test?

It may have been used when there was concern about a peanut allergy, especially after an exposure or when standard allergy testing was inconclusive. It may also help distinguish allergy to a specific peanut protein from other possible causes of food reactions.

How is the test performed?

A blood sample is collected and tested in the laboratory for Ara h 2-specific IgE. The result is reported as positive or negative, and it does not require deliberately eating peanut.

How do I prepare for the test?

Fasting is usually not required for this blood test. Tell your clinician about any medicines you take, and do not stop eating peanut or other foods unless your allergy specialist advises you to do so.

Reference range

Adult: 10-40 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

Peanut Ara h 2 IgE

Frequently asked questions

Does a positive result mean I have a peanut allergy?
It indicates peanut sensitization, but not necessarily a confirmed clinical allergy. Your clinician will interpret it alongside your symptoms, prior reactions, and other test results.
Does this test require me to eat peanut?
No. The test uses a blood sample and measures antibodies to a peanut protein without requiring exposure to peanut.
Why is this test listed as deprecated?
It is a legacy testing method that may be unavailable or replaced by other validated approaches for evaluating suspected peanut allergy. Ask your clinician about the currently preferred option.
  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