Skip to content

Deprecated Corn-Specific Immunoglobulin G (IgG) Antibody Test, Qualitative (RAST)

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

A legacy blood test that screens for corn-specific IgG antibodies. A positive result shows an immune response but does not by itself confirm a food allergy.

Quick summary

["This deprecated test may show whether your blood contains antibodies to corn, but it cannot diagnose a corn allergy by itself."]

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

Key facts at a glance

LOINC
21221-7
Short code
Deprecated Corn IgG RAST Ql
Synonyms
Deprecated Corn IgG 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 is a qualitative blood test for corn-specific IgG antibodies, traditionally labeled a RAST test. It is considered deprecated and may not be available or routinely recommended.

Why might I need this test?

It may be ordered to evaluate an immune response to corn or investigate a suspected food-related reaction. Results should be interpreted with your symptoms, exposure history, and other appropriate allergy testing.

How is the test performed?

A blood sample is collected and tested against corn proteins in the laboratory. Because the test is qualitative, the report generally indicates whether corn-specific IgG antibodies were detected rather than providing a measured concentration.

How do I prepare for the test?

Fasting is usually not required, but follow any instructions provided by the ordering clinician. Tell the clinician about recent corn consumption, symptoms, allergic conditions, and medicines you are taking.

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

Corn-specific IgG antibody (RAST), qualitative

Frequently asked questions

Does a positive result mean I am allergic to corn?
No. It shows that corn-specific IgG antibodies are detectable, but these antibodies do not reliably identify a true food allergy. Your clinician should interpret the result alongside your history and other appropriate tests.
Does this test diagnose celiac disease?
No. Although corn is a grain, this test looks for antibodies specific to corn rather than the antibodies used to evaluate celiac disease.
What should I do if I think I have a corn allergy?
Discuss your symptoms with an allergist or your clinician. A medical history and properly selected allergy testing, such as skin-prick testing or serum allergy-specific IgE testing, are generally more useful than this deprecated IgG test.
  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