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Deprecated Egg Yolk IgG Radioallergosorbent (RAST) Test, Qualitative

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

A historical qualitative blood test for egg yolk–specific IgG antibodies. It may indicate exposure but does not confirm egg allergy.

Quick summary

["A positive result shows egg yolk–specific IgG antibodies but does not by itself diagnose an egg allergy."]

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

Key facts at a glance

LOINC
21254-8
Short code
Deprecated Egg Yolk IgG RAST Ql
Synonyms
Deprecated Egg Yolk 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 test that looks for IgG antibodies directed against egg yolk proteins. RAST is an older laboratory method used to measure food-specific antibodies in blood.

Why might I need this test?

It may have been ordered to evaluate a suspected food-related immune response. However, this test is deprecated because food-specific IgG results generally do not reliably identify or confirm food allergy.

How is the test performed?

A blood sample is tested using the older RAST method. The result reports whether egg yolk–specific IgG antibodies were detected, without providing the same quantitative information as some newer tests.

How do I prepare for the test?

No special preparation is usually required for this type of blood test. Follow any instructions from the ordering clinician, particularly if the test will be replaced by another allergy evaluation.

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

Egg Yolk IgG RAST (Qualitative)

Frequently asked questions

Does a positive result mean I am allergic to eggs?
No. This test detects IgG antibodies, which can occur after exposure and are not specific for allergy. An IgE-based test, skin-prick testing, or a supervised oral food challenge may be more appropriate when clinically indicated.
What does a negative result mean?
It means that egg yolk–specific IgG antibodies were not detected by this test. It does not rule out an egg allergy or a reaction to another food.
Why is this test considered deprecated?
Food-specific IgG testing has not been shown to reliably diagnose food allergy and may produce confusing results. Modern allergy evaluation emphasizes medical history, targeted IgE testing, and, when needed, supervised food challenge.
  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