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Egg White-Specific IgG4, Serum — Radioallergosorbent Test, Qualitative

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

A qualitative blood test that detects IgG4 antibodies directed against egg-white proteins.

Quick summary

["A positive result shows egg-white-specific IgG4 but does not by itself confirm an egg allergy."]

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

Key facts at a glance

LOINC
26424-2
Short code
Deprecated Egg White IgG4 RAST Ql
Synonyms
Deprecated Egg White IgG4 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 test looks for IgG4 antibodies that react with proteins found in egg white. It is commonly described as a radioallergosorbent test, although laboratory methods may vary and the test is now considered deprecated.

Why might I need this test?

It may be used to assess immune reactivity to egg-white proteins in selected clinical situations. Results require professional interpretation and should not be used alone to diagnose a food allergy.

How is the test performed?

A blood sample is tested with egg-white allergen in the laboratory. Any egg-white-specific IgG4 that binds is detected, and the result is reported qualitatively as positive or negative.

How do I prepare for the test?

No special preparation is usually required. Tell your clinician about egg consumption, allergy symptoms, immunotherapy, and any medicines or biologic treatments that may affect antibody testing.

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.

A positive result indicates that egg-white-specific IgG4 is present, which may reflect previous exposure or a modified immune response and does not necessarily mean clinical allergy. A negative result does not rule out egg allergy. Symptoms, timing, other allergy testing, and sometimes a supervised food challenge are needed to determine clinical significance.

Short name

Egg White-Specific IgG4 (RAST)

Frequently asked questions

Does a positive result mean I am allergic to eggs?
No. Egg-specific IgG4 can occur in people who tolerate eggs, so this result alone does not diagnose egg allergy.
Is this the same as an egg-specific IgE test?
No. This test measures IgG4, while an egg-specific IgE test measures IgE, which is more closely associated with immediate allergic reactions.
Why might this test no longer be offered?
It is considered deprecated and may not be routinely available. A clinician can recommend more current allergy testing when appropriate.
  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