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Halibut-Specific IgG Antibody, Qualitative (RAST Method) — Deprecated

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

A deprecated blood test that checks for antibodies to halibut. A positive result indicates immune exposure but does not by itself diagnose food allergy.

Quick summary

["This old test detects halibut-specific IgG antibodies, but it cannot confirm a clinical fish allergy."]

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

Key facts at a glance

LOINC
21321-5
Short code
Deprecated Halibut IgG RAST Ql
Synonyms
Deprecated Halibut 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 IgG antibodies directed against halibut, a type of fish. The test was performed using a radioallergosorbent method, and it is now deprecated and generally unavailable.

Why might I need this test?

It was historically used to evaluate immune sensitization to halibut in people with a suspected fish allergy or unexplained symptoms after eating fish. Because food-specific IgG tests do not reliably identify clinical allergy, this test should not be used by itself to diagnose a food allergy.

How is the test performed?

A blood sample is tested in the laboratory for antibodies that bind to halibut allergen. The result is reported qualitatively, generally as detectable or not detectable, rather than with a numerical measurement.

How do I prepare for the test?

No special preparation is usually required, and fasting is generally unnecessary. Because this is a deprecated test, contact your healthcare professional before ordering it and follow any laboratory-specific instructions.

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

Halibut-Specific IgG

Frequently asked questions

Does a positive result mean I am allergic to halibut?
No. Halibut-specific IgG can occur after exposure without causing symptoms, so a positive result alone does not diagnose allergy.
Is this test still available?
This test is deprecated and may no longer be offered by most laboratories. A clinician can recommend a currently available evaluation when medically appropriate.
What should I do if I have symptoms after eating fish?
Discuss the reaction with your healthcare professional or allergist, especially if it involved hives, swelling, breathing difficulty, or other severe symptoms. Seek emergency care for breathing difficulty, throat swelling, fainting, or a rapidly progressing reaction.
  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