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Mushroom-Specific IgG, Qualitative — Legacy RAST (Deprecated)

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

A retired qualitative test for mushroom-specific IgG. A positive result indicates immune recognition or prior exposure but does not by itself diagnose mushroom allergy.

Quick summary

["A positive mushroom-specific IgG result shows exposure or immune recognition, not necessarily an allergy."]

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

Key facts at a glance

LOINC
21403-1
Short code
Deprecated Mushroom IgG RAST Ql
Synonyms
Deprecated Mushroom 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 deprecated test for antibodies directed against mushroom proteins. The term “RAST” refers to an older radioallergosorbent testing method, while “qualitative” indicates a positive or negative result rather than a measured concentration.

Why might I need this test?

Food-specific IgG tests have sometimes been included in panels evaluating perceived food sensitivities. They are not generally recommended as a stand-alone way to diagnose food allergy, and this particular test has been retired.

How is the test performed?

The laboratory uses an immunoassay to determine whether mushroom-specific IgG is detectable. The exact specimen and testing method cannot be confirmed from the abbreviated test name alone, so the original laboratory report should be consulted.

How do I prepare for the test?

No special preparation can be confirmed from the retired test name. Follow the ordering clinician’s and laboratory’s instructions, and do not stop allergy medicines or make major dietary changes without medical guidance.

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

Mushroom-Specific IgG Test

Frequently asked questions

Does a positive result mean I am allergic to mushrooms?
No. Detectable mushroom-specific IgG can occur after exposure and does not by itself establish an allergy, even though the legacy name includes “RAST.”
Why is this test listed as deprecated?
It is a retired test and may no longer be available. Current evaluation of possible food allergy more commonly uses the clinical history, skin-prick testing, and food-specific IgE testing.
Should I stop eating mushrooms because of a positive result?
Do not make major dietary changes based on this result alone. Discuss the finding with a healthcare professional, particularly if you have symptoms after eating mushrooms.
  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