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Baker’s Yeast-Specific IgG Antibody, Qualitative (RAST; Deprecated)

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

A legacy qualitative test for IgG antibodies to baker’s yeast. A positive result may indicate prior exposure or immune sensitization, not necessarily active infection or allergy.

Quick summary

["This outdated test can detect antibodies to baker’s yeast, but a positive result alone does not diagnose a yeast allergy or active infection."]

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

Key facts at a glance

LOINC
21607-7
Short code
Deprecated Baker's yeast IgG RAST Ql
Synonyms
Deprecated Baker's yeast 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 laboratory test looks for patient IgG antibodies directed against baker’s yeast, also called Saccharomyces cerevisiae. It uses a qualitative result, such as positive or negative.

Why might I need this test?

It may be considered in selected situations involving suspected yeast exposure, recurrent yeast-related symptoms, or evaluation of an immune response. Because this test is deprecated and is not routinely used, a clinician should explain why it is being ordered.

How is the test performed?

A patient sample, typically blood or serum, is tested for antibodies that bind to baker’s yeast antigen using a legacy RAST laboratory method. The outcome is reported qualitatively rather than as a measured concentration.

How do I prepare for the test?

Fasting is generally not required for this type of antibody test. Follow the laboratory’s instructions and tell your clinician about immune disorders, medicines that affect immunity, prior yeast infections, and any history of yeast allergy.

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

Baker’s yeast IgG antibody test

Frequently asked questions

Does a positive result mean I have a baker’s yeast allergy?
No. IgG antibodies are different from the IgE antibodies usually linked to immediate allergy, so this result alone does not diagnose a yeast allergy.
Does a positive result mean I currently have a yeast infection?
Not necessarily. It may indicate previous exposure or immune sensitization, and other tests may be needed to evaluate an active infection.
Why is this test described as deprecated?
It is a legacy test that is no longer routinely recommended or may not be available. Your clinician should determine whether its result is useful in your situation and whether newer testing is more 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