Brewer's Yeast-Specific IgG Antibodies, Qualitative (RAST)
A qualitative blood test for IgG antibodies directed against brewer's yeast. A positive result shows sensitization but does not by itself confirm a food allergy.
["This older test can show a brewer's yeast-specific IgG response, but it cannot determine whether you have a true allergy."]
Key facts at a glance
- LOINC
- 21608-5
- Short code
- Deprecated Brewer's yeast IgG RAST Ql
- Synonyms
- Deprecated Brewer'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 test looks for IgG antibodies against brewer's yeast in a blood sample. It uses an older radioallergosorbent-style testing method and is reported as positive or negative.
Why might I need this test?
It may have been ordered to evaluate an immune response to foods or beverages containing brewer's yeast, such as some beers, nutritional products, or yeast extracts. Because the test is deprecated, a clinician should confirm whether it is still available and appropriate.
How is the test performed?
A blood sample is tested with brewer's yeast antigen to determine whether detectable yeast-specific IgG antibodies are present. The laboratory reports the result qualitatively rather than as a measured concentration.
How do I prepare for the test?
No special preparation is usually required. Contact the ordering clinician or laboratory before the test because this assay is deprecated and may no longer be routinely offered.
Reference range
Adult: 10-40 U/LN/A
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 IgG antibodies directed against brewer's yeast are detectable, which may reflect prior exposure or an immune response. It does not establish a clinical food allergy, because food-specific IgG antibodies can occur without allergic symptoms. A negative result does not rule out allergy or other forms of intolerance.
Short name
Brewer's yeast IgG antibodies
Frequently asked questions
Does a positive result mean I am allergic to brewer's yeast?
How is this different from a brewer's yeast-specific IgE test?
Why is the test described as deprecated?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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