Mustard-Specific IgE Antibody, Qualitative (RAST) — Deprecated
A qualitative blood test for antibodies to mustard, used to assess possible mustard allergy. This older RAST-style test has been deprecated in favor of current allergy testing methods.
["A positive result suggests mustard sensitization, but it must be interpreted alongside symptoms and exposure history."]
Key facts at a glance
- LOINC
- 21404-9
- Short code
- Deprecated Mustard IgG RAST Ql
- Synonyms
- Deprecated Mustard 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 mustard-specific IgE antibodies in a blood sample. IgE is an immune-system protein that can react with mustard proteins in people who are sensitive to mustard.
Why might I need this test?
It may be used when a history of hives, swelling, wheezing, or other symptoms suggests a mustard allergy. Results can help guide evaluation, avoidance planning, and discussion with an allergy specialist.
How is the test performed?
A blood sample is tested in the laboratory for antibodies directed against mustard. This older RAST-style assay is qualitative, meaning it reports whether mustard-specific IgE was detected rather than providing a simple yes-or-no interpretation by itself.
How do I prepare for the test?
No special preparation or fasting is usually required for a blood-based allergy antibody test. Tell your clinician about any recent allergic reactions, mustard exposure, allergy treatments, and history of immunotherapy.
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 mustard-specific IgE antibodies are present, suggesting sensitization to mustard. This may support a mustard allergy when it is consistent with the person's symptoms and exposure history, but sensitization alone does not always mean a clinically important allergy. A negative result makes an immediate mustard allergy less likely but does not completely exclude it.
Short name
Mustard-specific IgE (RAST)
Frequently asked questions
Does a positive result mean I am definitely allergic to mustard?
Why is this test described as deprecated?
Can skin-prick testing replace this blood test?
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