Lobster-Specific IgG, Radioallergosorbent Test — Qualitative (Deprecated)
A qualitative blood test that looks for antibodies to lobster. This legacy test may reflect previous exposure but does not by itself confirm a food allergy.
["A positive result shows lobster-reactive antibodies, but it does not necessarily mean you have a lobster allergy."]
Key facts at a glance
- LOINC
- 21371-0
- Short code
- Deprecated Lobster IgG RAST Ql
- Synonyms
- Deprecated Lobster 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 radioallergosorbent test, or RAST, used to detect antibodies that react to lobster. The word “deprecated” indicates that this test format is no longer the preferred way to evaluate shellfish allergy.
Why might I need this test?
It may have been ordered to investigate a suspected lobster allergy or to identify previous exposure to lobster. Because RAST can refer to different antibody types, the exact laboratory method and report should be reviewed with a healthcare professional.
How is the test performed?
A blood sample is tested with laboratory reagents designed to detect lobster-reactive antibodies. The result is reported as detected or not detected rather than as a measured concentration.
How do I prepare for the test?
Fasting is generally not required for this blood test. Follow any instructions from the ordering clinician or laboratory, and tell them if you have recently eaten lobster or taken allergy medicines.
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 detectable result means that antibodies reacting to lobster are present. IgG antibodies commonly reflect prior exposure and are not usually sufficient to diagnose an immediate food allergy. If an allergy is suspected, a clinician may recommend a current shellfish-specific IgE test, skin-prick testing, or supervised food testing instead.
Short name
Lobster IgG RAST
Frequently asked questions
Does a positive result mean I have a lobster allergy?
Why is this test marked as deprecated?
Do I need to avoid eating lobster before this 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