Alpha-Lactalbumin IgG4 Antibody, Radioallergosorbent Test (RAST), Qualitative (Deprecated)
A qualitative, deprecated blood test that detects IgG4 antibodies to alpha-lactalbumin, a milk protein. It may indicate exposure or immune tolerance, not proven allergy.
["A positive result shows an immune response to alpha-lactalbumin but does not by itself confirm milk allergy."]
Key facts at a glance
- LOINC
- 26426-7
- Short code
- Deprecated A-Lactalb IgG4 RAST Ql
- Synonyms
- Deprecated A-Lactalb IgG4 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 qualitative laboratory test detects IgG4 antibodies directed against alpha-lactalbumin, a protein found in cow's milk. It uses the radioallergosorbent test (RAST) method and is marked as deprecated, so it may no longer be routinely available.
Why might I need this test?
It may be used to investigate a specific immune response to cow's milk protein. Results must be interpreted with symptoms and medical history because IgG4 commonly reflects previous exposure or immune tolerance and is not the same as allergy-related IgE.
How is the test performed?
A blood sample is tested with alpha-lactalbumin using a RAST laboratory method. The result is reported qualitatively as positive or negative, or as detected or not detected.
How do I prepare for the test?
No special preparation is usually required, although you should follow instructions from the laboratory. Tell your clinician about any dairy reactions and whether you have recently consumed milk products.
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.
◆Associated findings1
Short name
Alpha-Lactalbumin IgG4 (RAST)
Frequently asked questions
Does a positive result mean I have a cow's milk allergy?
How is this different from a standard milk allergy test?
Why is this test listed 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