Lactoglobulin-Specific IgG4 Antibodies, Qualitative — Radioallergosorbent Test (RAST)
A blood test that looks for IgG4 antibodies directed against lactoglobulin, a milk protein, and reports the result as positive or negative.
["This test can detect lactoglobulin-specific IgG4 antibodies, but the result must be interpreted alongside your symptoms and other allergy evaluation."]
Key facts at a glance
- LOINC
- 26434-1
- Short code
- Deprecated Lactoglob IgG4 RAST Ql
- Synonyms
- Deprecated Lactoglob 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 test examines a blood sample for IgG4 antibodies directed against lactoglobulin, a protein found in milk. It is performed using a radioallergosorbent test, or RAST, method and gives a qualitative positive or negative result.
Why might I need this test?
It may be considered when evaluating a possible reaction to milk or milk proteins. Your clinician will determine whether this test is appropriate based on your symptoms, exposure history, and other laboratory findings.
How is the test performed?
A blood sample is collected and tested in the laboratory using a RAST-type immunoassay to look for antibodies that recognize lactoglobulin. The laboratory reports whether lactoglobulin-specific IgG4 antibodies were detected.
How do I prepare for the test?
No special preparation or fasting is usually required. Follow any instructions from the laboratory, and tell your clinician about relevant food exposures, symptoms, allergies, and medicines before the test.
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 means lactoglobulin-specific IgG4 antibodies are detectable, but it does not by itself prove that lactoglobulin causes your symptoms. IgG4 antibodies may reflect prior exposure or immune tolerance and must be interpreted with your clinical history and other allergy tests. A negative result does not completely exclude milk-protein sensitivity.
Short name
Lactoglobulin IgG4 (RAST), qualitative
Frequently asked questions
Does a positive result mean I have a milk allergy?
Is this the same as testing for IgE-mediated milk allergy?
Should I avoid dairy if this test is positive?
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