Timothy Grass-Specific IgG4 Antibody, Qualitative RAST (Deprecated)
A qualitative blood test that detects IgG4 antibodies directed toward Timothy grass, an allergen found in some grass pollens.
["This test can show prior exposure to Timothy grass, but it does not by itself diagnose a grass allergy."]
Key facts at a glance
- LOINC
- 26431-7
- Short code
- Deprecated Timothy IgG4 RAST Ql
- Synonyms
- Deprecated Timothy 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 looks for IgG4 antibodies directed against Timothy grass in a blood sample, typically serum. These antibodies are part of the immune response to this grass allergen.
Why might I need this test?
It may be used to assess prior immune exposure to Timothy grass or to follow changes in the immune response to this allergen. It may also be relevant in some evaluations of allergen immunotherapy.
How is the test performed?
A laboratory uses a RAST-type method to determine whether Timothy grass-specific IgG4 is present. The result is reported qualitatively as detected or not detected rather than with a concentration value.
How do I prepare for the test?
No special preparation is usually required for a routine blood draw. Follow any instructions from the ordering clinician, particularly if the test is being tracked alongside allergy shots or other 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.
Detected IgG4 antibodies generally indicate that the immune system has encountered Timothy grass, but this result alone does not establish a clinical allergy. The interpretation depends on symptoms, exposure history, and other allergy testing. Because this test is marked deprecated, a current testing option may be more appropriate.
Short name
Timothy grass IgG4 antibody test
Frequently asked questions
Does a positive result mean I am allergic to Timothy grass?
How is this test different from a Timothy grass-specific IgE test?
Why is this test marked 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