Immunoglobulin G (IgG) Subclass Measurement (Serum)
This test measures the levels of different subclasses of Immunoglobulin G (IgG), a key antibody protein in your immune system. IgG subclasses help protect against bacteria, viruses, and toxins.
["Understanding your IgG subclass levels can help identify immune system function or deficiencies."]
Key facts at a glance
- LOINC
- 47342-1
- Short code
- Deprecated S pneum43 IgG Ser IA-mCnc
- Synonyms
- Deprecated S pneum43 IgG Ser IA-mCnc
- Category
- coagulation
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- ia
- CPT
- 82784
- 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
Why This Test Is Done
Doctors may order this test if you have symptoms like frequent infections, unusual fatigue, or immune system disorders. It can also be used to monitor conditions like lupus, rheumatoid arthritis, or certain immune deficiencies.
What to Expect Before the Test
No special preparation is needed. You’ll provide a blood sample, usually drawn from a vein in your arm. The test is quick and typically done in a lab setting.
What the Results Mean
IgG is divided into four subclasses (IgG1, IgG2, IgG3, IgG4). Abnormal levels in any subclass may indicate immune system issues, such as low resistance to infections or autoimmune diseases. Your doctor will interpret results in the context of your overall health.
Common Conditions Linked to IgG Subclass Levels
Low IgG subclass levels can be linked to conditions like common variable immunodeficiency (CVID), where the immune system struggles to produce enough antibodies. High levels might be seen in chronic infections or certain autoimmune diseases.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical significance: IgG subclasses play a critical role in immune defense. Variations can signal underlying immune dysfunction, guide treatment decisions for infections or autoimmune diseases, and help monitor long-term immune health. Your doctor will discuss results with you based on your medical history and symptoms.
Short name
IgG Subclass Levels
Frequently asked questions
What does a low IgG subclass mean?
How often should I get this test?
Can diet or supplements affect IgG subclass levels?
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 16, 2026. · Read our editorial policy