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, and play a role in immune responses.
["Understanding your IgG subclass levels can help identify immune system function or deficiencies."]
Key facts at a glance
- LOINC
- 27094-2
- Short code
- Deprecated S pneum4 IgG Ser-mCnc
- Synonyms
- Deprecated S pneum4 IgG Ser-mCnc
- Category
- coagulation
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- 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
What Does This Test Measure?
IgG is divided into four subclasses (IgG1, IgG2, IgG3, IgG4), each with distinct roles. This test evaluates the concentration of these subclasses in your serum. While IgG1 and IgG2 are most abundant, IgG3 and IgG4 are present in smaller amounts and can be important in certain immune conditions.
Why Might You Need This Test?
Doctors may order this test if you have symptoms like frequent infections, autoimmune diseases, or conditions affecting antibody production. It can also be part of diagnosing or monitoring immune-related disorders, such as common variable immunodeficiency (CVID) or certain infections.
Sample Collection and Preparation
A blood sample is drawn from a vein in your arm. The blood is processed to separate serum, which is then analyzed for IgG subclass levels. This test is typically done in a laboratory using immunoassay methods.
What Are the Possible Results?
Results show the concentration of each IgG subclass, though specific reference ranges vary by lab. Abnormal levels may indicate immune system issues, such as low antibody production or specific immune deficiencies.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
IgG subclass levels help diagnose or monitor conditions like CVID, where IgG2 or IgG3 may be low. High levels of certain subclasses might be seen in autoimmune diseases or chronic infections. Regular monitoring can guide treatment decisions for immune support or therapy.
Short name
IgG Subclass Levels
Frequently asked questions
What does a low IgG subclass mean?
How often should I get this test?
Can lifestyle or diet 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