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.
["IgG subclasses play vital roles in immune defense and can be checked if you have immune-related conditions or symptoms."]
Key facts at a glance
- LOINC
- 47344-7
- Short code
- Deprecated S pneum43 IgG sp2 Ser IA-mCnc
- Synonyms
- Deprecated S pneum43 IgG sp2 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
What Does This Test Measure?
IgG is divided into four subclasses (IgG1, IgG2, IgG3, IgG4), each with distinct functions. This test evaluates the concentration of these subclasses in your serum. IgG1 and IgG2 are most involved in fighting bacterial infections, while IgG3 has a strong role in activating immune responses. IgG4 is less common and may be linked to allergic reactions or autoimmune conditions.
Why Might You Need This Test?
Doctors may order this test if you have symptoms like frequent infections, autoimmune diseases (such as lupus or rheumatoid arthritis), allergies, or if you’re receiving treatments that affect your immune system. It can also help diagnose or monitor conditions like common variable immunodeficiency (CVID).
How Is the Test Performed?
A blood sample is drawn from a vein, typically in your arm. The serum (liquid part of blood after clotting) is then analyzed using an immunoassay method to measure IgG subclass levels.
What Do Results Mean?
Results show the concentration of each IgG subclass, though specific reference ranges vary by lab. Abnormal levels may indicate immune system dysfunction, allergic reactions, or other underlying health issues. Your healthcare provider will interpret results in the context of your medical history.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Low IgG subclass levels may suggest immune deficiencies, making you more prone to infections. High levels of certain subclasses (like IgG4) could be linked to autoimmune diseases or allergic responses. Monitoring these levels helps guide treatment plans for chronic conditions or immune-related disorders.
Short name
IgG Subclass Levels
Frequently asked questions
What causes IgG subclass levels to change?
How long does it take to get results?
Can lifestyle changes affect IgG subclass test results?
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