Immunoglobulin G (IgG) Subclass Measurement (Serum)
This test measures the levels of specific subclasses of Immunoglobulin G (IgG), a key antibody in your immune system. IgG subclasses help your body fight infections and provide long-term immunity.
["IgG subclasses play a vital role in immune defense and can help identify specific immune system responses or deficiencies."]
Key facts at a glance
- LOINC
- 8033-3
- Short code
- Deprecated S pneum3 IgG Ser IA-aCnc
- Synonyms
- Deprecated S pneum3 IgG Ser IA-aCnc
- 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 Might Be Ordered
Your healthcare provider may order this test to evaluate immune function, diagnose conditions like hypogammaglobulinemia (low antibody levels), or assess responses to treatments for autoimmune diseases or infections. It can also help monitor immune-related conditions such as chronic infections or certain cancers.
What to Expect Before the Test
No special preparation is usually needed. You may have a small needle inserted into a vein in your arm to draw a blood sample. If you’re nervous, let your healthcare provider know—they can help make the process more comfortable.
What the Test Results Mean
IgG subclasses are measured in mass concentration units (e.g., grams per liter). Results help determine if your immune system is producing the right types and amounts of antibodies. Abnormal levels may indicate immune system issues that need further medical evaluation.
Common Conditions Linked to IgG Subclass Testing
IgG subclass testing is often used in cases of recurrent infections, autoimmune diseases (like lupus or rheumatoid arthritis), or after treatments that weaken the immune system (e.g., chemotherapy). It can also be part of routine monitoring for certain genetic or congenital immune disorders.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance
Short name
IgG Subclass Levels
Frequently asked questions
What does it mean if my IgG subclass levels are low?
Can IgG subclass testing help diagnose autoimmune diseases?
How often should I get this test?
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