Immunoglobulin G (IgG) Subclass Measurement (Serum)
This test measures the levels of different subclasses of Immunoglobulin G (IgG), a type of antibody in your blood. IgG subclasses help protect your body against infections and play roles in immune responses.
["IgG subclasses help identify immune system function and potential deficiencies."]
Key facts at a glance
- LOINC
- 22551-6
- Short code
- Deprecated S pneum7 IgG Ser-aCnc
- Synonyms
- Deprecated S pneum7 IgG Ser-aCnc
- 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 the most abundant antibody in your blood and is divided into four subclasses (IgG1, IgG2, IgG3, IgG4). This test evaluates the concentration of each subclass, which can vary based on immune health, age, and certain medical conditions. Lower levels of specific subclasses may indicate immune system issues or certain diseases.
Why Might You Need This Test?
Your healthcare provider may order this test if you have symptoms of a weakened immune system, such as frequent infections, recurrent ear or sinus infections, or if you have conditions like lupus, rheumatoid arthritis, or certain autoimmune diseases. It may also be used to monitor immune responses in people with HIV, cancer, or after organ transplants.
How Is the Test Performed?
A blood sample is drawn from a vein, usually in your arm. The blood is then sent to a lab for analysis using an immunoassay method to measure the specific IgG subclasses. Results are typically available within a few days.
What Are the Possible Results?
Results show the concentration of each IgG subclass in milligrams per deciliter (mg/dL) or another relevant unit. While specific reference ranges vary by lab, lower or higher-than-expected levels may signal underlying health concerns that need further evaluation.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance
Short name
IgG Subclass Levels
Frequently asked questions
How can I prepare for this test?
Will I feel any discomfort during the test?
What if my results are abnormal?
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