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 is the most common antibody and helps protect your body from infections.
["IgG subclasses help identify immune system function and potential deficiencies."]
Key facts at a glance
- LOINC
- 96478-3
- Short code
- IgLON5 IgG Ser Ql CBA IFA
- Synonyms
- IgLON5 IgG Ser Ql CBA IFA
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- cba-ifa
- 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
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 unusual bruising. It may also be done to check for immune system disorders, such as hypogammaglobulinemia, or to monitor treatment for conditions like lupus or rheumatoid arthritis.
What to Expect Before the Test
No special preparation is needed for this blood test. You may have a small needle inserted into your arm to draw a blood sample. If you experience discomfort, let your healthcare provider know.
What the Test Results Mean
IgG subclasses are measured in arbitrary units (a.u.) or milligrams per deciliter (mg/dL). Results can help determine if your immune system is functioning properly or if there are specific subclasses involved in immune issues. Your healthcare provider will discuss the results with you in the context of your overall health.
Common Conditions Monitored
This test is often used to diagnose or monitor conditions like chronic infections, autoimmune diseases, or immune system disorders. Low levels of certain IgG subclasses may indicate an immune deficiency, while high levels might suggest overactive immune responses or certain diseases.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
IgG antibodies are divided into four subclasses (IgG1, IgG2, IgG3, IgG4), each playing a unique role in immunity. IgG2, for example, is important for fighting bacterial infections, while IgG1 is crucial for fighting viruses. Abnormal levels of these subclasses can indicate specific immune system problems, such as poor response to vaccines or recurrent infections. Your provider may use these results to tailor treatments, such as immune therapy or adjustments to medications.
Short name
IgG Subclass Levels
Frequently asked questions
What does a low or high IgG subclass level indicate?
How often should I get this test?
Can lifestyle changes 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