Immunoglobulin G (IgG) Subclass Measurement (Serum)
This test measures the levels of specific subclasses of Immunoglobulin G (IgG), a type of antibody in your blood. IgG is the most common antibody and plays a key role in defending against infections.
["IgG subclasses help assess immune function and identify potential deficiencies or imbalances."]
Key facts at a glance
- LOINC
- 50612-1
- Short code
- C pneum IgA+IgG+IgM Ser-Imp
- Synonyms
- C pneum IgA+IgG+IgM Ser-Imp
- Category
- chemistry
- 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
Why This Test Is Done
Your healthcare provider may recommend IgG subclass testing if you have symptoms of a weakened immune system, such as frequent infections, recurrent ear or sinus infections, or unexplained bruising or bleeding. It may also be used to monitor conditions like chronic infections, autoimmune diseases, or certain immune deficiencies.
What to Expect Before the Test
No special preparation is usually needed. You may be asked to fast for a few hours before the test if it involves drawing blood from a vein. Wear comfortable clothing and plan to stay for about 15 minutes while the blood is drawn.
A healthcare professional will insert a small needle into your arm to draw blood. You may feel a slight pinch, but it usually doesn’t cause significant discomfort. The blood sample will be sent to a lab for analysis.
You can return to your normal activities immediately. Apply gentle pressure to the site to stop any bleeding. If you experience excessive bruising, swelling, or pain, contact your healthcare provider.
IgG subclass results help determine if your immune system has specific deficiencies. Low levels of certain IgG subclasses might indicate problems with how your immune system fights certain types of infections. Your healthcare provider will discuss the results with you and may recommend further testing or treatments.
Abnormal IgG subclass levels can be linked to conditions such as primary immunodeficiency diseases, chronic infections, autoimmune diseases, or certain types of cancer. These results are used to guide treatment plans and monitor disease progression.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
IgG subclass testing is important for diagnosing and managing immune-related conditions. It helps tailor treatments to address specific weaknesses in your immune response, ensuring better management of infections and overall health.
Short name
IgG subclass testing
Frequently asked questions
What does an IgG subclass test measure?
How long does it take to get the results of this test?
Can I eat or drink before 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