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Serum Immunoglobulin G (IgG) Subclass Quantification (Screening)

Published: August 9, 2026Updated: August 16, 2026

This test measures different types of Immunoglobulin G (IgG), a key antibody protein in your immune system, to help identify if certain IgG subclasses are low or high.

Quick summary

["IgG subclasses help protect your body against infections and diseases; imbalances may indicate immune system issues."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
7827-9
Short code
C immitis IgM Ser-aCnc
Synonyms
C immitis IgM Ser-aCnc
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 doctor may order this test if you have symptoms like frequent infections, autoimmune conditions, or if certain antibodies are suspected to be insufficient or excessive. It can also be part of a broader evaluation for immune-related disorders.

What to Expect Before the Test

No special preparation is needed. You’ll provide a blood sample, usually drawn from a vein in your arm. The test is quick and typically done in a lab setting.

What the Results Mean

Results show levels of IgG1, IgG2, IgG3, and IgG4 subclasses. While reference ranges vary by lab, abnormal levels may signal immune dysfunction or other health concerns.

Common Conditions Linked to IgG Subclass Levels

Low IgG subclass levels may be linked to conditions like common variable immunodeficiency (CVID), where the immune system doesn’t produce enough antibodies. High levels could be associated with autoimmune diseases or chronic infections.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical significance: IgG subclasses play a role in immune defense, and their measurement helps diagnose or monitor conditions affecting antibody production or function, such as infections, autoimmune diseases, or immune deficiencies.

Short name

IgG subclass screening

Frequently asked questions

What does a screening test for IgG subclasses measure?
A screening test for IgG subclasses measures the relative amounts of the four main IgG subclasses (IgG1, IgG2, IgG3, IgG4) in your blood serum. This helps identify if any subclass is unusually low or high.
Can IgG subclass levels change over time?
Yes, IgG subclass levels can fluctuate due to infections, immune responses, medications, or underlying health conditions. Repeated testing may be needed to monitor changes.
What might cause abnormal IgG subclass results?
Abnormal IgG subclass results may be caused by immune system disorders (like CVID), autoimmune diseases, chronic infections, or certain medications. Always discuss results with your healthcare provider.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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