IgG Subclass 1 (Immunoglobulin G1) Antibody Level
This test measures the amount of Immunoglobulin G1 (IgG1), a type of antibody in your blood. IgG1 is part of your immune system and helps protect you from infections.
["IgG1 antibodies play a key role in fighting infections and immune responses."]
Key facts at a glance
- LOINC
- 101448-9
- Short code
- CASPR1
- Synonyms
- CASPR1 IgG SerPl Ql CBA IFA
- Category
- chemistry
- Sample
- serum
- Container
- Serum separator tube (SST) or red-top tube; plasma acceptable in heparin or EDTA tubes
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- cba-ifa
- CPT
- 86255
- SNOMED
- 445572007
- Specimen volume
- 1.0 mL serum or plasma (minimum 0.5 mL)
- Stability
- Stable for 7 days at 2-8°C; for extended storage, freeze at -20°C or below. Avoid repeated freeze-thaw cycles.
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 48–168 hours
- Order
- routine
What Is IgG1 Antibody Testing For?
IgG1 antibodies are a subset of antibodies that can be important in diagnosing certain immune-related conditions, such as autoimmune diseases or infections. Your doctor may order this test if they suspect a specific immune response or to monitor treatment effectiveness.
How Is This Test Performed?
A blood sample is taken from a vein, usually in your arm. The sample is then sent to a lab for analysis using an immunoassay method to measure IgG1 levels.
Why Might Your Doctor Order This Test?
Your doctor may recommend this test if you have symptoms related to immune system dysfunction, such as frequent infections, unexplained fatigue, or if you are being treated for an autoimmune condition. It can also help assess immune responses to vaccines or infections.
What Do Results Mean?
Results are not typically provided as a single numeric range since IgG1 levels can vary widely among individuals. Your doctor will interpret the results in the context of your health history and other test results.
Reference range
Negative (antibody not detected). Positive results indicate the presence of Contactin-associated protein 1 (CASPR1) IgG antibodies.N/A
No special patient preparation required. Specimen collection can be performed at any time of day.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
IgG1 antibodies are crucial for immune defense, and abnormal levels may indicate underlying immune system issues. This test helps clinicians evaluate immune function, diagnose conditions, or monitor treatment progress.
Short name
IgG1 Antibody
Frequently asked questions
Why was this IgG1 antibody test ordered?
What does a low IgG1 level mean?
Can IgG1 levels change over time?
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