What is a Complement C4?
Complement C4 is a vital protein produced in the liver that functions in the normal immunity of the body and is an essential part of the complement system that increases the functionality of the antibodies to fight against the antigens. They are involved in the classical pathway of the complement system which involves the identification and destruction of harmful bacteria, viruses and damaged or abnormal cells.
The complement C4 levels are measured using this test and give insights about how well the immune function is working i.e. whether it is working normally, is overactive or underactive. Abnormal C4 levels are suggestive of several autoimmune disorders, immune deficiencies, or inflammatory conditions.
How is the Test Performed?
The Complement C4 Test is conducted as part of the complement system panel and requires a simple blood draw.
Preparation
- No special preparation is required for the test
- It is advised to inform your healthcare provider about the medications and supplements you are taking.
Blood Draw
- Blood is drawn typically from the arm through a needle and placed in a chemically treated tube to avoid degradation of the sample.
Laboratory Analysis
- The blood sample is then analyzed using immunoassay techniques such as enzyme-linked immunoassay and nephelometry which are highly sensitive and give accurate results.
What are the symptoms that prompt this test?
Healthcare providers suggest Complement C4 in individuals based on the symptoms they are exhibiting for the accurate diagnosis and confirmation of the disease.
Symptoms Associated with Chronic Infections and Immune Deficiencies
- Recurring bacterial and viral infection mostly associated with sinus and respiratory tract
- Slow healing of the wound
- Fever and chill without a known reason
Symptoms Associated with Inflammatory Conditions
- Severe pain and stiffness
- Occurrence of skin related disorders like psoriasis
- Kidney and blood vessels inflammation
What are Normal Ranges for This Test?
The complement C4 values vary in individuals according to various factors such as age, gender, and other underlying medical conditions. The generally accepted reference range is given below;
Adults – 15-45 mg/dL
Children – 15-45 mg/dL
Neonates – Slightly lower than the levels of the adults.
**The reference range given above are for general guidelines only and may vary according to the assay used. **
What Happens if Test Results Show Abnormal Levels?
Abnormal levels of complement C4 is suggestive that an individual is suffering from the following disorders that are causing the disruption of C4 normal range;
Low Levels of Complement C4
- Hereditary angioedema
- Systemic lupus erythematosus
- Chronic bacterial or viral infection
- Liver disorders
- Immune deficiencies
High Levels of Complement C4
- Acute or chronic inflammation
- Autoimmune disorders including rheumatoid arthritis
- Cancer particularly blood cancer
Further testing including genetic testing, autoantibody test, and complement C3 test is advised.
