Complement C4
Also known as: C4, C4 (β1E Globulin), C4 Complement, Fourth Complement Component
Use
Quantitation of C4 is used to detect individuals with inborn deficiency of this factor or those with immunologic disease in whom hypercatabolism of complement causes reduced levels. These diseases include lupus erythematosus, serum sickness, certain glomerulonephritides, chronic active hepatitis, and others.
Special Instructions
C4 is used only by the classical pathway, so that it is decreased only when this arm is activated. In diseases activating the alternate pathway alone, C4 levels will be normal. Inherited as an autosomal recessive trait with close HLA linkage. Hereditary C4 deficiency has been associated with increased incidence of pyogenic bacterial infections.
Limitations
C4 levels may appear normal in diseases activating the alternate pathway alone. Factors such as excessive lipemia (>250 mg/dL) and rheumatoid factors (>200 IU/mL) can significantly increase the apparent C4 concentration, potentially leading to inaccurate results. Individual results may vary based on presence of concurrent diseases or genetic variability in complement protein levels.
Methodology
Immunoassay
Biomarkers
LOINC Codes
- 4498-2
- 4498-2
Result Turnaround Time
1-2 days
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
1 mL (adult), 0.5 mL (pediatric)
Minimum Volume
Not provided
Container
Red-top tube, gel-barrier tube
Collection Instructions
Allow serum to clot at room temperature for 15 to 30 minutes. Remove serum or plasma after centrifugation and transfer to a plastic transport tube.
Storage Instructions
Maintain specimen at room temperature.
Causes for Rejection
Excessive lipemia (>250 mg/dL) and rheumatoid factors (>200 IU/mL) significantly increase the apparent C4 concentration.
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 2 days |
| Refrigerated | 8 days |
| Frozen | 3 months |