C4 Complement, Functional, Serum
Use
This test is useful for the diagnosis of C4 deficiency and is also appropriate for investigating a patient with an undetectable total complement level. C4 is a component of the classical pathway in the complement system, and deficiency may lead to increased susceptibility to infections and autoimmune conditions such as systemic lupus erythematosus (SLE) or rheumatoid arthritis.
Special Instructions
The total complement assay (COM / Complement, Total, Serum) should be used as a preliminary screening tool for complement deficiencies before ordering individual component assays. Proper specimen handling is critical to prevent activation of the complement system before testing.
Limitations
Complement proteins may be present but nonfunctional, which this test can help detect. If low C4 functional levels are reported but C4 antigen levels are normal, confirmatory testing on a new serum specimen is recommended to rule out activation during shipping.
New York Approved
Methodology
Automated Analyzer (Clinical Chemistry)
Biomarkers
LOINC Codes
- 93978-5
- 93978-5
Result Turnaround Time
1-3 days
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
1 mL
Minimum Volume
0.5 mL
Container
Plastic vial, preferred Serum gel; acceptable Red top
Collection Instructions
Immediately after collection, place the tube on wet ice and allow to clot. Centrifuge at 4 degrees C, aliquot serum into a plastic vial, and freeze within 30 minutes. Use dry ice if not frozen immediately.
Patient Preparation
Fasting for 12 hours is preferred but not required.
Storage Instructions
Specimen stability is 14 days when frozen.
Causes for Rejection
Gross hemolysis, gross lipemia
Stability Requirements
| Temperature | Period |
|---|---|
| Frozen | 14 days |