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HelpTest Code C4 Complement C4, Serum
Reporting Name
Complement C4, SUseful For
Investigating an undetectable total complement
Confirming hereditary angioedema (with low C1 inhibitor)
Assessing disease activity in systemic lupus erythematosus, proliferative glomerulonephritis, rheumatoid arthritis, and autoimmune hemolytic anemia
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Specimen Type
SerumSpecimen Required
Supplies: Sarstedt Aliquot Tube 5 mL (T914)
Collection Container/Tube:
Preferred: Serum gel
Acceptable: Red top
Submission Container/Tube: Plastic vial
Specimen Volume: 1 mL
Collection Instructions: Centrifuge and aliquot serum into a plastic vial.
Specimen Minimum Volume
0.5 mL
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Serum | Refrigerated (preferred) | 7 days |
| Frozen | 28 days | |
| Ambient | 72 hours |
Reference Values
14-40 mg/dL
Test Classification
This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.CPT Code Information
86160
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| C4 | Complement C4, S | 4498-2 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| C4 | Complement C4, S | 4498-2 |
Clinical Information
The complement system is an integral part of the immune defenses. It can be activated via immune complexes (classic pathway) or by bacterial polysaccharides (alternative pathway). The classic complement pathway consists of recognition, (C1q, C1r, C1s), activation (C2, C3, C4), and attack (C5, C6, C7, C8, C9) mechanisms with respect to their role in antibody-mediated cytolysis. C4 is one of the activation proteins of the classic pathway.
In the absence of C4, immune complexes will not be cleared by C3 activation peptides, but bacterial infections can still be defended via the alternative pathway.
Complement component 4 may be decreased in systemic lupus erythematosus, early glomerulonephritis, immune complex disease, cryoglobulinemia, hereditary angioedema, and congenital C4 deficiency.
Interpretation
Complement component 4 levels will be decreased in acquired autoimmune disorders, in the active phase of lupus erythematosus, and in rheumatoid arthritis.
An undetectable C4 level (with normal C3) suggests a congenital C4 deficiency.
Levels will be increased in patients with autoimmune hemolytic anemia.
Cautions
The results are dependent on appropriate specimen transport.
Quantitation of specific proteins by nephelometric means may not be possible in lipemic sera due to the extreme light scattering properties of the specimen. Turbidity and particles in the specimen may result in extraneous light scattering signals, resulting in variable specimen analysis.
Reject Due To
| Gross hemolysis | OK |
| Gross lipemia | Reject |
| Gross icterus | OK |
Method Name
Nephelometry
Forms
If not ordering electronically, complete, print, and send a Renal Diagnostics Test Request (T830) with the specimen.
Day(s) Performed
Monday through Friday