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HelpTest ID: C4 Complement C4, Serum
Reporting Name
Complement C4, SUseful For
Investigating an undetectable total complement (CH50)
Confirming hereditary angioedema (with low C1 inhibitor)
Assessing disease activity in systemic lupus erythematosus, proliferative glomerulonephritis, rheumatoid arthritis, and autoimmune hemolytic anemia
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.
C4 may be decreased in systemic lupus erythematosus, early glomerulonephritis, immune complex disease, cryoglobulinemia, hereditary angioedema, and congenital C4 deficiency.
Interpretation
C4 levels will be decreased in acquired autoimmune disorders, in 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
Analytic Time
1 dayDay(s) and Time(s) Performed
Monday through Saturday; 3 p.m.
Clinical Reference
1. Ross SC, Densen P: Complement deficiency states and infection: epidemiology, pathogenesis, and consequences of neisserial and other infections in an immune deficiency. Medicine 1984;63:243-273
2. Frank MM: Complement in the pathophysiology of human disease. N Engl J Med 1987;316:1525-1530
3. Tiffany TO: Fluorometry, nephelometry, and turbidimetry. In Textbook of Clinical Chemistry. Edited by NW Tietz. Philadelphia, WB Saunders Company, 1986, pp 79-97
Method Name
Nephelometry
Specimen Type
SerumSpecimen Required
Container/Tube:
Preferred: Serum gel
Acceptable: Red top
Specimen Volume: 1 mL
Specimen Minimum Volume
0.5 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Serum | Refrigerated (preferred) | 7 days | |
| Frozen | 28 days | ||
| Ambient | 72 hours |
Reference Values
14-40 mg/dL
Test Classification
This test has been cleared or approved by the U.S. 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 |
Forms
If not ordering electronically, complete, print, and send a Renal Diagnostics Test Request (T830) with the specimen.
mml-Cerebrovascular, mml-Headache, mml-Demyelinating-Diseases, mml-Neuroimmunology, mml-Neuromuscular, mml-Pediatric, mml-Spinal-Cord