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HelpTest ID: C3 Complement C3, Serum
Reporting Name
Complement C3, SUseful For
Assessing disease activity in systemic lupus erythematosus
Investigating an undetectable total complement level
Clinical Information
The complement system is an integral part of the body's immune defenses. It can be activated via immune complexes (classic pathway) or by bacterial polysaccharides (alternative pathway). The primary complement pathway consists of recognition (Clq, Clr, Cls), activation (C4, C2, C3), and attack (C5, C6, C7, C8, C9) mechanisms with respect to their role in antibody-mediated cytolysis.
Complement component 3 activation involves cleavage by C3 convertase into C3a and C3b. When immune complexes are not involved, the alternate method of complement activation initiates the reactant sequence at C3, bypassing C1, C4, and C2.
Severe recurrent bacterial infections occur in patients with homozygous C3 deficiency and in those patients with low levels of C3 secondary to the absence of C3b activator.
Decreased C3 may be associated with acute glomerulonephritis, membranoproliferative glomerulonephritis, immune complex disease, active systemic lupus erythematosus, septic shock, and end-stage liver disease.
Interpretation
A decrease in C3 levels to the abnormal range is consistent with disease activation in systemic lupus erythematosus.
Report Available
Same day/1 to 2 daysDay(s) Performed
Monday through Friday
Clinical Reference
1. Willrich MAV, Braun KMP, Moyer AM, Jeffrey DH, Frazer-Abel A. Complement testing in the clinical laboratory. Crit Rev Clin Lab Sci. 2021;58(7):447-478. doi:10.1080/10408363.2021.19072972
2. Wong EKS, Kavanagh D. Diseases of complement dysregulation-an overview. Semin Immunopathol. 2018;40(1):49-64. doi:10.1007/s00281-017-0663-8
3. Prohaszka Z, Kirschfink M, Frazer-Abel A. Complement analysis in the era of targeted therapeutics. Mol Immunol. 2018;102:84-88. doi:10.1016/j.molimm.2018.06.001
4. Brodszki N, Frazer-Abel A, Grumach AS, et al. European Society for Immunodeficiencies (ESID) and European Reference Network on Rare Primary Immunodeficiency, Autoinflammatory and Autoimmune Diseases (ERN RITA) Complement Guideline: Deficiencies, Diagnosis, and Management. J Clin Immunol. 2020;40(4):576-591. doi:10.1007/s10875-020-00754-1
Method Name
Nephelometry
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
75-175 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 |
|---|---|---|
| C3 | Complement C3, S | 4485-9 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| C3 | Complement C3, S | 4485-9 |
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