C3 Complement Test (Serum) – Role in Autoimmune and Infectious Disease Monitoring
C3 Complement Test (Serum).
Synonyms: C3, Complement C3, C3 Complement Test
Abstract
C3 Complement Test: Complement levels, particularly C3, are valuable in monitoring autoimmune disease progression and detecting genetic deficiencies related to recurrent pyogenic infections.
Specimen Details
- Type: Serum
- Container: Red top tube
Storage Instructions
Allow the specimen to clot for 15–30 minutes at room temperature, followed by 30–60 minutes at 4°C. If the test is not performed immediately, refrigerate the serum at 4°C.
Reference Range
Fresh serum: 900–2000 μg/mL
Use
This test is used to:
- Detect inherited or acquired deficiencies of C3
- Monitor diseases involving excessive complement consumption, including:
- Systemic lupus erythematosus (SLE)
- Membranoproliferative glomerulonephritis
- Chronic active hepatitis
- Poststreptococcal glomerulonephritis
- Other infections
Methodology
- Radial Immunodiffusion (RID)
- Rate Nephelometry
Limitations
Measures both biologically active and inactive forms of C3, which may limit diagnostic specificity.
Additional Information
C3 constitutes approximately 70% of total complement proteins and is critical for both classical and alternative complement activation pathways. Elevated C3 levels may occur during acute phase inflammatory responses.
Decreased C3 levels are associated with lupus nephritis, subacute bacterial endocarditis, DIC, and rare inherited deficiencies. Although a decrease is rare, it may occur in chronic infections, hemolytic uremic syndrome, or immune complex diseases. C3 is also occasionally detectable on red cell surfaces in autoimmune hemolytic anemias via a Coombs’ test.
References
- Colvin RB, Bhan AK, McCluskey RT, eds. Diagnostic Immunopathology, Raven Press, 1988.
- Frank MM, “Complement in the Pathophysiology of Human Disease,” New Engl J Med, 1987, 316:1525–1530.
- Nusinow SR, Zuraw BL, Curd JG, “Hereditary and Acquired Deficiencies of Complement,” Med Clin North Am, 1985, 69:487–504.
- Jacobs, Demott, Finley, Horvat, Kasten.JR, & Tilzer, Laboratory Test Handbook, Lexi-Comp Inc, 1994.
