Complement components C3 and C4
| Specimen: |
5mL blood in plain tube.
The specimen should be placed once and transported immediately to the laboratory.
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| Method: |
Immunoassay.
Functional assay if primary deficiency is suspected.
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| Reference Interval: |
C3: 0.9-1.8 g/L
C4: 0.16-0.50 g/L.
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| Application: |
Monitoring activity of immune complex mediated disease eg, SLE, Cryoglobulinaemia.
Detection of primary deficiency of C3 or C4 (rare).
Assessment of angioedema, see also C1 esterase inhibitor.
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| Interpretation: |
Reduced C4 with or without reduced C3: activation by classical pathway (eg, SLE, immune complex disease / Cryoglobulinemia).
Reduced C3 with normal C4: activation by the alternative pathway (eg, sepsis, endotoxin).
Raised C3 and/or C4: acute phase response.
Reduced C4 normal C3 colon C1 inhibitor deficiency
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| Reference: |
Giglas P. In: Rose NR et al eds. Manual of Clinical Laboratory Immunology. 5th ed. ASM Press 1997.
Wen L et al. Journal of Allergy and Clinical Immunology. 2004; 113: 585-93.
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