The measurement of the C4 component of complement in serum is used to screen patients with deficient total complement concentration, screen for hereditary angioedema, evaluate disease activity in systemic lupus erythematosus, glomerulonephritis, rheumatoid arthritis, and autoimmune hemolytic anemia.
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Complement is a term that describes 20 specific serum proteins belonging to the globulins that, in combination with antigen-antibody complexes, cause lysis of erythrocytes sensitized to the antibody contained in the complex. The nine main components of the supplement are called C1 through C9.
Complement component C4 is one of the nine essential components of the complement protein complex and participates only in the classic pathway of complement activation. The C4 component is also found naturally in human colostrum. Complement component C4 deficiency is an inherited autosomal recessive trait that reduces infection resistance. The activation of complement functions occurs during phagocytic activity; microorganisms are destroyed, and an inflammatory response is also observed. Measuring C3 and C4 levels helps distinguish the cause of glomerulonephritis because C3 is decreased, but C4 is usually standard when the cause is post-streptococcal.
Possible Interpretations of Pathological Values
- Increase: Cancer, chronic urticaria, dermatomyositis, juvenile rheumatoid arthritis, keratoconus, rheumatoid arthritis
- Decrease: Chronic bronchitis, cigarette smoking, congenital C4 deficiency, cryoglobulinemia, glomerulonephritis, purple Henoch-Schoenlein, hepatitis (chronic active), hereditary angioedema, hyperglycemia seronegative, subacute bacterial endocarditis, systemic lupus erythematosus (active), interstitial tubular nephritis and uveitis (TINU syndrome)
Important Note
Laboratory test results are the most important parameter for diagnosing and monitoring all pathological conditions. Between 70% and 80% of diagnostic decisions are based on laboratory tests. Correct interpretation of laboratory results allows a doctor to distinguish "healthy" from "diseased."
Laboratory test results should not be interpreted solely based on the numerical result of a single analysis. They should be interpreted in relation to each individual case, family history, clinical findings, and the results of other laboratory tests and information. Your physician should explain the importance of your test results.
At Diagnostiki Athinon, we answer any questions you may have about the test you perform in our laboratory and contact your doctor to ensure you receive the best possible medical care.
