Description
C4 test measures the amount of C4 proteins in your blood. These proteins are part of your complement system, an important part of your immune system that helps kill disease-causing bacteria and viruses.By measuring complement C4 levels, especially in how they compare with other parts of the complement system, it can diagnose and monitor treatment of certain diseases. One of the diseases that commonly involves abnormal C4 is systemic lupus erythematosus, or lupus, an autoimmune disorder.Decreased C4 level is associated with acute systemic lupus erythematosis, glomerulonephritis, immune complex disease, cryoglobulinemia, congenital C4 deficiency and generalized autoimmune disease.Higher-than-normal complement C4 values may be a sign of cancer or ulcerative colitis. Lower-than-normal complement C4 values could indicate: bacterial infections. hepatitis. malnutrition.
If autoimmunedisorder especially lupus is suspected then symptoms may include rash in the shape of a butterfly across your cheeks,mouth or nose ulcers,hair loss,joint pain and swelling,extreme tiredness,swelling around your eyes, and in your hands and feet and pain in your chest when breathing deeply.A complement test may be used to monitor people with an autoimmune disorder. It is also used to see if treatment for their condition is working. For example, people with active lupus erythematosus may have lower-than-normal levels of the complement proteins C3 and C4.Complement activity varies throughout the body. For example, in people with rheumatoid arthritis, complement activity in the blood may be normal or higher-than-normal, but much lower-than-normal in the joint fluid.
Normal Results
The normal results for this test are:
Total blood complement level: 41 to 90 hemolytic units
C1 level: 14.9 to 22.1 mg/dL
C3 levels: 88 to 201 mg/dL
C4 levels: 15 to 45 mg/dL
Note: mg/dL = milligrams per deciliter.
Increased complement activity may be seen in Cancer,Certain infections,Ulcerative colitis and Decreased complement activity may be seen in Cirrhosis,Glomerulonephritis,Hereditary angioedema,Hepatitis,Kidney transplant rejection,Lupus nephritis,Malnutrition,Systemic lupus erythematosus,Rare inherited complement deficiencies.
If your C3 and C4 levels are reduced, this may be a sign that you have lupus. Usually total complement level is also slightly lower in this situation. Low C3 and C4 levels may also be a sign of alcoholic liver disease, but this is less common. A deficiency in complement C4 levels has been linked to different forms of kidney disease and chronic hepatitis. It has also been found in a number of childhood diseases, including Henoch-Schonlein purpura, a type of inflammation of the blood vessels or Childhood diabetes mellitus.Higher-than-normal complement C4 values may be a sign of cancer or ulcerative colitis.Lower-than-normal complement C4 values could indicate bacterial infections,hepatitis,malnutrition,rejection of a kidney transplant,systemic lupus erythematosus, which is an autoimmune disease affecting the skin, joints, kidneys, and other organs,lupus nephritis, which is a kidney disorder that often occurs as a result of systemic lupus erythematosus,cirrhosis, which indicates significant liver damage,glomerulonephritis, which is a type of kidney disease,hereditary angioedema, which is a rare but serious autoimmune disease that causes swelling in various parts of the body.
