Measurements of serum complement components C3 is useful in the diagnosis and monitoring of immune complex disease e.g. SLE (Systemic lupus erythematosus) and some blood associated infectious diseases. Complement concentrations are acute phase proteins and may be normal, despite complement consumption, in some inflammatory and infective disorders. C3 alone is often decreased in infectious disease (septicaemia, endocarditis).
Measurement of serum complement is useful in the monitoring of specific immune complex diseases e.g SLE and infectious diseases post streptococcal disease, subacute bacterial endocarditis.
Though genetic deficiencies of C3 are exceedingly rare, deficiencies in other components which are more common (though still very rare) can result in low C3.
The normal adult range for C3 is 90-180mg/dl.
Values <1mg/dl can be found in active immune complex disease, septicaemia, bacteraemia, post streptococcal glomerulonephritis or diseases associated with nephritic factor. Low levels of C3 associated with low levels of C4 demonstrate classical pathway activation and strongly suggest immune complex disease. They are found most commonly in cases of active SLE (Systemic lupus erythematosus). Low levels of C3 associated with normal levels of C4 demonstrate alternative pathway activation suggestive of infectious disease or nephritic factor activity.
Although in some long standing SLE patients C3 levels remain low, which does not necessarily denote active disease, a sudden fall in levels does usually indicate exacerbation of disease activity and a risk of renal damage.
The complement C3 test results vary depending on the person's health history, age, and sex. The normal range for the complement C3 test is 80 to 160 milligrams per deciliter or 0.8 to 1.6 grams per liter.
The complement levels in the blood rise after an injury or injection, but when the complement system responds to a disease, your complement levels go down.
High C3 complement levels indicate inflammation in the body. The inflammation could be due to ulcerative colitis or other acute diseases like sarcoma, leukemia, or Hodgkin's Lymphoma.
These are all different types of cancer. However, increased levels of C3 are not the main indication of cancer.
Elevated C3 complement levels are also observed in people with diabetes. Therefore, other tests are necessary to confirm the diagnosis.
Higher-than-normal levels of C3 proteins can indicate that you’ve just had an infection and your immune system is responding to it.
If you get treatment for a disease such as lupus, high levels of C3 indicate that the treatment works.
Increased C3 levels may also be a sign of:
- Heart attack (myocardial infarction) and other heart problems.
- Sarcoidosis (inflammatory disease).
- Thyroid disease
- Ulcerative colitis
If C3 values are abnormally high or low, additional tests or procedures may be ordered to narrow or confirm the suspected cause.
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