How to Read Complement C3 Test Report

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Complement C3 Test:

Complement C3 is the most important and abundantly found protein of the complement system. Complement system is an important part of the immune system that assists in killing the disease-causing bacteria and viruses. This test measures the amount of C3 proteins present in blood. This helps the doctor in diagnosing and monitoring certain autoimmune diseases like lupus.

Factors involved to understand the normal range of Complement C3 levels:

  1. What is the normal range of Complement C3 test?
  2. What do high Complement C3 levels mean?
  3. Causes of high levels of Complement C3
  4. What do low levels of Complement C3 mean?
  5. Causes of low levels of Complement C3
  6. Are there any risks associated with Complement C3 test?
  7. What other tests are ordered along with Complement C3 test?

What is the normal range of Complement C3 test?

The normal range of Complement C3 blood test is 80-160 milligrams per deciliter (mg/dL) or 0.8 to 1.6 g/L. Some laboratories have a normal range between 88-252 mg/dL for men and 88-206 mg/dL for women. These ranges vary from laboratory to laboratory.

What do high Complement C3 levels mean?

Higher than normal levels of Complement C3 protein indicate a variety of conditions, most commonly associated with inflammation. These levels could be indicative of conditions such as cancer, viral infections, metabolic syndrome, heart disease, and several others.

Causes of high levels of Complement C3

Increased complement C3 activity is associated with injury or inflammation. Conditions such as cancer and ulcerative colitis also cause an increase in the C3 levels in blood. High levels of complement C3 protein is observed during acute and chronic inflammation and in other conditions such as thyroiditis, acute myocardial infarction, etc.

What do low levels of Complement C3 mean?

Lower than normal levels of complement C3 in blood can indicate an inherited component deficiency. Decreased complement C3 activity is also associated with recurrent bacterial infections and autoimmune diseases such as systemic lupus erythematosus.

Causes of low levels of Complement C3

Lower levels of complement proteins are caused due to increased activation or an inherited deficiency. Inherited deficiency leads to increased frequency of recurrent microbial infections. C3 levels are generally decreased in conditions such as:

  • Recurrent bacterial infections
  • Septicemia
  • Fungal or parasite infections
  • Autoimmune diseases such as lupus and rheumatoid arthritis
  • Different forms of kidney diseases
  • Congenital or acquired C3 deficiency

C3 and C4 levels are also decreased in several other conditions such as alcoholic liver disease, cirrhosis, malnutrition, and serum sickness. Mishandling of the samples may affect the results and give falsely low results.

Are there any risks associated with Complement C3 test?

Risks associated with a blood test are minor and may include:

  • Excessive bleeding
  • Fainting or feeling lightheaded
  • Hematoma
  • Infection
  • Bruising at the site of puncture, etc.

These do not require specific treatments and may fade away on their own.

What other tests are ordered along with Complement C3 test?

Often, a Complement C4 test is ordered along with C3 test as in certain conditions, such as lupus, both the components are low. This helps the doctor rule out various problematic conditions and makes the diagnosis easier. A total complement activity test, or CH50, is also ordered by the health-care provider.

Other blood tests include tests to estimate the amount of antibodies in blood in cases of injury, inflammations, and infections, erythrocyte sedimentation rate (ESR), and C-reactive protein estimation tests. In some cases, kidney function tests, liver function tests, and other tests are ordered by the health-care provider to determine if the kidneys, liver, and muscles are involved. A follow-up testing is generally ordered depending upon the results of these tests.

Since Complement C3 is a simple blood test, no special preparation is required. However, it is important to give your health-care provider all the information about the herbs, medicines, vitamins, and supplements you may be taking. Test results may vary according to the method used, age, different laboratories, etc. and it is important to discuss with your health-care provider about what the results may mean for you.Increased levels of lipids, haemolysis,may affect the assay result of this test.

Complement tests are generally ordered when the doctor suspects that signs and symptoms observed, point to an autoimmune disorder. It is also ordered to determine the severity of the disorder, if present, and to monitor the progress of an ongoing treatment.


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