How to Read Complement C4 Test Report

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Complement C4 Test:

Complement C4 is an integral part of the complement system which is a vital part of our immune system. Complement C4 is involved in eliminating certain infection. The complement C4 test measures the amount of this component in blood. The test is often ordered when signs and symptoms of an autoimmune disease are observed.

Factors involved to understand the normal range of Complement C4 levels:

  1. What is normal range of Complement C4 test?
  2. What do high levels of Complement C4 mean?
  3. Causes of high levels of Complement C4
  4. What do low levels of Complement C4 mean?
  5. Causes of low levels of Complement C4
  6. Precautions to be taken to maintain normal levels of Complement C4
  7. Are there any risks associated with Complement C4 test?
  8. What other tests are ordered along with Complement C4 test?

What is normal range of Complement C4 test?

Normal range for complement C4 in blood is 16-48 mg/dL. Normal results may vary from laboratory to laboratory.

What do high levels of Complement C4 mean?

Higher than normal levels of complement C4 are generally during chronic or acute inflammation. It may also be a sign of cancer or ulcerative colitis. Increased levels of complement C4 indicate various conditions such as:

  • Thyroiditis
  • Acute myocardial infarction
  • Sarcoidosis
  • Juvenile rheumatoid arthritis
  • Viral infections
  • Non-alcoholic fatty liver disease
  • Metabolic syndrome
  • Diabetes and heart disease

Higher concentrations of complement C4 may not exactly indicate the condition present but it helps the doctor to determine involvement of immune system with the condition.

Causes of high levels of Complement C4

Inflammatory conditions lead to an increase in C4 levels in the blood. The levels of C4 rise with low-grade inflammation. Inflammatory conditions that cause an increase in C4 levels include:

  • Obesity, C4 levels increase with BMI
  • Skin conditions such as psoriasis, dermatitis, and hives
  • Ulcerative colitis and Crohn’s disease
  • Psoriatic arthritis and rheumatoid arthritis
  • Rheumatic fever
  • Inflammation and kidney failure
  • Certain types of cancers such as Hodgkin’s lymphoma, leukemia, and sarcoma
  • Infection or injury

Levels of C4 are also seen to be elevated during pregnancy and due to use of certain drugs such as cimetidine.

What do low levels of Complement C4 mean?

Lower than normal levels of complement C4 are associated with autoimmune disorders such as systemic lupus erythematosus. They could also indicate a number conditions such as:

  • Bacterial infections
  • Hepatitis
  • Malnutrition
  • Cirrhosis
  • Lupus nephritis
  • Rare inherited complement deficiencies

Lower C4 levels may also be a sign of alcoholic liver disease. If C4 levels are lower because of acute or chronic infections, treatment of underlying condition brings the C4 levels back to normal.

Causes of low levels of Complement C4

Several conditions cause a decrease in the complement C4 levels. These include:

  • Recurrent bacterial infections
  • Autoimmune diseases
  • Hereditary complement deficiency
  • Hereditary or acquired angioedema
  • Several kidney diseases such as IgA nephropathy, lupus nephritis
  • Kidney transplant rejections
  • Chronic liver disease
  • A high fat diet

Precautions to be taken to maintain normal levels of Complement C4

Autoimmune diseases involve a lot of factors and may vary from one person to another. It is important to work with your healthcare provider to treat the underlying conditions that may cause your complement levels to be abnormal.

To prevent decrease in the levels of C4, it is advised to refrain from over eating and reducing intake of fatty foods. Supplements such as mangosteen are thought to boost up C4 levels. Avoiding cannabis, exposure to heavy metals and allergens is recommended to avoid C4 levels from going lower than normal.

Certain lifestyle and dietary changes can help reduce the risk of chronic inflammation and prevent the elevation in C4 levels. These changes may include losing weight, exercises, getting enough sleep, reducing stress, consuming an anti-inflammatory diet, etc.

Are there any risks associated with Complement C4 test?

Most people don’t experience any serious side effects with blood tests. If complications arise, although they are very rare, they include:

  • Soreness at the area of puncture
  • Mild bruising or throbbing at the area
  • Excessive bleeding
  • Fainting or feeling lightheaded
  • Infection at the site of punctures

They do not require any treatment and may gradually fade on their own.

What other tests are ordered along with Complement C4 test?

Along with complement C4 test, a total complement activity test or CH50 test is recommended. The test estimates all the nine components of the complement system. A separate complement C3 test is also ordered along with complement C4 test. This is because in certain conditions, like lupus, both the components are low.

Additional testing is advised when the doctor suspects the presence of an autoimmune disease. If the doctor suspects lupus, additional blood tests are ordered to check the functioning of the immune system. These tests include measurement of antibodies in blood, sedimentation rate or ESR, C-reactive protein test, and kidney and liver function test panels.

A follow up testing or treatment is recommended based on the results of these tests.

The test requires no special preparation. Complement C4 test is often ordered when the doctor suspects signs and symptoms of autoimmune diseases. The complement activity is measured to determine the severity of the disorder or to check if the treatment is working.

Test results may vary according to the underlying conditions and discussing with your doctor about what the results may mean for you is important. Your doctor may recommend other tests to confirm the diagnosis of suspected autoimmune disorders.


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