What is complement C3 Test?

An essential and abundant protein of the human body’s immune system, the complement component 3 is more commonly known as C3. This protein forms a part of the complement system that becomes the first line of defence against germs and viruses when the body is under attack due to an illness. The complement C3 blood test measures the activity of this protein and compares it to other components in the complement system.

A doctor can diagnose a condition such as an infection, a disease, or an autoimmune disorder, monitor a patient’s existing condition, and keep track of its progress with the test results.

What is the complement C3 used for?

The complement C3 test measures the activity of proteins that help boost the immune system in the body. Anyone with a deficiency of this protein is more likely to develop certain infections or diseases. As an inflammatory marker, this test indicates chronic bacterial or fungal infections, parasitic infections, oedema or swelling, and symptoms of autoimmune disorders.

Understanding the test results of the complement C3 Test

Test results depend on numerous factors ranging from age, sex, existing conditions, and medical history. 88 to 201 milligrams per deciliter (mg/dL) or 0.88 to 2.01 grams per litre is considered the normal range. Elevated or lower complement C3 levels could be signs of an underlying condition that a doctor can diagnose. 

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Frequently Asked Questions:

1. Why do I need the complement C3 test?

A doctor may recommend the complement C3 test to diagnose an infection or monitor an autoimmune disorder when the immune system is malfunctioning. When a patient shows any symptoms of an infection, lupus, kidney or liver conditions, hereditary autoimmune conditions, or even gastrointestinal diseases, it may result in altered C3 protein levels in the body.

2. What happens during a complement C3 test?

During this test, a healthcare professional draws blood from the vein in the arm. After applying an antiseptic, an elastic is wrapped on the upper arm resulting in better blood flow. After they draw blood, the punctured area is covered with a bandage. Blood is collected in a tube and sent for evaluation to a laboratory.

3. What is the normal range for the complement C3 test?

Worldwide, 88 to 201 milligrams per deciliter (mg/dL) or 0.88 to 2.01 grams per litre is the normal range for the test results. Although this range may slightly differ from laboratory to laboratory, it is best advised to consult with a doctor to understand the specific meaning of the test results.

4. What does it mean if your complement C3 is high?

Higher-than-normal or elevated C3 levels indicate that the immune system is active right after an infection or injury. Higher levels could also indicate complex conditions such as diabetes, heart attack, cancer, leukaemia, or ulcerative colitis. If a patient is already under treatment for lupus, higher C3 protein levels usually indicate that the treatment is working.

5. What causes lower C3 levels?

Lower-than-normal C3 levels indicate a range of conditions in a patient. It could be a sign of autoimmune conditions such as lupus or Crohn’s disease, cirrhosis, bacterial infection, malnutrition, hepatitis, hereditary angioedema, chronic kidney or liver conditions, rare inherited complement deficiencies, or even organ rejection. It is advisable to seek a doctor’s professional opinion.

6. What does the C3 complement test for?

The complement component 3 test helps a doctor better understand how a patient’s immune system is working at the moment. By understanding the amount of C3 proteins in the body as compared to other components in the complement system, a doctor can diagnose, monitor, and track certain infections, immune deficiencies, or autoimmune disorders in the patient’s body.

7. Are there any preparations needed before the test?

There are no preparations needed for this test. It is a simple procedure of a healthcare professional drawing blood from the vein at the back of the hand. During needle insertion, some people feel a sting or prick. While there are no side effects of having blood drawn, minor risks include excessive bleeding or lightheadedness.

8. Why is C3 low in lupus?

When a patient is diagnosed with lupus (an autoimmune condition), his/her body suffers from an impaired immune system response. The clear indicator of this is lower C3 and C4 levels in the body. In fact, with lupus, the total complement level in the body is lower-than-normal. The complement C3 test is one of the many tests used to diagnose this condition.

9. What is a complement C3 deficiency?

Complement component 3 (C3) deficiency is a condition that affects C3, the most important and abundant protein in the complement system. This condition is characterised by lower C3 levels that can be either inherited or acquired. Individuals with C3 deficiency are more prone to severe, recurrent infections caused by gram-negative and gram-positive bacteria.
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