Complement 3 (C3) Test

complement c3 test

Last Updated December 20th, 2021

What is the Complement 3 test?

The complement test measures the level of C3 protein in the blood. The protein is an important component of the complement system which in turn is a vital part of the immune system. The complement system enhances the efficiency of the immune system for clearing invading pathogens and damaged or dead cells from the body. The system is made up of more than 30 proteins which are mainly synthesized by the liver.

The nine major proteins of this system are designated from C1 to C9. C3 is one of the main proteins of the system and it contains 13 different domains. Its deficiency can lead to various infections and the test is used to monitor various immune complex diseases like SLE and some other blood associated infectious diseases. One of the major causes of abnormal C3 levels is lupus erythematosus which is an autoimmune disorder.

The nine different proteins along with the other ones, form different protein complexes in response to an infection. They approach an infection in three different pathways which ultimately lead to the formation of one complex, which is the membrane attack complex (MAC). THE MAC binds itself to the surface of the invading microbe and acts to destroy the same.

It also mobilises the WBCs and attracts them to the site of infection while stimulating the process of phagocytosis. The components of the complement system can be measured together or individually. One of the common tests that are used is the total hemolytic complement or a CH50 measurement. In general, the C3 and C4 proteins are the most frequently measured ones. In some cases, each of the nine components can be measured independently to look for any specific hereditary traits or deficiencies.
Low levels of C3 can be seen in case of infections and other immunity related illnesses. In the case of an autoimmune disease, the complement system can be affected and the levels of C3 can decrease. The doctor might need to check the integrity of the entire system depending on the symptoms and the medical history of the patient. In some rare cases, the patient may have an inherited deficiency of the protein. The abnormal levels of the C3 protein are also associated with the following diseases and conditions.

Acute bacterial infections
Kidney disease
High levels are associated with conditions like cancer, ulcerative colitis or thyroiditis.

Why do I need to undergo a Complement 3 test?

The test is used for various reasons, some of which are mentioned below.

– To diagnose the cause of periodic microbial infections like pneumonia, meningitis, gonorrhea or angioedema.

– Help diagnose and monitor the progress in the treatment of acute or chronic autoimmune diseases such as lupus and rheumatoid arthritis.

– To monitor immune complex-related diseases and conditions such as glomerulonephritis, serum sickness, and vasculitis.

The low levels of the protein can also be associated with symptoms like the ones mentioned below.

– Extreme Fatigue
– Muscle or joint pain
– Unintended weight loss
– Muscle Weakness or paralysis

The test is also done to check for any autoimmune disorder, especially lupus. The following are the common symptoms of lupus.

– Rash in the shape of a butterfly on the face.
– Mouth or nose ulcers
– Hair loss
– Joint pain and swelling
– Extreme tiredness
– Swelling around the eyes, and in hands and feet
– Pain in the chest while breathing deeply

How is the test performed?

The test is simple and the process is similar to any other blood test. It involves the collection of a blood sample from the patient through the process known as a venipuncture. In this process, a needle is inserted into a vein to draw the required volume of blood. The following steps describe the process in detail.

– At first, a band is tied in the upper arm to make the veins swell with blood, thus making them easily visible. The collection site is generally around the elbow region and the healthcare practitioner disinfects the collection site with an antiseptic swab. In some cases, the collection site may also be chosen from the back of the hand.

– In the next step, a small needle is inserted into the vein and the required volume of blood is drawn through it in an attached vial. A stinging sensation is felt when the needle is inserted.

– Once the collection is complete, the band is then loosened to reduce pressure on the veins and the needle is gently withdrawn. Some amount of pressure is applied on the site through a gauze or a cotton piece to prevent any excessive bleeding. The spot is then covered with a sterile bandage and the sample is sent to the laboratory for testing.

– The entire process is safe and is generally completed within five to ten minutes. Since the size of the veins can differ depending on the individual, multiple punctures may be needed for some patients before the right vein is found.

– A few patients might feel dizzy or lightheaded after the collection process and may require special care. Soreness or bruising in and around the collection site is common and is generally cured within a few days.

Hematoma or accumulation of blood under the skin can also occur at times. Infection or excessive bleeding from the collection site is rare but might happen in exceptional cases, which needs immediate treatment.

What is the price for a Complement 3 test in India? 

The cost of the test varies between Rs 400 to Rs 1200 depending on the location and facilities provided in the testing center.

When will I get the test results?

Depending on the laboratory, the test results are generally delivered within 24 to 72 hours.

What is the normal range for a Complement 3 test?

The normal range of C3 protein for all age groups is between 88 to 201 milligrams per deciliter (mg/dL)

What do the results mean?

The test results depend on a number of factors and an abnormal result does not necessarily indicate a problem. The doctor has to look into the symptoms and case history to make a correct diagnosis. In many cases, when the low levels are due to a particular health condition, they return to normal once the condition is resolved. Apart from immune diseases and bacterial infections, lower levels are also associated with the following illnesses.

– Hereditary and acquired angioedema
– Various types of kidney disease and kidney transplant rejection.
– Fungal or other parasitic infections like malaria.
– Serum sickness.
– Hereditary angioedema

The higher levels of the protein can be due to chronic inflammation. Other than that higher levels are associated with the following diseases.

– Cancer (leukemia, Hodgkin lymphoma or sarcoma)
Ulcerative colitis
– Thyroiditis
– Acute myocardial infarction
– Juvenile rheumatoid arthritis

Do I need to fast for the Complement 3 test?

No fasting or any special preparation is needed before the test.

What else do I need to know before I appear for a Complement 3 test?

The test serves an important function in pointing out some inherent conditions that can benefit the patient in the long run. A few points regarding the test are noted for providing a broader outlook about it.

– While the test does not indicate a particular disease, it points out that the immune system is related to the conditions.

– In case only your C3 complement components are low and all other protein levels are normal, it may be due to an inherited deficiency.

– In case you are being treated for a particular autoimmune disease like lupus and your C3 and C4 levels move up, it indicates that the treatment is working.

– For the right diagnosis, this test can also be accompanied by other blood tests like sedimentation rate, C-reactive protein tests, etc. to determine the exact nature of the ailment.

Can pregnant women undergo a Complement 3 test?

Pregnant women can undergo the test without any restrictions.

Is the Complement 3 test possible for new-born babies?

The test is possible for new-born babies as per the doctor’s advice.


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