Does this test have other names?
Complement component 3, C3
What is this test?
This test measures the amount of C3 proteins in your blood. These proteins are part of your complement system. This is an important part of your immune system. It helps kill bacteria and viruses that cause disease.
C3 protein is the most important and abundant protein in the complement system. It covers microbes to destroy them. The test measures complement C3 levels and how they compare with other parts of the complement system. With this information, your healthcare provider can diagnose and track treatment of certain diseases. One of the diseases that often causes abnormal C3 is systemic lupus erythematosus (SLE). Lupus is an autoimmune disorder.
Why do I need this test?
You may need this test if your healthcare provider thinks you may have lupus or another autoimmune disease. Symptoms of lupus may include:
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Rash in the shape of a butterfly across your cheeks
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Mouth or nose ulcers
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Hair loss
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Headache
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Light sensitivity
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Fever
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Joint pain and swelling
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Extreme tiredness
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Swelling around your eyes, and in your hands and feet
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Pain in your chest when breathing deeply
You may also have the test if you get repeated bacterial infections. And if you have been diagnosed with an autoimmune disease, you may have this test to track its progress.
What other tests might I have along with this test?
Your healthcare provider may also order a total complement activity test. This is also called CH50. This test measures all nine components of the complement system, from C1 to C9.
Healthcare providers often order a complement C4 test along with a complement C3 test. In certain diseases, both components are low. In other diseases, only one component is low. In lupus, both C3 and C4 levels are usually low.
If your healthcare provider thinks you may have lupus, you may have other blood tests to see how your immune system is working. These may include:
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Tests to measure antibodies in your blood
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Erythrocyte sedimentation rate (ESR) and C-reactive protein tests, which measure inflammation
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Panels of tests to see if your kidneys, liver, and muscles are affected
What do my test results mean?
Test results may vary depending on your age, gender, health history, and other things. Your test results may be different depending on the lab used. They may not mean you have a problem. Ask your healthcare provider what your test results mean for you.
The normal range for a complement C3 blood test is 75 to 175 milligrams per deciliter (mg/dL), or 0.75 to 1.75 grams per liter (g/L).
Your complement levels will often rise very high just after an infection or injury. When your complement system responds to ongoing disease such as lupus, levels usually go down.
You can inherit a deficiency in your complement C3. But it's much more common to acquire a deficiency. If only your C3 complement level is low and all other complement components are normal, it's usually because of an inherited component deficiency. This makes it more likely that you will develop certain autoimmune disorders.
More often, you will have low levels of several complement components at once. This is the result of an acquired disease. If your C3 and C4 levels are reduced, this may be a sign that you have lupus. With lupus, your total complement level may be slightly lower. Low C3 and C4 levels may also be a sign of alcoholic liver disease. But this is less common.
Other conditions linked to low C3 levels include:
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C3 deficiency, a condition that causes recurrent bacterial infections
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Different forms of kidney disease
If you are being treated for a disease like lupus and your complement C3 and C4 levels go up, it is usually a sign that your treatment is working.
How is this test done?
The test is done with a blood sample. A needle is used to draw blood from a vein in your arm or hand.
Does this test pose any risks?
Having a blood test with a needle has some risks. These include bleeding, infection, bruising, and feeling lightheaded. When the needle pricks your arm or hand, you may feel a slight sting or pain. Afterward, the site may be sore.
What might affect my test results?
If the blood sample is mishandled, your C3 levels may be falsely low. If the C3 test is done as part of a total complement activity test, the test should be repeated if low levels are found.
How do I get ready for this test?
You don't need to prepare for this test. Tell your healthcare provider about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illegal drugs you may use.
FAQs
Complement C3 is a blood test that measures the activity of a certain protein. This protein is part of the complement system. The complement system is a group of nearly 60 proteins that are in blood plasma or on the surface of some cells.
Is C3 high or low in lupus? ›
In lupus, both C3 and C4 levels are usually low.
Is C3 an inflammatory marker? ›
Increased C3 levels may also be a sign of: Heart attack (myocardial infarction) and other heart problems. Sarcoidosis (inflammatory disease). Some types of cancer.
What diseases are associated with complement C3? ›
Decreased C3 may be associated with acute glomerulonephritis, membranoproliferative glomerulonephritis, immune complex disease, active systemic lupus erythematosus, septic shock, and end-stage liver disease.
What is complement C3 inflammation? ›
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.
Is C3 a tumor marker? ›
Complement C3 may be used as a marker for the diagnosis of early-stage PC, while complement C4b1 and apoE are closely correlated with tumor development, reflecting the biological behavior of PC, and thus may be used as diagnostic markers of advanced PC.
Is C3 elevated in rheumatoid arthritis? ›
Results: Levels of complement C3, significantly elevated in RA, axSpA and PsA patients, were associated with the prevalence of cardiometabolic risk factors. Hard clustering analysis identified two distinctive phenotypes of patients depending on the complement C3 levels and insulin sensitivity state.
What number is positive for lupus? ›
The initial requirement of the criteria for lupus diagnosis is a positive ANA test with a titer of at least 80. The numerical value of the titer refers to the ratio of blood serum being evaluated to a dilution agent.
What indicates lupus on a CBC? ›
Complete blood count (CBC): checks for low counts of red blood cells, white blood cells and platelets. Complement tests: measures the level of complement — proteins in your blood that help destroy foreign substances. Low levels of complement can indicate lupus.
What clinical infections are associated with C3? ›
[7] A deficiency of C3 is associated with severe recurrent pyogenic infections early in life. [8] Deficiencies of the late common pathway (C5, C6, C7, C8, and C9) are associated with increased Neisseria infections, including Neisseria meningitidis and Neisseria gonorrhoeae.
The University Reference Laboratories normal range for C3 is 80–178 mg/dl, for C4 is 12–42 mg/dl, for CRP is 0.0–3.0 mg/l, and for ESR is 0–14 mm/h for males under 50 years old, 0–19 mm/h for females under 50 years old, 0–19 for males between 50 and 80 years old, and 0–29 mm/h for females between 50 and 80 years old.
What is the most sensitive marker for inflammation? ›
C-reactive protein (CRP), the classic acute-phase protein, is not directly involved in the coagulation process but is an exquisitely sensitive objective marker of inflammation, tissue damage, and infection.
What bacteria is commonly associated with C3 deficiency? ›
Inherited C3 deficiency results in repeated, severe infections starting from birth, especially those of the respiratory tract. Organisms such as Streptococcus pneumoniae and Hemophilus influenzae are the most frequent causes of infection.
What activates C3 complement? ›
The C3 protein is essential for turning on (activating) the complement system. The presence of foreign invaders triggers the C3 protein to be cut (cleaved) into two smaller pieces. One of these pieces, called C3b, interacts with several other proteins on the surface of cells to trigger the complement system's response.
What are the symptoms of C3 deficiency? ›
Recurrent fever
- Abnormality of metabolism/homeostasis. Recurrent fever.
- Abnormality of the genitourinary system. Nephrotic syndrome. Renal insufficiency.
- Abnormality of the immune system. Decreased circulating complement C3 concentration. ...
- Abnormality of the respiratory system. Recurrent pneumonia.
In C3G, tiny filtering units in the kidney (glomeruli) become damaged and leak red blood cells, which appear in the urine and change its color. Excess protein in the urine (proteinuria): This happens when higher than normal amounts of protein leak into the urine, causing the urine to look foamy, cloudy, and/or dark.
What is complement C3 in the pancreas? ›
Complement Component C3 Is Highly Expressed in Human Pancreatic Islets and Prevents β Cell Death via ATG16L1 Interaction and Autophagy Regulation. Cell Metab.
What happens if C3 and C4 are high? ›
If your results show increased levels or activity of complement proteins, it may mean that your body has acute or chronic inflammation. Increased levels may be a sign of the following conditions: Certain types of cancer, such as leukemia or non-Hodgkin lymphoma.
What does C3 complement protein deficiency lead to? ›
Deficiencies in the alternative pathway: C3, factors D, B, and properdin. Inherited C3 deficiency results in repeated, severe infections starting from birth, especially those of the respiratory tract.
