One of the ways your body protects itself from bacteria and viruses is by producing antibodies to fight them. Another way is through your immune system.
Your immune system can respond to threats before your body forms antibodies. For example, your skin helps keep germs out of your body. Chemicals in your blood help heal cells that are injured by infection. Special proteins help “tag” pathogens for destruction.
Your complement system is part of your innate immune system. It consists of a set of nine proteins, numbered C1 through C9. They help your body recognize foreign cells that may cause disease. Certain health problems can cause deficiencies in these proteins.
Your doctor can order blood tests to check your complement protein levels. One of these tests is the C1 esterase inhibitor test or C1-INH test. The C1-INH test can help your doctor determine if you have enough C1-INH.
Why is the test ordered?
Your doctor may order a C1-INH test if you have unexplained inflammation or swelling, known as edema. Your doctor may also order a C1-INH test to assess you for hereditary angioedema (HAE). Symptoms of HAE are:
- swelling in feet, face, hands, airway, and gastrointestinal wall
- abdominal pain
- nausea and vomiting
Your doctor can use a C1-INH test to learn how you’re responding to treatment for autoimmune diseases, such as systemic lupus erythematosus (SLE), as well.
How is the test administered?
You don’t need to take special steps to prepare for a C1-INH test. All it requires is a blood sample.
A nurse or technician will take a sample of your blood using a needle. They will collect your blood in a tube. Then they will send it to a lab for analysis. Your doctor will explain your results, once they’re available.
What are the risks of the test?
The C1-INH test involves minimal risks. You may experience some discomfort when your blood is drawn. You may also feel some pain at the puncture site during or after your blood draw.
Other potential risks of a blood draw include:
- difficulty obtaining a sample, resulting in multiple needle sticks
- excessive bleeding at the needle site
- accumulation of blood under your skin, known as a hematoma
- fainting as a result of blood loss
- infection at the puncture site
