Complement Fixation Test to C. burnetii

Written by Ann Pietrangelo | Published on August 20, 2012
Medically Reviewed by George Krucik, MD

What Is a Complement Fixation Test to C. Burnetii?

A complement fixation test to C. burnetii is a blood test that checks for antibodies to Coxiella burnetii (C. burnetii) bacteria in your bloodstream.

Why Is the Test Ordered?

C. burnetii can cause Q fever. You may be exposed to the bacteria through contact with infected animals. Veterinarians, ranchers, and others who work with animals are at an increased risk of infection. If you work with animals and have symptoms of Q fever, your doctor may order this test.

When you are exposed to C. burnetii bacteria, your body defends against the attack by forming antibodies. Detecting these antibodies in your blood will help your doctor diagnose Q fever.

According to the Centers for Disease Control and Prevention, about 3 percent of healthy people in the U.S. and as many as 20 percent of people in high-risk professions (veterinarians, ranchers, etc.) have higher-than-normal levels of antibodies because they were exposed to C. burnetii bacteria sometime in the past (CDC).

Doctors sometimes order two complement fixation tests and space them out by several weeks to see if your antibody levels change. An increase in your antibody levels will tell your doctor that you have a current infection.

How the Test Is Performed

A complement fixation test is a routine blood test. No preparation or fasting is required.

A nurse will disinfect an area of skin on your arm or hand. He or she will wrap an elastic band around your upper arm to make your vein swell with blood.

A needle will be inserted into your vein and your blood drawn into a small vial. You will likely feel a prick from the needle or a slight stinging sensation. When the vial is full, the nurse will remove the elastic band and needle and place a small bandage over the puncture site. The blood test should take only a few minutes.

Most people feel little pain during or after the test. In rare cases, patients may experience lightheadedness, excessive bleeding, or an infection at the puncture site. If you have any of these symptoms, contact your doctor immediately.

Your blood sample will be sent to a laboratory for analysis and your doctor will go over the results with you.

What the Test Results Mean

If antibodies to C. burnetii are detected, it means that you are infected with or have at least been exposed to the bacteria. Your doctor may need to order additional compliment fixation tests to determine whether you have an active infection.

the test is done when you first start having symptoms, it may be too early in the infection for the antibodies to be detected in your blood. Your doctor may have to repeat the test in a few weeks to see if yourantibody levels have changed.

About Q Fever

Q fever is a bacterial infection that can affect the heart, lungs, liver, and other parts of your body. You can become sick after contact with infected animal feces, milk, urine, and birth by-products, such as placenta from sheep, cattle, and goats.

People who work with animals should wash their hands often and disinfect potentially contaminated areas thoroughly. Those who have a weak immune system have a greater risk of developing Q fever. People with heart valve defects are also at a higher risk and may have more severe cases of Q fever.

About 50 percent of people who are infected with C. burnetii never have any symptoms at all. If you have them, symptoms of Q fever usually develop within two to three weeks of exposure to the bacteria. Symptoms may include:

  • cough
  • high fever
  • chest pain
  • headache
  • jaundice (yellowing of the skin)
  • muscle pain
  • shortness of breath
  • clay-colored stools
  • diarrhea
  • abdominal pain
  • fatigue
  • chills and night sweats
  • rash

Most cases of Q fever are mild, but serious complications can sometimes occur. Q fever is considered chronic if it continues for more than six months.

Treating Q Fever

The most effective treatment for Q fever is antibiotics, such as doxycycline. Antibiotics are most effective if you start taking them when your symptoms first begin. Rather than wait, doctors often begin treatment before the blood test results are in.

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