Tularemia test; Serology for Francisella tularensis
Antibodies defend the body against some bacteria, viruses, fungi, or other foreign substances called antigens. Certain cells of the immune system cause the body to produce antibodies during an active infection.
When you first get sick, few antibodies may be detected. Antibody production increases during the course of an infection. For this reason, antibody tests are often repeated several weeks after the first test is done, so the results can be compared. A rising level of antibodies tells the health care provider that there is an infection.
This test looks for antibodies to F. tularensis in the clear liquid portion of the blood, which is called the serum. (This technique is called serology.) The presence of these antibodies means you have a current or past infection with F. tularensis. In some cases, a single high level of antibodies that are specific to F. tularensis may mean you have an infection.
There is no special preparation.
When the needle is inserted to draw blood, you may feel moderate pain, or only a prick or stinging sensation. Afterward, there may be some throbbing.
This blood test may be performed when tularemia is suspected.
Antibodies are absent. However, during the first few days to weeks of exposure to an antigen, there may be slight antibody production. As the disease progresses, more antibodies will be present. If a disease is suspected, the test may need to be repeated several weeks after the first test.
Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results
If antibodies are detected, there has been exposure to Francisella tularensis (possible tularemia).
Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight but may include:
A serology test can determine whether you have ever been exposed to a certain antigen, but this does not mean that you have a current infection. Increasing antibody levels are more likely to indicate a current infection.
Schaffner W. Tularemia and other Francisella infections. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007 chap 332.
Penn RL. Francisella tularensis (Tularemia). In: Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Diseases. 7th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2009:chap 119.