This blood test looks for antibodies against Francisella tularensis, the bacteria that cause the disease tularemia.

This blood test may be performed when tularemia is suspected.

Antibodies defend the body against bacteria, viruses, fungi, or other foreign substances, calledantigens. Certain cells 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 indeed an infection.

This test specifically 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 particular antibodies indicates a current or previous infection with F. tularensis. In some cases, a single high level of antibodies specific to F. tularensis can indicate 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.