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Anthrax - blood test
Anthrax serology test; Antibody test for anthrax; Serologic test for B. anthracis
How the test is performed
A blood sample is needed. For information on how this is done, see: Venipuncture
The blood sample is sent to a lab where serology tests are done to look for the bacteria that cause anthrax.
How to prepare for the test
There is no special preparation.
How the test will feel
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.
Why the test is performed
This test may be performed when anthrax is suspected.
A normal result means no antibodies to the anthrax bacteria was seen in your blood sample. However, during the early stages of infection, your body may only produce a few antibodies, which the blood test may miss. The test may need to be repeated in 10 days - 2 weeks.
Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your doctor about the meaning of your specific test results.
What abnormal results mean
An abnormal result means antibodies to B. anthracis have been detected and you may have anthrax disease. However, some people come in contact with the bacteria and do not develop the disease.
To determine if you have a current infection, your health care provider will look for an increase in the antibody count after a few weeks.
What the risks are
There is very little risk involved with having your blood taken. 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:
- Excessive bleeding
- Fainting or feeling light-headed
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
The best test for diagnosing anthrax is a culture of affected tissue or blood.
Martin GJ, Friedlander AM. Bacillus anthracis (Anthrax). In: Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Diseases. 7th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2009:chap 208.
Reviewed By: Linda Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington School of Medicine; Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School, Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.