Anthrax blood test

Definition

The anthrax blood test is used to measure substances (proteins) called antibodies, which are produced by the body in reaction to the bacteria that cause anthrax.

Alternative Names

Anthrax serology test; Antibody test for anthrax; Serologic test for B. anthracis

How the Test is Performed

A blood sample is needed.

How to Prepare for the Test

There is no special preparation.

How the Test will Feel

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or slight bruising. This soon goes away.

Why the Test is Performed

This test may be performed when the health care provider suspects you have anthrax infection. The bacteria that cause anthrax is called Bacillus anthracis.

Normal Results

A normal result means no antibodies to the anthrax bacteria were 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 to 2 weeks.

Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your provider about the meaning of your specific test results.

What Abnormal Results Mean

An abnormal result means antibodies to the bacteria have been detected and you may have anthrax disease. But, some people come in contact with the bacteria and do not develop the disease.

To determine if you have a current infection, your provider will look for an increase in the antibody count after a few weeks as well as your symptoms and physical exam findings.

Risks

There is little risk involved with having your blood taken. Veins and arteries vary in size from one person to another and from one side of the body to the other. Taking blood 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 lightheaded
• Multiple punctures to locate veins
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

Considerations

The best test for diagnosing anthrax is a culture of affected tissue or blood.

References

Hall GS, Woods GL. Medical bacteriology. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 23rd ed. St Louis, MO: Elsevier; 2017:chap 58.

Martin GJ, Friedlander AM. Bacillus anthracis (anthrax). In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Philadelphia, PA: Elsevier; 2020:chap 207.