Tests Anthrax tests fall into two categories: those for exposure and presence of anthrax in the environment and those for infection. Nasal swab tests can reveal the presence of spores, and thus exposure, but a positive test does not indicate infection. Even a person exposed to spores will not become ill unless the spores germinate, a process that can take up to 60 days. Therefore, nasal swabs are not recommended to document anthrax exposure or illness.
Anthrax infection is diagnosed by culturing the bacterium, using a specimen appropriate to the form of the disease suspected (such as from blood, skin lesions, or respiratory secretions) or by measuring
antibodies in the blood. For inhalational anthrax, a chest X-ray can also be helpful, as can a test of
cerebrospinal fluid if signs of
meningitis are present.
Culturing of a sample (from either an environmental source or a bodily fluid, such as blood) can take several hours to several days. The specimen is incubated in artificial media, where the bacteria can grow. (Click here for more about
blood culture.) Conventional biochemical tests are then performed to identify the bacteria, and
susceptibility testing is done to select the best antibiotic for therapy.
A rapid test that could potentially be used on both environmental and body fluid samples has been developed. This test bypasses the need for culturing and detects the anthrax
DNA directly. In 2001,the FDA approved this assay as an investigational test on human specimens.
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