Anthrax laboratory findings

Initial evaluation of patients suspected of having anthrax should be similar to the standard evaluation for patients with an acute febrile illness and should have an emphasis on obtaining pre-treatment blood and other appropriate cultures.^[1] When systemic anthrax is present, abnormalities in laboratory tests include anemia, thrombocytopenia, and leukocytosis particularly in the latter stages of the disease. Other laboratory findings are hyponatremia, increased BUN, elevated transaminase levels, hypoalbuminemia, and elevated troponin. Cell cultures from the initial skin lesion, blood, CSF, or pleural fluid can identify the organism and possibly the toxins. In injection anthrax, the typical laboratory finding is an inflammatory pattern with a low CRP. A normal PT/PTT at admission does not exclude coagulopathy nor DIC.

Show below is a table depicting the tests are used in the diagnosis and monitoring of systemic anthrax.^[2]

* Note that topical swabs from skin lesions will not pick up B. anthracis. Detection in smears or by culture requires lifting the edge of the eschar with tweezers (this gives no pain unless there is secondary infection) and obtaining fluid from underneath. The fluid will probably be sterile if the patient has been treated with an antibiotic.