Public - Anthrax - Diagnosis

Module information



		Prevention
		Screening
		Diagnosis
		Consultation for Diagnosis
		Hospitalization
		Therapy
		Patient Education
		Consultation for Management
		Follow-up

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Diagnosis
Obtain a travel or exposure history in patients with suspected anthrax. Consider cutaneous anthrax in patients with an enlarging painless eschar surrounded by edema and an exposure history. Consider the diagnosis of inhalational anthrax in patients with fever, respiratory symptoms, and an appropriate exposure history. Consider GI anthrax in patients with fever, GI symptoms, and an appropriate exposure history. Obtain appropriate laboratory studies in patients with suspected anthrax, including culture of blood or infected material and acute and convalescent titers. Obtain a chest x-ray in patients with suspected inhalational anthrax; consider a chest CT in certain patients. Consider the broad differential diagnosis of lower respiratory tract infections with widening of the mediastinum. Consider the broad differential diagnosis of cutaneous anthrax. Consider the broad differential diagnosis of GI anthrax. Consider other infections in the differential diagnosis of anthrax meningitis.
Laboratory and Other Studies for Anthrax (table)
Differential Diagnosis of Anthrax (table)


Obtain a travel or exposure history in patients with suspected anthrax.
Ask about: Travel to the Middle East, Africa, South America, or Asia Exposure to wool, hides, or animal hair from the Middle East, Africa, or Asia Agricultural exposure through direct contact with infected sick or dying animals or through the handling of infected carcasses or tissues Exposure to concentrated forms of anthrax in a laboratory setting or as a result of an intentional release of a bioweapon containing anthrax spores Determine if the patient fits the characteristics of a high-risk exposed group if disease is the result of a bioterrorist attack.
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Consider cutaneous anthrax in patients with an enlarging painless eschar surrounded by edema and an exposure history.
Consider the diagnosis of cutaneous anthrax in patients with: Chills, fever, and constitutional symptoms An enlarging, painless lesion with eschar surrounded by edema, usually on the neck, face, hands, or arms Lesions that start as papules and get progressively larger Vesicular satellite lesions, which may or may not be present See figure Cutaneous Anthrax Ulcer With Vesicle and Ring. See figure Cutaneous Anthrax Ulcer With Black Eschar.
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Consider the diagnosis of inhalational anthrax in patients with fever, respiratory symptoms, and an appropriate exposure history.
Consider the diagnosis of inhalational anthrax in patients with: Shortness of breath Fever, chills Cough (minimally or not productive) Chest pain or discomfort Nausea or vomiting Fatigue, malaise, lethargy Headache Altered mental status, confusion Myalgias Diaphoresis Neck pain Exposure history Suspect inhalational anthrax when the constellation of symptoms is present in a person at high risk for its development. Recognize that meningitis occurs frequently in inhalational anthrax.
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Consider GI anthrax in patients with fever, GI symptoms, and an appropriate exposure history.
Consider GI anthrax in patients with: Nausea Vomiting Malaise Lower GI bleeding Hematochezia Abdominal pain Fever Acute abdomen Bloody diarrhea Sepsis A history of ingestion of poorly cooked infected meat Possible inhalation of anthrax-containing material
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Obtain appropriate laboratory studies in patients with suspected anthrax, including culture of blood or infected material and acute and convalescent titers.
For cutaneous anthrax: Order Gram stain and culture of unroofed vesicle, ulcer base or edge, or eschar. Collect a second swab for PCR Obtain a punch biopsy for immunohistochemical testing If the patient has not received antibiotics, obtain a second biopsy for culture, Gram stain, PCR, and frozen-tissue immunohistochemical testing Collect acute serum (within 7 days of symptom onset) and convalescent serum (14 to 35 days after symptom onset) Collect blood for culture and PCR if systemic involvement is suspected For inhalational anthrax: Obtain blood for smear, culture, and PCR If available, obtain sputum for Gram stain and culture If present, collect pleural fluid for Gram stain, culture, and PCR Collect acute serum (within 7 days of symptom onset) and convalescent serum (14 to 35 days after symptom onset) For GI anthrax: Order culture on stool specimen Obtain blood for smear, blood culture, and PCR If present, obtain ascites and send for Gram stain, culture, and PCR For anthrax meningitis: Obtain blood and CSF for Gram stain, culture, and PCR See table Laboratory and Other Studies for Anthrax.
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Obtain a chest x-ray in patients with suspected inhalational anthrax; consider a chest CT in certain patients.
Obtain chest x-ray films in a patient with fever who is in a high-risk group during an anthrax outbreak to look for a widened mediastinum with or without pleural effusion. Obtain chest CT in: All patients with fever and a widened mediastinum on chest x-ray film and no history of chest trauma High-risk patients with fever and pleural effusions or infiltrates on chest x-ray film during an anthrax outbreak High-risk patients with fever and chest pain during an anthrax attack, even if the chest x-ray film appears normal See table Laboratory and Other Studies for Anthrax. See figure Mediastinal Widening in Inhalational Anthrax. See figure Mediastinal Widening With Pleural Effusion in Inhalational Anthrax.
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Consider the broad differential diagnosis of lower respiratory tract infections with widening of the mediastinum.
Consider other lower respiratory tract infections and pneumonias in the differential diagnosis of inhalational anthrax as well as noninfectious causes such as sarcoidosis, lymphoma, traumatic injury, or aneurysm. Obtain a thorough history and physical exam. Send sputum cultures for bacterial pathogen testing. Send blood cultures for bacterial pathogen testing. Send nasal swab for influenza testing. Obtain a thoracentesis on patients with pleural effusions. Obtain a chest CT scan if a widened mediastinum is seen on chest x-ray film. See table Differential Diagnosis of Anthrax.
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Consider the broad differential diagnosis of cutaneous anthrax.
Consider spider bites, bacterial and rickettsial infections such as tularemia, scrub typhus, rat bite fever, fungal infection (blastomycosis, histoplasmosis), and mycobacterial infection (M. marinum) in the differential diagnosis of cutaneous anthrax. Send a culture swab of fluid from underneath an eschar for culture and Gram stain, preferably before initiating antibiotic therapy. Send material from a full-thickness punch biopsy for immunohistochemical staining and PCR if the patient has been on antibiotics or the swab Gram-stain result is negative. Send serologies or cultures for tularemia and serologies for rickettsial diseases. Ask about a history of a spider bite. See table Differential Diagnosis of Anthrax.
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Consider the broad differential diagnosis of GI anthrax.
Consider infectious diarrheas and IBD in the differential diagnosis of GI anthrax. Send stool and blood samples for culture and stool samples for ova and parasite exam and C. difficile toxin in patients with bloody diarrhea. Obtain a colonoscopy in patients with fever and bloody diarrhea if stool culture and toxin results are negative. Order a colonoscopy immediately in patients with a widened mediastinum and bloody diarrhea. See table Differential Diagnosis of Anthrax.
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Consider other infections in the differential diagnosis of anthrax meningitis.
Consider other bacterial and viral meningoencephalitides in the differential diagnosis of anthrax meningitis. Obtain a lumbar puncture in any patient with suspected anthrax and headache or mental status changes. See table Differential Diagnosis of Anthrax.
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