Thread: Unmasking Anthrax and Smallpox

Unmasking Anthrax and Smallpox

Since the 2001 bioterrorism incident in the United States, when people were infected with anthrax spores delivered through the mail, physicians have worried about their ability to diagnose future cases of the illness. Diagnostic algorithms have been published to help clinicians differentiate inhalational anthrax from influenza or community-acquired pneumonia (CAP). However, it is unclear whether these diagnostic aids will successfully identify anthrax cases in real practice situations.

In addition, the Centers for Disease Control and Prevention (CDC) have released a strategy for risk stratification in patients suspected of having smallpox. But does it work? Using a case presentation format, this article will examine the challenges of diagnosing infection with anthrax or smallpox and evaluate what strategies, if any, can improve a physician’s diagnostic accuracy. We will compare syndromes and clinical presentations commonly seen in the emergency department with anthrax and smallpox cases that can mimic these clinical entities. Finally, we will discuss findings that suggest one of these two bioterrorism agents and put them into a real-world clinical context.

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PULMONARY CASE #1

A 45-year-old man who works for the Internal Revenue Service presents to the emergency department complaining of cough, fever, headache, vomiting, and malaise for several days. He also reports shortness of breath but denies rhinorrhea. His vital signs are: heart rate, 115; blood pressure, 133/88; temperature, 102°F; respirations, 20, with an oxygen saturation of 98% on room air.

Physical examination

Physical examination finds the patient alert but in mild distress. His throat is slightly red. His heart rate is tachycardic without murmurs or rubs. His lungs show a questionable decreased breath sound in the right lower lobe with mild crackles. Abdominal and skin examinations are benign.

Laboratory test results are:

white blood cell (WBC) count, 12,900/mm3 with 69% polymorphonuclear leukocytes and no bands; hemoglobin, 14 g/dl; hematocrit, 42%; and a platelet count within normal limits. Blood chemistry results are: sodium, 135 mEq/L; potassium, 4.1 mEq/L; chloride, 100 mEq/L; bicarbonate, 26 mEq/L; blood urea nitrogen (BUN), 16 mg/dl; creatinine, 0.9 mg/dl; and glucose, 105 mg/dl. Chest films reveal a right lower lobe infiltrate and mild left lower lobe atelectasis (see image below).

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Applying the tools to the case

[HIDE]Case #1. This was a case of pneumonia. Applying the pneumonia versus anthrax rules from the Kuehnert study, this patient would have scored a two (one point each for tachycardia and nausea and vomiting), which is below the three points needed to diagnose anthrax. This tool would have accurately diagnosed pneumonia. [/HIDE]

PULMONARY CASE #2

A 53-year-old man who works for the New York Times presents to the emergency department complaining of fever, chills, sore throat, headache, and malaise for three days. He also reports a cough, dyspnea, night sweats, and vomiting for one day. His vital signs are: pulse, 110; blood pressure, 128/80; temperature, 99°F; respirations, 24, with an oxygen saturation of 93% on room air.

Physical examination

This patient is also alert but in mild to moderate distress with associated shortness of breath. The HEENT examination is unremarkable. His heart rate is tachycardic without murmurs, rubs, or gallops. Auscultation of the lungs reveals decreased breath sounds and rhonchi in the left base. Abdominal and skin examinations are normal.

Laboratory test results are:

Laboratory test results are: WBC count, 7500/mm3 with 76% polymorphonuclear leukocytes and 8% bands; hemoglobin, 15.5 g/dl; hematocrit, 46.9%; and a platelet count within normal limits. Blood chemistry results are: sodium, 138 mEq/L; potassium, 4.1 mEq/L; chloride, 102 mEq/L; bicarbonate, 26 mEq/L; BUN, 19 mg/dl; creatinine, 1 mg/dl; and glucose, 102 mg/dl. Chest films reveal infiltrates in multiple lobes, a normal mediastinum, an elevated diaphragm secondary to volume loss, and no pleural effusions (see image below).

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Applying the tools to the case

[HIDE]Case #2. This patient had anthrax. Using the pneumonia versus anthrax scoring system yields indeterminate results. If applied as strictly reported, the patient would receive one point each for a normal WBC, nausea and vomiting, and tachycardia. This produces a score of three, the number of points required to diagnose anthrax. However, this patient had 8% bands. The authors did not discuss what the presence of bands means in the setting of a normal WBC count. It is highly debatable whether a patient with 8% bands should be considered to have a normal WBC. The authors’ inadequate definition of a normal WBC leaves this patient’s real score in question.

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PULMONARY CASE #3

A 61-year-old man who works for the post office presents to the emergency department complaining of sweats, fatigue, myalgias, fevers, chills, headache, and vomiting for two days. He also reports a dry cough with no shortness of breath, rhinorrhea, or conjunctivitis. His vital signs are: pulse, 116; blood pressure, 141/90; temperature, 100.8°F; respirations, 18, with an oxygen saturation of 97% on room air.

Physical examination

The patient is alert and does not look particularly ill, although he appears mildly dehydrated. The HEENT examination is unremarkable. His heart rate is tachycardic without murmurs, rubs, or gallops. His lungs are clear to auscultation and percussion. Abdominal and skin examinations are unremarkable.

Laboratory test results are:

Laboratory test results are: WBC count, 9700/mm3 with 79% polymorphonuclear leukocytes and no bands; hemoglobin, 14.8 g/dl; hematocrit, 44.7%; and a platelet count within normal limits. Blood chemistry results are: sodium, 134 mEq/L; potassium, 3.4 mEq/L; chloride, 98 mEq/L; bicarbonate, 20 mEq/L; BUN, 23 mg/dl; creatinine, 1 mg/dl; and glucose, 105 mg/dl. Chest films reveal a wide mediastinum but are otherwise unremarkable (see image below).

A viral upper respiratory tract syndrome is a reasonable diagnosis for this patient. After intravenous hydration and antiemetics, he could be discharged home without antibiotics and advised to maintain close follow-up with his primary care physician

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Applying the tools to the case

[HIDE]Case #3. This patient had viral syndrome. He amassed five points, suggesting a diagnosis of anthrax (for no nasal symptoms, low sodium, and a wide mediastinum). Under this scoring system, the patient would have been misdiagnosed as having anthrax.
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PULMONARY CASE #4

An 89-year-old woman presents to the emergency department complaining of fever, cough, weakness, and muscle aches for three days. She denies chills, headache, vomiting, shortness of breath, or rhinorrhea. Her past medical history includes chronic obstructive pulmonary disease (COPD), hypertension, and renal insufficiency. She is retired and lives at home. Her vital signs are: pulse, 120; blood pressure, 106/50; temperature, 102.4°F; respirations, 18, with an oxygen saturation of 93% on room air.

Physical examination

Laboratory test results are: WBC count, 8100/mm3 with 78% polymorphonuclear leukocytes and no bands; hemoglobin, 13.8 g/dl; hematocrit, 42.3%; and a platelet count within normal limits. Urinalysis was negative except for the presence of 3 to 5 WBCs per high-powered field and moderate bacteria. Blood chemistry results are: sodium, 134 mEq/L; potassium, 3.9 mEq/L; chloride, 102 mEq/L; bicarbonate, 25 mEq/L; BUN, 39 mg/dl; creatinine, 1.4 mg/dl; and glucose, 105 mg/dl. Chest films reveal a normal mediastinum and findings suggestive of COPD with possible blunting of the costovertebral angles (see image below).

Laboratory test results are:

Laboratory test results are: WBC count, 9700/mm3 with 79% polymorphonuclear leukocytes and no bands; hemoglobin, 14.8 g/dl; hematocrit, 44.7%; and a platelet count within normal limits. Blood chemistry results are: sodium, 134 mEq/L; potassium, 3.4 mEq/L; chloride, 98 mEq/L; bicarbonate, 20 mEq/L; BUN, 23 mg/dl; creatinine, 1 mg/dl; and glucose, 105 mg/dl. Chest films reveal a wide mediastinum but are otherwise unremarkable (see image below).

This patient’s diagnosis is not clear. Considering a diagnosis of viral syndrome versus dehydration would be a sensible approach. Admitting the patient, obtaining cultures, and administering oxygen and antibiotics that cover a possible urinary tract infection would be reasonable as well.
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Applying the tools to the case

[HIDE]Case #4. This was another case of anthrax. Whether this patient receives a score of three or six points is in question. Six points could be given if two points each were allotted for tachycardia and absence of rhinorrhea and one point each for hyponatremia and absence of headache. However, after examining the patient’s chart more closely, it appears that the reported history may be incorrect. Although the patient said she had no rhinorrhea, she was using azelastine nasal spray and loratidine, medications for seasonal allergies and rhinorrhea. In addition, most emergency physicians would not consider a sodium level of 134 mg/dl as hyponatremia. Once again, the usefulness of this scoring system is questionable.
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