A checklist of symptoms and signs may help distinguish anthrax from nonanthrax illnesses with minimal need for diagnostic testing, according to a study recently published in the Annals of Internal Medicine.
It is approximated that following a wide-area aerosol release of Bacillus anthracis spores over a populated area, half of people who inhale the spores would die, even with modern critical care. As a result of this, and because B anthracis has previously been used as a biological weapon, the United States government categorizes it as a tier 1 select agent that poses a threat to public health and safety. Following a wide-area aerosol release of B anthracis spores, healthcare providers will need to identify patients with pulmonary anthrax infection quickly. These people will need combination intravenous antimicrobials, and should be separated from persons who may be given oral antimicrobials for uncomplicated cutaneous illness or postexposure prophylaxis. A wide-area aerosol release of B anthracis spores would require a mass screening of the affected population with minimal reliance on time‑consuming diagnostic testing. Further, inaccurate screening criteria may delay or deny care for people who are truly sick.
Having effective triage that includes screening criteria based on presenting signs and symptoms that differentiate cases from those with nontarget illnesses could be the key difference between successful mass care and chaos by improving patient outcomes and resource use. Therefore, this study aimed to develop a checklist that rapidly distinguishes most anthrax from nonanthrax illnesses based on clinical presentation and to identify patients requiring diagnostic testing after a population exposure.
In total, 408 case patients with inhalation, ingestion, and cutaneous anthrax and primary anthrax meningitis were included, along with 657 control patients. Multivariable exact logistic regression tests were used to identify signs and symptoms that may independently add value to the checklist.
Multivariable regression analysis identified 9 consistently significant independent predictors of anthrax for possible inclusion in the algorithm: altered mental status, tachypnea, fever, dyspnea, skin lesion, abnormal heart or lung sounds, increased girth, absence of cold symptoms, and hypothermia. The final checklist included the following signs and symptoms: heart rate, respiratory rate, temperature, mental status, diaphoresis, dyspnea, severe headache, characteristic skin lesions, increased girth, and abnormal lung sounds. Researchers identified tachypnea, extreme tachycardia, altered mental status, or severe headache as major signs, which could function as a rapid screening method, which may be obtained by paramedical assessments.
Checklist-directed triage without diagnostic testing correctly classified 95% of 353 adult anthrax case patients and 76% of 647 control patients; the false-negative rate was 5% and the false-positive rate was 24%. Diagnostic testing was needed for triage in up to 5% of anthrax case patients and 15% of control patients and improved overall test characteristics. When pediatric patients were included, checklist sensitivity and specificity were minimally affected. When only inhalation anthrax cases or higher-quality case reports were investigated, the checklist sensitivity increased to 97% and 98%, respectively. Diagnostic testing seldom improved checklist sensitivity but did play a role in decreasing false-positive results and increased specificity from 76% to 89% (95% CI, 73%-79% and 87%-92%, respectively).
The first decision node of recently published guidelines from the Centers for Disease Control and Prevention for anthrax mass casualty events asks, “[Does this patient have] clinical findings of inhalation/other systemic anthrax warranting admission?” The study authors concluded that, “Our proposed checklist provides public health and medical responders with a rapid means to answer this critical question after a [wide-area aerosol release of B anthracis spores], when quickly finding patients with anthrax with minimal investigation is paramount.”
Disclosure: This study was funded by the U.S. Department of Health and Human Services.
Hupert N, Person M, Hanfling D, Traxler RM, Bower WA, Hendricks K. Development and performance of a checklist for initial triage after an anthrax mass exposure event [published online March 19, 2019]. Ann Intern Med. doi: 10.7326/M18-1817