Background: Population exposure to Bacillus anthracis spores could cause mass casualties requiring complex medical care. Rapid identification of patients needing anthrax-specific therapies will improve patient outcomes and resource use.
Objective: To develop a checklist that rapidly distinguishes most anthrax from nonanthrax illnesses on the basis of clinical presentation and identifies patients requiring diagnostic testing after a population exposure.
Design: Comparison of published anthrax case reports from 1880 through 2013 that included patients seeking anthrax-related care at 2 epicenters of the 2001 U.S. anthrax attacks.
Setting: Outpatient and inpatient.
Patients: 408 case patients with inhalation, ingestion, and cutaneous anthrax and primary anthrax meningitis, and 657 control patients.
Measurements: Diagnostic test characteristics, including positive and negative likelihood ratios (LRs) and patient triage assignation.
Results: Checklist-directed triage without diagnostic testing correctly classified 95% (95% CI, 93% to 97%) of 353 adult anthrax case patients and 76% (CI, 73% to 79%) of 647 control patients (positive LR, 3.96 [CI, 3.45 to 4.55]; negative LR, 0.07 [CI, 0.04 to 0.11]; false-negative rate, 5%; false-positive rate, 24%). Diagnostic testing was needed for triage in up to 5% of case patients and 15% of control patients and improved overall test characteristics (positive LR, 8.90 [CI, 7.05 to 11.24]; negative LR, 0.06 [CI, 0.04 to 0.09]; false-negative rate, 5%; false-positive rate, 11%). Checklist sensitivity and specificity were minimally affected by inclusion of pediatric patients. Sensitivity increased to 97% (CI, 94% to 100%) and 98% (CI, 96% to 100%), respectively, when only inhalation anthrax cases or higher-quality case reports were investigated.
Limitations: Data on case patients were limited to nonstandardized, published observational reports, many of which lacked complete data on symptoms and signs of interest. Reporting bias favoring more severe cases and lack of intercurrent outbreaks (such as influenza) in the control populations may have improved test characteristics.
Conclusion: A brief checklist covering symptoms and signs can distinguish anthrax from other conditions with minimal need for diagnostic testing after known or suspected population exposure.
Primary funding source: U.S. Department of Health and Human Services.