The Primary Care Differential Diagnosis of Inhalational Anthrax

Abstract

Inhalational anthrax is an extremely rare infectious disease with nonspecific initial symptoms, thus making diagnosis on clinical grounds difficult. After a covert release of anthrax spores, primary care physicians will be among the first to evaluate cases. This study defines the primary care differential diagnosis of inhalational anthrax. In May 2002, we mailed survey instruments consisting of 3 randomly chosen case vignettes describing patients with inhalational anthrax to a nationwide random sample of 665 family physicians. Nonrespondents received additional mailings. Physicians were asked to provide their most likely nonanthrax diagnosis for each case. The response rate was 36.9%. Diagnoses for inhalational anthrax were grouped into 35 diagnostic categories, with pneumonia (42%), influenza (10%), viral syndrome (9%), septicemia (8%), bronchitis (7%), central nervous system infection (6%), and gastroenteritis (4%) accounting for 86% of all diagnoses. Diagnoses differed significantly between cases that proved to be fatal and those that proved to be nonfatal. Inhalational anthrax resembles common diagnoses in primary care. Surveillance systems for early detection of bioterrorism events that rely only on diagnostic codes will be hampered by false-positive alerts. Consequently, educating frontline physicians to recognize and respond to bioterrorism is of the highest priority.