The Primary Care Differential Diagnosis of Inhalational Anthrax

Abstract

PURPOSE Inhalational anthrax is an extremely rare infectious disease with nonspecifi c initial symptoms, thus making diagnosis on clinical grounds diffi cult. After a covert release of anthrax spores, primary care physicians will be among the fi rst to evaluate cases. This study defi nes the primary care differential diagnosis of inhalational anthrax. METHODS 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. RESULTSThe response rate was 36.9%. Diagnoses for inhalational anthrax were grouped into 35 diagnostic categories, with pneumonia (42%), infl uenza (10%), viral syndrome (9%), septicemia (8%), bronchitis (7%), central nervous system infection (6%), and gastroenteritis (4%) accounting for 86% of all diagnoses. Diagnoses differed signifi cantly between cases that proved to be fatal and those that proved to be nonfatal.CONCLUSIONS 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. INTRODUCTIONC overt release of anthrax (Bacillus anthracis) spores as an act of terrorism will result in the unknowing and unsuspected exposure of persons. Some of those exposed will become infected through inhalation of spores; many of these persons will manifest some of the constellation of symptoms that can be associated with inhalational anthrax.1 For frontline clinicians-typically physicians, physician assistants, and nursepractitioners in primary care offi ces, urgent care centers, and emergency departments-early recognition of and response to inhalational anthrax is of paramount importance on both individual and populationwide levels. Inhalational anthrax is an extremely rare infectious disease. In 11 recent cases associated with bioterrorism, initial diagnoses were diverse, including gastroenteritis, bacterial meningitis, nonspecifi c viral syndrome, and bronchitis.3-7 A diagnosis of inhalational anthrax can be supported by imaging studies. Defi nitive diagnosis, however, depends on detection of B anthracis through culture, immunohistochemistry, or polymerase chain reaction. 1,8 In past anthrax outbreaks, initial diagnoses were aided by contextual information, such as occupation.9 Covert bioterrorism involving a rare pathogen robs the clinician of most contextual diagnostic clues.Early detection of bioterrorism events has become a national priority since September 11, 2001. 10,11 of electronic medical data has been proposed as one approach providing the "extreme timeliness of detection" necessary for appropriate response. 12 Electronic surveillance uses signal detection theory to id...

Rapid Assessment of Agents of Biological Terrorism: Defining the Differential Diagnosis of Inhalational Anthrax Using Electronic Communication in a Practice-Based Research Network

“…We used 11 clinical case vignettes of inhalational anthrax that have been described elsewhere, [5][6][7] as well as 2 cases of infl uenza and 1 case of Legionella pneumonia. From these 14 cases, 3 were randomly selected and sent by e-mail in random order to each participant along with a cover letter describing the study.…”

“…5 Response rates were compared using the chi-square test. Median response times were compared using the Kruskal-Wallis statistic.…”

“…5 This approach was laborious and did not have the extreme timeliness required for rapidly emerging diseases. This study assesses the feasibility, timeliness, and validity of using similar case vignette methods enhanced by electronic distribution to a limited, nonrandom set of physicians within a regional practice-based research network (PBRN).…”

Anthrax

“…Early studies of inhalation anthrax demonstrated that inhaled spores are phagocytosed by macrophages in the lungs and transported to the pulmonary-associated lymph nodes where germination and vegetative growth occur, followed by bacteraemia and dissemination to the rest of the body (Lyncoln et al, 1964; Henderson et al, 1956;Ross, 1957). Initial signs and symptoms of inhalation anthrax are non-specific and might include sore throat, mild fever and muscle aches; these symptoms might initially be mistaken for an upper respiratory infection (Temte & Zinkel, 2004;Lucey, 2005). Approximately two to three days later, infected patients generally become progressively ill as respiratory symptoms develop, including severe dyspnoea and hypoxaemia and the disease progresses with development of hypotension, diaphoresis, worsening dyspnoea, shock, cyanosis and stridor (Holty et al, 2006 …”

In this Issue: The Patient-Clinician Relationship and Practice-Based Network Research

“…9 A related study 10 in this issue shows the diffi culty of relying only on diagnostic codes for surveillance for inhalational anthrax outbreaks.…”