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A Clinical Tool for Anthrax Meningitis Screening in Mass Casualty Settings

Amesh A. Adalja, MD, FACP, FACEP, FIDSA, April 1, 2016

One of the most ominous complications of anthrax infections is meningitis. Anthrax meningitis is often fatal, and assessing the possibility of its presence is an important component of clinical management, as it changes not only prognosis but also treatment.

Meningitis in its late stages isn’t subtle, but the need exists to exclude meningitis upon diagnosis or strong clinical suspicion of anthrax. This is usually accomplished via a lumbar puncture. However, in a mass casualty setting, such as might occur during a biological weapons attack, this procedure would be cumbersome and could not be performed, necessitating a means to conduct clinical screening. A new paper, published in Clinical Infectious Diseases, develops a screening tool for this purpose.

 

Systematic Review Beginning with 1880

To develop a clinical screening tool, the Centers for Disease Control and Prevention (CDC) conducted a systematic review of the anthrax medical literature from 1880 to the present. The aim of the review was to discover clinical signs and symptoms that would predict the presence of meningitis and also to determine if any treatments were associated with survival.

After culling the results of the literature search, 225 reports of 363 cases of systemic anthrax were included. Important aspects of the cases were that most occurred in adults and males, almost all required hospitalization, and only 37% survived. The majority of systemic anthrax cases began initially with cutaneous infection (52%), with 23% beginning with inhalation.

Meningitis was present in 36% of cases, with 89% confirmed (requiring CSF or brain examination). Important features of these cases included:

  • No sex or age differences were noted in adults, but children in the 6-12-year age group were more likely to develop meningitis than those under 1 year of age.
  • Univariate predictors of a 3-fold risk of meningitis included the presence of nausea/vomiting, fevers/chills, and headache.
  • Altered mental status, loss of consciousness, meningeal signs, and the presence of neurological deficits were strongly associated with meningitis.
  • Hemorrhagic CSF was present in the majority of cases.
 

Mortality Predictors

Several aspects of cases were associated with mortality: adulthood (vs. children), presence of altered mental status, and higher peripheral and CSF leukocyte counts. All survivors received a bactericidal antibiotic, with most receiving combination therapy. Administration of antitoxin was not associated with survival.

 

4-Item Screening Tool

From analysis of the data, a 4-item assessment tool was developed. The presence of 2 of 4 (LR +26.5) of the following are needed to establish that meningitis is probable in a case of systemic anthrax:

1. Severe headache
2. Altered mental status
3. Meningeal signs
4. Other neurological signs

Conversely, patients who have none of the 4 can be presumed to not have meningitis (LR –0.12) and can be treated according to the nonmeningitis treatment guidance in a mass casualty setting.

 

Improving Care of Anthrax Patients

Before the development of this tool, clinicians were without a validated method to determine the likelihood of meningitis, so this is a welcome development. Implementing anthrax treatment guidance in a mass casualty setting, in which crisis or contingency standards of care are in operation, is daunting (if not impossible), since assessing a patient for meningitis is a key decision point and a lumbar puncture is unlikely to be able to be performed. This simply implemented tool provides an evidence-driven approach to optimizing the treatment of anthrax.

 

Reference

Kathorios-Lanwermeyer S, Holty J, Person M, et al. Identifying meningitis during a mass casualty incident: systematic review of systemic anthrax since 1880. Clin Infect Dis 2016. http://cid.oxfordjournals.org/content/early/2016/03/29/cid.ciw184.abstract. Accessed March 30, 2016.