Is it influenza or anthrax? A decision analytic approach to the treatment of patients with influenza-like illnesses

Distinguishing Respiratory Features of Category A/B Potential Bioterrorism Agents from Community-Acquired Pneumonia

Differentiating between illness caused by community-acquired respiratory pathogens versus infection by biothreat agents is a challenge. This review highlights respiratory and clinical features of category A and B potential biothreat agents that have respiratory features as their primary presenting signs and symptoms. Recent world events make such a reminder that the possibility of rare diseases and unlikely events can occur timely for clinicians, policymakers, and public health authorities. Despite some distinguishing features, nothing can replace good clinical acumen and a strong index of suspicion in the diagnosis of uncommon infectious diseases.

Identifying Meningitis During an Anthrax Mass Casualty Incident: Systematic Review of Systemic Anthrax Since 1880

BACKGROUND

Bacillus anthracis, the causative agent of anthrax, is a potential bioterrorism agent. Anthrax meningitis is a common manifestation of B. anthracis infection, has high mortality, and requires more aggressive treatment than anthrax without meningitis. Its rapid identification and treatment are essential for successful management of an anthrax mass casualty incident.

METHODS

Three hundred six published reports from 1880 through 2013 met predefined inclusion criteria. We calculated descriptive statistics for abstracted cases and conducted multivariable regression on separate derivation and validation cohorts to identify clinical diagnostic and prognostic factors for anthrax meningitis.

RESULTS

One hundred thirty-two of 363 (36%) cases with systemic anthrax met anthrax meningitis criteria. Severe headache, altered mental status, meningeal signs, and other neurological signs at presentation independently predicted meningitis in the derivation cohort and were tested as a 4-item assessment tool for use during anthrax mass casualty incidents. Presence of any 1 factor on admission had a sensitivity for finding anthrax meningitis of 89% (83%) in the adult (pediatric) validation cohorts. Anthrax meningitis was unlikely in the absence of any of these signs or symptoms (likelihood ratio [LR]- = 0.12 [0.19] for adult [pediatric] cohorts), while presence of 2 or more made meningitis very likely (LR+ = 26.5 [30.0]). Survival of anthrax meningitis was predicted by treatment with a bactericidal agent (P = .005) and use of multiple antimicrobials (P = .01).

CONCLUSIONS

We developed an evidence-based assessment tool for screening patients for meningitis during an anthrax mass casualty incident. Its use could improve both patient outcomes and resource allocation in such an event.

Use of outcomes to evaluate surveillance systems for bioterrorist attacks

Background

Syndromic surveillance systems can potentially be used to detect a bioterrorist attack earlier than traditional surveillance, by virtue of their near real-time analysis of relevant data. Receiver operator characteristic (ROC) curve analysis using the area under the curve (AUC) as a comparison metric has been recommended as a practical evaluation tool for syndromic surveillance systems, yet traditional ROC curves do not account for timeliness of detection or subsequent time-dependent health outcomes.

Methods

Using a decision-analytic approach, we predicted outcomes, measured in lives, quality adjusted life years (QALYs), and costs, for a series of simulated bioterrorist attacks. We then evaluated seven detection algorithms applied to syndromic surveillance data using outcomes-weighted ROC curves compared to simple ROC curves and timeliness-weighted ROC curves. We performed sensitivity analyses by varying the model inputs between best and worst case scenarios and by applying different methods of AUC calculation.

Results

The decision analytic model results indicate that if a surveillance system was successful in detecting an attack, and measures were immediately taken to deliver treatment to the population, the lives, QALYs and dollars lost could be reduced considerably. The ROC curve analysis shows that the incorporation of outcomes into the evaluation metric has an important effect on the apparent performance of the surveillance systems. The relative order of performance is also heavily dependent on the choice of AUC calculation method.

Conclusions

This study demonstrates the importance of accounting for mortality, morbidity and costs in the evaluation of syndromic surveillance systems. Incorporating these outcomes into the ROC curve analysis allows for more accurate identification of the optimal method for signaling a possible bioterrorist attack. In addition, the parameters used to construct an ROC curve should be given careful consideration.

Rapid diagnostic testing for seasonal influenza: an evidence-based review and comparison with unaided clinical diagnosis

BACKGROUND

Worldwide, seasonal influenza imposes a considerable health and economic burden. Clinical diagnosis of influenza-like illness (ILI) is complicated by non-specific symptomatology. Rapid flu tests (RFTs) impact treatment decisions and may improve patient care; yet, recommendations for RFT use are broad, and the performance of unaided clinical diagnosis relative to RFTs is unclear.

OBJECTIVES

To determine age-stratified, overall sensitivities and specificities of the widely studied RFT, QuickVue® (Quidel Corporation, San Diego, CA), and clinical diagnosis of ILI by meta-analysis and to seek factors associated with poorer clinical diagnostic discrimination.

METHODS

A systematic literature review was conducted using article selection criteria identifying studies indexed in PubMed/MEDLINE, the Cochrane Library, and other pertinent sources of studies reporting sensitivity, specificity, and effects of RFTs and clinical diagnosis on decision-making for patients with ILI.

RESULTS

QuickVue's® diagnostic specificity exceeds that of unaided clinical diagnosis by 29-31%. False-positive results occur approximately 8.2 times more frequently by unaided clinical diagnosis than by the RFT alone. These findings were unaffected by seasonal variations in disease prevalence. RFTs reduce diagnostic testing, antibiotic use, and emergency department utilization while increasing antiviral prescription rates. No systematic relationship between the broadness of clinical diagnostic criteria for influenza and diagnostic performance was observed across studies included in this review.

CONCLUSIONS

Use of RFTs improves seasonal influenza diagnostic specificity above that based on unaided clinical diagnosis irrespective of the broadness of clinical diagnostic criteria, and affects clinical decision-making. These results provide an improved framework upon which to diagnose influenza, design future RFT studies, and modify existing recommendations for improved ILI patient management.

Agreement of decision analyses and subsequent clinical studies in infectious diseases

PURPOSE

Decision analysis techniques can compare management strategies when there are insufficient data from clinical studies to guide decision making. We compared the outcomes of decision analyses and subsequent clinical studies in the infectious disease literature to assess the validity of the conclusions of the decision analyses.

METHODS

A search strategy to identify decision analyses in infectious disease topics published from 1990 to 2005 was developed and performed using PubMed. Abstracts of all identified articles were reviewed, and infectious disease-related decision analyses were retained. Subsequent clinical trials and observational studies that corresponded to these decision analyses were identified using prespecified search strategies. Clinical studies were considered a match for the decision analysis if they assessed the same patient population, intervention, and outcome. Agreement or disagreement between the conclusions of the decision analysis and clinical study were determined by author review.

RESULTS

The initial PubMed search yielded 318 references. Forty decision analyses pertaining to 29 infectious disease topics were identified. Of the 40, 16 (40%) from 13 infectious disease topics had matching clinical studies. In 12 of 16 (75%), conclusions of at least 1 clinical study agreed with those of the decision analysis. Three of the 4 decision analyses in which conclusions disagreed were from the same topic (management of febrile children).

CONCLUSIONS

There was substantial agreement between the conclusions of decision analyses and clinical studies in infectious diseases, supporting the validity of decision analysis and its utility in guiding management decisions.

Bioterrorism-Related Inhalational Anthrax: Can Extrapolated Adult Guidelines Be Applied to A Pediatric Population?

OBJECTIVE

Since the 2001 anthrax attacks, an extensive body of literature has evolved, but there has been a limited focus on the management of pediatric-specific issues. We looked at the symptom complexes of all pediatric patients presenting to the emergency department of our hospital during this period and examined whether their presentations would likely allow current guidelines to be used as potential screening criteria to identify children infected with anthrax.

METHODS

We retrospectively reviewed emergency department records of all adult and pediatric patients (up to the age of 21 years) at Inova Fairfax Hospital during this time, when a large, and at the time ill-defined, group in the Washington, DC, metropolitan area was at risk for pulmonary anthrax. Two cases of anthrax infection were identified at this hospital in exposed adult postal workers. Screening algorithms (described by Mayer et al. and Hupert et al.) were applied to adult and pediatric patients with the presence of fever (38 degrees C), tachycardia, or other symptoms compatible with pulmonary anthrax. Specifically, the usefulness of these guidelines as potential screening tools to identify possibly infected children was examined.

RESULTS

Of 767 pediatric patients seen in the emergency department during the study period, 312 met criteria for review (41%; 95% CI: 37-44%). Four adult patients (0.4%; 95% CI: 0.1-0.9%) had at least five clinical symptoms, fever, and tachycardia; two of them had inhalational anthrax. No pediatric patient presented with five or more clinical symptoms. Twelve children (3.9%; 95% CI: 2-6.6%) presented with four clinical symptoms; five of the 12 had neither fever nor tachycardia. Children, particularly infants and toddlers, presented with nonspecific symptom complexes primarily limited to fever, vomiting, cough, and trouble breathing.

CONCLUSIONS

Existing guidelines are likely to be unreliable as a screening tool for inhalational anthrax in children, largely because of the children's inability to adequately communicate a suggestive symptom complex.

Symptomatic predictors of influenza virus positivity in children during the influenza season

BACKGROUND

Symptomatic predictors of the etiology of infectious diseases are necessary when quick action is required in treatment, as with cases of influenza or anthrax, or for when patient isolation is required, as with cases of severe acute respiratory syndrome (SARS). Predictors of influenza virus infection during the influenza season have previously been evaluated in adult studies of the antiviral agent zanamivir; cough and temperature > or =37.8 degrees C predicted influenza virus positivity in 79% of those evaluated.

METHODS

Fever and other respiratory symptoms were examined to determine their value in predicting influenza virus-positive status in children. Data analyzed were from a clinical trial of zanamivir in children 5-12 years of age and from a trial of oseltamivir in children 1-12 years of age.

RESULTS

In the pediatric study of zanamivir, as in the adult zanamivir study, cough and fever were the best predictors of influenza virus infection; a temperature > or =38.2 degrees C plus cough predicted 83% (95% CI, 79%-88%) of illnesses that were determined to be influenza virus positive. Cough (positive predictive value, 70%; 95% CI, 64%-75%), but not fever, was the best predictor of influenza virus-positive status in children aged 5-12 years in the oseltamivir trials, but neither cough nor fever were successful predictors in young children 1-4 years of age. The latter findings appeared to be the result of less symptomatic diversity among patients recruited for this trial, such that subjects who were determined to be influenza virus positive and subjects who were influenza virus negative had similar symptoms.

CONCLUSIONS

The results of these studies suggest that, during the influenza season, symptomatic predictors of influenza virus infection are applicable to identification of cases in children, although confirmation of predictive values in subjects 1-4 years of age may require further study of additional signs/symptoms.

Binary bacterial toxins: biochemistry, biology, and applications of common Clostridium and Bacillus proteins

Certain pathogenic species of Bacillus and Clostridium have developed unique methods for intoxicating cells that employ the classic enzymatic "A-B" paradigm for protein toxins. The binary toxins produced by B. anthracis, B. cereus, C. botulinum, C. difficile, C. perfringens, and C. spiroforme consist of components not physically associated in solution that are linked to various diseases in humans, animals, or insects. The "B" components are synthesized as precursors that are subsequently activated by serine-type proteases on the targeted cell surface and/or in solution. Following release of a 20-kDa N-terminal peptide, the activated "B" components form homoheptameric rings that subsequently dock with an "A" component(s) on the cell surface. By following an acidified endosomal route and translocation into the cytosol, "A" molecules disable a cell (and host organism) via disruption of the actin cytoskeleton, increasing intracellular levels of cyclic AMP, or inactivation of signaling pathways linked to mitogen-activated protein kinase kinases. Recently, B. anthracis has gleaned much notoriety as a biowarfare/bioterrorism agent, and of primary interest has been the edema and lethal toxins, their role in anthrax, as well as the development of efficacious vaccines and therapeutics targeting these virulence factors and ultimately B. anthracis. This review comprehensively surveys the literature and discusses the similarities, as well as distinct differences, between each Clostridium and Bacillus binary toxin in terms of their biochemistry, biology, genetics, structure, and applications in science and medicine. The information may foster future studies that aid novel vaccine and drug development, as well as a better understanding of a conserved intoxication process utilized by various gram-positive, spore-forming bacteria.