Huang DT, Weissfeld LA, Kellum JA, et al Risk Prediction With Procalcitonin and Clinical Rules in Community-Acquired Pneumonia
Article Outline
Discussion Points
What is already known on this topic: Procalcitonin is a biomarker that appears to correlate with bacterial infection.
What question this study addressed: Does a procalcitonin level add prognostic information for pneumonia patients in conjunction with scoring systems such as the Pneumonia Severity Index or CURB-65?
What this study adds to our knowledge: Among 1,651 patients with community-acquired pneumonia in 28 US emergency departments, procalcitonin levels did not add prognostic information for most pneumonia patients. Among higher-risk groups by Pneumonia Severity Index score, low procalcitonin level predicted lower mortality.
How this might change clinical practice: Clinicians should continue using validated prognostic scoring systems for pneumonia. Low procalcitonin level could be considered as a factor for selected patients who would otherwise be considered high risk to be treated in a lower acuity setting.
A. In this study,2 the authors chose to look at the relationship of procalcitonin and pneumonia. What is already known about procalcitonin levels and infection? Can the procalcitonin level differentiate between viral and bacterial disease? Is procalcitonin level correlated with outcome in bacterial illness?
B. Create a schematic conceptual model that shows how procalcitonin and Pneumonia Severity Index are related to pneumonia outcomes. What are the likely shapes of these relationships? Procalcitonin level can be treated as a continuous variable, can be divided—as these authors do—into several categories, or can be treated as a binary (low, high) variable. What are the advantages and disadvantages of each approach? According to your model, do you expect progressively higher procalcitonin levels to correlate with progressively worse outcomes or do you expect normal procalcitonin levels to predict good outcomes and abnormal values to have similar frequencies of adverse outcome regardless of the magnitude of the elevation? What are the advantages and disadvantages of choosing all-cause death at 30 days as the primary outcome of interest? When emergency physicians determine the disposition (home, regular bed, monitored bed, ICU) of pneumonia patients, are they thinking about 30-day mortality or something else? What other outcomes might be of interest? What assumptions must be made about hospital admission to justify the use of 30-day mortality as an outcome in this study? Are these assumptions likely to be correct? The authors use likelihood ratios to describe their results (Table 3). What is a positive likelihood ratio (LR+)? A negative likelihood ratio (LR−)? Contrast likelihood ratios to other measures of test performance and describe their advantages and disadvantages. Why, in theory at least, are likelihood ratios particularly useful at the bedside? What does the negative likelihood ratio of 0.09 (95% confidence interval 0.02 to 0.36) found in this study mean quantitatively and qualitatively? What numbers is it based on (calculate it!)?
Multicenter studies make it possible to enroll large numbers of subjects and offer a greater chance for external generalizability but present analytic challenges. What are some of the analytic challenges that arise from multicenter studies and what are some of the techniques used to overcome these? Consider issues about the presentation of results and the statistical analysis of the data. In this study, what information about the role of individual study sites would help readers better understand and interpret the meaning of the results? What would you choose as the next step in evaluating the effect of procalcitonin testing on pneumonia patients? Should we start using it in clinical practice and see how we like it? Should we test it in an external validation set (how is this done)? Should we conduct a randomized controlled trial? How would you design such a trial? What would the intervention be? What would the outcome of interest be?
References
- . Journal Club Questions: Miller AH, Nazeer S, Pepe P, et al (Acutely decompensated heart failure in a county emergency department: a double blind randomized controlled comparison of nesiritide versus placebo treatment). Ann Emerg Med. 2008;51:580–582
- Risk prediction with procalcitonin and clinical rules in community-acquired pneumonia. Ann Emerg Med. 2008;52:48–58
SEE RELATED ARTICLE, P. 48.
Editor's Note: You are reading the fourth installment of Annals of Emergency Medicine Journal Club. This bimonthly feature seeks to improve the critical appraisal skills of emergency physicians and other interested readers through a guided critique of actual Annals of Emergency Medicine articles. Each Journal Club will pose questions that encourage readers—be they clinicians, academics, residents, or medical students—to critically appraise the literature. Answers to these questions will appear in the December 2008 issue.Please see the preamble to the May 2008 issue for a detailed description of the goals and operational details of Annals of Emergency Medicine Journal Club.1 Questions are rated “novice,” 
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PII: S0196-0644(08)00848-2
doi:10.1016/j.annemergmed.2008.05.033
© 2008 American College of Emergency Physicians. Published by Elsevier Inc. All rights reserved.
Refers to article:
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Risk Prediction With Procalcitonin and Clinical Rules in Community-Acquired Pneumonia
, 17 March 2008
