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Procalcitonin is not recommended as a “rule-out” test for bacterial pneumonia; studies have not found a threshold at which bacterial pneumonia can be reliably distinguished from viral pneumonia based on procalcitonin levels.

Empiric antibacterial agents are recommended regardless of procalcitonin level at time of presentation.

Based on limited data and because of the potential for complications (eg, hyperglycemia), the IDSA/ATS guidelines recommend against corticosteroids in the treatment CAP of any severity.

Corticosteroids are recommended for patients with CAP who may also have severe septic shock, acute exacerbation of asthma or COPD, or adrenal insufficiency.

Pneumonia has classically been considered in terms of the infecting organism (Table 9–8) (eFigures 9–7, 9–8, 9–9, and 9–10). This approach facilitates discussion of characteristic clinical presentations but is a limited guide to patient management since specific microbiologic information is usually not available at initial presentation. Current classification schemes emphasize epidemiologic factors that predict etiology and guide initial therapy. Pneumonia may be classified as community-acquired (CAP) or nosocomial and, within the latter, as hospital-acquired (HAP) or ventilator-associated (VAP). These categories are based on differing settings and infectious agents and require different diagnostic and therapeutic interventions. Anaerobic pneumonia and lung abscess can occur in both hospital and community settings and warrant separate consideration.

Table 9–8.Characteristics of selected pneumonias.

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