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Community-acquired pneumonia: Initial evaluation and site of care based on severity assessment in adults

Community-acquired pneumonia: Initial evaluation and site of care based on severity assessment in adults
  Severity score* Site of care Microbiologic evaluation
Mild

PSI: I or II

or

CURB-65: 0		 Ambulatory care
  • COVID-19 and influenza testing when incidence is high and results would change managementΔ
  • Otherwise, testing is usually not needed
Moderate

PSI: III or IV

or

CURB-65: 1 to 2		 General medical ward
  • Blood cultures
  • Sputum Gram stain and culture
  • Urine streptococcal antigen
  • Legionella testing◊
  • Testing for respiratory viruses during respiratory virus season or when community incidence is high (PCR preferred)§
  • HIV screening¥
Severe

PSI: IV or V

or

CURB-65: ≥3

and/or

Fulfillment of ATS/IDSA criteria for ICU admission‡		 ICU
  • Blood cultures
  • Sputum Gram stain and culture
  • Urine streptococcal antigen test
  • Legionella testing◊
  • Testing for respiratory viruses (PCR preferred)§
  • Bronchoscopy specimens for Gram stain, fungal stain, aerobic, fungal culture, and molecular testing (when feasible)†
  • HIV screening¥
CAP presents along a continuum of severity. For practical purposes, we typically categorize CAP as mild, moderate, or severe. Severity assessment is based on clinical judgement and can be aided by severity scores, such as the PSI or the CURB-65 score. We generally prefer the PSI as it is better validated; however, many clinicians prefer the CURB-65 as it is easier to use. The three levels of severity correspond to the three levels of care (ambulatory care, hospital admission to the general medical ward, and ICU). The severity assessment and site of care each inform the initial microbiologic evaluation and empiric antibiotic selection. For all patients, we modify our approach based on patient-specific factors such as epidemiologic exposures and ability to care for oneself at home. Refer to the UpToDate topic on the treatment of CAP for further detail.

ATS: American Thoracic Society; CAP: community-acquired pneumonia; COVID-19: coronavirus disease 2019; ICU: intensive care unit; IDSA: Infectious Diseases Society of America; PaO2/FiO2: arterial oxygen tension to fraction of inspired oxygen; PCR: polymerase chain reaction; PSI: Pneumonia Severity Index.

* Severity scores should be used as an adjunct to clinical judgment. Patients with early signs of sepsis (eg, patients fulfilling minor ATS/IDSA criteria) or rapidly progressive illness are not well represented in severity scoring systems. Patients with these features may warrant hospitalization and/or ICU admission regardless of score. Conversely, older age may be overrepresented in severity scores; this should be taken into account when determining site of care.

¶ Because age >65 years is a criterion in the CURB-65 score, patients with CURB-65 scores of 1 who are older than 65 years may also be reasonably treated in the ambulatory setting.

Δ Refer to the UpToDate content on the diagnosis of influenza and COVID-19 for details.

◊ PCR on sputum sample is preferred for the diagnosis of Legionella spp because it detects most clinically relevant Legionella spp. The urine antigen test is an acceptable alternative when PCR is not available but is specific for Legionella pneumophila serogroup 1.

§ The approach to testing for respiratory viruses varies among institutions. At a minimum, testing for SARS CoV-2 and influenza should be performed (PCR preferred). However, testing is often expanded to include adenovirus, parainfluenza virus, respiratory syncytial virus, and human metapneumovirus. The specific assay used (eg, PCR, antigen test) may also vary among institutions and multiplex PCR assays are becoming increasingly available. While use of these assays increases the likelihood of detecting a micro-organism, the predictive value of these results is not clear. For example, the detection of a viral pathogen does not rule out the possibility of bacterial coinfection. Similarly, some viral and bacterial pathogens can colonize the airways; their detection does not definitively indicate infection.

¥ Refer to UpToDate content on screening and diagnosis of HIV infection for detail.

‡ ATS and IDSA major criteria for ICU admission include either septic shock with need for vasopressor support and/or respiratory failure with need for mechanical ventilation. If major criteria are not met, patients should also be considered for ICU admission if 3 or more of the following minor criteria are present: altered mental status, hypotension requiring fluid support, temperature <36°C/96.8°F, respiratory rate ≥30 breaths/minute, PaO2/FiO2 ratio ≤250, blood urea nitrogen ≥20 mg/dL (7 mmol/L), leukocyte count <4000 cells/microL, platelet count <100,000/mL, or multilobar infiltrates.

† We generally weigh the benefits of obtaining a microbiologic diagnosis against the risks of the bronchoscopy (eg, need for intubation, bleeding, bronchospasm, pneumothorax) on a case-by-case basis. When pursuing bronchoscopy, we usually send specimens for aerobic and anaerobic culture, Legionella culture, fungal stain and culture, and testing for viral pathogens (influenza, adenovirus, parainfluenza, respiratory syncytial virus, and human metapneumovirus).
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