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The University of Louisville Journal of Respiratory Infections

Abstract

Background: There exists a large body of literature to help identify, diagnose, treat, and manage community-acquired pneumonia (CAP). Despite this, there is little data that directly compares the clinical syndromes and complications of pure bacterial pneumonia to pure viral pneumonia. Our study compares the clinical presentation, morbidity and mortality of viral vs. bacterial etiologies of CAP.

Methods: This was a secondary data analysis of the Community-Acquired Pneumonia Organization (CAPO) international study database. Data was collected concerning patient demographics, physical examination findings, laboratory findings, radiological findings, severity of illness, and clinical outcomes and stratified according to the two study groups, CAVP and CABP. A microbiological diagnosis of CABP was based on the isolation of a bacterium from a respiratory sample, blood culture and/or identification of a urinary antigen for Streptococcus or Legionella; microbiological diagnosis of CAVP was based on polymerase chain reaction or antigen detection from respiratory samples.

Results: Our study included 1,913 patients. Of these, 286 (15.0%) had viral infection, while 1,627 (85.0%) had CAVP. We found that bacterial CAP patients are older, more frequently male, and suffer from a higher proportion of comorbidities when compared to viral CAP patients. Comparison of physical exam findings and laboratory values failed to find a clinically significant difference between bacterial and viral CAP patients. When comparing severity of illness, bacterial CAP patients had greater frequency of PSI ≥ class IV; however, viral CAP patients more frequently needed ICU admission, ventilator support, vasopressor support, and had higher rate of in hospital mortality.

Conclusions: Our study confirms the extreme difficulty differentiating CABP from CAVP using demographics, physical exam, or x-ray findings. We found no major clinical or laboratory findings distinguishing CABP from CAVP. The increased severity of illness of CAVP compared to bacterial etiologies shows that PSI scores may not be an accurate indicator of severity of disease. More studies are needed to identify the best process of care for patients with CAP, including the potential benefits of routine respiratory viral panel testing and empiric antiviral therapy.

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