Influenza Testing and Treatment Among Patients Hospitalized With Community-Acquired Pneumonia

Chest. 2022 Sep;162(3):543-555. doi: 10.1016/j.chest.2022.01.053. Epub 2022 Feb 5.


Background: Influenza is a leading cause of community-acquired pneumonia (CAP), and results of influenza tests can direct therapy. However, among adults hospitalized with CAP, little is known about the frequency and timing of influenza testing, treatment, and their associations with outcomes.

Research question: In patients with CAP, is testing for influenza associated with antiviral treatment and shorter antibiotic courses, and is early treatment associated with better clinical outcomes?

Study design and methods: This study included adults admitted with pneumonia in 2010 to 2015 to 179 US hospitals contributing to the Premier database. We assessed influenza testing and compared antimicrobial utilization and the outcomes of test-positive, test-negative, and untested patients. Associations of early antiviral treatment (oseltamivir) with 14-day in-hospital mortality, hospital length of stay, and cost were studied.

Results: Among 166,268 patients with CAP, 38,703 (23.3%) were tested for influenza, of whom 11.5% tested positive. Testing increased from 15.4% to 35.6% from 2010 to 2015 and was 28.9% during flu season (October-May) vs 8.2% in June to September. Patients testing positive for influenza received antiviral agents more often and antibacterial agents less often and for shorter courses than patients testing negative (5.3 vs 6.4 days; P < .001). Influenza-positive patients receiving oseltamivir on hospital day 1 (n = 2,585) experienced lower 14-day in-hospital mortality (adjusted OR, 0.75; 95% CI, 0.59-0.96), lower costs (adjusted ratio of means, 0.88; 95% CI, 0.81-0.95), and shorter length of stay (adjusted ratio of means, 0.88; 95% CI, 0.84-0.93) vs patients receiving oseltamivir later or not at all (n = 1,742).

Interpretation: Even during flu season, most patients with CAP in this study went untested for influenza. A positive influenza test result was associated with antiviral treatment, and early treatment was associated with lower mortality, suggesting that more widespread testing might improve patient outcomes.

Keywords: influenza; mortality; oseltamivir; testing.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Anti-Bacterial Agents / therapeutic use
  • Antiviral Agents / therapeutic use
  • Community-Acquired Infections* / diagnosis
  • Community-Acquired Infections* / drug therapy
  • Hospitalization
  • Humans
  • Influenza, Human* / diagnosis
  • Influenza, Human* / drug therapy
  • Oseltamivir / therapeutic use
  • Pneumonia* / diagnosis
  • Pneumonia* / drug therapy
  • Retrospective Studies


  • Anti-Bacterial Agents
  • Antiviral Agents
  • Oseltamivir