Clinical, laboratory and radiologic characteristics of 2009 pandemic influenza A/H1N1 pneumonia: Primary influenza pneumonia versus concomitant/secondary bacterial pneumonia

Joon Y. Song, Hee J. Cheong, Jung Y. Heo, Ji Y. Noh, Hwan S. Yong, Yoon K. Kim, Eun Y. Kang, Won S. Choi, Yu M. Jo, Woo J. Kim

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

Background Although influenza virus usually involves the upper respiratory tract, pneumonia was seen more frequently with the 2009 pandemic influenza A/H1N1 than with seasonal influenza. Methods From September 1, 2009, to January 31, 2010, a specialized clinic for patients (aged ≥15years) with ILI was operated in Korea University Guro Hospital. RT-PCR assay was performed to diagnose 2009 pandemic influenza A/H1N1. A retrospective case-case-control study was performed to determine the predictive factors for influenza pneumonia and to discriminate concomitant/secondary bacterial pneumonia from primary influenza pneumonia during the 2009-2010 pandemic. Results During the study period, the proportions of fatal cases and pneumonia development were 0·12% and 1·59%, respectively. Patients with pneumonic influenza were less likely to have nasal symptoms and extra-pulmonary symptoms (myalgia, headache, and diarrhea) compared to patients with non-pneumonic influenza. Crackle was audible in just about half of the patients with pneumonic influenza (38·5% of patients with primary influenza pneumonia and 53·3% of patients with concomitant/secondary bacterial pneumonia). Procalcitonin, C-reactive protein (CRP), and lactate dehydrogenase were markedly increased in patients with influenza pneumonia. Furthermore, procalcitonin (cutoff value 0·35ng/ml, sensitivity 81·8%, and specificity 66·7%) and CRP (cutoff value 86·5mg/IU, sensitivity 81·8%, and specificity 59·3%) were discriminative between patients with concomitant/secondary bacterial pneumonia and patients with primary influenza pneumonia. Conclusions Considering the subtle manifestations of 2009 pandemic influenza A/H1N1 pneumonia in the early stage, high clinical suspicion is required to detect this condition. Both procalcitonin and CRP would be helpful to differentiate primary influenza pneumonia from concomitant/secondary bacterial pneumonia.

Original languageEnglish
Pages (from-to)e535-e543
JournalInfluenza and other Respiratory Viruses
Volume5
Issue number6
DOIs
Publication statusPublished - 2011 Nov

Keywords

  • 2009 H1N1
  • C-reactive protein
  • Influenza
  • Pneumonia
  • Procalcitonin

ASJC Scopus subject areas

  • Epidemiology
  • Pulmonary and Respiratory Medicine
  • Public Health, Environmental and Occupational Health
  • Infectious Diseases

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