title: 'Presenting CXR phenotype of H1N1' flu compared with contemporaneous non-H1N1, community acquired pneumonia, during pandemic and post-pandemic outbreaks'.
abstract: OBJECTIVE
  To review, phenotype and assess potential prognostic value of initial chest X-ray findings in patients with H1N1 influenza during seasonal outbreaks of 2009 and 2010, in comparison with non-H1N1, community acquired pneumonia (CAP).
  
  
  METHODS
  We retrospectively identified 72 patients admitted to hospital with pneumonia during the seasons of 2009 and 2010. H1N1 cases were confirmed by virology PCR. Presenting chest X-rays were jointly read by 2 radiologists, who were 'blinded' to further patient details and divided into 6 zones. Total number of opacified zones, the pattern and distribution of changes and length of hospital stay were recorded.
  
  
  RESULTS
  Patients with H1N1 demonstrated more opacified zones (mean of 2.9 compared with 2.0; p=0.006), which were bilateral in two-thirds compared with a quarter of those with non-H1N1 CAP (p=0.001). H1N1 radiographs were more likely to be 'patchy' versus 'confluent' changes of non-H1N1 CAP (p=0.03) and more often demonstrated peripheral distribution (p=0.01). H1N1 patients tended to stay in hospital longer (not significant; p=0.08). A positive correlation existed between number of affected zones and length of inpatient stay, which was statistically significant for the cohorts combined (p=0.02). The findings were the same for the two evaluated seasons.
  
  
  CONCLUSIONS
  H1N1 patients demonstrated more extensive disease, which was more likely bilateral, 'patchy', and peripheral in distribution. With increasing global cases of H1N1, knowledge of the typical findings of the H1N1 presenting chest X-ray may assist with early triage of patients, particularly where rapid viral testing is not available.
authors.affiliation: Department of Radiology, New Royal Infirmary Edinburgh, 51 Little France Crescent, Edinburgh, EH16 4SA, UK. Electronic address: Fiona.Minns@nhslothian.scot.nhs.uk.
authors.forename: F C
authors.initials: FC
authors.lastname: Minns
authors.affiliation: Department of Radiology, New Royal Infirmary Edinburgh, 51 Little France Crescent, Edinburgh, EH16 4SA, UK. Electronic address: draideen@gmail.com.
authors.forename: A Ni
authors.initials: AN
authors.lastname: Mhuineachain
authors.affiliation: Clinical Research Imaging Centre, University of Edinburgh, 47 Little France Crescent, Edinburgh, Midlothian EH16 4TJ, UK. Electronic address: Edwin-vanbeek@ed.ac.uk.
authors.forename: E J R
authors.initials: EJ
authors.lastname: van Beek
authors.affiliation: Department of Radiology, New Royal Infirmary Edinburgh, 51 Little France Crescent, Edinburgh, EH16 4SA, UK. Electronic address: drgillritchie@hotmail.com.
authors.forename: G
authors.initials: G
authors.lastname: Ritchie
authors.affiliation: Department of Respiratory Medicine, New Royal Infirmary, Edinburgh, UK. Electronic address: adam.hill318@nhs.net.
authors.forename: A
authors.initials: A
authors.lastname: Hill
authors.affiliation: Department of Radiology, New Royal Infirmary Edinburgh, 51 Little France Crescent, Edinburgh, EH16 4SA, UK. Electronic address: john.murchison@nhslothian.scot.nhs.uk.
authors.forename: J T
authors.initials: JT
authors.lastname: Murchison
mesh_terms: D017714:Community-Acquired Infections / Q000000981:diagnostic imaging / Q000453:epidemiology; D003937:Diagnosis, Differential; D004196:Disease Outbreaks / Q000706:statistics & numerical data; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype; D009980:Influenza A virus; D007251:Influenza, Human / Q000000981:diagnostic imaging* / Q000453:epidemiology; D007902:Length of Stay / Q000706:statistics & numerical data; D008168:Lung / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D058873:Pandemics / Q000706:statistics & numerical data*; D010641:Phenotype; D011014:Pneumonia / Q000000981:diagnostic imaging* / Q000453:epidemiology; D013902:Radiography, Thoracic / Q000706:statistics & numerical data*; D012189:Retrospective Studies
keywords: Chest radiography Swine’flu; H1N1; Outbreaks 2009 and 2010; Pandemic and post-pandemic H1N1