title: Concordance between European and US case definitions of healthcare-associated infections.
abstract: BACKGROUND
  Surveillance of healthcare-associated infections (HAI) is a valuable measure to decrease infection rates. Across Europe, inter-country comparisons of HAI rates seem limited because some countries use US definitions from the US Centers for Disease Control and Prevention (CDC/NHSN) while other countries use European definitions from the Hospitals in Europe Link for Infection Control through Surveillance (HELICS/IPSE) project. In this study, we analyzed the concordance between US and European definitions of HAI.
  
  
  METHODS
  An international working group of experts from seven European countries was set up to identify differences between US and European definitions and then conduct surveillance using both sets of definitions during a three-month period (March 1st -May 31st, 2010). Concordance between case definitions was estimated with Cohen's kappa statistic (κ).
  
  
  RESULTS
  Differences in HAI definitions were found for bloodstream infection (BSI), pneumonia (PN), urinary tract infection (UTI) and the two key terms "intensive care unit (ICU)-acquired infection" and "mechanical ventilation". Concordance was analyzed for these definitions and key terms with the exception of UTI. Surveillance was performed in 47 ICUs and 6,506 patients were assessed. One hundred and eighty PN and 123 BSI cases were identified. When all PN cases were considered, concordance for PN was κ = 0.99 [CI 95%: 0.98-1.00]. When PN cases were divided into subgroups, concordance was κ = 0.90 (CI 95%: 0.86-0.94) for clinically defined PN and κ = 0.72 (CI 95%: 0.63-0.82) for microbiologically defined PN. Concordance for BSI was κ = 0.73 [CI 95%: 0.66-0.80]. However, BSI cases secondary to another infection site (42% of all BSI cases) are excluded when using US definitions and concordance for BSI was κ = 1.00 when only primary BSI cases, i.e. Europe-defined BSI with "catheter" or "unknown" origin and US-defined laboratory-confirmed BSI (LCBI), were considered.
  
  
  CONCLUSIONS
  Our study showed an excellent concordance between US and European definitions of PN and primary BSI. PN and primary BSI rates of countries using either US or European definitions can be compared if the points highlighted in this study are taken into account.
authors.affiliation: Institute for Hygiene and Environmental Medicine, Charité - University Medicine Berlin, Campus Benjamin Franklin, Hindenburgdamm 27, D-12203, Berlin, Germany. sonja.hansen@charite.de.
authors.forename: Sonja
authors.initials: S
authors.lastname: Hansen
authors.forename: Dorit
authors.initials: D
authors.lastname: Sohr
authors.forename: Christine
authors.initials: C
authors.lastname: Geffers
authors.forename: Pascal
authors.initials: P
authors.lastname: Astagneau
authors.forename: Alexander
authors.initials: A
authors.lastname: Blacky
authors.forename: Walter
authors.initials: W
authors.lastname: Koller
authors.forename: Ingrid
authors.initials: I
authors.lastname: Morales
authors.forename: Maria Luisa
authors.initials: ML
authors.lastname: Moro
authors.forename: Mercedes
authors.initials: M
authors.lastname: Palomar
authors.forename: Emese
authors.initials: E
authors.lastname: Szilagyi
authors.forename: Carl
authors.initials: C
authors.lastname: Suetens
authors.forename: Petra
authors.initials: P
authors.lastname: Gastmeier