title: Methicillin-resistant Staphylococcus aureus risk profiling: who are we missing?
abstract: BACKGROUND
  Targeted screening of patients at high risk for methicillin-resistant Staphylococcus aureus (MRSA) carriage is an important component of MRSA control programs, which rely on prediction tools to identify those high-risk patients. Most previous risk studies reported a substantial rate of patients who are eligible for screening, but failed to be enrolled. The characteristics of these missed patients are seldom described. We aimed to determine the rate and characteristics of patients who were missed by a MRSA screening programme at our institution to see how the failure to include these patients might impact the accuracy of clinical prediction tools.
  
  
  RESULTS
  From March-June 2010 all patients admitted to 13 internal medicine wards at the University of Geneva Hospital (HUG) were prospectively screened for MRSA carriage. Of 1968 patients admitted to the ward, 267 patients (13.6%) failed to undergo appropriate MRSA screening. Forty-one (2.4%) screened patients were MRSA carriers at admission. On multivariate regression, patients who were missed by screening were more likely to be aged < 50 years (OR 2.4 [1.4-3.9]), transferred to internal medicine from another ward in the hospital (OR 2.8 [1.1-7.1]), and have a history of malignancy (OR 3.2[2.1-5.1]). There was no significant difference in the rate of previous MRSA carriage between screened and unscreened patients.
  
  
  CONCLUSIONS
  Our findings highlight the potential bias that "missed" patients may introduce into MRSA risk scores. Reporting on the proportions and characteristics of missed patients is essential for accurate interpretation of MRSA prediction tools.
authors.affiliation: Infection Control Program, University of Geneva Hospitals and Faculty of Medicine, 4 Rue Gabrielle Perret-Gentil, Geneva 1211, Switzerland. stephan.harbarth@hcuge.ch.
authors.forename: Janet
authors.initials: J
authors.lastname: Pasricha
authors.forename: Stephan
authors.initials: S
authors.lastname: Harbarth
authors.forename: Thibaud
authors.initials: T
authors.lastname: Koessler
authors.forename: Veronique
authors.initials: V
authors.lastname: Camus
authors.forename: Jacques
authors.initials: J
authors.lastname: Schrenzel
authors.forename: Gilles
authors.initials: G
authors.lastname: Cohen
authors.forename: Didier
authors.initials: D
authors.lastname: Pittet
authors.forename: Arnaud
authors.initials: A
authors.lastname: Perrier
authors.forename: Anne
authors.initials: A
authors.lastname: Iten