title: Studying factors related to pressure ulcers prevention: a marginal scale model for modelling heterogeneity among hospitals.
abstract: OBJECTIVE
  The purpose of this study was to analyse risk factors associated with the presence of pressure ulcer development in patients referred to several Italian hospitals, taking properly into account the within-hospital outcome correlation.
  
  
  METHODS
  We analysed data from a prevalence survey coordinated by the European Pressure Ulcer Advisory Panel on 12,000 hospitalized patients in Italy, collecting information on patient's risk, presence of ulcers and prevention measures. The article describes the bases which generalized estimating equations rely on as well as their statistical properties. The article compares different model specifications in the light of background knowledge of the survey data and model assumptions, and discusses the potential for this modelling approach to apply in similar statistical situations.
  
  
  RESULTS
  In accordance with existing literature, factors associated with pressure ulcers in hospitalized patients were identified as Braden scale, age and assistance-connected aspects. Between-hospital variability seemed to be explained by the adopted degree of prevention (use of preventive equipment combined with a repositioning strategy).
  
  
  CONCLUSIONS
  Modelling the covariance matrix or the scale argument of the correlated binary responses (presence/absence of pressure ulcers) by using moment estimators based on generalized estimating equations prevents optimistic inference and provides an important insight into the role of structural differences among hospitals.
authors.affiliation: Unit of Cancer Epidemiology, C.P.O. Piemonte and University of Torino, Torino, Italy.
authors.forename: Ileana
authors.initials: I
authors.lastname: Baldi
authors.forename: Alberto
authors.initials: A
authors.lastname: Ferrando
authors.forename: Francesca
authors.initials: F
authors.lastname: Foltran
authors.forename: Giovannino
authors.initials: G
authors.lastname: Ciccone
authors.forename: Dario
authors.initials: D
authors.lastname: Gregori
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D005260:Female; D019538:Health Care Surveys; D006761:Hospitals; D006801:Humans; D007558:Italy / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D003668:Pressure Ulcer / Q000453:epidemiology / Q000209:etiology / Q000517:prevention & control*; D011787:Quality of Health Care; D012307:Risk Factors; D055815:Young Adult