title: A robustified modeling approach to analyze pediatric length of stay.
abstract: OBJECTIVE
  Length of stay (LOS) is an important measure of the cost of pediatric hospitalizations, but the guidelines developed so far are not rigorously evidence-based. This study demonstrates a robust gamma mixed regression approach to analyze the positively skewed LOS variable, which has implications for future studies of pediatric health care management.
  
  
  METHODS
  The robustified approach is applied to analyze hospital discharge data on childhood gastroenteritis in Western Australia (n=514). The model accounts for demographic characteristics and co-morbidities of the patients, as well as the dependency of LOS outcomes nested within the 58 hospitals in the State. The method is compared with the standard linear mixed regression with trimming of extreme observations.
  
  
  RESULTS
  For the empirical application, the linear mixed regression results are sensitive to the magnitude of trimming. The identified significant factors from the robust regression model, namely infection, failure to thrive, and iron deficiency anemia are resistant to high-LOS outliers.
  
  
  CONCLUSIONS
  Robust gamma mixed regression appears to be a suitable alternative to analyze the clustered and positively skewed pediatric LOS, without transforming and trimming the data arbitrarily.
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Curtin University of Technology, Perth, Western Australia, Australia. andy.lee@curtin.edu.au
authors.forename: Andy H
authors.initials: AH
authors.lastname: Lee
authors.forename: Michael
authors.initials: M
authors.lastname: Gracey
authors.forename: Kui
authors.initials: K
authors.lastname: Wang
authors.forename: Kelvin K W
authors.initials: KK
authors.lastname: Yau
mesh_terms: D002673:Child, Hospitalized / Q000706:statistics & numerical data*; D005260:Female; D005759:Gastroenteritis / Q000208:ethnology; D006801:Humans; D007223:Infant; D007902:Length of Stay / Q000706:statistics & numerical data*; D008297:Male; D015233:Models, Statistical; D012044:Regression Analysis; D014904:Western Australia