Modelling interrupted time series to evaluate prevention and control of infection in healthcare

V. Gebski, K. Ellingson, J. Edwards, J. Jernigan, D. Kleinbaum

Research output: Contribution to journalArticlepeer-review

40 Scopus citations


The most common methods for evaluating interventions to reduce the rate of new Staphylococcus aureus (MRSA) infections in hospitals use segmented regression or interrupted time-series analysis. We describe approaches to evaluating interventions introduced in different healthcare units at different times. We compare fitting a segmented Poisson regression in each hospital unit with pooling the individual estimates by inverse variance. An extension of this approach to accommodate potential heterogeneity allows estimates to be calculated from a single statistical model: a 'stacked' model. It can be used to ascertain whether transmission rates before the intervention have the same slope in all units, whether the immediate impact of the intervention is the same in all units, and whether transmission rates have the same slope after the intervention. The methods are illustrated by analyses of data from a study at a Veterans Affairs hospital. Both approaches yielded consistent results. Where feasible, a model adjusting for the unit effect should be fitted, or if there is heterogeneity, an analysis incorporating a random effect for units may be appropriate.

Original languageEnglish (US)
Pages (from-to)2131-2141
Number of pages11
JournalEpidemiology and infection
Issue number12
StatePublished - 2012
Externally publishedYes


  • Methicillin-resistant S. aureus (MRSA)
  • modelling
  • public health

ASJC Scopus subject areas

  • Epidemiology
  • Infectious Diseases


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