title: Outcomes of an intervention to improve hospital antibiotic prescribing: interrupted time series with segmented regression analysis.
abstract: OBJECTIVE
  To evaluate an intervention to reduce inappropriate use of key antibiotics with interrupted time series analysis.
  
  
  METHODS
  The intervention is a policy for appropriate use of Alert Antibiotics (carbapenems, glycopeptides, amphotericin, ciprofloxacin, linezolid, piperacillin-tazobactam and third-generation cephalosporins) implemented through concurrent, patient-specific feedback by clinical pharmacists. Statistical significance and effect size were calculated by segmented regression analysis of interrupted time series of drug use and cost for 2 years before and after the intervention started.
  
  
  RESULTS
  Use of Alert Antibiotics increased before the intervention started but decreased steadily for 2 years thereafter. The changes in slope of the time series were 0.27 defined daily doses/100 bed-days per month (95% CI 0.19-0.34) and pound 1908 per month (95% CI pound 1238- pound 2578). The cost of development, dissemination and implementation of the intervention ( pound 20133) was well below the most conservative estimate of the reduction in cost ( pound 133296), which is the lower 95% CI of effect size assuming that cost would not have continued to increase without the intervention. However, if use had continued to increase, the difference between predicted and actual cost of Alert Antibiotics was pound 572448 (95% CI pound 435696- pound 709176) over the 24 months after the intervention started.
  
  
  CONCLUSIONS
  Segmented regression analysis of pharmacy stock data is a simple, practical and robust method for measuring the impact of interventions to change prescribing. The Alert Antibiotic Monitoring intervention was associated with significant decreases in total use and cost in the 2 years after the programme was implemented. In our hospital, the value of the data far exceeded the cost of processing and analysis.
authors.affiliation: Department of Clinical Pharmacology, University of Dundee, Dundee DD1 9SY, Dundee.
authors.forename: Faranak
authors.initials: F
authors.lastname: Ansari
authors.forename: Kirsteen
authors.initials: K
authors.lastname: Gray
authors.forename: Dilip
authors.initials: D
authors.lastname: Nathwani
authors.forename: Gabby
authors.initials: G
authors.lastname: Phillips
authors.forename: Simon
authors.initials: S
authors.lastname: Ogston
authors.forename: Craig
authors.initials: C
authors.lastname: Ramsay
authors.forename: Peter
authors.initials: P
authors.lastname: Davey
mesh_terms: D000900:Anti-Bacterial Agents / Q000191:economics / Q000627:therapeutic use*; D011307:Drug Prescriptions / Q000592:standards; D017723:Drug Utilization Review; D019983:Guideline Adherence; D006785:Hospitals, University; D006801:Humans; D010564:Personnel, Hospital; D010607:Pharmacy Service, Hospital / Q000706:statistics & numerical data; D010818:Practice Patterns, Physicians' / Q000592:standards*; D015397:Program Evaluation; D012044:Regression Analysis
chemical_list: D000900:Anti-Bacterial Agents