title: Do patient safety events increase readmissions?
abstract: OBJECTIVE
  Adverse safety events in the hospital could impose extra costs not only due to longer stays and corrective treatments, but also due to deaths and readmissions. The effects of safety events on readmissions have rarely been analyzed. Large, all-payer and all-diagnosis databases permit new tests. This study will simultaneously test the effects of safety events on risks of deaths and readmission.
  
  
  METHODS
  The population is a selection of almost 1.5 million adult surgery patients initially treated in 1088 short stay hospitals. These are patients at risk for at least 1 of 9 types of patient safety event, as specified in software in the public domain from the Agency for Healthcare Research and Quality. The main data sources are 7 statewide databases of hospitalizations in 2004, maintained by Agency for Healthcare Research and Quality's Healthcare Cost and Utilization Project. We control for many factors affecting readmission or death, particularly the severity of illness, chronic comorbidities, age, and payer group. Separate models are used for each type of safety event and a composite model is used for any safety event.
  
  
  RESULTS
  Among the patients at risk for any of the patient safety events, 2.6% had at least one safety event. The 3-month readmission rate was about 17% for those with no safety event, but about 25% when a safety event was recorded. The corresponding rates for readmission within 1 month were 11% and 16%. The in-hospital death rate was 1.3% with no safety event, but 9.2% with a safety event. After risk adjustment, the relative risk of readmission within 3 months was about 1.20 (P < 0.01), ranging from 1.14 to 1.56 for specific types of events. The risk-adjusted result for readmission within 1 month associated with at least one safety event was 1.17 (P < 0.01). However, the models for specific safety events gave a significantly high risk of readmission within 1 month for only 2 of the more common types of safety events.
  
  
  CONCLUSIONS
  Hospital readmissions are one way that safety events can have costly consequences. More attention is warranted to assess the full extra cost of safety events, the factors influencing the rate of safety events, and strategies for health plans to improve incentives for safety.
authors.affiliation: Agency for Healthcare Research and Quality, 540 Gaither Road, Rockville, MD 20850, USA. bernard.friedman@ahrq.hhs.gov
authors.forename: Bernard
authors.initials: B
authors.lastname: Friedman
authors.forename: William
authors.initials: W
authors.lastname: Encinosa
authors.forename: H Joanna
authors.initials: HJ
authors.lastname: Jiang
authors.forename: Ryan
authors.initials: R
authors.lastname: Mutter