title: Variations in the hospital standardized mortality ratios in Korea.
abstract: OBJECTIVE
  The hospital standardized mortality ratio (HSMR) has been widely used because it allows for robust risk adjustment using administrative data and is important for improving the quality of patient care.
  
  
  METHODS
  All inpatients discharged from hospitals with more than 700 beds (66 hospitals) in 2008 were eligible for inclusion. Using the claims data, 29 most responsible diagnosis (MRDx), accounting for 80% of all inpatient deaths among these hospitals, were identified, and inpatients with those MRDx were selected. The final study population included 703 571 inpatients including 27 718 (3.9% of all inpatients) in-hospital deaths. Using logistic regression, risk-adjusted models for predicting in-hospital mortality were created for each MRDx. The HSMR of individual hospitals was calculated for each MRDx using the model coefficients. The models included age, gender, income level, urgency of admission, diagnosis codes, disease-specific risk factors, and comorbidities. The Elixhauser comorbidity index was used to adjust for comorbidities.
  
  
  RESULTS
  For 26 out of 29 MRDx, the c-statistics of these mortality prediction models were higher than 0.8 indicating excellent discriminative power. The HSMR greatly varied across hospitals and disease groups. The academic status of the hospital was the only factor significantly associated with the HSMR.
  
  
  CONCLUSIONS
  We found a large variation in HSMR among hospitals; therefore, efforts to reduce these variations including continuous monitoring and regular disclosure of the HSMR are required.
  
  
  
  The hospital standardized mortality ratio (HSMR) has been widely used because it allows for robust risk adjustment using administrative data and is important for improving the quality of patient care.
  
  
  
  All inpatients discharged from hospitals with more than 700 beds (66 hospitals) in 2008 were eligible for inclusion. Using the claims data, 29 most responsible diagnosis (MRDx), accounting for 80% of all inpatient deaths among these hospitals, were identified, and inpatients with those MRDx were selected. The final study population included 703 571 inpatients including 27 718 (3.9% of all inpatients) in-hospital deaths. Using logistic regression, risk-adjusted models for predicting in-hospital mortality were created for each MRDx. The HSMR of individual hospitals was calculated for each MRDx using the model coefficients. The models included age, gender, income level, urgency of admission, diagnosis codes, disease-specific risk factors, and comorbidities. The Elixhauser comorbidity index was used to adjust for comorbidities.
  
  
  
  For 26 out of 29 MRDx, the c-statistics of these mortality prediction models were higher than 0.8 indicating excellent discriminative power. The HSMR greatly varied across hospitals and disease groups. The academic status of the hospital was the only factor significantly associated with the HSMR.
  
  
  
  We found a large variation in HSMR among hospitals; therefore, efforts to reduce these variations including continuous monitoring and regular disclosure of the HSMR are required.
authors.affiliation: Medical Affairs, Janssen, Seoul, Korea.
authors.forename: Eun-Jung
authors.initials: EJ
authors.lastname: Lee
authors.affiliation: Health Insurance Review & Assessment Research Institute, Health Insurance Review and Assessment Service, Seoul, Korea.
authors.forename: Soo-Hee
authors.initials: SH
authors.lastname: Hwang
authors.affiliation: Institute of Health Policy and Management, Medical Research Center, Seoul National University, Seoul, Korea.
authors.forename: Jung-A
authors.initials: JA
authors.lastname: Lee
authors.affiliation: Institute of Health Policy and Management, Medical Research Center, Seoul National University, Seoul, Korea ; Department of Health Policy and Management, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Yoon
authors.initials: Y
authors.lastname: Kim
mesh_terms: D017052:Hospital Mortality; D006761:Hospitals / Q000706:statistics & numerical data*; D006801:Humans; D016015:Logistic Models; D017063:Outcome Assessment, Health Care / Q000592:standards; D011787:Quality of Health Care / Q000592:standards; D056910:Republic of Korea
keywords: Hospital mortality; Outcome assessment; Quality of health care