Relationship between discharge practices and intensive care unit in-hospital mortality performance: evidence of a discharge bias

Med Care. 2009 Jul;47(7):803-12. doi: 10.1097/MLR.0b013e3181a39454.


Context: Current intensive care unit performance measures include in-hospital mortality after intensive care unit admission. This measure does not account for deaths occurring after transfer to another hospital or soon after discharge and therefore, may be biased.

Objective: Determine how transfer rates to other acute care hospitals and early post-discharge mortality rates impact hospital performance assessments using an in-hospital mortality model.

Design, setting, and participants: Data were retrospectively collected on 10,502 eligible intensive care unit patients across 35 California hospitals between 2001 and 2004.

Measures: We calculated the rates of acute care hospital transfers and early post-discharge mortality (30-day overall mortality-30-day in-hospital mortality) for each hospital. We assessed hospital performance with standardized mortality ratios (SMRs) using the Mortality Probability Model III. Using regression models, we explored the relationship between in-hospital SMRs and the rates of hospital transfers or early post-discharge mortality. We explored the same relationship using a 30-day SMR.

Results: In multivariable models, for each 1% increase in patients transferred to another acute care hospital, there was an in-hospital SMR reduction of -0.021 (-0.040-0.001). Additionally, a 1% increase in early post-discharge mortality was associated with an in-hospital SMR reduction of -0.049 (-0.142-0.045). Assessing hospital performance based upon 30-day mortality end point resulted in SMRs closer to 1.0 for hospitals at high and low ends of in-hospital mortality performance.

Conclusions: Variations in transfer rates and potentially discharge timing appear to bias in-hospital SMR calculations. A 30-day mortality model is a potential alternative that may limit this bias.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Bias
  • California
  • Critical Care / statistics & numerical data*
  • Female
  • Health Care Surveys
  • Health Facility Size
  • Healthcare Disparities / statistics & numerical data*
  • Hospital Mortality*
  • Humans
  • Intensive Care Units / statistics & numerical data
  • Male
  • Middle Aged
  • Multivariate Analysis
  • Outcome Assessment, Health Care / methods
  • Outcome Assessment, Health Care / standards
  • Patient Discharge / statistics & numerical data*
  • Patient Transfer / statistics & numerical data
  • Practice Patterns, Physicians' / statistics & numerical data*
  • Predictive Value of Tests
  • Quality Indicators, Health Care / statistics & numerical data
  • Regression Analysis
  • Retrospective Studies
  • Risk Adjustment / methods
  • Risk Adjustment / standards
  • Sensitivity and Specificity
  • Statistics, Nonparametric
  • Time Factors
  • Young Adult