The 30-day risk-adjusted mortality measures for heart attack, heart failure, and pneumonia are produced from Medicare claims and enrollment data using a sophisticated statistical model. The model predicts patient-level deaths for any cause within 30 days of hospital admission for heart attack or heart failure or pneumonia, whether the patients die while still in the hospital or die after discharge. It calculates a "risk-adjusted" hospital mortality rate that can be used to compare mortality across hospitals. Mortality measures for heart attack, heart failure and pneumonia based on this model have been endorsed by the National Quality Forum (NQF), the non-profit public-private partnership organization that endorses national healthcare performance measures.
The statistical model for computing 30-day risk-adjusted mortality rate measures is a "hierarchical regression model." This type of model is based on the assumption that any heart attack or heart failure or pneumonia patients treated at a particular hospital will experience a level of quality of care that applies to all patients treated for the same condition in that hospital. In other words, the expected risk of death for two similar heart attack or heart failure or pneumonia patients treated in the same hospital would be more alike than the risk of death for the same two patients treated in two different hospitals.
The likelihood that an individual patient will die is therefore a combination of:
Each hospital's "30-day risk-adjusted mortality rate" is computed in several steps. First, the predicted 30-day mortality for a particular hospital obtained from the hierarchical regression model is divided by the expected mortality for that hospital, which is also obtained from the regression model. Predicted mortality is the rate of deaths from heart attack or heart failure or pneumonia that would be anticipated in the particular hospital during the 12-month period, given the patient case mix and the hospital's unique quality of care effect on mortality.
Expected mortality is the rate of deaths from heart attack or heart failure or pneumonia that would be expected if the same patients with the same characteristics had instead been treated at an "average" hospital, given the "average" hospital's quality of care effect on mortality for patients with that condition. This ratio is then multiplied by the national unadjusted mortality rate for the condition for all hospitals to compute a "risk-adjusted mortality rate" for the hospital. So, the higher a hospital's predicted 30-day mortality rate, relative to expected mortality for the hospital's particular case mix of patients, the higher its adjusted mortality rate will be. Hospitals with better quality will have lower rates.