Variation in Diagnostic Coding of Patients With Pneumonia and Its Association With Hospital Risk-Standardized Mortality Rates A Cross-sectional Analysis

Background: Most U.S. hospitals publicly report 30-day risk-standardized mortality rates for pneumonia. Rates exclude severe cases, which may be assigned a secondary diagnosis of pneumonia and a principal diagnosis of sepsis or respiratory failure. By assigning sepsis and respiratory failure codes more liberally, hospitals might improve their reported performance. Objective: To examine the effect of the definition of pneumonia on hospital mortality rates. Design: Cross-sectional study. Setting: 329 U. S. hospitals. Patients: Adults hospitalized for pneumonia (as a principal diagnosis or secondary diagnosis paired with a principal diagnosis of sepsis or respiratory failure) between 2007 and 2010. Measurements: Proportion of patients with pneumonia coded with a principal diagnosis of sepsis or respiratory failure and risk-standardized mortality rates excluding versus including a principal diagnosis of sepsis or respiratory failure. Results: When the definition of pneumonia was limited to patients with a principal diagnosis of pneumonia, the risk-standardized mortality rate was significantly better than the mean in 4.3% of hospitals and significantly worse in 6.4%. When the definition was broadened to include patients with a principal diagnosis of sepsis or respiratory failure, this rate was better than the mean in 11.9% of hospitals and worse in 22.8% and the outlier status of 28.3% of hospitals changed. Among hospitals in the highest quintile of proportion of patients coded with a principal diagnosis of sepsis or respiratory failure, outlier status under the broader definition improved in 7.6% and worsened in 40.9%. Among those in the lowest quintile, 20.0% improved and none worsened. Limitation: Only inpatient mortality was studied. Conclusion: Variation in use of the principal diagnosis of sepsis or respiratory failure may bias efforts to compare hospital performance regarding pneumonia outcomes.