Variation in diagnostic coding of patients with pneumonia and its association with hospital risk-standardized mortality rates: a cross-sectional analysis

Abstract

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.

Primary funding source: Agency for Healthcare Research and Quality.

Figure 1.. Variation in hospital rate of coding a principal diagnosis of sepsis/respiratory failure among patients with pneumonia.

Figure 2.. Hospital pneumonia mortality rates and proportion of pneumonia cases with a principal diagnosis of sepsis/respiratory failure.

Hospitals are divided into 2 equal groups at the median proportion of sepsis/respiratory failure cases.

Figure 3.. Early admission to the ICU or treatment with invasive mechanical ventilation or vasopressors among patients with pneumonia and a principal diagnosis of sepsis/respiratory failure.

ICU = intensive care unit.

Figure 4.. Risk-standardized mortality rates for each hospital including or excluding patients with a principal diagnosis of sepsis/respiratory failure.

The vertical line represents the mean risk-standardized mortality rate excluding sepsis/respiratory failure. The horizontal line represents the mean risk-standardized mortality rate including sepsis/respiratory failure. Including patients with sepsis/respiratory failure causes a hospital’s outlier status to improve, worsen, or remain the same.

Figure 5.. Number of hospitals whose performance improved, remained the same, or declined when sepsis/respiratory failure cases were included in the definition of pneumonia.