Variations in coding practices related to pneumonia cases may bias efforts to compare quality of care among hospitals, according to an article published in Annals of Internal Medicine.

Pneumonia is the most common reason for emergency hospitalization in the United States, making it an appropriate target for quality improvement initiatives and public reporting of hospital quality.

Hospital risk-standardized mortality rates for pneumonia are publicly reported but exclude more severe cases of pneumonia, which are coded as sepsis or respiratory failure with pneumonia as a secondary diagnosis.

Researchers studied hospital records for 329 U.S. hospitals to examine the effect of the definition of pneumonia on hospital mortality rates.

The records showed that the risk-standardized mortality rate tended to increase when sepsis or respiratory failure were included in a broader definition of pneumonia in hospitals that assigned these codes to a greater proportion of patients and to decrease when hospitals applied these codes to a smaller proportion of cases.

The researchers conclude that performance measures based on pneumonia coding may misclassify some hospitals and weaken confidence in public reporting.