Hospital-Acquired Pneumonia among Inpatients via the Emergency Department: A Propensity-Score Matched Analysis

Background: Hospital-acquired pneumonia (HAP) is an inflammatory condition of the lung that develops at least 48–72 h after admission. HAP is contracted by both intensive care unit (ICU) and non-ICU patients, but no studies have examined the risk of HAP in patients admitted to the emergency department (ED). This study investigated the risk of developing HAP in ED patients and compared the occurrence of HAP 3–10 days after the first day of hospitalization in patients hospitalized via ED with those hospitalized via outpatient clinics. Methods: We analyzed the 2010 National Inpatient Sample data collected by the Health Insurance Review and Assessment Service in South Korea. After propensity score matching for age, sex, residential area, hospital, and diseases, 153,130 inpatients (76,565 admitted via ED and 76,565 admitted via outpatient clinics) were included in the analysis. The diagnosis of pneumonia was based on the International Classification of Diseases and Related Health Problems 10th Revision (Pneumonia, all (J12–J18); Pneumonia, bacterial (J13–J15); Pneumonia, non-bacterial (J12, J16, J17); and Pneumonia, unspecified (J18)). Results: The percentage of newly diagnosed cases of pneumonia in inpatients admitted via ED was significantly higher than that in inpatients admitted via outpatient clinics. After propensity score matching for baseline characteristics, the likelihood of developing pneumonia (excluding the category of ‘Pneumonia, non-bacterial’) in inpatients hospitalized via ED was significantly increased by 1.33–1.97-fold. The cumulative incidence of pneumonia was also significantly higher in patients admitted via ED than in those hospitalized via outpatient clinics. Conclusions: ED visits may be an important risk factor for the development of HAP.