The impact of emergency department observation units on United States emergency department admission rates

Objective: Prior studies suggesting that the presence of emergency department (ED) observation units decrease overall ED hospital admissions have been either single-center studies or based on model simulations. The objective of this preliminary national study is to determine if the presence of ED observation units is associated with hospitals having lower ED admission rates. Methods: We conducted a retrospective cross-sectional analysis using the 2010 National Hospital Ambulatory Care Survey and estimated ED risk-standardized hospital admission rates (RSHAR) for each center. The following were excluded from the study: ages <18 years, leaving prior to completion of ED visit, died in the ED, transferred to another facility, and missing disposition. Hospitals with less than 30 ED visits or unknown observation unit status were also excluded. We used linear regression analysis to determine the association between ED RSHAR and presence of observation units. Results: There were 24,232 ED visits in 315 hospitals in the United States. Of these, 82 (20.6%) hospitals had an ED observation unit. The average ED risk-standardized hospital admission rates for hospitals with observation units and without hospital observation units were 13.7% (95% confidence interval [CI]: 11.3-16.0) and 16.0% (95% CI: 14.1-17.7), respectively. The difference of 2.3% was not statistically significant. Conclusions: In this preliminary study, we did not find an association between the presence of observation units and ED hospital admission rates. Further studies with larger sample sizes should be performed to further evaluate the impact of ED observation units on ED hospital admission rates.