The comparability of emergency department waiting time performance data

Abstract

Objective: To examine whether the reported urgency mix of an emergency department's (ED's) patients is associated with its waiting time performance. Design and setting: Cross-sectional analysis of data on patient urgency mix and hospital ED performance reported on the MyHospitals website for July 2009 - June 2010. Main outcome measures: ED performance assessed as the proportion of patients whose care was initiated within the recommended time frame for each of four triage categories. Results: Data for 158 hospitals showed that EDs with a higher proportion of patients assigned to the emergency category have poorer waiting time performance, after adjusting for hospital characteristics. Conversely, EDs with a higher proportion of patients assigned to the non-urgent category perform better. If performance scores were adjusted for reported patient urgency mix and hospital peer group, mean adjustments would be modest in size (3.7-7.1 percentage points, depending on the category), but for individual EDs the differences could be large (as large as 31 percentage points) and hospital waiting time performance rankings would be substantively impacted. Conclusion: Since ED performance is related to reported patient urgency mix, adjusting for casemix in the ED may be warranted to ensure valid comparisons between hospitals. Further investigation of the validity of performance measures and appropriate adjustment for differences in hospital and patient characteristics is required if public reporting is to meet its goals.