Emergency Department Volume and Racial and Ethnic Differences in Waiting Times in the United States

BACKGROUND: Racial and ethnic differences in emergency department (ED) waiting times have been observed previously. OBJECTIVES: We explored how adjusting for ED attributes, particularly visit volume, affected racial/ethnic differences in waiting time. RESEARCH DESIGN: We constructed linear models using generalized estimating equations with 2007-2008 National Hospital Ambulatory Medical Care Survey data. SUBJECTS: We analyzed data from 54,819 visits to 431 US EDs. MEASURES: Our dependent variable was waiting time, measured from arrival to time seen by physician, and was log transformed because it was skewed. Primary independent variables were individual race/ethnicity (Hispanic and non-Hispanic white, black, other) and ED race/ethnicity composition (covariates for percentages of Hispanics, blacks, and others). Covariates included patient age, triage assessment, arrival by ambulance, payment source, volume, region, and teaching hospital. RESULTS: Geometric mean waiting times were 27.3, 37.7, and 32.7 minutes for visits by white, black, and Hispanic patients. Patients waited significantly longer at EDs serving higher percentages of black patients; per 25 point increase in percent black patients served, waiting times increased by 23% (unadjusted) and 13% (adjusted). Within EDs, black patients waited 9% (unadjusted) and 4% (adjusted) longer than whites. The ED attribute most strongly associated with waiting times was visit volume. Waiting times were about half as long at low-volume compared with high-volume EDs (P<0.001). For Hispanic patients, differences were smaller and less robust to model choice. CONCLUSIONS: Non-Hispanic black patients wait longer for ED care than whites primarily because of where they receive that care. ED volume may explain some across-ED differences.