Geography, Not Health System Affiliations, Determines Patients' Revisits to the Emergency Department.

<bold>Objectives: </bold>To determine how frequently patients revisit the emergency department after an initial encounter, and to describe revisit capture rates for the same hospital, health system, and geographic region.<bold>Data Sources/study Setting: </bold>Florida state data from January 1, 2010, to June 30, 2011, from the Healthcare Cost and Utilization Project.<bold>Study Design: </bold>This is a retrospective cohort study of emergency department return visits among Florida adults over an 18-month period. We evaluated pairs of index and 30-day return emergency department visits and compared capture rates for hospital, health system, and geographic units.<bold>Data Collection/extraction Methods: </bold>Data were obtained from the Agency for Healthcare Research and Quality's Healthcare Cost and Utilization Project and the American Hospital Association Annual Survey Database.<bold>Principal Findings: </bold>Among 9,416,212 emergency department visits, 22.6 percent (2,124,441) were associated with a 30-day return. Seventy percent (1,477,772) of 30-day returns occurred to the same hospital. The 30-day return capture rates were highest within the same geographic area: county-level capture at 92 percent (IQR=86-96 percent) versus health system capture at 75 percent (IQR = 68-81 percent).<bold>Conclusions: </bold>Acute care utilization patterns are often independent of health system boundaries. Current population-based health care models that attribute patients to a single provider or health system may be strengthened by considering geographic patterns of acute care utilization. [ABSTRACT FROM AUTHOR]