We describe the recidivism characteristics of an adult emergency department (ED) observation unit population and determine whether rates differ according to demographic or clinical features.

This prospective observational cohort study of a protocol-driven ED observation unit reviewed all discharged ED observation unit patients who returned within 14 days of discharge for an unscheduled ED visit or direct inpatient admission to the study hospital, or a proximate affiliated hospital, during 6 consecutive months. Age, sex, initial ED observation unit diagnosis, ED observation unit length of stay, and return visit disposition were determined from hospital databases and confirmed by chart review. All return visits were classified as related or unrelated to the index visit.

There were 55,727 ED visits, with 4,348 patients admitted to the ED observation unit, of whom 80.7% (3,509) were discharged. Patients with or without a return visit were similar in terms of age (56.9 years [standard deviation (SD) 19.5 years]), percentage of male patients (40.0%), or initial ED observation unit length of stay (15.0 hours [SD 6.0 hours]). Of discharged ED observation unit patients, 375 (10.8%) had a return visit, of which 277 (7.9%) were related. Of return visits, 86.3% of patients had only 1 return visit, 11.6% had 2, and 2.1% had 3 or more; 4.2% of returns occurred at an affiliated hospital. Time to first return visit was clustered within the first week for related visits, with a mean time to return of 4.5 days (SD 3.9 days). On return visit, 40.2% of patients were treated and discharged from the ED, 36.2% were treated in the ED and admitted, 14.4% were treated in the ED and then the ED observation unit and discharged home, 12.3% were directly admitted to the hospital, and 2.5% were treated in the ED and then the ED observation unit and admitted. Among common conditions, related return visit rates were highest for headache (16.1%), back pain (13.8%), and abdominal pain (12.7%) and lowest for chest pain (3.6%). As a group, therapeutic protocols, and specifically painful conditions, had significantly higher related return visit rates than diagnostic protocols (10.8% versus 5.1%).

Patients who return after an ED observation unit visit are similar to patients who do not return in terms of age, sex, or initial length of stay. However, ED observation unit recidivism rates do differ according to observation category, with painful conditions showing the highest recidivism rates.