Observation stays are composing an increasing proportion of unscheduled hospitalizations in the United States, with unclear consequences for the quality of care. This study used a nationally representative data set of commercially insured patients hospitalized from the emergency department (ED) to compare 30-day postdischarge unplanned care events after an observation stay versus a short inpatient admission.

This was a retrospective analysis of ED hospitalizations using the 2015 Truven MarketScan Commercial Claims and Encounters data set. Adult observation stays and short inpatient hospitalizations of 2 days or less were identified and followed for 30 days from hospital discharge to identify unplanned care events, defined as a subsequent inpatient admission, observation stay, or return ED visit. A propensity score analysis was used to compare rates of unplanned events after each type of index hospitalization.

Among the propensity-weighted cohorts, patients with an index observation stay were 28% more likely to experience any unplanned care event within 30 days of discharge compared with those with a short inpatient admission (20.4% versus 15.9%; risk ratio 1.28; 95% confidence interval [CI] 1.21 to 1.34). Specifically, patients in the observation stay group had substantially higher rates of postdischarge observation stays (4.8% versus 1.9%; odds ratio 2.60; 95% CI 2.15 to 3.16) and ED revisits with discharge (11.1% versus 8.8%; odds ratio 1.26; 95% CI 1.21 to 1.44) compared with those in the inpatient group, but were less likely to be readmitted as inpatients (6.4% versus 7.2%; odds ratio 0.90; 95% CI 0.83 to 0.96).

Commercially insured patients with an observation stay from the ED have a higher risk of postdischarge acute care events compared with similar patients with a short inpatient admission. Additional research is necessary to determine the extent to which quality of care, including care transitions, may differ between these 2 groups.