Methods
Study design
In this retrospective cohort study, the sample included
all episodes of inpatient care experienced by patients admitted
from the ED to the inpatient setting at a 420-bed
hospital in southern Sweden during 2011–2012 and discharged
before 1 December 2012. The 30-day readmission
rate for discharged patients at this hospital was previously
estimated to be about 9 %. For the purposes of this study,
an increase of 2 % was considered to be clinically relevant.
To limit bias, the study material was not subject to further
restrictions. Post hoc power calculations were performed
to determine the number of strata (see cut-offs in
the Statistical Analysis section) of inpatient bed occupancy
to use for group comparisons (α = 0.05, 1-β = 0.80) [17].