Who breaches the four-hour emergency department wait time target? A retrospective analysis of 374,000 emergency department attendances between 2008 and 2013 at a type 1 emergency department in England

Table 3 Results of multivariate logistic regression to predict breaching the four h target

Variable	Odds ratio with 95% confidence interval	P-Value
Arrival hour^a
20:00–7:59	1.50 (1.47 to 1.54)	<0.001
Day of the week^b
Monday	1.50 (1.43 to 1.56)	<0.001
Tuesday	1.29 (1.24 to 1.35)	<0.001
Wednesday	1.27 (1.21 to 1.33)	<0.001
Thursday	1.11 (1.06 to 1.16)	<0.001
Friday	1.09 (1.04 to 1.14)	<0.001
Sunday	1.18 (1.13 to 1.23)	<0.001
Age (if younger than 4)	0.84 (0.83 to 0.85)	<0.001
Age (if 4 or older)	1.20 (1.19 to 1.23)	<0.001
Self-referral^c	0.59 (0.57 to 0.60)	<0.001
Investigation category^d
Point of care	1.10 (1.01 to 1.19)	<0.001
Labs, point of care	2.41 (2.32 to 2.51)	<0.001
Simple imaging, labs, point of care	2.24 (2.16 to 2.51)	<0.001
Complex imaging, simple imaging, laboratory tests, point of care	4.86 (4.63 to 5.10)	<0.001
Number of attendances in the previous financial year	1.008 (1.006 to 1.011)	<0.001
Year^e
2009	1.63 (1.53 to 1.74)	<0.001
2010	2.25 (2.12 to 2.39)	<0.001
2011	4.64 (4.39 to 4.91)	<0.001
2012	4.92 (4.66 to 5.21)	<0.001
2013	4.28 (4.00 to 4.57)	<0.001
Season
October–February inclusive (high season)^f	1.63 (1.59 to 1.66)	<0.001

^aCompared to arrival between 8:00–19:59
^bThe reference day was Saturday
^cCompared to all other types of referral: emergency services, general medical practitioner, dental practitioners, dental practices, community dental services, police, work, educational establishments, and local authority social services
^dComparison category is “no investigations ordered”
^eThe reference year was 2008
^fCompared to ED attendances in March–September inclusive (Low season)
Model metrics: R² = 12%