The relationship between ED LOS and the pathology service

Table 21 shows the factors which make significant contributions to the changes of ED LOS with consideration of the correlation between presentations at the same hospital in the same calendar year. The model accounts for 24% of the variation in ED LOS. The inclusion of TAT and the number of tests ordered in the model explains more than 10% of the variation in ED LOS.
Table 21 shows that, everything else being equal, every 60 minute increase in maximum test turnaround time was, on average, associated with a 9.84% increase in ED LOS (95% CI: 9.49% to 10.19%; p<.0001). This constitutes strong evidence that the pathology test turnaround time affects patients’ length of stay within the ED when controlling for patient age, triage category, number of tests conducted during the ED stay and ED mode of separation and taking into account the correlation between presentations at the same hospital in the same calendar year. Another important factor related to the pathology testing revealed by this analysis is the number of tests ordered for each presentation. Each additional five tests ordered within a presentation was, on average, associated with a 2.84% increase in ED LOS after adjustment for the other factors in the model, a small but significant effect (95% CI: 1.68% to 4.29%; p<.0001).

Variables		% change#^ (95% CI)	p-value
Age (for each additional 5 years)		1.14(1.03, 1.25)	<.0001
Triage category	Immediately life threatening (1)	1.00	<.0001
	Imminently life threatening (2)	11.30(5.73, 16.87)	<.0001
	Potentially life threatening (3)	33.84(27.49, 40.19)	<.0001
	Potentially serious (4)	32.99(27.57, 38.41)	<.0001
	Less urgent (5)	40.70(35.25, 46.15)	<.0001
TAT (Max, for each additional 60 minutes)		9.84(9.49, 10.19)	<.0001
# of tests (for each additional 5 tests)		2.84(1.54, 4.15)	<.0001
	Admitted/transferred to another ward/hospital	1.00
	Admitted: Died in ED	-1.23(-16.12, 13.67)	0.87
	Departed: Treatment completed	-30.90(-32.04, -29.77)	<.0001
	Left at own risk	-43.26(-47.04, -39.49)	<.0001
^The percent change in the LOS for one defined unit increase in the independent variable while all other variables in the model are held constant

Table 21. The relationship between ED LOS and TAT: model results.

The model helps us understand of the contribution of pathology testing, TAT and the number of tests in particular, to ED LOS. However, a large proportion of variation in ED LOS is not accounted for by the model and more information, such as patients’ condition, treatment received, and clinical staffing levels, would greatly assist further investigation of this issue.