Results

There was a greater proportion of female patients in the dataset than males (47.1% males, χ²=95, df=1, p<0.0001). This pattern was consistent across each of the four hospitals (χ²=4.1, df=3, p=.25). The median age of patients at the first presentation (in cases where multiple presentations occurred within the analysis period) was 51 years (IQR: 31-72).

ED length of stay (ED LOS)

The median LOS was 5 hours and 35 minutes (IQR: 3 hours and 39 minutes to 7 hours and 51 minutes). Overall, 74.53% of the presentations had a stay longer than 4-hours (95% CI 74.05% to 75.02%). The duration of the 95^th percentile ED LOS was 878 minutes (14 hours and 38 minutes). Among the four hospitals, the median ED LOS was consistently the shortest at Hospital A and, with the exception of 2008, consistently the longest at Hospital F (Table 16).

Year	Hospital	Number of ED presentations meeting criteria	Median LOS (minutes)	Median TAT (minutes)	Median number of tests
2008	A	1932	308	49	4
	D	1116	351	68	6
	E	2612	326	51	5
	F	2199	349	68	5
2009	A	2105	296	48	4
	D	1095	367	72	6
	E	2406	312	48	4
	F	2040	385	69	5
2010	A	2208	323	46	4
	D	1166	355	72	6
	E	2472	349	63	4
	F	1981	367	77	5
2011	A	2140	301	53	4
	D	1255	332	53	5
	E	2473	325	55	4
	F	2014	382	66	5

Table 16. Median LOS, TAT, and number of tests by hospital and year.

Pathology testing characteristics

Maximum test TAT before discharge

The median maximum test TAT before discharge from ED was 58 minutes (IQR: 40-88 minutes). The duration of the 95^th percentile maximum test TAT was 3 hours and 40 minutes. There was a moderate positive correlation between maximum TAT and LOS (ρ=0.42; 95% CI: 0.39-0.41). The median TAT at Hospital A was the shortest and at Hospital F it was the longest among four hospitals (see Table 16). This was the same pattern observed for LOS.

Number of tests

Half the presentations involved a minimum of four pathology tests (IQR: 3-6 tests). The number of tests varied more between the calendar years for Hospitals D and E than Hospitals A and F (Table 16). There was a weak positive correlation between the number of tests in a test order episode and ED LOS (ρ=0.14; 95% CI: 0.12-0.15).

Number of pathology departments involved

Of the presentations meeting the inclusion criteria, 77.52% included tests from two pathology departments, most often clinical chemistry and haematology. The results in Table 17 suggest that, as more pathology departments were involved in fulfilling the test order, both the maximum test TAT and the ED LOS were longer.

Number of labs	Number of test order episodes	Median TAT (minutes)	Median LOS (minutes)
1	1857	43	280
2	24197	56	335
3	4760	77	360
4	381	84	379
5	17	91	409
6	2	104	548

Table 17. The number of test order episodes which involved one through six different pathology departments, and the associated median TAT and LOS.

Test order type

EMR was implemented through 2008 and 2009, and became available at Hospital A in 2010, while at Hospitals D, E, and F it was also available for the 2009 period. Each test order episode could be created exclusively using the paper system, exclusively using the EMR system, or using a combination of the two systems. After the implementation of EMR was complete at all hospital EDs, (i.e., 2010), around 74% (in 2010) to 76% (in 2011) of test order episodes were created using EMR; around 2% (in both 2010 and 2011) used only the paper system; and 22% (in 2011) to 24% (in 2010) used a combination of both EMR and paper systems (Figure 3).

Figure 3. Percentage of test order episodes of each order type across the study period.

Across all hospital EDs the median TAT and ED LOS were longest for presentations where the test order episode was created using both the paper and EMR systems compared to presentations where the test order episode was created using the paper or EMR system exclusively (Table 18).

Hospital	Order Type	Number of ED presentations meeting criteria	Median TAT (minutes)	Median LOS (minutes)
A	Paper	4080	48	302
	Paper/EMR	960	83	354
	EMR	3345	47	301
D	Paper	1159	68	353
	Paper/EMR	789	101	384
	EMR	2675	59	335
E	Paper	2818	50	323
	Paper/EMR	1388	82	378
	EMR	5757	52	319
F	Paper	2289	69	351
	Paper/EMR	1400	105	429
	EMR	4545	65	363

Table 18. Median LOS and TAT by hospital and order type.

ED presentation characteristics

Triage category

More than 85% of presentations were triaged as potentially life threatening or potentially serious (categories 3 and 4, respectively). Figure 4 shows that the distribution of patient volume between triage categories was not uniform across the four hospitals (χ²=815, df=12, p<0.0001).

Figure 4. Percentage of ED presentations by triage category in each hospital.

The median test TAT and ED LOS were shorter for presentations with the triage category of immediately life threatening (category 1) than for presentations in the other four triage categories (Table 19).

Triage	Number of ED presentations meeting criteria	Median TAT (IQR) (minutes)	Median LOS (QIR) (minutes)
Immediately life threatening (1)	309	54 (36,77)	271 (175,418)
Imminently life threatening (2)	3541	60 (43,89)	293 (209,410)
Potentially life threatening (3)	14682	58 (40,89)	335 (240,471)
Potentially serious (4)	11928	56 (39,86)	353 (250,490)
Less urgent (5)	754	53 (36,82)	317 ((220,452)

Table 19. Median LOS and TAT by triage category.

Mode of separation

Of the presentations meeting the inclusion criteria, 41.70% had their treatment completed within the ED and were discharged to home, and 56.17% of patients were eventually admitted or transferred to another ward or hospital (Table 20). The median TATs of the different modes of separation varied from 49 to 65 minutes and the median LOS ranged from 246 to 395 minutes (Table 20). Both median TAT and median LOS were longer for patients who were admitted and discharged as an inpatient within ED than for patients with another mode of separation.

ED mode of separation	Number of ED presentations meeting criteria	Median TAT (minutes)	Median LOS (minutes)
Admitted/transferred to another ward/hospital	17534	62	395
Admitteed: Died in ED	40	65	302
Departed: Treatment	13015	54	282
Left at own risk	625	49	246

Table 20. Median LOS and TAT by ED mode of separation.