Table 1.

Characteristics of the study population by study period and CT scan status

	Study period								All years 2003–2015 (2 375 787)
	The past period (2003–2005) (n=519 286)				The recent period (2013–2015) (n=572 642)
	Without CT scan (n=473 120)		With CT scan (n=46 166)		Without CT scan (n=477 462)		With CT scan (n=95 180)		Without CT scan (n=2 072 348)		With CT scan (n=303 439)
	N	%	N	%	N	%	N	%	N	%	N	%
Female	237 021	50.1	21 232	46.0	248 412	52.0	43 865	46.1	1 057 280	51.0	137 988	45.5
Age groups
18–44 years	134 467	28.4	10 954	23.7	145 181	30.4	20 075	21.1	621 452	30.0	67 456	22.2
45–64 years	144 820	30.6	12 797	27.7	150 139	31.4	27 225	28.6	651 941	31.5	87 319	28.8
65–74 years	91 075	19.2	8447	18.3	83 797	17.6	16 798	17.6	368 070	17.8	53 332	17.6
75+ years	102 758	21.7	13 968	30.3	98 345	20.6	31 082	32.7	430 885	20.8	95 332	31.4
Indigenous status	31 708	6.7	2111	4.6	32 061	6.7	4540	4.8	137 806	6.6	14 156	4.7
SEIFA
Least disadvantage	129 988	27.5	12 522	27.1	130 427	27.3	27 885	29.3	595 921	28.8	90 660	29.9
Less disadvantage	89 310	18.9	8495	18.4	87 703	18.4	17 850	18.8	364 787	17.6	53 241	17.5
Moderate disadvantage	91 594	19.4	9112	19.7	99 533	20.8	19 549	20.5	449 532	21.7	65 203	21.5
High disadvantage	89 421	18.9	8923	19.3	95 607	20.0	18 104	19.0	388 311	18.7	57 090	18.8
Highest disadvantage	70 595	14.9	6900	14.9	61 291	12.8	11 344	11.9	262 172	12.7	35 691	11.8
Unknown	2212	0.5	214	0.5	2901	0.6	448	0.5	11 625	0.6	1554	0.5
ARIA
Major cities	411 062	86.9	38 086	82.5	416 708	87.3	84 046	88.3	1 807 380	87.2	261 292	86.1
Inner regional areas	29 622	6.3	3663	7.9	19 675	4.1	3508	3.7	108 562	5.2	15 908	5.2
Outer regional areas	16 251	3.4	2155	4.7	19 417	4.1	3814	4.0	75 935	3.7	13 210	4.4
Remote	8968	1.9	1283	2.8	10 654	2.2	1901	2.0	44 727	2.2	7336	2.4
Very remote	6205	1.3	894	1.9	8167	1.7	1458	1.5	28 389	1.4	4731	1.6
Unknown	1012	0.2	85	0.2	2841	0.6	453	0.5	7355	0.4	962	0.3
Number of morbidity (MACSS)  (median-IQR)	2	2–3	4	2–6	2	2–3	4	2–6	2	2–3	3	2–6
Major clinical conditions
Mental and behaviour disorders	11 065	2.3	2015	4.4	15 514	3.2	3296	3.5	61 756	3.0	11 109	3.7
Circulatory system	35 636	7.5	7038	15.2	38 534	8.1	12 434	13.1	162 138	7.8	41 737	13.8
Digestive system	31 437	6.6	5026	10.9	38 055	8.0	10 678	11.2	150 492	7.3	32 897	10.8
Endocrine	9160	1.9	823	1.8	11 074	2.3	1381	1.5	46 268	2.2	5165	1.7
Musculoskeletal system	21 153	4.5	1532	3.3	21 477	4.5	2819	3.0	93 520	4.5	9231	3.0
Respiratory system	15 013	3.2	2918	6.3	17 001	3.6	5241	5.5	68 859	3.3	17 149	5.7
Injury	23 483	5.0	7165	15.5	31 608	6.6	17 913	18.8	126 703	6.1	53 420	17.6
Cancer	21 608	4.6	5389	11.7	22 465	4.7	7520	7.9	96 232	4.6	28 783	9.5
Funding sources
Public	447 927	94.7	42 612	92.3	416 248	87.2	75 202	79.0	1 894 581	91.4	258 126	85.1
Private	25 193	5.3	3554	7.7	61 214	12.8	19 978	21.0	177 767	8.6	45 313	14.9
Unplanned admissions
No	316 762	67.0	6089	13.2	259 764	54.4	9387	9.9	1 245 273	60.1	34 058	11.2
Yes	156 358	33.0	40 077	86.8	217 698	45.6	85 793	90.1	827 075	39.9	269 381	88.8
Transferred from secondary hospitals
No	459 539	97.1	41 742	90.4	455 496	95.4	88 480	93.0	1 990 570	96.1	277 994	91.6
Yes	13 581	2.9	4424	9.6	21 966	4.6	6700	7.0	81 778	3.9	25 445	8.4
Surgical procedure
No	457 900	96.8	42 803	92.7	449 708	94.2	87 721	92.2	1 975 259	95.3	280 008	92.3
Yes	15 220	3.2	3363	7.3	27 754	5.8	7459	7.8	97 089	4.7	23 431	7.7
Morbidity group
0–1	103 369	21.85	6165	13.35	116 826	24.47	13 361	14.04	514 216	24.81	46 686	15.4
2–5	349 557	73.88	27 175	58.86	329 844	69.08	54 377	57.13	1 452 109	70.07	175 377	57.8
6+	20 194	4.27	12 826	27.78	30 792	6.45	27 442	28.83	106 023	5.12	81 376	26.82

ARIA, Accessibility Remoteness of Australia Index; SEIFA, Socio-economic Indexes for Areas.