Table 1 Baseline characteristics of U.S. patients presenting to the ED, stratified by medical imaging utilization, NHAMCS 2012–2016
| Â | All N(%) | No Imaging N(%) | Any imaging N(%) | X-Ray N(%) | CT Scan N(%) | P value |
|---|---|---|---|---|---|---|
27,665 | 19,271(69.7) | 8394(30.3) | 6922(25.0) | 1367(4.9) | Â | |
Sex | ||||||
 Female | 13,542(48.9) | 9606(70.9) | 3936(29.1) | 3170(23.4) | 625(4.6) | < 0.0001 |
 Male | 14,123(51.1) | 9665(68.4) | 4458(31.6) | 3752(26.6) | 742(5.3) | |
Age category | ||||||
  < 1 year | 3191(12.2) | 2448(76.7) | 743(23.3) | 653(20.5) | 68(2.1) | < 0.0001 |
 1–6 year | 9447(36.2) | 7400(78.3) | 2047(21.7) | 1829(19.4) | 187(2.0) | |
 6–12 year | 6390(24.5) | 4325(67.7) | 2065(32.3) | 1759(27.5) | 291(4.6) | |
 12–18 year | 7033(27.0) | 4118(58.6) | 2915(41.4) | 2271(32.3) | 628(8.9) | |
Ethnic | ||||||
 Hispanic | 6776(24.5) | 4908(72.4) | 1868(27.6) | 1516(22.4) | 272(4.0) | < 0.0001 |
 Non-Hispanic | 20,889(75.5) | 14,363(68.8) | 6526(31.2) | 5406(25.9) | 1095(5.2) | |
Race | ||||||
 White | 14,692(68.9) | 9859(67.1) | 4833(32.9) | 3928(26.7) | 902(6.1) | < 0.0001 |
 Black | 5773(27.1) | 4227(73.2) | 1546(26.8) | 1353(23.4) | 180(3.1) | |
 Asian | 557(2.6) | 393(70.6) | 164(29.4) | 136(24.4) | 19(3.4) | |
 Other | 315(1.5) | 231(73.3) | 84(26.7) | 71(22.5) | 11(3.5) | |
Residence | ||||||
 Private residence | 26,783(99.2) | 18,599(69.4) | 8184(30.6) | 6747(25.2) | 1323(4.9) | 0.1114 |
 Nursing home | 36(0.1) | 22(61.1) | 14(38.9) | 10(27.8) | 7(19.4) | |
 Homeless | 27(0.1) | 20(74.1) | 7(25.9) | 6(22.2) | 2(7.4) | |
 Other | 156(0.6) | 96(61.5) | 60(38.5) | 51(32.7) | 12(7.7) | |
Insurance | ||||||
 Private insurance | 7572(29.7) | 4819(63.6) | 2753(36.4) | 2193(29.0) | 543(7.2) | < 0.0001 |
 Medicare | 235(0.9) | 156(66.4) | 79(33.6) | 61(26.0) | 19(8.1) | |
 Medicaid or CHIP | 15,448(60.6) | 11,212(72.6) | 4236(27.4) | 3562(23.1) | 569(3.7) | |
 Uninsured | 1546(6.1) | 1093(70.7) | 453(29.3) | 365(23.6) | 81(5.2) | |
 Other | 692(2.7) | 459(66.3) | 233(33.7) | 200(28.9) | 46(6.6) | |
Arrival by Ambulance | ||||||
 No | 25,059(93.6) | 17,562(70.1) | 7497(29.9) | 6219(24.8) | 1093(4.4) | < 0.0001 |
 Yes | 1711(6.4) | 1032(60.3) | 679(39.7) | 518(30.3) | 247(14.4) | |
Visit year | ||||||
 2012 | 6641(24.0) | 4526(68.2) | 2115(31.8) | 1714(25.8) | 393(5.9) | < 0.0001 |
 2013 | 5709(20.6) | 4088(71.6) | 1621(28.4) | 1357(23.8) | 240(4.2) | |
 2014 | 5906(21.3) | 4193(71.0) | 1713(29.0) | 1425(24.1) | 272(4.6) | |
 2015 | 4954(17.9) | 3400(68.6) | 1554(31.4) | 1259(25.4) | 262(5.3) | |
 2016 | 4455(16.1) | 3064(68.8) | 1391(31.2) | 1167(26.2) | 200(4.5) | |
Visit month | ||||||
 Dec-Feb | 6718(24.3) | 4705(70.0) | 2013(30.0) | 1697(25.3) | 305(4.5) | 0.0006 |
 Mar-May | 7055(25.5) | 4866(69.0) | 2189(31.0) | 1820(25.8) | 360(5.1) | |
 Jun-Aug | 6745(24.4) | 4815(71.4) | 1930(28.6) | 1562(23.2) | 312(4.6) | |
 Sep-Nov | 7147(25.8) | 4885(68.4) | 2262(31.6) | 1843(25.8) | 390(5.5) | |
Day of Week | ||||||
 Sunday | 4109(14.9) | 2902(70.6) | 1207(29.4) | 1018(24.8) | 168(4.1) | 0.3082 |
 Monday | 4478(16.2) | 3117(69.6) | 1361(30.4) | 1110(24.8) | 227(5.1) | |
 Tuesday | 4008(14.5) | 2781(69.4) | 1227(30.6) | 1010(25.2) | 201(5.0) | |
 Wednesday | 3805(13.8) | 2668(70.1) | 1137(29.9) | 934(24.5) | 192(5.0) | |
 Thursday | 3808(13.8) | 2613(68.6) | 1195(31.4) | 974(25.6) | 201(5.3) | |
 Friday | 3617(13.1) | 2484(68.7) | 1133(31.3) | 940(26.0) | 190(5.3) | |
 Saturday | 3840(13.9) | 2706(70.5) | 1134(29.5) | 936(24.4) | 188(4.9) | |
Arrival time | ||||||
 Morning | 5529(20.4) | 3857(69.8) | 1672(30.2) | 1368(24.7) | 272(4.9) | 0.0001 |
 Afternoon | 7383(27.2) | 5052(68.4) | 2331(31.6) | 1904(25.8) | 385(5.2) | |
 Evening | 5872(21.6) | 3993(68.0) | 1879(32.0) | 1572(26.8) | 292(5.0) | |
 Night | 8344(30.8) | 5936(71.1) | 2408(28.9) | 1996(23.9) | 395(4.7) | |
Triage level | ||||||
 Immediate and Emergent | 1465(7.4) | 921(62.9) | 544(37.1) | 414(28.3) | 148(10.1) | < 0.0001 |
 Urgent and Semi-urgent | 6746(33.9) | 4100(60.8) | 2646(39.2) | 2000(29.6) | 566(8.4) | |
 Nonurgent | 11,698(58.8) | 8669(74.1) | 3029(25.9) | 2737(23.4) | 273(2.3) | |
Temperature | ||||||
 36 C-38 C | 22,667(86.9) | 15,719(69.3) | 6948(30.7) | 5651(24.9) | 1199(5.3) | 0.8118 |
  < =36 C | 684(2.6) | 475(69.4) | 209(30.6) | 161(23.5) | 39(5.7) | |
  > 38 C | 2742(10.5) | 1918(69.9) | 824(30.1) | 774(28.2) | 43(1.6) | |
Diastolic BP | ||||||
 60–80 | 11,502(41.6) | 7482(65.0) | 4020(35.0) | 3225(28.0) | 734(6.4) | < 0.0001 |
  < 60 | 13,541(48.9) | 10,228(75.5) | 3313(24.5) | 2875(21.2) | 396(2.9) | |
  > 80 | 2622(9.5) | 1561(59.5) | 1061(40.5) | 822(31.4) | 237(9.0) | |
Systolic BP | ||||||
 80–120 | 11,152(40.3) | 7604(68.2) | 3548(31.8) | 2873(25.8) | 596(5.3) | < 0.0001 |
  < 80 | 10,238(37.0) | 7966(77.8) | 2272(22.2) | 2047(20.0) | 200(2.0) | |
  > 120 | 6275(22.7) | 3701(59.0) | 2574(41.0) | 2002(31.9) | 571(9.1) | |
Heart Rate | ||||||
  < 60 | 7589(27.4) | 4618(60.9) | 2971(39.1) | 2302(30.3) | 607(8.0) | < 0.0001 |
 60–90 | 2687(9.7) | 1979(73.7) | 708(26.3) | 584(21.7) | 131(4.9) | |
  > 90 | 17,389(62.9) | 12,674(72.9) | 4715(27.1) | 4036(23.2) | 629(3.6) | |
Pulse Oximetry | ||||||
  < 95 | 788(3.3) | 444(56.3) | 344(43.7) | 316(40.1) | 39(4.9) | < 0.0001 |
  > =95 | 23,430(96.7) | 16,214(69.2) | 7216(30.8) | 5934(25.3) | 1214(5.2) | |
Pain level | ||||||
 Mild | 9097(54.0) | 7123(78.3) | 1974(21.7) | 1649(18.1) | 300(3.3) | < 0.0001 |
 Moderate | 4677(27.8) | 2613(55.9) | 2064(44.1) | 1650(35.3) | 364(7.8) | |
 Very severe | 3062(18.2) | 1608(52.5) | 1454(47.5) | 1152(37.6) | 286(9.3) | |
Injury/poisoning | ||||||
 Injury/trauma | 8963(33.5) | 4886(54.5) | 4077(45.5) | 3551(39.6) | 703(7.8) | < 0.0001 |
 Overdose/poisoning | 280(1.0) | 241(86.1) | 39(13.9) | 37(13.2) | 5(1.8) | |
 Adverse effect of medical/surgical treatment | 296(1.1) | 236(79.7) | 60(20.3) | 47(15.9) | 17(5.7) | |
 Not related to any above | 17,112(64.0) | 13,111(76.6) | 4001(23.4) | 3119(18.2) | 603(3.5) | |
 Questionable injury status | 81(0.3) | 66(81.5) | 15(18.5) | 10(12.3) | 5(6.2) | |
72 h Revisit | ||||||
 Yes | 1029(4.1) | 745(72.4) | 284(27.6) | 223(21.7) | 53(5.2) | 0.0429 |
 No | 24,092(95.9) | 16,728(69.4) | 7364(30.6) | 6053(25.1) | 1201(5.0) | |
Cancer | ||||||
 Yes | 74(0.3) | 45(60.8) | 29(39.2) | 23(31.1) | 8(10.8) | 0.0974 |
 No | 27,591(99.7) | 19,226 | 8365 (30.3) | 6899 (35.9) | 1359 (4.9) | |
Cerebral Cardiovascular disease | ||||||
 Yes | 16(0.1) | 6(37.5) | 10(62.5) | 8(50.0) | 6(37.5) | 0.0051 |
 No | 27,649(99.9) | 19,265 (69.8) | 8384(30.3) | 6914(35.9) | 1361 (4.9) | |
Congestive Heart Failure | ||||||
 Yes | 8(0.1) | 3(37.5) | 5(62.5) | 4(50.0) | 1(12.5) | 0.0478 |
 No | 27,657(99.9) | 19,268(69.8) | 8389(30.3) | 6918(35.9) | 1366 (4.9) | |
COPD | ||||||
 Yes | 135(0.5) | 63(46.7) | 72(53.3) | 70(51.9) | 1(0.7) | < 0.0001 |
 No | 27,530(99.5) | 19,208(69.8) | 8322(30.3) | 6852(35.7) | 1366 (5.0) | |
HIV | ||||||
 Yes | 17(0.1) | 13(76.5) | 4(23.5) | 3(17.6) | 1(5.9) | 0.5411 |
 No | 27,648(99.9) | 19,258(69.8) | 8390(30.3) | 6919(35.9) | 1366 (5.0) | |