Table 2. Patient Characteristics of Full Study Cohort and by Triage Group.
| Characteristic | Participant group, No. (%)a | |||
|---|---|---|---|---|
| Overall (N = 5 315 176) | Correct triage (n = 3 601 916) | Overtriage (n = 1 537 129) | Undertriage (n = 176 131) | |
| Age category, y | ||||
| 18-29 | 1 015 662 (19.1) | 564 716 (15.7) | 417 492 (27.2) | 33 454 (19.0) |
| 30-39 | 815 214 (15.3) | 492 144 (13.7) | 297 843 (19.4) | 25 227 (14.3) |
| 40-49 | 707 641 (13.3) | 464 538 (12.9) | 220 648 (14.4) | 22 455 (12.7) |
| 50-59 | 785 815 (14.8) | 546 290 (15.2) | 212 631 (13.8) | 26 894 (15.3) |
| 60-69 | 733 716 (13.8) | 540 933 (15.0) | 165 871 (10.8) | 26 912 (15.3) |
| 70-79 | 622 107 (11.7) | 482 695 (13.4) | 117 363 (7.6) | 22 049 (12.5) |
| ≥80 | 635 021 (11.9) | 510 600 (14.2) | 105 281 (6.8) | 19 140 (10.9) |
| Sex | ||||
| Female | 2 962 867 (55.7) | 2 035 993 (56.5) | 838 211 (54.5) | 88 663 (50.3) |
| Male | 2 352 309 (44.3) | 1 565 923 (43.5) | 698 918 (45.5) | 87 468 (49.7) |
| Race and ethnicity | ||||
| Asian | 590 576 (11.1) | 407 941 (11.3) | 164 240 (10.7) | 18 395 (10.4) |
| Black | 800 984 (15.1) | 491 746 (13.7) | 277 160 (18.0) | 32 078 (18.2) |
| Hispanic | 1 137 459 (21.4) | 747 455 (20.8) | 352 281 (22.9) | 37 723 (21.4) |
| Non-Hispanic White | 2 336 058 (44.0) | 1 655 750 (46.0) | 607 392 (39.5) | 72 916 (41.4) |
| Unknown, missing, or otherb | 450 099 (8.5) | 299 024 (8.3) | 136 056 (8.9) | 15 019 (8.5) |
| English is primary language | 4 868 004 (91.6) | 3 294 538 (91.5) | 1 411 936 (91.9) | 161 530 (91.7) |
| Standardized NDI, mean (SD)c | 0.06 (0.97) | 0.02 (0.96) | 0.14 (0.99) | 0.12 (0.98) |
| Encounter during office hoursd | 1 787 363 (33.6) | 1 260 714 (35.0) | 469 277 (30.5) | 57 372 (32.6) |
| Patient arrived by ambulance | 933 633 (17.6) | 751 999 (20.9) | 142 897 (9.3) | 38 737 (22.0) |
| KPNC member at encounter date | 4 281 599 (80.6) | 3 012 831 (83.6) | 1 130 722 (73.6) | 138 046 (78.4) |
| High-risk medicationse | ||||
| Immunosuppression | 64 523 (1.2) | 50 433 (1.4) | 11 657 (0.8) | 2433 (1.4) |
| Chemotherapy | 197 575 (3.7) | 155 889 (4.3) | 35 535 (2.3) | 6151 (3.5) |
| Insulin or sulfonylurea | 533 872 (10.0) | 416 288 (11.6) | 92 687 (6.0) | 24 897 (14.1) |
| Anticoagulation | 345 323 (6.5) | 281 291 (7.8) | 50 759 (3.3) | 13 273 (7.5) |
| COPS2 risk levelf | ||||
| Low (<20) | 2 655 487 (50.0) | 1 724 218 (47.9) | 851 057 (55.4) | 80 212 (45.5) |
| Medium (20 to <65) | 1 976 329 (37.2) | 1 319 655 (36.6) | 590 549 (38.4) | 66 125 (37.5) |
| High (≥65) | 683 360 (12.9) | 558 043 (15.5) | 95 523 (6.2) | 29 794 (16.9) |
| Recent health care utilization (past 30 d) | ||||
| Any hospitalization | 217 835 (4.1) | 175 472 (4.9) | 33 897 (2.2) | 8466 (4.8) |
| Any intensive care | 41 512 (0.8) | 33 946 (0.9) | 5200 (0.3) | 2366 (1.3) |
| Any ED encounter | 734 264 (13.8) | 517 756 (14.4) | 192 580 (12.5) | 23 928 (13.6) |
| Study year | ||||
| 2016 | 1 015 732 (19.1) | 668 405 (18.6) | 316 188 (20.6) | 31 139 (17.7) |
| 2017 | 1 068 197 (20.1) | 712 669 (19.8) | 320 395 (20.8) | 35 133 (19.9) |
| 2018 | 1 108 704 (20.9) | 750 359 (20.8) | 320 516 (20.9) | 37 829 (21.5) |
| 2019 | 1 155 638 (21.7) | 785 820 (21.8) | 331 598 (21.6) | 38 220 (21.7) |
| 2020 | 966 905 (18.2) | 684 663 (19.0) | 248 432 (16.2) | 33 810 (19.2) |
Abbreviations: COPS2, Comorbidity Point Score, version 2; ED, emergency department; KPNC, Kaiser Permanente Northern California; NDI, Neighborhood Deprivation Index.
Percentages have been rounded and might not total 100. Only 2 variables had missingness greater than 0.5%. All patient and visit characteristic differences by triage category (correct, overtriage, or undertriage) were significant with P < .001. Percentages for age, race, and COPS2 represent column percentages within each respective type of characteristic (age, race, or COPS2). Other percentages represent the absolute percent of encounters with these variables within each row and column.
Includes American Indian or Alaska Native, Native Hawaiian or other Pacific Islander, and more than 1 race.
The NDI for each census tract is based on 13 socioeconomic measures. Scores range from −3.6 to 2.8, with higher values indicating more neighborhood deprivation (lower socioeconomic status). The missingness rate for NDI was 0.8%.
Office hours were defined as ED arrival times from 9 am to 5 pm, Monday through Friday. Nonoffice hours were defined as ED arrival times outside of these time windows.
Active treatment with chemotherapy, immunosuppressants, anticoagulants, and insulin or sulfonylureas was defined as a medication dispensed within the past 6 months.
Indicates a longitudinal comorbidity score based on 12 months of patient data.41 The missingness rate for COPS2 was 18.2%, which is similar to that for non-KPNC membership (19.4%). Nonmembers generally do not have COPS2 scores because the score’s calculation relies on membership for at least 1 month in the quarter the score is calculated.