Approaches with reference standards and measures in the validation of Australasian Triage System, Canadian Triage and Acuity System (CTAS), Emergency Severity Index (ESI) and Manchester Triage Systems (MTS)
| Approaches | All | CTAS (14 studies) | ESI (21 studies) | MTS (14 studies) |
| 1. Agreement of assigned urgency levels with objective standard criteria set for studies (criterion validity) | 9 | 1 | 3 | 7 |
| 2. Overtriage and undertriage (criterion validity) | 8 | 1 | 3 | 5 |
| 3. Sensitivity and specificity for certain outcomes (criterion validity) | 7 | – | 4 | 4 |
| 4. Associations between actual urgency levels of patients and measures in EDs (construct validity) | ||||
| Overall admissions | 33 | 11 | 17 | 8 |
| ED length of stay | 19 | 6 | 12 | 1 |
| Number of resource used in EDs | 17 | 4 | 13 | 2 |
| Mortality | 9 | 2 | 4 | 4 |
| Admissions to intensive care or monitored units | 8 | 4 | 2 | 1 |
| Costs | 7 | 3 | 3 | 1 |
| Leaving without being seen | 3 | 2 | 1 | – |
| Waiting times before examinations by physicians | 1 | 1 | – | – |
| Referrals to outpatients after the discharge from EDs | 1 | – | 1 | – |
| 5. Associations between actual urgency levels of patients and outcomes after hospitalisation (construct validity) | ||||
| In-hospital mortality | 8 | 2 | 5 | 2 |
| Hospital length of stay | 6 | 1 | 2 | 3 |
| Costs after hospitalisation | 1 | 1 | – | – |
| Six-month survival | 1 | – | 1 | – |
| Thirty-day mortality | 1 | – | – | 1 |