Table 3.

Under-triage rates in the included studies

Study	Main findings
Brown et al. (2019) [58]	The majority of injured younger patients were transported to a TC (n = 578, 55%) whereas the majority of injured older patients were transported to a non-TC (n = 232 [40%], P < 0.001) The odds of transporting older trauma patients to TCs in Australia decreased with age as those who aged 65 to 74 years had a 48% reduction in the rate of TC transport (adjusted OR 0.52, 95% CI 0.35–0.78) compared to 63% reduction for others aged ≥ 85 years (adjusted OR 0.37, 95% CI 0.24–0.55) Overall, a fall from standing resulted in more than 53% reduced odds of TC transport (adjusted OR 0.47, 95% CI 0.33–0.67) Positive predictors of TC transport included motor vehicle crash (adjusted OR 2.5, 95% CI 1.6–4.0) and male gender (adjusted OR 1.4, 95% CI 1.1–1.8)
Chang et al. (2008) [46]	The rate of under-triage among older trauma patients was 50% compared to 18% for younger trauma patients (P < 001) Older trauma patients who aged ≥ 65 years had a 52% reduced chance to be transported to TCs (OR, 0.48; 95% CI 0.30–0.76) after controlling of possible confounding factors (year, sex, physiology, injury, or mechanism criteria, transport reasons, prehospital care provider training level, presence or absence of 18 specific injuries, and jurisdictional region)
Cox et al. (2014) [37]	In a univariate logistic analysis, with each increase of age by one year, the chance of being transported to TCs decreased by 2 percent (OR 0.982, 95% CI 0.982–0.983) The unadjusted odds of transporting injured older adults to a TC was 57% lower (OR 0.431; 95% CI 0.416, 0.446) than for injured younger adults
Davis et al. (2012) [38]	For injured patients who aged 15 to 54 years, 83% of them were positively triaged by Florida Trauma Triage Algorithm (FTTA) and 86% had ISS > 15 (OR 2.88, 95% CI 2.44–3.41). The OR for patients with ISS > 15 was 6.53 (95% CI 4.07–10.47) In comparison, injured patients who aged ≥ 55 years, 59% of them who were positively triaged by FTTA and 64% had ISS > 15 (OR 1.03, 95% CI 0.93–1.15). (OR 1.67, 95% CI 1.08–2.58). The OR of the triaging effect for patients aged ≥ 55 years with ISS > 15 was slightly increased (OR 1.67, 95% CI 1.08–2.58) compared to those with lower injury severity (i.e., ISS 0–15) (OR 1.00, 95% CI 0.89–1.12)
Garwe et al. (2017) [47]	Older injured adults had a higher chance of being transferred to non-TCs in comparison with younger trauma patients (53% vs. 34%, p < 0.05) Older injured patients also had a less chance to be transported by HEMS (14.6% vs. 20%, p < 0.05) After controlling for confounding factors and distance measures, the study showed that older trauma patients had a significantly less chance of being transported to and treated at TCs (OR = 0.54, 95% CI 0.52–0.56), whether they were initially transported by ambulance from the scene (OR = 0.47, 95% CI 0.44–0.50) or through inter-facility transfers from non-TCs (OR = 0.63, 95%CI 0.59–0.68)
Garwe et al. (2020) [55]	The results of this study showed that 57% of older trauma patients were treated at non-TCs compared to 43% at TCs Patients treated at TCs were younger, predominantly (P < 0.05) male, had traffic-related or penetrating injuries, more likely to be transported by ambulance from the injury scene, and injured to place close from tertiary or level III TCs Patients aged ≥ 65 years had a disproportionately higher rate of treatment at non-TCs than that at TCs (82% vs 64%) and the majority of the injuries (82%) were fall-related
Horst et al. (2020) [56]	The median under-triage rate for older trauma patients was 50.5% (Inter-quartile Range [IQR], 38.2–60.1%)
Ichwan et al. (2015) [48]	When the outcome is determined as ISS > 15, the current triage guidelines showed a high sensitivity for younger adults (87%; 95% CI 86%-87%), but a significantly decreased sensitivity for older adults (61%; 95% CI 60%-62%)
Kodadek et al. (2015) [42]	There was a reduction trend in transporting patients to lower TCs with increased NISS as 76%.2 of patients with NISS < 9 were transported to lower or non-TCs which then decreased to 66.2% with NISS between 9 to 15, and 44.8% with NISS between 16 to 24 However, for patients who had NISS ≥ 25, 54.1% of them were treated at lower or non-TCs Even when older trauma patients living in rural areas were excluded, the rate for under-triage was still high (55.8%) For older trauma patients, most injuries treated at lower or non-TCs as well as those at higher level TCs were resulted from falls (71.3% and 59.3%, respectively). However, 16.5% of patients with injuries resulted from motor vehicle accidents were treated at higher level TCs compared to only 5% who were treated at lower or non-TCs (P < 0.001)
Meyers et al. (2019) [50]	The proportion of geriatric patients meeting physiological criteria of the Trauma Triage Destination Plans (TTDP) who were transported to TCs was 24.4% pre-TTDP and 24.4% post-TTDP Few patients bypassed a closer hospital to a TC (pre-TTDP, 12.6% [n = 250; 95% CI 11.1–14.1]; post-TTDP, 11.9% [n = 282; 95% CI 10.6–13.2] Even when trauma was within 60 min from a TC, still few patients bypassed to a TC (pre TTDP, 17.9% [n = 220; 95% CI 15.8–20.1]; post-TTDP, 16.7% [n = 248; 95% CI 14.8–18.6]) Although no difference was found between the pre- and post-time interval when the trauma occurred more than 60 min from a TC (pre-TTDP, 4.0% [n = 30; 95% CI 2.6–5.3]; post-TTDP, 3.9% [n = 34; 95% CI 2.6–5.1]), the rate for transporting patients to a TC declined dramatically when the 60 min threshold was crossed at both intervals (pre-TTDP 13.9% decrease; post-TTDP 12.8% decrease) Increasing age was associated with decreased rates of TC transport (P < 0.05). The rates of TC transport for patients aged 50–59 years pre- and post-TTDP were 30.5% (n = 185; 95% CI 26.9–34.2) and 30.7% (n = 213; 95% CI 24.5–36.9), compared to patients > 80 years pre- and post-TTDP 19.9% (n = 157; 17.09–22.65) and 19.5% (n = 185; 17.0–22.0; P < 0.05) Almost 3% of the entire study population of older trauma patients were transported through HEMS although 31% of them met the trauma triage criterion (≥ 60 min from the nearest TC)
Nakamura et al. (2012) [51]	Under-triage rate was relatively constant, but then progressively increased after the age of ≥ 60 years and reached a rate of 58% to 62.2% among older patients aged > 90 years
Newgard et al. (2016) [52]	The sensitivity and specificity of current trauma triage criteria: For ISS > 15: sensitivity 75.9%, 95% CI 72.3–79.2%; specificity 77.8%, 95% CI 77.1–78.5% (Area Under the Curve (AUC) 0.77 [0.75–0.79]), (146 out of 605 patients were under-triaged) For serious traumatic brain injury: sensitivity 64.5%, 95% CI 60.8–68.2%; specificity 77.4%, 95% CI 76.6–78.1% (AUC 0.71 [0.69–0.73]), (225 out of 634 patients were under-triaged) For serious chest injury: sensitivity 57.2%, 95% CI 52.6–61.7%; specificity 76.5%, 95% CI 75.8–77.3% (AUC 0.67 [0.65–0.69]), (194 out of 453 patients were under-triaged) For serious abdominal-pelvic injury: sensitivity 38.6%, 95% CI 32.4–44.9%; specificity 75.6%, 95% CI 74.9–76.4% (AUC 0.57 [0.54–0.60]), (143 out of 233 patients were under-triaged)
Newgard, et al. (2019) [43]	The study showed the poor sensitivity of the current trauma triage criteria as they identified only 117 out of 320 patients who had ISS > 15 and those whose injuries required a major non-orthopedic surgery The sensitivity of current trauma triage criteria for older trauma patients was 36.6% (95% CI 31.2–42.0%) and the specificity was 90.1% (95% CI 89.2%–91.0%) Out of the 5021 injured older adults who are included in this study, only 803 (16%) were initially transported to higher-level TC Of the 583 patients who met the current triage criteria, 222 (38.1%) were transported to higher-level TC When measuring triage based on the hospital destination, 114 patients of 320 who had an ISS > 15 or those who required non-orthopedic surgery were initially transported to a Level I/II TC (sensitivity 35.6%; 95% CI 30.1%–41.1%) Patients who did not have serious injuries or require specialised operations (n = 4701), 689 of them were transported to TCs (specificity, 85.3% [95% CI 84.3%–86.3%]) Of patients who were seriously injured but transported to non-TCs (n = 206), 51 (24.8%) of them were ultimately transported to higher-level TCs. This resulted in a sensitivity of 50.8% (95% CI 45.0%– 56.6%) and specificity of 84.5% (95% CI 83.5%–85.6%) when the triage is defined by final destination to higher-level TCs
Phillips et al. (1996) [39]	Among injured older adults aged ≥ 55 years, the sensitivity was 29% with an under-triage rate of 71% while the specificity of the triage criteria was 92.6% with an over-triage of 7.4% Among injured younger adults aged 15–54 years, the sensitivity was 64% with an under-triage rate of 36% while the specificity of the triage criteria was 88.7% with an over-triage of 11.3%. Although the rate of under-triage wasbelow the target level of not more than 5%, the study argued that this rate is comparable to the results of other studies The rate of under-triage among older trauma patients increased with age; reaching a rate of 81.9% for those aged ≥ 85 years According to the mechanism of injury, the triage criteria were highly sensitive to gunshot wounds (under-triage rate of 5%) and significantly less sensitive to falls (under-triage rate of 94.3%)
Pracht et al. (2011) [40]	The rates of TC treatment decreased with age as 50.31% of patients aged 65 to 74 years were treated at TCs compared to 35.85% among patients aged 75 years to 84 years and 27.19% among patients aged ≥ 85 years
Staudenmayer et al. (2013) [53]	Older trauma patients were significantly under-triaged in pre-hospital care (32.8% of patients with ISS > 15 were under-triaged) When under-triage is defined to include all patients transported to non-TCs either they had ISS > 15 or a procedure including interventional radiology or non-orthopedic surgery, the rate of under-triage increased to 44%
Uribe-Leitz et al. (2020) [57]	For trauma patients aged ≥ 65 years old, 26.5% of them were treated at TCs compared to 73.5% at non-TCs The rate of under-triage for patients with ISS > 15 was 46.3% The rate of under-triage increased with age; reaching 57% for patients aged > 80 years (OR 1.52; 95% CI 1.52–1.61)