In our study, undertriage rate was 12.35% among patients included in our regional database as they received first care at non-level I centers. This result is above the recommendations of less than 5% as set by the ACSCOT (3). Many European and American studies reported similar or even higher undertriage rate (4,14,15,16). In a comparable health system also benefiting from physician on scene and medical dispatching, French authors reported higher undertriage rate about 18% (7). Voskens et al. reported a 21.6% (95% CI,18.0-25.7) rate of undertriage. In their study, allocation of trauma patients to the appropriate level of trauma care was guided by the Dutch Field Triage Protocol and their ambulance care system was nursebased (17).
In paramedic-led prehospital systems, undertriage was higher: Schellenberg and al reported 16% undertriage (21), Xiang and al reported 34% (14).
Our findings showed no association between undertriage and in-hospital mortality, contrary to other studies (6,18,19). Probably because a large amount of undertriaged patients (n = 202, 63.1%) were admitted in the center considered as level II because there is no neurosurgery department nor thoracic surgery department but yet offers large 24-hour in-house resources (intensive care, general and orthopedic surgeons, emergency physicians, radiology). Some of these patients were secondarily transferred to a level 1 center but no data were available about the reason of such transfer, or about vital status at secondary hospital discharge. Pickering et al. reported no difference in outcomes for direct referral to a trauma center versus initial triage to a local hospital in their systematic review (19).
In our study, penetrating trauma were rare, counting for only 4.56%. This is consistent with other French and European series. An interesting finding was that compared to road traffic accident, fall and gunshot/stab wounds were protective for undertriage. Schellenberg et al. also reported higher risk for undertriage following blunt trauma, especially motor vehicle collisions (21). When the gravity is not as obvious as these penetrating injuries, we should search for other predictors to guide field triage. In our study, any age showed a tendency toward higher risk of undertriage, except age of 51 to 65 years that was a predictive factor of undertriage. Nakahara et al. found the same result in the group 45–54 years (22). On the opposite, most studies reported higher age cut-off for undertriage risk: ≥ 55 years (14), ≥ 65 years (6,18), ≥ 80 years (23). In our study, the field triage criteria for level I were: respiratory failure (SpO2 < 90% despite oxygen supply), hypotension (MAP < 100 mmHg despite 1000 mL of fluid resuscitation) GCS ≤ 8, use of vasopressor or blood transfusion. Hence, a possible explanation is that in our trauma system, neither age ,nor comorbidity excluded referral at level 1 centers. Indeed, previous studies have reported improved outcomes for elderly patients admitted in higher levels of trauma care (24–26) Some authors even suggested that treating severely injured elderly trauma patients in designated geriatric trauma centers or units may be associated with statistically significant gains in likelihood of survival (27,28). Bradburn et al. assessed a specific protocol to identify high-risk geriatric injured patients which lead to significant reduced mortality (29)
Several studies found that patients suffering from head injury were more affected by undertriage (14,15). We did not report that trend. On the opposite, GSC ≤ 8 was a protective factor for undertriage. So was the need for endotracheal intubation regardless of the GSC.
A new finding of this study is that patient who benefited from a FAST were less undertriaged regardless of hemodynamic condition. Ultrasound-based clinical pathways might enhance the speed of injured patient assessment. But effectiveness of ultrasound-based clinical pathways to triage algorithms lacks evidence and its benefit remains unclear (30). In our study, FAST was not mandatory, not integrated in the field triage algorithm and results were not available. We ignored if triage decision was or not based on FAST results. We hypothesized that when an effusion was detected, physicians would consider patients to require higher care (e.G. a level 1 center referral). Another hypothesis considered that physicians performing FAST were more experienced with better assessment capacities than other colleagues. In our cohort, ultrasonography was performed in 2.7% cases in 2011 while it was in 34.9% in 2017. It may contribute to lower undertriage rate in the next years. Further explorations are needed to integrate FAST in our field triage algorithm and assess its performance.
Air transport also appeared to be protective against undertriage compared to ground transport regardless of severity (ISS) and transit time from scene to hospital. It might be explained by highest availability of helicopter emergency medical service (HEMS) in level I center. Therefore, we assumed that physicians using HEMS tended to facilitate the referral of patients to their level 1 center instead. Nevertheless, we showed no influence of transport on in-hospital mortality. Other studies did no report strong evidence of any benefice of HEMS on in-hospital mortality among injured patients (31,32,33)
Fukuma et al. showed that physiological variables plus lactate on-scene significantly increased the predictive value for immediate intervention for hemorrhage (Area Under the Curve 0.882, 95% CI 0.839–0.925) compared to that using physiological variables only (AUC 0.837, 95% CI 0.787–0.887, p = 0.0073) (34). It may be interesting to investigate the role of on-scene lactate measuring during field triage and its impact on undertriage.
One strength of our study was to use ISS score (16 or more) to assess trauma severity and undertriage, as most of the studies to date, and as recommended by the American College of Surgeons (3). In 2019, a systematic review reported four categories to define undertriage: based on ISS, formula for mis-triage (1—sensitivity), need for life-saving emergency intervention and patients triaged to a non-trauma center (4). This statement led to significant heterogeneity that complicates comparison across studies. The standardization of undertriage definition is a priority to estimate the true rate among different studies and clarify the role of triage tools. Also, French and American level’s center categorization in trauma system are different. In France, levels are approved by the regional agency for health and their definition is common for every region in the country, whereas American trauma categories can vary from state to state. On the opposite, the American college of surgeons (ACS) does not designate trauma centers but it verifies the presence of the resources listed in Resources for Optimal Care of the Injured Patient (3). Finally, ACS reports five levels while French system has three.
This study has several limitations. First, exact locations of the on-scene trauma were not available in the database. Thus we could not evaluate the distance towards the nearest trauma center and definitive destination. Whether the physician decision was based on the triage algorithm, their own clinical judgment or any other element was not reported. Some missing data could also have influenced the destination such as chronic conditions, result of the FAST, trauma center overcrowding.