This study, with a high response rate, show that the majority of Norwegian trauma hospitals adhere to the national criteria for activation of the trauma team implemented in 2015. However, the study also reveals that there are considerable differences in how trauma teams are activated, who activates them and how the use of trauma triage criteria are documented.

In 2010, Larsen et al. investigated potential differences in TTA criteria among Norwegian hospitals. They found large variations among the 49 included hospitals, where no single criteria were common to all hospitals, with a wide variation of physiological threshold values and 156 different criteria used [3]. Since then, the establishment of a national trauma systems framework, which was last revised in 2023 [12], a Norwegian trauma registry (2015) [19] and the Norwegian National Advisory Unit on Trauma [20] have contributed to system improvements for the care of the severely injured. The implementation of these formal bodies and their related continuous quality assessments are likely to have provided a more common understanding of the need for standardization. Our findings show a notable systemic improvement compared to previous findings. When comparing rates of overtriage and undertriage among hospitals, we observed no relations between these and the level of adherence (Additional File 1). The establishment of uniform guidelines, a national trauma system framework and continuous quality assessment might provide a reasonable explanation to the strong adherence to NTrC. A study from The Netherlands in 2015 surprisingly found that only 38% of the hospitals adhered to a pre-defined TTA protocol, despite the existence of national guidelines [21]. In 2017, a new TTA algorithm based on a modified two-tier ACS-COT trauma triage criteria; The Swedish National Trauma Triage Criteria (SNTTC), was introduced in Sweden [22]. The safety and efficacy of SNTTC were investigated in a study published in 2019, but did not investigate the nationwide adherence of this algorithm [23]. In 2018, a Danish nationwide study found that, although all hospitals had formalized TTA criteria, the criteria were diverse between the hospitals [24]. The majority (68%) of hospitals used a point-scoring system, whereas 23% used a more traditional stepwise approach using the criteria outlined by ACS-COT and the remaining 4.5% used a combination of the two systems [24]. The authors recommended the establishment of a national consensus based on uniform and evidence-based criteria [24]. A recent Canadian study showed great variability among TTA in hospitals, with no overarching structure providing national guidelines [25]. In 2018, van Rein and colleagues underlined the need for improvement of triage protocols and compliance rate in a systematic review [26]. Findings from their included studies showed a variation in adherence rates from 21 to 93% for triage protocols, and 41% to 94% for specific criteria categories [26]. The authors’ focus was on the adherence of triage protocols on an EMS provider level and not on the implementation on a system level. Therefore, when evaluating adherence to protocols it is important to distinguish between studies that evaluate the adherence of TTA protocols on system versus provider level.

In 2021, a new revised national US guideline for the field triage of injured patients based on the most updated science was published [27]. Previous guidelines were slow to be implemented among providers despite the use of evidence-based data and consensus processes [28, 29]. The authors described that only 17% of the states had implemented the revised guidelines, while another 61% used an older or other protocol [28]. Therefore, the authors underlined the importance of “creating new ways of disseminating, implementing, and monitoring adherence to realizing the true potential of the guideline” [27]. Based on our results and experiences from other countries, we argue that a national all-encompassing organizational structure supplying national guidelines and providing consistent verification and review, will result in a more unified common approach to the severely injured trauma patient. This also underlines the common challenge and need for uniform protocols across countries, regions and systems.

In the Norwegian system, no formal description of a multilevel-tiered trauma response is described [12]. The 2014-guidelines from ACS-COT recommended the use of tiered TTA, which again was underlined in the 2021-revised guidelines [6, 27]. A study published in 2012 by Rehn et al. described a beneficial effect of a tiered TTA by reducing the undertriage from 28.4 to 19.1% [8]. In 2022, a new study within the same hospital found increased undertriage after re-introduction of a single tiered response and the authors concluded that a two-tiered TTA provided better patient care [30]. The NTR Annual report from 2020 showed that undertriage in trauma is a common event in Norway, and any intervention to reduce these rates should be evaluated [31]. In our study, we found that the majority of Norwegian hospitals employ a one-tiered TTA system, while only three hospitals use a tiered approach. The development of these teams should be observed in combination with local and historical traditions, and might reflect specific needs, local administrative adjustments or adherence to protocols recommended in the literature. However, these results are comparable to previous studies, showing national variations in mature trauma systems [21, 25].

In our study, we found that that there is a good institutional adherence to NTrC. However, knowledge on the individual clinician’s adherence is also important to evaluate on efficiency and precision of specific TTA criteria [32]. Several investigations have looked into the precision of TTA criteria [27], though there is sparse knowledge on the actual TTA process and who actually requests trauma team activation. Our study found that the organizational structure allows for different practices among hospitals and even within hospitals, as different professions are involved in the TTA decision. In a study by Gutacker et al., they investigated how interventions to reduce unwanted practice variation affected individual clinicians and hospitals [33]. They concluded that practice variation were greater among clinicians compared to their attributable hospitals, even when taken the amount of case-mix adjusted patient variation into account [33]. In our study, most hospitals allowed for several professions to request for TTA. This enables practice variation among hospitals on TTA, which in combination with individual interpretation of TTA criteria may lead to different practice patterns among hospitals. When comparing quality indicators among hospitals which is likely to be affected by these factors, one must consider which interventions should be introduced to reduce clinical practice variation.

Continuous assessment of clinical practices requires valid documentation. We found considerable variations on how the use of different TTA criteria were documented. In addition, 71% of the respondents did not document who requested TTA in each case. Even though there is scarce knowledge on these subjects in the existing literature, we suspect the lack of documentation is prevalent in other systems as well. Although there is a high adherence to NTrC, several vitals elements regarding decision making process and documentation needs to be addressed. Several studies have been performed into the precision (i.e. sensitivity and specificity) of specific trauma criteria [27], though their validity and ability to assess quality of care can be questioned if their use is not consistent among institutions. Wennberg stated “there is variation in the utilization of health services that cannot be explained by variation in patient illness or patient preferences” [34]. We argue, that awareness of potential differences in the decision-making process of TTA is as important as the specific criteria themselves. TTA is a dynamic process as information pertaining to the event itself will increase as time passes. Uncertainties during this process imply that not only the TTA criteria, but also the process, accessible information and inter-individual differences may influence the results of TTA. The study results uncover differences in the decision-making process of TTA and there are currently no national guidelines on who can request TTA, or the dynamics of people involved in the individual trauma care.

The first limitation of the study was the design where surveys investigating a practice may differ from actual integration in clinical practice for a variety of reasons. Surveys are based on self-reported data, where respondents may not have knowledge on all aspects of the subject to be investigated and may be prone to recall-bias. However, a cross-sectional design was easy to perform and allowed for sampling of knowledge from respondents involved in the everyday care of these patients. Secondly, the survey may not have been designed to capture all facets of the integration process, including elements that are not readily apparent to the participants or are not part of the survey's focus (e.g., patient education). A strength of the study is the high response rate, allowing us to include the majority of Norwegian hospitals admitting trauma patients, providing us with a good overview of national implementation. Another strength is that the respondents were dedicated health personnel who worked as either trauma registrars or trauma coordinators, and for this reason were well acquainted with the criteria and the hospital's routines.