Detailed information gain and therapeutic impact of whole body computed tomography supplementary to conventional radiological diagnostics in blunt trauma emergency treatment: a consecutive trauma centre evaluation

This prospective observational investigation from 1 st November 2011 to 31 st December 2017 took place in one of the 12 Swiss trauma centres officially designated for the treatment of highly specialized medicine (HSM). The study was approved by the local ethics committee (PB_2018-00079-AG/SO 2012-008; NCT registered). Trauma treatment followed ATLS^© standards [1] and ER team activation criteria (ERTAC) as published recently [17, 18], with a routine use of CI and a subsequent liberal application of WBCT as soon as ERTAC were fulfilled as the standard approach. The concrete execution depended on trauma leaders’ valuation of single cases. Study nurses not involved in the treatment of patients evaluated all consecutive WBCT imaging procedures undertaken at the hospital in patients aged ≥ 16 years within 24 h of traumatic blunt injury. All WBCT-patients who did not undergo the defined CI were excluded from the analysis (Fig. 1).

So-called ‘complete standard CI’ for this investigation was defined as the execution of all of the following three ER radiological examinations: focused assessment with sonography for trauma (FAST) performed by the resident radiologist on duty, and plain emergency radiographs (XR) of the chest (CXR) and pelvis (PXR), each with the patient supine and undertaken by radiology technicians. After CI, WBCT imaging followed for all patients using a standardized scanning protocol with the patient positioned supine, starting from the head and ending at the hip region, just distal to the trochanter minor, using the Toshiba Aquilion CXL (Toshiba Corp.^©, Tokyo, Japan). Procedure began with a head and neck scan with both arms and hands positioned next to the body; in a second step the arms were positioned above the head, if possible, followed by two helical scans: first scan from frontal sinus to the first thoracic vertebral body, second helical scan from the shoulders to the distal trochanter minor region under biphasic contrast agent injection. A resident radiologist primarily evaluated the scans with an initial report. Within 24 h of the examination the images were reviewed by a senior radiologist and a definitive WBCT report was generated in all cases. For this investigation all definitive radiology reports were used for further evaluation and comparison of the results.

Findings in CI were compared to the findings of subsequent WBCT limited to the relevant body regions only: CXR to CT scan of the thorax (with and without the thoracic spine), FAST to CT scan of the abdomen (without the lumbar spine region) and PXR to CT scan of the pelvis. In addition, the results of combined CI were compared to the relevant combined CT-regions. The body regions head, neck and extremities (other than the hip and shoulder) were excluded from this evaluation, because they could not be evaluated by specified CI. Given the restricted value of plain emergency radiographs of the chest and pelvis for the assessment of spine, findings were elaborated for both, including and not including spine injuries in the comparison to WBCT reports. A radiological finding in WBCT was defined as ‘new’ or ‘missed’ if it had not already been identified by CI. The definition of ‘missed injuries’ was based on previous trauma reviews [19]. A finding was defined as false positive if it had been identified by CI before, but not in subsequent WBCT. Findings were categorized as injury-related or incidental (not trauma related). The abbreviated injury severity score (AIS) [20] and resultant Injury Severity Score (ISS) were applied in a standardized manner to determine the injury severity of single lesions or specified body regions, both for single radiological examinations and for the maximum (‘final’) information on patients’ injury sequelae at hospital discharge according to all records. A ‘partial ISS’ was calculated using AIS solely for the thorax, abdomen and pelvis. AIS and ISS-values were calculated by an Association for the Advancement of Automotive Medicine (AAAM) AIS-qualified study nurse using the relevant definitions of the AIS 2005 version of the TraumaRegister DGU^® of the German Trauma Society (https://​www.​traumaregister-dgu.​de/​index.​php?​id=​433&​L=​1). The differences between CI and WBCT as measured on the AIS and ISS were categorized into 3 groups: (a) as ‘false high’ if FAST or XR findings were found to be more than one AIS point higher than verified in WBCT, (b) ‘false low’ if WBCT was more than one point higher than CI, and (c) ‘equal’ if AIS values did not differ more than one AIS point between imaging techniques. Further comparison of imaging techniques also included the number of patients requiring surgical procedures and/or emergency interventions, both overall and in single body regions. ‘Interventions’ were subclassified as (a) ‘immediate interventions’ (< 6 h following admittance) or (b) surgical procedures in the operation room > 6 h following hospital admittance (yes/no). ‘Immediate interventions’ were again subdivided into (a) ER interventions such as thoracic drainage or embolization and (b) surgical interventions in the operation room (OR) including craniotomy, thoracotomy, laparotomy, revascularization, stabilization of the pelvis and stabilization of extremities. Furthermore, interventions were grouped according to the body region involved based on the AIS study regions (thorax, abdomen and pelvis). Change of trauma treatment procedure was defined as any intervention resulting directly from new trauma-related findings diagnosed by WBCT but not by CI. A change in subsequent management based on incidental findings was recorded in cases, where additional diagnostic or therapeutic investigations were recommended by the radiologist in charge. Treatment consequences were defined as the sum of both a change of trauma treatment procedures and/or a change of further management based on incidental findings.

Results are presented as numbers and percentages or means and where appropriate medians with corresponding parameters (minimum, 25th percentile, median, 75% percentile and maximum). Missing data were excluded variable-wise. All statistical tests were two-tailed. Student’s t test for paired comparison was used to test for differences of means and chi-square analysis was used to test categorical data. Spearman correlations (rho) were calculated to test for the correspondence of conventional and WBCT diagnostics and to test for the influence of the ISS. Data were analysed using SPSS™ for Windows 24 (Armonk^©, NY: IBM Corp, USA), and a p- value < 0.05 was considered significant.

In 69.7% of cases at least one injury finding was documented by WBCT. The number of injury related findings detected by WBCT ranged from 0 to 21 per case. Comparing WBCT vs. CI as defined according to equivalent body regions revealed that significantly more injury findings and more severe injuries (partial ISS) were detected by WBCT (Table 2).

Overall, in 24.1% (n = 306) injury findings were diagnosed both in CI and WBCT. In an additional 8.8% (n = 112) a suspected traumatic lesion was identified by CI, of which n = 19 could not be verified in WBCT. In contrast, WBCT in 73.7% (n = 937) found at least one injury-related finding (range 1–18). In an additional 2.0% (n = 26) findings were unclear, e.g., unexplained free fluid. Therefore, in 44.5% (n = 565) injury findings were missed by CI (Table 1).

With regard to patients’ final injury severity and restricted to findings per se as detected by WBCT, patients demonstrated a mean ISS of 9.3 (Table 1), whereas 41.0% (n = 521) had an ISS < 8 at discharge. Overall, 28.4% of cases (n = 361) yielded an AIS ≥ 2 in at least one of the body regions examined.

Comparing WBCT with CI of the thorax, abdomen and pelvis revealed a significantly higher mean injury severity detected by WBCT in all body regions (Table 2), with an overall mean difference of ISS 1.9. Table 3a–c show detailed differences between radiological modalities per body region with regard to diagnosed injury severity and subsequent surgical interventions. The thoracic region was found to have the highest discrepancy with regard to injury severity (AIS) as diagnosed by WBCT vs. CXR (0.4; Table 2). If the thoracic spine is included (vs. excluded) in the analysis of the thoracic region, then a false low AIS for CXR was found in 15.0% (vs. 4.2%) and a false high AIS in 1.3% (vs. 6.3%). 4.7% (n = 9) of the false low group had to undergo subsequent thoracic surgery (including the spine) vs. 6.3% (n = 1) of the false high group compared to overall 3.1% needing surgery (Table 3a). Analogous data for the abdominal and pelvic regions are given in Table 3b, c.

Additionally, the maximum AIS in any of the body regions thorax, abdomen and pelvis was calculated for the comparison of findings in defined CI vs. WBCT, in line with the gold standard of the final injury severity coding at hospital discharge (Table 4a). Concerning ‘partial ISS’ a significantly higher injury severity was found in WBCT vs. CI (mean difference 1.9; p < 0.001; Table 2).

Comparing the highest AIS of single body regions, i.e., the maximum difference in injury severity per body region between WBCT and CXR (Table 4b), 22.0% (n = 279) of cases demonstrated a false low result in CI in at least one of the three regions.

In 90.0% (n = 1144) of cases at least one incidental finding was diagnosed with WBCT (Table 1). On average 3.4 (range 0–15) incidental findings were detected per patient. WBCT identified significantly more incidental findings compared to CI (88.4% vs. 28.9%; p < 0.001). In 47.8% (n = 608) at least one incidental finding was only found in WBCT and not in CI. In 17.5% (n = 222) incidental findings were judged diagnostically as requiring further management (diagnostic or therapeutic), i.e., resulted in a recommendation by the radiology specialist for further diagnostic work-up or a follow-up inspection or was directly followed by a clinical intervention. In n = 87 of these cases (39%) it was recommended that further diagnostics should be performed by the patient’s general practitioner after discharge.

40.5% of individuals underwent trauma-related interventions (Table 1), of which 199 cases (15.7%) involved the three investigated body regions (Table 3a–c) including the spine and 147 cases (11.6%) without the spine. Table 4 shows the maximum difference in injury severity of the three body regions. Overall, 22.0% (n = 279) showed a difference of at least 2 AIS-points in at least one of the three investigated body regions. The incidence for this diagnostic difference following WBCT increased significantly with increasing ISS (Spearman rho = 0.32, p < 0.001).

In 16.8% (n = 213) of all patients, trauma treatment was changed based on new injury findings detected by WBCT in the three body regions (Table 5) which corresponds to a ‘number needed to profit’ (NNP) of 6 patients. Within this group, 23.0% (n = 49) of treatments were performed in an emergency setting, 59.6% (n = 127) were operations performed later in the AIS regions thorax, abdomen or pelvis (including spinal involvement) vs. 38.5% (n = 82) without the spine. Studying more in detail the potential interrelation of early (pre-) clinical injury information (i.e., early trauma team activation criteria) with the subsequent information gain and/ or treatment change obtained by the execution of WBCT found only low correlations in univariate analysis (r < 0.25; Suppl. Table A). Table 5 shows additional data on resulting change of treatment and surgical emergency interventions with regard to final injury severity of patients (categorized ISS). The incidence for a change of treatment resulting from the execution of WBCT following CI increased significantly with increasing ISS (Spearman rho = 0.33, p < 0.001). Accordingly, the NNP from WBCT decreased from 25 for patients with an ISS < 7 up to nearly 2 for patients with an ISS > 25 at final evaluation.

This study has several shortcomings. Even though data were acquired prospectively for all consecutive trauma WBCT cases, this investigation, following its study objective and subsequent comparative design, purposely only reports patients suffering blunt trauma who underwent both CI as defined and subsequent WBCT. If we had also included WBCT cases with incomplete CI imaging, the investigation would have been disadvantaged by a major number of missing cases in the detailed comparison of body regions. We excluded penetrating trauma from this study to homogenize the study population, because it is typically associated with different injuries and treatment regimens, and our cases are few. The decision to use WBCT in individual cases was taken by the trauma leader on duty, which could be seen as a potential confounder, even though internal hospital guidelines recommend its standard use as soon as trauma team activation criteria [17] were actually fulfilled after primary evaluation of the patient in the ER. The evaluation is restricted to the cohort investigated due to its monocenter design and, ultimately, includes more older or less severely injured than several other study groups [29‐33]. Given established literature data [35] and own experience, WBCT was executed instead of sequential CTs of single body regions as soon as more than one region were suspected to be injured or following high energy trauma. Such procedure based on the observation, that with such an approach serial CTs may be avoided, less injury sequelae information will be lost, and radiation exposure could be avoided for patients indeed in need for CT. Given the main objective of the study, i.e., a somehow post-hoc view on the resulting impact of WBCT in the treatment of trauma patients compared to defined standard CI, this work did not preferentially investigate predictive clinical factors indicating WBCT in this context. The weak correlations found between tested trauma team activation criteria and investigated outcome variables further underline the complexity of such an alternative approach. Therefore, the study also did not analyse other clinical predictors (e.g., blood pressure) possibly meliorating the pre-test probability for the use of WBCT. Some readers may argue that the detailed differences identified may only be of practical value if there are clinical consequences. However, from an evidence-based approach and given the missing information to date, our study objective was to provide precise data, such as sensitivity and specificity rates for the described diagnostic procedure in the ER treatment of the injured.