Trauma registries constitute an useful tool for monitoring trauma patient care, since they accurately reflect management and care in different settings.1,2 This allows not only improvement of individual treatment but also reorganization of the general care profile and logistics applied in the management of severe trauma patients, as well as comparisons among different registries for benchmarking purposes.1–4

The outcome of trauma patients is mainly determined by the initial severity of the physiological and anatomical injuries secondary to trauma itself. Severity of injury can be evaluated by severity scales obtained from the analysis of large cohorts of patients.5 Of all the prognostic scores used in trauma patients, the Trauma and Injury Severity Score (TRISS) is currently the most widely used tool, and is regarded as the standard method. In this regard, TRISS methodology determines the probability of survival based on a logistic regression model that includes anatomical evaluation by means of the Injury Severity Score (ISS), physiological evaluations using the Revised Trauma Score (RTS), patient age and type of trauma (blunt or penetrating).4 The following equation is applied:

Coefficients b0–b3 were derived from the logistic regression analysis of the American database MTOS (US Major Trauma Outcome Study). This was not a population-based database, participation was voluntary, and it involved hospitals with a special interest in trauma.

The pilot phase of the Spanish Intensive Care Unit Trauma Registry (RETRAUCI) has been recently conducted in 13 Intensive Care Units (ICUs).6 Our objective was to validate TRISS methodology almost 30 years later as an auditing tool for mortality prediction in the Spanish ICU Trauma Registry, taking into consideration the mechanisms of injury (blunt or penetrating).

The pilot phase of the RETRAUCI was conducted from 23 November 2012 to 31 January 2015. Thirteen ICUs distributed throughout Spain collected data. The RETRAUCI is endorsed by the Trauma and Neurointensive Care Working Group of the Spanish Society of Intensive Care Medicine (SEMICYUC). Ethics Committee approval for the registry was obtained. No specific interventions were required for this study.

A total of 2242 patients formed the global cohort of the pilot phase of the RETRAUCI. Patient dropout from the sample was due to different reasons, the most important being inability to determine hospital outcome in 21.1% of the cases, due to patient transfer to the corresponding reference hospital. In most cases, transfer was done to another country, making follow-up impossible. The flowchart in Fig. 1 summarizes the final sample of 1405 patients included in the study.

Figure 1.

Flowchart of the patients in the pilot phase of RETRAUCI included in the study.

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The mean patient age was 46.7 (19.4) years, and 80.3% were males. The mean ISS score was 21.3 (12.1). A total of 1305 patients suffered blunt trauma (92.9%) as the main mechanism of injury, while the remaining 100 patients (7.1%) presented penetrating trauma. Table 1 shows the data referred to patient epidemiology, acute management, resource utilization and main outcome.

The observed mortality rate (including ICU and post-ICU stay) was 18% (253 patients), with a predicted mortality rate of 16.9%. In patients with blunt trauma, the observed and predicted mortality rates were 18.5% and 17.1%, respectively. In penetrating trauma, the observed and predicted mortality rates were 12% and 14.2%, respectively. Table 2 shows the distribution of patients who died in groups with low (<10%), intermediate (10–50%) and high predicted mortality (>50%).

The global sample of 1405 patients presented an area under the ROC curve of 0.889 (95% CI: 0.867–0.911), with S=50.9%, Sp=96.2%, PPV=74.6% and NPV=89.9%. Patients with blunt trauma (Fig. 2) presented an area under the ROC curve of 0.887 (95% CI: 0.864–0.910), with S=50.6%, Sp=96.2%, PPV=75.3% and NPV=89.6%, while patients with penetrating trauma (Fig. 2) presented an area under the ROC curve of 0.919 (95% CI: 0.859–0.979), with S=58.3%, Sp=95.5%, PPV=63.6% and NPV=94.4%.

Figure 2.

Discrimination based on the area under the receiver operating characteristic (ROC) curve for patients with blunt (A) and penetrating trauma (B).

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The results of the Hosmer–Lemeshow (HL) goodness-of-fit test, in both in the total cohorts of patients of patients and distributed according to the mechanism of trauma (blunt or penetrating) are shown in Table 3. The correlation between predicted and observed mortality is shown in Fig. 3.

Figure 3.

Calibration curve comparing predicted and observed mortality. Dashed lines indicate 95% CI.

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Our study shows that TRISS methodology applied in the sample of patients included in the pilot phase of the RETRAUCI presented good levels of discrimination with inadequate calibration, especially in patients with blunt trauma. Penetrating trauma showed better discrimination and good calibration. Altogether, these results suggest that newly calibrated (b coefficient) scales are necessary in our setting.

Our sample of patients offers an initial picture of patients with severe trauma admitted to the ICUs of our setting, taking into account the severity of injury, the care provided, length of stay and mortality. These Units represent level I and II centers. Such patients usually present high ISS values, important resource utilization, and high mortality. The TRISS methodology is based on the degree of anatomical injury (ISS), physiological response (RTS) and functional reserve (age). It was first developed in the 1980s through several logistic regression models5,9 with different b coefficients considering blunt or penetrating injuries. Several updates have been made since then.

When applied to our patients, TRISS showed good discrimination with inadequate calibration – a fact that limits the use of this prognostic model. This observation is consistent with other studies, and in general, with other prognostic scores in the ICU setting, where the main shortcoming corresponds to inadequate calibration despite good discrimination.10 It must be noted that in our sample of patients, those with penetrating injury showed good calibration. This fact is consistent with previous studies differentiating between blunt and penetrating trauma. In the latter type of trauma, discrimination and calibration is better, perhaps due to lesser improvement in their specific care.11,12

Poor calibration and discrimination does not necessarily refer to the quality of the care provided but rather to incorrect application of the model to a population with specific characteristics.13 In addition, TRISS is considered to present lower sensitivity for blunt trauma, since it underestimates brain injury; does not consider multiple injuries in the same anatomical area; and does not consider age on an individual basis. In our sample of patients, on taking into account the different mortality groups, TRISS underestimated mortality when the predicted mortality was <60% and overestimated it when the predicted mortality was >60% (Fig. 3).

Mortality prediction according to TRISS has therefore been questioned14,15: its clinical application has shown opposite results,16–18 especially when used in non-MTOS patients.19,20 The best way to increase its predictive value is to use local correction factors to adjust for b coefficients.20–22 The results of our study confirm that newly developed b coefficients are needed for trauma patients admitted to Spanish ICUs.

New scores have been developed in an attempt to improve the predictive value of TRISS. Some of them are the ASCOT (A Severity Characterization Of Trauma), which includes gender, 5 age categories and different anatomic scales; the ICISS (International Classification of Diseases Ninth revision based injury severity score); the NISS (New Injury Severity Score); the RISC (Revised Injury Severity Classification score); or the pediatric BIG score. However, although they have slightly improved the predictive ability of TRISS methodology, the latter remains the most widely used tool in clinical practice.12,20,23–25

Our study has a number of limitations – some attributable to the TRISS model itself, and other specific of our sample. The most relevant are (a) the limited number of patients for this kind of analysis despite the multicenter nature of the study. This corresponds to the pilot phase of the RETRAUCI. With a growing number of centers recruiting patients, we expect to solve this issue in the future; (b) up to 21% of the patients were lost for hospital outcome evaluation. This was due to the large number of patients from different countries that are admitted to our ICUs and are subsequently transferred to their reference hospitals at home, thereby making follow-up impossible.

In sum, TRISS methodology in the Spanish RETRAUCI showed good levels of discrimination, with inadequate calibration, especially in blunt trauma. Penetrating trauma showed better discrimination and good calibration. Altogether, these results suggest that newly calibrated (b coefficient) scales are necessary in our setting.

Carlos García-Fuentes, Luis Terceros-Almanza (Hospital Universitario 12 Octubre), Iker García-Sáez, Ruth Salaberria-Udabe (Hospital Universitario de Donostia), Cecilia Carbayo-Górriz (Complejo Hospitalario de Torrecárdenas), Carmen Corcobado-Márquez (Hospital General Universitario de Ciudad Real), Javier Trujillano-Cabello (Hospital Universitari Arnau de Vilanova), Eduardo Miñambres-García (Hospital Universitario Marqués de Valdecilla), Amanda Lesmes-González (Hospital Universitario de Getafe).

RETRAUCI received funding from the Fundación Mutua Madrileña during three years for the development of a web-based database, granted to the principal investigator (Dr. Chico-Fernández, AP117892013), on behalf of the Trauma and Neurointensive Care Working Group of the SEMICYUC.

All authors listed in the study declare that they have no conflicts of interest.