Norwegian survival prediction model in trauma: modelling effects of anatomic injury, acute physiology, age, and co‐morbidity

Abstract

IntroductionAnatomic injury, physiological derangement, age, and injury mechanism are well-founded predictors of trauma outcome. We aimed to develop and validate the first Scandinavian survival prediction model for trauma.MethodsEligible were patients admitted to Oslo University Hospital Ullevål within 24 h after injury with Injury Severity Score ≥ 10, proximal penetrating injuries or received by a trauma team. The derivation dataset comprised 5363 patients (August 2000 to July 2006); the validation dataset comprised 2517 patients (August 2006 to July 2008). Exclusion because of missing data was < 1%. Outcome was 30-day mortality. Logistic regression analysis incorporated fractional polynomial modelling and interaction effects. Model validation included a calibration plot, Hosmer–Lemeshow test and receiver operating characteristic (ROC) curves.ResultsThe new survival prediction model included the anatomic New Injury Severity Score (NISS), Triage Revised Trauma Score (T-RTS, comprising Glascow Coma Scale score, respiratory rate, and systolic blood pressure), age, pre-injury co-morbidity scored according to the American Society of Anesthesiologists Physical Status Classification System (ASA-PS), and an interaction term. Fractional polynomial analysis supported treating NISS and T-RTS as linear functions and age as cubic. Model discrimination between survivors and non-survivors was excellent. Area (95% confidence interval) under the ROC curve was 0.966 (0.959–0.972) in the derivation and 0.946 (0.930–0.962) in the validation dataset. Overall, low mortality and skewed survival probability distribution invalidated model calibration using the Hosmer–Lemeshow test.ConclusionsThe Norwegian survival prediction model in trauma (NORMIT) is a promising alternative to existing prediction models. External validation of the model in other trauma populations is warranted.

Validating performance of TRISS, TARN and NORMIT survival prediction models in a Norwegian trauma population

“…Age and comorbidity affect trauma survival independently,16 but the studied prediction models differ markedly regarding these factors. TRISS employs full separate sets of coefficients for paediatric patients (< 14 years) and dichotomizes age (< 55 or ≥ 55 years) in adult patients, thus predicting an identical age‐related reduction in trauma survival in a 56‐year‐old and an 86‐year‐old patient.…”

“…Eligible16 were all patients received at OUH‐U with trauma team activation (TTA), except those suffering from medical conditions or injuries unsuited for Abbreviated Injury Scale (AIS) scoring (i.e., drowning, hypothermia, asphyxia, spontaneous subarachnoid haemorrhage, or cardiac arrest, entered in OUH‐TR because of TTA). Included were also all patients with documented anatomical injury ISS ≥ 10 according to the Abbreviated Injury Scale 1990, Update 1998 (AIS'98),18 and/or with head injuries scored as AIS ≥ 3, and/or with penetrating injuries towards the head, neck, torso, and/or proximal to elbow or knee irrespective of ISS.…”

“…Physiological derangement on arrival was classified according to the Triage Revised Trauma Score (T‐RTS) 16, 23. The T‐RTS range (0–12) is defined as the sum of the clinical category values of Glasgow Coma Scale (GCS) score, Systolic Blood Pressure (SBP), and Respiratory Rate (RR) (Table 1).…”

“…The T‐RTS range (0–12) is defined as the sum of the clinical category values of Glasgow Coma Scale (GCS) score, Systolic Blood Pressure (SBP), and Respiratory Rate (RR) (Table 1). Such scoring of physiological data into clinical categories, based on information from text in addition to numerical raw data, substantially reduces the number of patient exclusions due to missing data 16. For patients arriving at OUH‐U intubated and in general anaesthesia, GCS and RR were scored based on values documented immediately prior to intubation.…”

“…NORMIT, Norwegian prediction Model in Trauma; NORMIT 2, update in present study; TRISS, Trauma Score Injury Severity Score; TRISS 09, updated 2009; TARN, UK Trauma Audit and Research Network prediction model; TARN 12, updated 2012; TARN 09, updated 2009; TARN Ps04, original model; OUH–TR, Oslo University Hospital Trauma Registry; US NTDB, US National Trauma Data Bank; AIS, Abbreviated Injury Score; *Reference 16, †Present study, ‡Reference 7, §Reference 12, ¶ Reference 10, **Reference 15, ††Reference 14.…”