title: External validation of the Norwegian survival prediction model in trauma after major trauma in Southern Finland.
abstract: BACKGROUND
  The Norwegian Survival Prediction Model in Trauma (NORMIT) is a newly developed outcome prediction model for patients with trauma. We aimed to compare the novel NORMIT to the more commonly used Trauma and Injury Severity Score (TRISS) in Finnish trauma patients.
  
  
  METHODS
  We performed a retrospective open-cohort study, using the trauma registry of Helsinki university hospital's trauma unit, including severely injured patients (new injury severity score > 15) admitted from 2007 to 2011. We used 30-day in-hospital mortality as the primary outcome, and discharge functional outcome as a secondary outcome of interest. Model performance was evaluated by comparing discrimination (by area under the receiver operating characteristic curve [AUC]), using a re-sample bootstrap technique, and by assessing calibration (GiViTI belt).
  
  
  RESULTS
  We identified 1111 patients fulfilling the study inclusion criteria. Overall mortality was 13% (n = 147). NORMIT showed slightly better discrimination for mortality prediction (AUC = 0.83, 95% confidence interval [CI] = 0.80-0.86 vs. AUC = 0.79, 95% CI = 0.75-0.83, P = 0.004) and functional outcome prediction (AUC = 0.78, 95% CI = 0.76-0.82 vs. AUC = 0.75, 95% CI = 0.72-0.78, P < 0.001) than TRISS. Calibration testing revealed poor calibration for both NORMIT and TRISS (P < 0.001), by giving too pessimistic predictions (predicted survival significantly lower than actual survival).
  
  
  CONCLUSIONS
  NORMIT and TRISS showed good discrimination, but poor calibration, in this mixed cohort of severely injured trauma patients from Southern Finland. We found NORMIT to be a feasible alternative to TRISS for trauma patient outcome prediction, but trauma prediction models with improved calibration are needed.
authors.affiliation: Department of Neurosurgery, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.
authors.forename: R
authors.identifier: http://orcid.org/0000-0003-4243-9591
authors.initials: R
authors.lastname: Raj
authors.affiliation: Töölö Trauma Unit, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.
authors.forename: T
authors.initials: T
authors.lastname: Brinck
authors.affiliation: Division of Intensive Care, Department of Anaesthesiology, Intensive Care and Pain Medicine, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.
authors.forename: M B
authors.initials: MB
authors.lastname: Skrifvars
authors.affiliation: Töölö Trauma Unit, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.
authors.forename: L
authors.initials: L
authors.lastname: Handolin
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000465:Algorithms; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D005260:Female; D005387:Finland / Q000453:epidemiology; D017052:Hospital Mortality; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D009664:Norway; D011237:Predictive Value of Tests; D012042:Registries; D015203:Reproducibility of Results; D012189:Retrospective Studies; D016019:Survival Analysis; D015599:Trauma Severity Indices; D016896:Treatment Outcome; D014947:Wounds and Injuries / Q000401:mortality*; D055815:Young Adult