title: Validation of the revised injury severity classification score in patients with moderate-to-severe traumatic brain injury.
abstract: BACKGROUND
  By analysing risk-adjusted mortality ratios, weaknesses in the process of care might be identified. Traumatic brain injury (TBI) is the main cause of death in trauma, and thus it is crucial that trauma prediction models are valid for TBI patients. Accordingly, we assessed the validity of the RISC score in TBI patients by internal and external validation analyses.
  
  
  METHODS
  Patients with moderate-to-severe TBI admitted to the TraumaRegister DGU® (TR-DGU) and the trauma registry of Helsinki University Hospital (TR-THEL) in 2006-2011 were included in this retrospective open cohort study. Definition of moderate-to-severe TBI was head abbreviated injury scale of 3 or higher. Subgroup analysis for patients with isolated and polytrauma TBI was performed. The performance of the RISC score was evaluated by assessing its discrimination (area under the curve, AUC) and calibration (Hosmer-Lemeshow [H-L] test).
  
  
  RESULTS
  Among the 9106 and 809 patients with moderate-to-severe TBI admitted to TR-DGU and TR-THEL, unadjusted mortality was 26% and 23%, respectively. Internal and external validation of the RISC score showed good discrimination (TR-DGU AUC 0.89, 95% confidence interval [CI] 0.88-0.90 and TR-THEL AUC 0.84, 95% CI 0.81-0.87), but poor calibration (p<0.001) in patients with moderate-to-severe TBI. Subgroup analysis found the discrimination only to be modest in isolated TBI (AUC 0.76) and calibration to be particularly poor in polytrauma TBI (TR-DGU H-L=4356, p<0.001; TR-THEL H-L 112, p<0.001).
  
  
  CONCLUSIONS
  The RISC score was found to be of limited predictive value in patients with moderate-to-severe TBI. A new general trauma scoring system that includes TBI specific prognostic factors is warranted.
authors.affiliation: Department of Neurosurgery, Töölö Hospital, Helsinki University Hospital, Topeliuksenkatu 5, PB 266, FI-00029 HUS, Helsinki, Finland. Electronic address: rahul.br.raj@icloud.com.
authors.forename: Rahul
authors.initials: R
authors.lastname: Raj
authors.affiliation: Department of Orthopedics and Traumatology, Töölö Hospital, Helsinki University Hospital, Topeliuksenkatu 5, PB 266, FI-00029 HUS, Helsinki, Finland. Electronic address: tuomas.brinck@hus.fi.
authors.forename: Tuomas
authors.initials: T
authors.lastname: Brinck
authors.affiliation: Department of Intensive Care, Meilahti Hospital, Helsinki University Hospital, Haartmaninkatu 4, PB 340, FI-00029 HUS, Helsinki, Finland. Electronic address: markus.skrifvars@hus.fi.
authors.forename: Markus B
authors.initials: MB
authors.lastname: Skrifvars
authors.affiliation: Department of Neurosurgery, Töölö Hospital, Helsinki University Hospital, Topeliuksenkatu 5, PB 266, FI-00029 HUS, Helsinki, Finland. Electronic address: riku.kivisaari@hus.fi.
authors.forename: Riku
authors.initials: R
authors.lastname: Kivisaari
authors.affiliation: Department of Neurosurgery, Töölö Hospital, Helsinki University Hospital, Topeliuksenkatu 5, PB 266, FI-00029 HUS, Helsinki, Finland. Electronic address: jari.siironen@hus.fi.
authors.forename: Jari
authors.initials: J
authors.lastname: Siironen
authors.affiliation: Institute for Research in Operative Medicine (IFOM), Faculty of Health, University of Witten/Herdecke, Cologne Merheim Medical Centre, Ostmerheimer Straße 200, Cologne 51109, Germany. Electronic address: rolf.lefering@uni-wh.de.
authors.forename: Rolf
authors.initials: R
authors.lastname: Lefering
authors.affiliation: Department of Orthopedics and Traumatology, Töölö Hospital, Helsinki University Hospital, Topeliuksenkatu 5, PB 266, FI-00029 HUS, Helsinki, Finland. Electronic address: lauri.handolin@hus.fi.
authors.forename: Lauri
authors.initials: L
authors.lastname: Handolin
mesh_terms: D015998:Abbreviated Injury Scale; D001930:Brain Injuries / Q000145:classification / Q000175:diagnosis*; D006801:Humans; D015601:Injury Severity Score; D011379:Prognosis; D012042:Registries; D012189:Retrospective Studies
keywords: External validation; Prognostic model; Revised injury severity classification score; TR-DGU; TR-THEL; Trauma register; Traumatic brain injury