title: Internationally comparable diagnosis-specific survival probabilities for calculation of the ICD-10-based Injury Severity Score.
abstract: BACKGROUND
  The International Statistical Classification of Diseases, 10th Revision (ICD-10)-based Injury Severity Score (ICISS) performs well but requires diagnosis-specific survival probabilities (DSPs), which are empirically derived, for its calculation. The objective was to examine if DSPs based on data pooled from several countries could increase accuracy, precision, utility, and international comparability of DSPs and ICISS.
  
  
  METHODS
  Australia, Argentina, Austria, Canada, Denmark, New Zealand, and Sweden provided ICD-10-coded injury hospital discharge data, including in-hospital mortality status. Data from the seven countries were pooled using four different methods to create an international collaborative effort ICISS (ICE-ICISS). The ability of the ICISS to predict mortality using the country-specific DSPs and the pooled DSPs was estimated and compared.
  
  
  RESULTS
  The pooled DSPs were based on a total of 3,966,550 observations of injury diagnoses from the seven countries. The proportion of injury diagnoses having at least 100 discharges to calculate the DSP varied from 12% to 48% in the country-specific data set and was 66% in the pooled data set. When compared with using a country's own DSPs for ICISS calculation, the pooled DSPs resulted in somewhat reduced discrimination in predicting mortality (difference in c statistic varied from 0.006 to 0.04). Calibration was generally good when the predicted mortality risk was less than 20%. When Danish and Swedish data were used, ICISS was combined with age and sex in a logistic regression model to predict in-hospital mortality. Including age and sex improved both discrimination and calibration substantially, and the differences from using country-specific or pooled DSPs were minor.
  
  
  CONCLUSIONS
  Pooling data from seven countries generated empirically derived DSPs. These pooled DSPs facilitate international comparisons and enables the use of ICISS in all settings where ICD-10 hospital discharge diagnoses are available. The modest reduction in performance of the ICE-ICISS compared with the country-specific scores is unlikely to outweigh the benefit of internationally comparable Injury Severity Scores possible with pooled data.
  
  
  METHODS
  Prognostic and epidemiological study, level III.
authors.affiliation: From the Department of Surgical Sciences, Anesthesiology and Intensive Care (R.G.), and Uppsala Clinical Research Center (R.G.), Uppsala University, Uppsala, Sweden; National Center for Health Statistics (M.W., L.-H.C.), Centers for Disease Control and Prevention, Hyattsville, Maryland; Injury Prevention Research Unit (P.G., C.C., J.L.), University of Otago, Dunedin, New Zealand; Institut national de santé publique du Québec (INSPQ) (Y.R.), Montréal, Québec, Canada; Austrian Road Safety Board (R.B.), Research and Knowledge Management, Vienna, Austria; Programa de Prevención de Lesiones por Causas Externas (C.U.), Instituto Nacional de Epidemiología, Dr "J.H.Jara," ANLIS Malbran, Argentina; Accident Analysis Group (J.L.), Odense University Hospital and IST/Biostatistics University of Southern Denmark, Odense C, Denmark; Research Centre for Injury Studies (J.H., G.H.), Flinders University, Adelaide, Australia.
authors.forename: Rolf
authors.initials: R
authors.lastname: Gedeborg
authors.forename: Margaret
authors.initials: M
authors.lastname: Warner
authors.forename: Li-Hui
authors.initials: LH
authors.lastname: Chen
authors.forename: Pauline
authors.initials: P
authors.lastname: Gulliver
authors.forename: Colin
authors.initials: C
authors.lastname: Cryer
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Robitaille
authors.forename: Robert
authors.initials: R
authors.lastname: Bauer
authors.forename: Clotilde
authors.initials: C
authors.lastname: Ubeda
authors.forename: Jens
authors.initials: J
authors.lastname: Lauritsen
authors.forename: James
authors.initials: J
authors.lastname: Harrison
authors.forename: Geoff
authors.initials: G
authors.lastname: Henley
authors.forename: John
authors.initials: J
authors.lastname: Langley
mesh_terms: D000328:Adult; D001118:Argentina; D001315:Australia; D001317:Austria; D002170:Canada; D002423:Cause of Death; D003718:Denmark; D005260:Female; D017052:Hospital Mortality; D006801:Humans; D038801:International Classification of Diseases / Q000145:classification*; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009520:New Zealand; D010351:Patient Discharge / Q000706:statistics & numerical data; D011237:Predictive Value of Tests; D011336:Probability; D016019:Survival Analysis; D013548:Sweden; D015599:Trauma Severity Indices; D014947:Wounds and Injuries / Q000145:classification / Q000175:diagnosis* / Q000401:mortality* / Q000628:therapy