title: External validation of a pre-operative nomogram predicting peri-operative mortality risk after liver resections for malignancy.
abstract: OBJECTIVE
  A pre-operative nomogram using a population-based database to predict peri-operative mortality risk after liver resections for malignancy has recently been developed. The aim of the present study was to perform an external validation of the nomogram using data from a high volume institution.
  
  
  METHODS
  The National Inpatient Sample (NIS) database (2000-2004) was used initially to construct the nomogram. The dataset for external validation was obtained from a high volume centre specializing in hepatobiliary surgery. Validation was performed using calibration plots and concordance index.
  
  
  RESULTS
  A total of 794 patients who underwent liver resection from the years 2000-2010 at the external institute were included in the validation set with an observed mortality rate of 1.6%. The mean total points for this sample of patients was 124.9 [standard error (SE) 1.8, range 0-383] which translates to a nomogram predicted mortality rate of 1.5%, similar to the actual observed overall mortality rate. The nomogram concordance index was 0.65 [95% confidence interval (CI) 0.46-0.82] and calibration plots stratified by quartiles revealed good agreement between the predicted and observed mortality rates.
  
  
  CONCLUSIONS
  The present study provides an external validation of the pre-operative nomogram to predict the risk of peri-operative mortality after liver resection for malignancy.
authors: University of Nebraska Medical Center, Omaha, NE, USA.
authors: Mashaal
authors: M
authors: Dhir
authors: Srinevas K
authors: SK
authors: Reddy
authors: Lynette M
authors: LM
authors: Smith
authors: Fred
authors: F
authors: Ullrich
authors: James Wallis
authors: JW
authors: Marsh
authors: Allan
authors: A
authors: Tsung
authors: David A
authors: DA
authors: Geller
authors: Chandrakanth
authors: C
authors: Are
mesh_terms: D000368:Aged; D003661:Decision Support Techniques; D005260:Female; D006498:Hepatectomy / Q000401:mortality*; D017052:Hospital Mortality; D006801:Humans; D008113:Liver Neoplasms / Q000401:mortality* / Q000601:surgery*; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D049451:Nomograms; D018579:Patient Selection; D059035:Perioperative Period; D015203:Reproducibility of Results; D018570:Risk Assessment; D012307:Risk Factors; D013997:Time Factors; D016896:Treatment Outcome; D014481:United States