title: Validation of an economic model of paliperidone palmitate for chronic schizophrenia.
abstract: OBJECTIVE
  Model validation is important, but seldom applied in chronic schizophrenia. Validation consists of verifying the model itself for face validity (i.e., structure and inputs), cross-validation with other models assessing the same issue, and comparison with real-life outcomes. The primary purpose was to cross-validate a recent pharmacoeconomic model comparing long-acting injectable (LAI) antipsychotics for treating chronic schizophrenia in Sweden. The secondary purpose was to provide external validation.
  
  
  METHODS
  The model of interest was a decision tree analysis with a 1-year time horizon with costs in 2011 Swedish kroner. Drugs analyzed included paliperidone palmitate (PP-LAI), olanzapine pamoate (OLZ-LAI), risperidone (RIS-LAI), haloperidol (HAL-LAI), and oral olanzapine (oral-OLZ). Embase and Medline were searched from 1990-2012 for models examining LAIs. Articles were retrieved, with data extracted for all drugs compared including: expected costs, rates of hospitalization, proportion of time not in relapse, and associated QALYs. Outcomes from the model of interest were compared with those from other articles; costs were projected to 2012 using the consumer price index.
  
  
  RESULTS
  Twenty-six studies were used for validation; 14 of them provided evidence for cross-validation, 13 for external validation, and four for cost. In cross-validation, cost estimates varied -1.8% (range: -12.4-20.1%), hospitalizations 5.2% (-12.1-3.1%), stable disease 2.5% (-5.6-1.5%), QALYs 9.0% (4.3% after removing outliers). All estimates of clinical outcomes were within 15%. In external validation, hospitalization rates varied by 6.3% (-0.7-11.3%). The research was limited by data availability and validity of the original results.
  
  
  CONCLUSIONS
  Other models validated the outputs of our model very well.
authors.affiliation: Leslie Dan Faculty of Pharmacy, University of Toronto , Toronto, ON , Canada.
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Einarson
authors.forename: Michiel E H
authors.initials: ME
authors.lastname: Hemels
mesh_terms: D014150:Antipsychotic Agents / Q000008:administration & dosage / Q000191:economics* / Q000627:therapeutic use*; D002908:Chronic Disease; D003663:Decision Trees; D003692:Delayed-Action Preparations; D006760:Hospitalization / Q000191:economics / Q000706:statistics & numerical data; D006801:Humans; D007555:Isoxazoles / Q000008:administration & dosage / Q000191:economics* / Q000627:therapeutic use*; D018803:Models, Economic; D000068882:Paliperidone Palmitate; D010168:Palmitates / Q000008:administration & dosage / Q000191:economics* / Q000627:therapeutic use*; D019057:Quality-Adjusted Life Years; D012008:Recurrence; D015203:Reproducibility of Results; D012559:Schizophrenia / Q000188:drug therapy*; D013548:Sweden
chemical_list: D014150:Antipsychotic Agents; D003692:Delayed-Action Preparations; D007555:Isoxazoles; D010168:Palmitates; D000068882:Paliperidone Palmitate