title: Applying diagnosis and pharmacy-based risk models to predict pharmacy use in Aragon, Spain: the impact of a local calibration.
abstract: BACKGROUND
  In the financing of a national health system, where pharmaceutical spending is one of the main cost containment targets, predicting pharmacy costs for individuals and populations is essential for budget planning and care management. Although most efforts have focused on risk adjustment applying diagnostic data, the reliability of this information source has been questioned in the primary care setting. We sought to assess the usefulness of incorporating pharmacy data into claims-based predictive models (PMs). Developed primarily for the U.S. health care setting, a secondary objective was to evaluate the benefit of a local calibration in order to adapt the PMs to the Spanish health care system.
  
  
  METHODS
  The population was drawn from patients within the primary care setting of Aragon, Spain (n = 84,152). Diagnostic, medication and prior cost data were used to develop PMs based on the Johns Hopkins ACG methodology. Model performance was assessed through r-squared statistics and predictive ratios. The capacity to identify future high-cost patients was examined through c-statistic, sensitivity and specificity parameters.
  
  
  RESULTS
  The PMs based on pharmacy data had a higher capacity to predict future pharmacy expenses and to identify potential high-cost patients than the models based on diagnostic data alone and a capacity almost as high as that of the combined diagnosis-pharmacy-based PM. PMs provided considerably better predictions when calibrated to Spanish data.
  
  
  CONCLUSIONS
  Understandably, pharmacy spending is more predictable using pharmacy-based risk markers compared with diagnosis-based risk markers. Pharmacy-based PMs can assist plan administrators and medical directors in planning the health budget and identifying high-cost-risk patients amenable to care management programs.
authors.affiliation: Aragon Health Science Institute, 25, Gomez Laguna Ave, Zaragoza 50009, Spain. acalderon.iacs@aragon.es
authors.forename: Amaia
authors.initials: A
authors.lastname: Calderón-Larrañaga
authors.forename: Chad
authors.initials: C
authors.lastname: Abrams
authors.forename: Beatriz
authors.initials: B
authors.lastname: Poblador-Plou
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Weiner
authors.forename: Alexandra
authors.initials: A
authors.lastname: Prados-Torres
mesh_terms: D003953:Diagnosis-Related Groups; D057286:Electronic Health Records; D005252:Fees, Pharmaceutical; D005260:Female; D006801:Humans; D016014:Linear Models; D016015:Logistic Models; D008297:Male; D017059:Models, Econometric; D009313:National Health Programs / Q000191:economics; D010593:Pharmaceutical Services / Q000191:economics / Q000706:statistics & numerical data*; D012372:ROC Curve; D020379:Risk Adjustment; D012307:Risk Factors; D013030:Spain; D014481:United States