title: The Drug Derived Complexity Index (DDCI) Predicts Mortality, Unplanned Hospitalization and Hospital Readmissions at the Population Level.
abstract: OBJECTIVE
  to develop and validate the Drug Derived Complexity Index (DDCI), a predictive model derived from drug prescriptions able to stratify the general population according to the risk of death, unplanned hospital admission, and readmission, and to compare the new predictive index with the Charlson Comorbidity Index (CCI).
  
  
  METHODS
  Population-based cohort study, using a record-linkage analysis of prescription databases, hospital discharge records, and the civil registry. The predictive model was developed based on prescription patterns indicative of chronic diseases, using a random sample of 50% of the population. Multivariate Cox proportional hazards regression was used to assess weights of different prescription patterns and drug classes. The predictive properties of the DDCI were confirmed in the validation cohort, represented by the other half of the population. The performance of DDCI was compared to the CCI in terms of calibration, discrimination and reclassification.
  
  
  METHODS
  6 local health authorities with 2.0 million citizens aged 40 years or above.
  
  
  RESULTS
  One year and overall mortality rates, unplanned hospitalization rates and hospital readmission rates progressively increased with increasing DDCI score. In the overall population, the model including age, gender and DDCI showed a high performance. DDCI predicted 1-year mortality, overall mortality and unplanned hospitalization with an accuracy of 0.851, 0.835, and 0.584, respectively. If compared to CCI, DDCI showed discrimination and reclassification properties very similar to the CCI, and improved prediction when used in combination with the CCI.
  
  
  CONCLUSIONS
  DDCI is a reliable prognostic index, able to stratify the entire population into homogeneous risk groups. DDCI can represent an useful tool for risk-adjustment, policy planning, and the identification of patients needing a focused approach in everyday practice.
authors.affiliation: Department of Clinical Pharmacology and Epidemiology, Mario Negri Sud Foundation, Santa Maria Imbaro (CH), Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Robusto
authors.affiliation: Department of Clinical Pharmacology and Epidemiology, Mario Negri Sud Foundation, Santa Maria Imbaro (CH), Italy.
authors.forename: Vito
authors.initials: V
authors.lastname: Lepore
authors.affiliation: Department of Clinical Pharmacology and Epidemiology, Mario Negri Sud Foundation, Santa Maria Imbaro (CH), Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: D'Ettorre
authors.affiliation: Center for Outcomes Research and clinical Epidemiology, Pescara (PE), Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Lucisano
authors.affiliation: Center for Outcomes Research and clinical Epidemiology, Pescara (PE), Italy.
authors.forename: Giorgia
authors.initials: G
authors.lastname: De Berardis
authors.affiliation: Regional Health Agency of Puglia, Bari (BA), Italy.
authors.forename: Lucia
authors.initials: L
authors.lastname: Bisceglia
authors.affiliation: IRRCS Mario Negri Milano, Milano (MI), Italy.
authors.forename: Gianni
authors.initials: G
authors.lastname: Tognoni
authors.affiliation: Center for Outcomes Research and clinical Epidemiology, Pescara (PE), Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Nicolucci
mesh_terms: D000328:Adult; D000368:Aged; D015331:Cohort Studies; D015897:Comorbidity; D016208:Databases, Factual; D011307:Drug Prescriptions; D005260:Female; D006760:Hospitalization; D006801:Humans; D015994:Incidence; D007558:Italy; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D009026:Mortality; D010359:Patient Readmission; D011159:Population Surveillance; D016016:Proportional Hazards Models; D012042:Registries; D012307:Risk Factors