title: Methodological issues on the use of administrative data in healthcare research: the case of heart failure hospitalizations in Lombardy region, 2000 to 2012.
abstract: Administrative data are increasingly used in healthcare research. However, in order to avoid biases, their use requires careful study planning. This paper describes the methodological principles and criteria used in a study on epidemiology, outcomes and process of care of patients hospitalized for heart failure (HF) in the largest Italian Region, from 2000 to 2012.
  
  
  
  Data were extracted from the administrative data warehouse of the healthcare system of Lombardy, Italy. Hospital discharge forms with HF-related diagnosis codes were the basis for identifying HF hospitalizations as clinical events, or episodes. In patients experiencing at least one HF event, hospitalizations for any cause, outpatient services utilization, and drug prescriptions were also analyzed.
  
  
  
  Seven hundred one thousand, seven hundred one heart failure events involving 371,766 patients were recorded from 2000 to 2012. Once all the healthcare services provided to these patients after the first HF event had been joined together, the study database totalled about 91 million records. Principles, criteria and tips utilized in order to minimize errors and characterize some relevant subgroups are described.
  
  
  
  The methodology of this study could represent the basis for future research and could be applied in similar studies concerning epidemiology, trend analysis, and healthcare resources utilization.
authors.affiliation: Department of Management Economics and Industrial Engineering, Politecnico di Milano, Milan, Italy.
authors.forename: Cristina
authors.initials: C
authors.lastname: Mazzali
authors.affiliation: MOX-Department of Mathematics, Politecnico di Milano, Via Bonardi 9, 20133, Milan, Italy. anna.paganoni@polimi.it.
authors.forename: Anna Maria
authors.identifier: 0000-0002-8253-3630
authors.initials: AM
authors.lastname: Paganoni
authors.affiliation: Department of Mathematics, Università degli Studi di Milano, Milan, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Ieva
authors.affiliation: Department of Management Economics and Industrial Engineering, Politecnico di Milano, Milan, Italy.
authors.forename: Cristina
authors.initials: C
authors.lastname: Masella
authors.affiliation: Ospedale Uboldo, AO Melegnano, Milan, Italy.
authors.forename: Mauro
authors.initials: M
authors.lastname: Maistrello
authors.affiliation: AO San Carlo di Milano, Milan, Italy.
authors.forename: Ornella
authors.initials: O
authors.lastname: Agostoni
authors.affiliation: IRCCS Fondazione S. Maugeri di Lumezzane, Brescia, Italy.
authors.forename: Simonetta
authors.initials: S
authors.lastname: Scalvini
authors.affiliation: De Gasperis Cardiocenter, Niguarda-Ca'Granda hospital, Milan, Italy.
authors.forename: Maria
authors.initials: M
authors.lastname: Frigerio
mesh_terms: D000368:Aged; D000553:Ambulatory Care; D016208:Databases, Factual; D003695:Delivery of Health Care; D005260:Female; D006302:Health Services Research / Q000379:methods*; D006333:Heart Failure / Q000453:epidemiology; D006739:Hospital Administration; D006760:Hospitalization; D006801:Humans; D007558:Italy / Q000453:epidemiology; D008297:Male; D010351:Patient Discharge
keywords: Administrative databases; Comorbidity; Epidemiological studies; Healthcare services utilization; Heart failure; High dimensional data methods