title: Use of demographic and pharmacy data to identify patients included within both the Clinical Practice Research Datalink (CPRD) and The Health Improvement Network (THIN).
abstract: OBJECTIVE
  Pharmacoepidemiology researchers often utilize data from two UK electronic medical record databases, the Clinical Practice Research Datalink (CPRD) and The Health Improvement Network (THIN), and may choose to combine the two in an effort to increase sample size. To minimize duplication of data, previous studies examined the practice-level overlap between these databases. However, the proportion of overlapping patients remains unknown. We developed a method using demographic and pharmacy variables to identify patients included in both CPRD and THIN, and applied this method to measure the proportion of overlapping patients who initiated the oral anti-diabetic drug saxagliptin.
  
  
  METHODS
  We conducted a cross-sectional study among patients initiating saxagliptin in CPRD and THIN between October 2009 and September 2012. Within both databases, we identified patients: (i) ≥18 years, (ii) newly prescribed saxagliptin, and (iii) with ≥180 days enrollment prior to saxagliptin initiation. Demographic data (birth year, sex, patient registration date, family number, and marital status) and prescriptions (including dates) for the first two oral anti-diabetic drugs prescribed within the study period were used to identify matching patients.
  
  
  RESULTS
  Among 4202 CPRD and 3641 THIN patients initiating saxagliptin, 2574 overlapping patients (61% of CPRD saxagliptin initiators; 71% of THIN saxagliptin initiators) were identified. Among these patients, 2474 patients (96%) perfectly matched on all demographic and prescription data.
  
  
  CONCLUSIONS
  Within each database, over 60% of patients initiating saxagliptin were included within both CPRD and THIN. Combined demographic and prescription data can be used to identify patients included in both CPRD and THIN.
authors.affiliation: Center for Clinical Epidemiology and Biostatistics, Department of Biostatistics and Epidemiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA.|Center for Pharmacoepidemiology Research and Training, Department of Biostatistics and Epidemiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: Dena M
authors.initials: DM
authors.lastname: Carbonari
authors.affiliation: Center for Clinical Epidemiology and Biostatistics, Department of Biostatistics and Epidemiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA.|Center for Pharmacoepidemiology Research and Training, Department of Biostatistics and Epidemiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: M Elle
authors.initials: ME
authors.lastname: Saine
authors.affiliation: Center for Clinical Epidemiology and Biostatistics, Department of Biostatistics and Epidemiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: Craig W
authors.initials: CW
authors.lastname: Newcomb
authors.affiliation: AstraZeneca UK Limited, London, UK.
authors.forename: Betina
authors.initials: B
authors.lastname: Blak
authors.affiliation: Center for Clinical Epidemiology and Biostatistics, Department of Biostatistics and Epidemiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA.|Center for Pharmacoepidemiology Research and Training, Department of Biostatistics and Epidemiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: Jason A
authors.initials: JA
authors.lastname: Roy
authors.affiliation: Center for Clinical Epidemiology and Biostatistics, Department of Biostatistics and Epidemiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA.|Center for Pharmacoepidemiology Research and Training, Department of Biostatistics and Epidemiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA.|HealthCore, Inc., Wilmington, DE, USA.
authors.forename: Kevin
authors.initials: K
authors.lastname: Haynes
authors.affiliation: Department of Global Pharmacovigilance and Epidemiology, Bristol-Myers Squibb, Hopewell, NJ, USA.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Wood
authors.affiliation: Clinical Practice Research Datalink, London, UK.
authors.forename: Arlene M
authors.initials: AM
authors.lastname: Gallagher
authors.affiliation: IMS Health, London, UK.
authors.forename: Harshvinder
authors.initials: H
authors.lastname: Bhullar
authors.affiliation: Department of Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: Serena
authors.initials: S
authors.lastname: Cardillo
authors.affiliation: Center for Clinical Epidemiology and Biostatistics, Department of Biostatistics and Epidemiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA.|Center for Pharmacoepidemiology Research and Training, Department of Biostatistics and Epidemiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: Sean
authors.initials: S
authors.lastname: Hennessy
authors.affiliation: Center for Clinical Epidemiology and Biostatistics, Department of Biostatistics and Epidemiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA.|Center for Pharmacoepidemiology Research and Training, Department of Biostatistics and Epidemiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA.|Rutgers Biomedical and Health Sciences, Rutgers, the State University of New Jersey, Newark, NJ, USA.
authors.forename: Brian L
authors.initials: BL
authors.lastname: Strom
authors.affiliation: Center for Clinical Epidemiology and Biostatistics, Department of Biostatistics and Epidemiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA.|Center for Pharmacoepidemiology Research and Training, Department of Biostatistics and Epidemiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA.|Department of Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: Vincent
authors.initials: V
authors.lastname: Lo Re
mesh_terms: D000218:Adamantane / Q000031:analogs & derivatives* / Q000627:therapeutic use; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D016208:Databases, Factual / Q000706:statistics & numerical data*; D004151:Dipeptides / Q000627:therapeutic use*; D057286:Electronic Health Records / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D007004:Hypoglycemic Agents / Q000627:therapeutic use; D008297:Male; D010604:Pharmacy / Q000706:statistics & numerical data*; D006113:United Kingdom / Q000453:epidemiology
chemical_list: D004151:Dipeptides; D007004:Hypoglycemic Agents; C502994:saxagliptin; D000218:Adamantane
keywords: Clinical Practice Research Datalink (CPRD); The Health Improvement Network (THIN); overlap; pharmacoepidemiology