title: Identification of antithrombotic drugs related to total joint replacement using anonymised free-text notes: a search strategy in the Clinical Practice Research Datalink.
abstract: OBJECTIVE
  We aimed to design and test a method to extract information on antithrombotic therapy from anonymised free-text notes in the Clinical Practice Research Datalink (CPRD).
  
  
  METHODS
  General practice database representative of the UK.
  
  
  METHODS
  All patients undergoing total hip replacement (THR, n=25,898) or total knee replacement (TKR, n=22,231) between January 2008 and October 2012 were included. Antithrombotic drug use related to THR or TKR was identified using anonymised free text and prescription data.
  
  
  METHODS
  Internal validity of our newly designed method was determined by calculating positive predictive values (PPVs) of hits for predefined keywords in a random sample of anonymised free-text notes. In order to determine potential detection bias, total joint replacement (TJR) patient characteristics were compared as per their status of exposure to antithrombotics.
  
  
  RESULTS
  PPVs ranging between 97% and 99% for new oral anticoagulants (NOAC) or low-molecular weight heparins (LMWH) exposure related to TJR were obtained with our method. Our search strategy increased detection rates by 57%, yielding a total proportion of 18.5% of all THR and 18.6% of all TKR surgeries. Identified users of NOACs and LMWHs were largely similar with regards to age, sex, lifestyle, disease and drug history compared to patients without identified drug use.
  
  
  CONCLUSIONS
  We have developed a useful method to identify additional exposure to NOACs or LMWHs with TJR surgery.
authors.affiliation: Division of Pharmacoepidemiology & Clinical Pharmacology, Utrecht University, Utrecht, The Netherlands Department of Epidemiology, CAPHRI School for Public Health and Primary Care, Maastricht University, Maastricht, The Netherlands.
authors.forename: Johannes Th
authors.initials: JT
authors.lastname: Nielen
authors.affiliation: Department of Pharmacy, Sint Maartenskliniek, Nijmegen, The Netherlands Department of Pharmacy, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Bart J F
authors.initials: BJ
authors.lastname: van den Bemt
authors.affiliation: Department of Internal Medicine, Division of Rheumatology, Maastricht University Medical Centre, Maastricht, The Netherlands.
authors.forename: Annelies
authors.initials: A
authors.lastname: Boonen
authors.affiliation: Department of Epidemiology, CAPHRI School for Public Health and Primary Care, and CARIM School for Cardiovascular Diseases, Maastricht University, Maastricht, The Netherlands.
authors.forename: Pieter C
authors.initials: PC
authors.lastname: Dagnelie
authors.affiliation: Department of Orthopaedics, Maastricht University Medical Center, Maastricht, The Netherlands.
authors.forename: Pieter J
authors.initials: PJ
authors.lastname: Emans
authors.affiliation: Department of Clinical Pharmacy and Toxicology, Maastricht University Medical Center, Maastricht, The Netherlands.
authors.forename: Nicole
authors.initials: N
authors.lastname: Veldhorst
authors.affiliation: Department of Clinical Pharmacy, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Arief
authors.initials: A
authors.lastname: Lalmohamed
authors.affiliation: Division of Pharmacoepidemiology & Clinical Pharmacology, Utrecht University, Utrecht, The Netherlands.
authors.forename: Tjeerd-Pieter
authors.initials: TP
authors.lastname: van Staa
authors.affiliation: Division of Pharmacoepidemiology & Clinical Pharmacology, Utrecht University, Utrecht, The Netherlands Department of Clinical Pharmacy and Toxicology, Maastricht University Medical Center, Maastricht, The Netherlands.
authors.forename: Frank
authors.initials: F
authors.lastname: de Vries
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000925:Anticoagulants / Q000627:therapeutic use*; D019644:Arthroplasty, Replacement, Hip; D019645:Arthroplasty, Replacement, Knee; D016208:Databases, Factual; D004363:Drug Utilization / Q000706:statistics & numerical data; D005260:Female; D005343:Fibrinolytic Agents / Q000627:therapeutic use*; D006801:Humans; D008297:Male; D008875:Middle Aged; D055815:Young Adult
chemical_list: D000925:Anticoagulants; D005343:Fibrinolytic Agents
keywords: EPIDEMIOLOGY; ORTHOPAEDIC & TRAUMA SURGERY; STATISTICS & RESEARCH METHODS