title: Validity of psoriatic arthritis and capture of disease modifying antirheumatic drugs in the health improvement network.
abstract: OBJECTIVE
  The aims of this study are to examine the validity of diagnostic codes for psoriatic arthritis in The Health Improvement Network (THIN) and to examine the agreement between General Practitioner (GP) report and prescription records for disease modifying antirheumatic drugs (DMARDs).
  
  
  METHODS
  Questionnaires were sent to the GPs of 100 randomly selected patients with at least one medical record code for psoriatic arthritis. The positive predictive value (PPV) for a GP confirmed diagnosis was calculated, and alternative algorithms were examined to determine which method resulted in the highest PPV.
  
  
  RESULTS
  The PPV for a single code for psoriatic arthritis was 85% (95%CI: 75.8-91.7%). Adding a prescription for a DMARD increased the PPV to 91% but with a substantial loss in sensitivity. Agreement between GPs and prescription data for use of an oral DMARD was 69%.
  
  
  CONCLUSIONS
  The diagnosis codes for psoriatic arthritis used in THIN are valid. All prescriptions for DMARDs may not be accounted for in THIN.
authors.affiliation: Perelman School of Medicine at the University of Pennsylvania, USA.
authors.forename: Alexis
authors.initials: A
authors.lastname: Ogdie
authors.forename: Sara
authors.initials: S
authors.lastname: Alehashemi
authors.forename: Thorvardur Jon
authors.initials: TJ
authors.lastname: Love
authors.forename: Yihui
authors.initials: Y
authors.lastname: Jiang
authors.forename: Kevin
authors.initials: K
authors.lastname: Haynes
authors.forename: Sean
authors.initials: S
authors.lastname: Hennessy
authors.forename: Hyon
authors.initials: H
authors.lastname: Choi
authors.forename: Joel M
authors.initials: JM
authors.lastname: Gelfand
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D018501:Antirheumatic Agents / Q000627:therapeutic use*; D015535:Arthritis, Psoriatic / Q000175:diagnosis / Q000188:drug therapy*; D059019:Clinical Coding / Q000592:standards*; D003430:Cross-Sectional Studies; D016208:Databases, Factual / Q000706:statistics & numerical data; D057286:Electronic Health Records / Q000706:statistics & numerical data*; D005260:Female; D058005:General Practitioners; D006801:Humans; D008297:Male; D008499:Medical Records / Q000706:statistics & numerical data; D008875:Middle Aged; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D011795:Surveys and Questionnaires
chemical_list: D018501:Antirheumatic Agents
keywords: database; disease modifying antirheumatic drug (DMARD); pharmacoepidemiology; psoriatic arthritis; the health improvement network; validation