title: Dispensing data captures individual-level use of aspirin for cardiovascular disease prevention, despite availability over-the-counter.
abstract: OBJECTIVE
  To assess the level of agreement in aspirin use measured by self-report and dispensing data.
  
  
  METHODS
  We assessed preventive cardiovascular medication use (prescription-only statins and blood pressure-lowering therapy; and aspirin-also available over-the-counter) at baseline in participants in the New Zealand IMPACT trial for whom these medications were prescribed by their general practitioner. A trial nurse not involved in their ongoing health care obtained participants' self-reported aspirin use data. We obtained dispensing data from the national pharmaceutical dispensing database and assessed agreement between the two measures using kappa coefficients.
  
  
  RESULTS
  Of the 513 trial participants, 36% were women, 50% were of Māori ethnicity, and 45% had a history of cardiovascular disease. The level of agreement between self-reported aspirin use and dispensing data was substantial (kappa 0.75, 95% CI 0.69 to 0.82). The level of agreement in aspirin use measured by these two sources of data was similar to that for statin and blood pressure-lowering therapy use, for all participants combined, for subgroups according to ethnicity (Māori and non-Māori) and history of cardiovascular disease.
  
  
  CONCLUSIONS
  Despite its availability over-the-counter, aspirin use in patients for whom cardiovascular medications are indicated can be assessed accurately from dispensing data.
authors.affiliation: Department of Epidemiology & Biostatistics, University of Auckland, Private Bag 92019, Auckland Mail Centre, Auckland 1142, New Zealand. v.selak@auckland.ac.nz.
authors.forename: Vanessa
authors.initials: V
authors.lastname: Selak
authors.forename: Yulong
authors.initials: Y
authors.lastname: Gu
authors.forename: Natasha
authors.initials: N
authors.lastname: Rafter
authors.forename: Sue
authors.initials: S
authors.lastname: Crengle
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Kerr
authors.forename: Chris
authors.initials: C
authors.lastname: Bullen
mesh_terms: D000959:Antihypertensive Agents / Q000627:therapeutic use; D001241:Aspirin / Q000627:therapeutic use*; D002318:Cardiovascular Diseases / Q000517:prevention & control*; D062313:Databases, Pharmaceutical; D011307:Drug Prescriptions / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000627:therapeutic use; D008297:Male; D009520:New Zealand; D010975:Platelet Aggregation Inhibitors / Q000627:therapeutic use*; D016032:Randomized Controlled Trials as Topic; D057566:Self Report
chemical_list: D000959:Antihypertensive Agents; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D010975:Platelet Aggregation Inhibitors; D001241:Aspirin