title: Comparability of self-reported medication use and pharmacy claims data.
abstract: BACKGROUND
  Many studies of medicine use rely on self-reports. Based on pharmacy claims data, this analysis tests whether such self-reports constitute a valid and reliable data source.
  
  
  METHODS
  Linked data from the Canadian Community Health Survey and the Ontario Drug Benefit Program were used to estimate the agreement, based on kappa statistics, between seniors' self-reported medication use and the claims data. Health, demographic and socio-economic factors associated with the likelihood of agreement were modeled with logistic regression.
  
  
  RESULTS
  The prevalence of antihypertensive medication use among Ontario residents aged 65 or older was about 40% in 2001, based on both self-report and pharmacy claims, and in 2005, it was 52% for self-report and 49% based on claims data. The prevalence of oral diabetes medication use was comparable between the two data sources. Overall agreement between self-reported and claims data was "good" to "very good" for oral diabetes medications (kappa = 0.79 in 2001; 0.87 in 2005), but "moderate" for antihypertensive medications (kappa = 0.46 in 2001; 0.55 in 2005). Agreement improved somewhat from 2001 to 2005, with implementation of a more targeted survey question.
  
  
  CONCLUSIONS
  Self-reports appear to be an accurate data source for measuring medication use; however, for antihypertensive medications, self-reports by the oldest and sickest subpopulations should be used cautiously.
authors.affiliation: University of Toronto. sara.allin@utoronto.ca
authors.forename: Sara
authors.initials: S
authors.lastname: Allin
authors.forename: Ahmed M
authors.initials: AM
authors.lastname: Bayoumi
authors.forename: Michael R
authors.initials: MR
authors.lastname: Law
authors.forename: Audrey
authors.initials: A
authors.lastname: Laporte
mesh_terms: D002170:Canada; D006801:Humans; D010593:Pharmaceutical Services; D010594:Pharmacies; D057566:Self Report; D011795:Surveys and Questionnaires
keywords: aged; antihypertensive agents; diabetes; drug prescriptions; drug utilization; health surveys