title: Methods for evaluation of medication adherence and persistence using automated databases.
abstract: OBJECTIVE
  Our aim was to perform a systematic review of the methods currently being used to assess adherence and persistence in pharmacoepidemiological and pharmacoeconomic studies using automated databases.
  
  
  METHODS
  A MEDLINE search of English language literature was performed to identify studies published between January 1, 1980 and March 31, 2004 that evaluated adherence, compliance, persistence, switching, or discontinuations of medications using automated dispensing data (pharmacy records). Two study investigators independently reviewed the abstracts and articles to determine relevant studies according to specified criteria.
  
  
  RESULTS
  A total of 136 articles met the criteria for evaluation. The types of measures of adherence and persistence commonly reported include the medication possession ratio and related measures of medication availability (77 studies), discontinuation/continuation (58 studies), switching (34 studies), medication gaps (13 studies), refill compliance (7 studies), and retentiveness/turbulence (4 studies). Specific issues considered include the assessment of exposed time to drug therapy and specification of the follow-up period.
  
  
  CONCLUSIONS
  The terminology, definitions, and methods to determine adherence and persistence differ greatly in the published literature. The appropriateness and choice of the specific measure employed should be determined by the overall goals of the study, as well as the relative advantages and limitations of the measures.
authors.affiliation: Meyers Primary Care Institute, University of Massachusetts Medical School, Fallon Foundation, Fallon Community Health Plan, Worcester, MA 01605, USA. sandrade@meyersprimary.org
authors.forename: Susan E
authors.initials: SE
authors.lastname: Andrade
authors.forename: Kristijan H
authors.initials: KH
authors.lastname: Kahler
authors.forename: Feride
authors.initials: F
authors.lastname: Frech
authors.forename: K Arnold
authors.initials: KA
authors.lastname: Chan
mesh_terms: D016208:Databases, Factual; D011307:Drug Prescriptions / Q000706:statistics & numerical data*; D004358:Drug Therapy / Q000706:statistics & numerical data; D006801:Humans; D010349:Patient Compliance; D010594:Pharmacies; D017891:Pharmacoepidemiology