Measures of adherence based on self-report exhibited poor agreement with those based on pharmacy records

  • Line Guénette
    Affiliations
    Faculté de pharmacie, Université Laval, Québec, Canada, and Unité de recherche en santé des populations, Hôpital Saint-Sacrement du CHA, 1050, chemin Sainte-Foy, Québec, QC G1S 4L8 Canada
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  • Jocelyne Moisan
    Correspondence
    Corresponding author. Tel.: 418 682 7511 ext 4654; fax: 418 682 7962.
    Affiliations
    Faculté de pharmacie, Université Laval, Québec, Canada, and Unité de recherche en santé des populations, Hôpital Saint-Sacrement du CHA, 1050, chemin Sainte-Foy, Québec, QC G1S 4L8 Canada
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  • Michel Préville
    Affiliations
    Centre de recherche sur le vieillissement, Institut universitaire de gériatrie de Sherbrooke, 1036, rue Belvédère Sud, Sherbrooke, Québec, Canada J1H 4C4
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  • Richard Boyer
    Affiliations
    Centre de recherche Fernand-Seguin, Hopital Louis-Hypolite Lafontaine, 7331, rue Hochelaga, Montréal, Québec, Canada H1N 3V2
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      Abstract

      Objective

      To assess the level of agreement between a self-reported measure of adherence with prescribed drug and a measure of adherence based on pharmacy data.

      Methods

      During an in-home interview, people aged 65+ were asked to report all prescription drugs they had taken in the preceding month. For each drug, a four-item questionnaire was used to determine self-reported adherence. In the pharmacy records, each drug that had been filled at least four times was analyzed, and the percentage of days with the drug available was calculated. Two types of adherence were studied: (1) adherence by individual, and (2) adherence by drug. The level of agreement was assessed using kappa (κ) statistics and proportions of agreement.

      Results

      We compared the adherence measures among 189 individuals (880 drugs). Among all, 90 individuals (48%) self-reported adherence, whereas 95 individuals (50%) were adherent according to the records. The level of agreement between these two measures was slight (κ = 0.16 [95% CI: 0.02–0.30]). Individuals self-reported to be adherent for 81% of the drugs, while pharmacy records showed adherence for 83% of them (κ = 0.13 [95% CI: 0.05–0.20]).

      Conclusion

      Self-reported measures of adherence exhibited poor agreement with those based on pharmacy records.

      Keywords

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