Original Article

Hypertension Research (2008) 31, 2037–2043; doi:10.1291/hypres.31.2037

Patients' Self-Reported Adherence to Cardiovascular Medication Using Electronic Monitors as Comparators

Andreas Zeller1, Esther Ramseier1, Anne Teagtmeyer1 and Edouard Battegay1,2

  1. 1Medical Outpatient Department, University Hospital Basel, Basel, Switzerland
  2. 2Division of Internal Medicine, University Hospital Zürich, Zürich, Switzerland

Correspondence: Andreas Zeller, M.D., Medical Outpatients Department, University Hospital Basel, Petersgraben 4, CH-4031 Basel, Switzerland. E-mail: zellera@uhbs.ch

Received 22 July 2008; Accepted 17 September 2008.

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Abstract

The aim of this study was to evaluate self-reporting of adherence to cardiovascular medication using electronic pillboxes (medical event monitoring system [MEMS]) as the gold standard comparator. In total, 78 individuals (52% hypertensives, 21% diabetics, 27% with dyslipidemia) were recruited prospectively from an outpatient clinic setting in Switzerland. Participants completed two self-report measures (visual analogue scale [VAS] and a validated self-reporting questionnaire) at baseline and were asked to use MEMS as their pillbox for the subsequent 10 weeks. Patients expressed their medication adherence behaviour on a VAS (0 mm=“I never take any tablets”; 100 mm=“I take all tablets as prescribed”) and entered one of six numbers (from 1: perfect adherence to 6: non-adherence) on the questionnaire. Medication compliance was monitored for 75 d on average. Mean (±SD, range) scores for MEMS with respect to timing adherence, correct dosing, and self-administration adherence were 79±25% (8–100%), 83±20% (24–100%), and 92±17% (54–118%), respectively. A majority of participants (78.8%) over-reported their adherence to the VAS (93±7 mm, 73–100), and VAS scores correlated poorly with MEMS recordings (Spearman's ρ for timing adherence, correct dosing, self-administration adherence 0.29 [p=0.018], 0.24 [p=0.051], 0.26 [p=0.036], respectively). Similarly, we found no correlation between adherence as expressed in the questionnaire and MEMS (regression coefficients < 0.1). We conclude that a majority of patients over-report adherence to cardiovascular medication if asked to complete a visual analogue scale and a validated questionnaire. Therefore, using self-reporting as the sole means of assessing medication compliance is insufficiently accurate to detect poor adherence.

Keywords:

hypertension, adherence, compliance, self-reporting

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