Self-reported versus ‘true’ adherence in heart failure patients: a study using the Medication Event Monitoring System

BACKGROUND: Adherence to (non)pharmacological treatment is important in heart failure (HF) patients, since it leads to better clinical outcome. Although self-reported and objectively measured medication adherence in HF patients have been compared in previous studies, none of these studies have used an evidence-based cutpoint to differentiate between adherence and non-adherence. METHODS: In 37 HF patients (mean age 68 ± 10 years, 27 % female, 40 % NYHA functional class III-IV), medication (ACEi/ARB) adherence was objectively measured using the Medication Event Monitoring System (MEMS). Adherence to and importance of taking medication was also assessed by self-report using the Revised HF Compliance Questionnaire. RESULTS: All patients reported that adherence was (highly) important to them and that they 'always' took their medication as prescribed (i.e. 100 % adherence). However, when measured by the MEMS, only 76 % of all patients were adherent. Non-adherent patients more often had a complex medication regimen (78 % vs. 21 %, P < .01), more often depressive symptoms (75 % vs. 29 %, P = .04) and a shorter history of HF (8 vs. 41 months, P = .04), compared with adherent patients. CONCLUSIONS: Medication adherence measured by the MEMS was remarkably lower than self-reported adherence. Given the evidence of its importance, further efforts are needed to improve adherence to the pharmacological regimen in HF patients.