Aims:
To assess adherence to medical treatment in patients with heart failure (HF) using a specific questionnaire and measurement of the serum concentration of digoxin.
Methods and result:
This was a pilot study which included 40 patients with symptomatic HF and a clinical indication for digoxin. The assessment of adherence to the medical regime was based on two different methods: (i) the CARDIA-Questionnaire and
(ii) the measurement of serum digoxin concentration (SDC) at 1 and 6 months. All patients were placed on digoxin treatment (target SDC 0.6–0.8 ng/mL) at baseline. Poor adherence was defined if the patient self-reported taking ≤75% of the prescribed HF medication or had an SDC < 0.4 ng/mL (subtherapeutic range) at the follow-up visits. During the entire follow-up, the proportion of patients with poor adherence was 15% as assessed by the questionnaire, 20% as assessed by the SDC, and 25% if both methods were combined.
Conclusion:
Although HF is a symptomatic disease, the proportion of patients with poor adherence to the medical regime in our study was high (up to 25%). The objective methodology based on the measurement of the SDC identified a higher
number of patients with poor adherence when compared with the CARDIA-Questionnaire.
Comment:
This paper is the first to examine the issue of adherence in HF using a combination of questionnaire and objective measurement. Findings relating to each measurement are comparable with other studies. The authors also raise some important points relating to cut-offs and definitions.
Variation in how medication adherence is defined makes it difficult to compare studies, what level of adherence should we be aiming for? The study also refers to optimal ‘self-care’ management and this is important. Medication adherence is a small component of an overall regime which includes lifestyle change, symptom monitoring and symptom reporting.
Many studies report that across the behaviours medication adherence is highest with very low levels of adherence in relation to other behaviours. Would better gains be made if interventions were to concentrate on these areas also?