ABSTRACT
BACKGROUND: Currently, most available data on the medication adherence of patients with chronic heart failure are based on indirect methods. We examined the level of adherence to medical therapy using a direct method - serum drug level testing. METHODS: We carried out a prospective single-centre registry of patients with chronic heart failure (LEVEL-CHF registry), in whom we analysed serum levels of the medications prescribed for the treatment of heart failure: angiotensin converting enzyme inhibitors, angiotensin receptor blockers, beta-blockers and mineralocorticoid receptor antagonists. We labelled a patient as non-adherent if at least one serum level of a prescribed drug was unmeasurable (below the detection limit). Patients with all tested drugs identifiable in serum were labelled as adherent. We enrolled 274 patients (208 men and 66 women) mean age 62 years. RESULTS: 82.5% of patients were adherent and 17.5% non-adherent to prescribed medications. 3.6% were completely non-adherent without any detectable drugs in serum. Patients aged <60 years were more likely to be non-adherent than older patients (OR 2.15). No other clinical or laboratory parameters predicted non-adherence. CONCLUSIONS: A significant proportion of outpatients with chronic heart failure were non-adherent to treatment when assessed by a direct method of serum drug level testing. Non-adherence was more likely in younger patients.
