Medication beliefs are associated with phosphate binder non-adherence in hyperphosphatemic haemodialysis patients

Abstract

OBJECTIVES: Patients with end-stage kidney disease receiving haemodialysis (HD) are at risk of cardiovascular disease and bone disorders related to high levels of serum phosphate. We studied the association between medication beliefs and depressive symptoms, with non-adherence to phosphate binding medication in a group of HD patients at risk of complications due to hyperphosphatemia.DESIGN: Cross-sectional design.METHODS: Baseline data from 112 patients participating in a randomized controlled trial, evaluating an adherence intervention, are presented. All patients had serum phosphate levels >1.6 mmol/l at baseline. Adherence was measured by (1) serum phosphate and (2) Medication Adherence Report Scales (MARS). Beliefs about Medicines (BMQ) and depressive symptoms (PHQ-9) were also evaluated.RESULTS: Beliefs about Medicines Questionnaire necessity, but not concerns, beliefs were found to correlate with serum phosphate (r = -.23, p < .05) and self-reported adherence (r = .35, p < .01). In regression models, controlling for demographic, clinical and psychological variables, necessity beliefs explained the variance of serum phosphate (β = -.22, p = .01) and self-reported adherence (β = .30, p ≤ .01). Both BMQ concerns and depressive symptoms were not related to non-adherence.CONCLUSION: Patients' beliefs about the necessity of their prescribed phosphate binding medications explain variation in non-adherence levels, measured both subjective and objectively. Dialysis patient's medication beliefs are potentially modifiable targets for future interventions. Statement of contribution What is already known on this subject? Haemodialysis patients are at risk of cardiovascular disease and bone disorders related to high levels of serum phosphate, yet adherence to phosphate binders remains suboptimal. Treatment beliefs have been shown to predict adherence to phosphate binders. What does this study add? In patients who are at risk of complications due to high phosphate levels, beliefs regarding the necessity of phosphate binders are associated with treatment non-adherence as measured by a physiological proxy (serum phosphate levels) and self-report. Depression does not appear to be related to phosphate binder non-adherence.