European hemodialysis patient satisfaction with phosphate binders is associated with serum phosphorus levels: the Dialysis Outcomes and Practice Patterns Study (DOPPS)

Abstract

Background Hemodialysis patients are commonly prescribed phosphate binders (PB) to manage serum phosphorus levels, as hyperphosphatemia is strongly associated with poorer survival. Non-adherence with the PB prescription is associated with elevated serum phosphorus levels. We studied associations between patient satisfaction with their PB and serum phosphorus levels and mortality rates. Methods Adult hemodialysis patients in Germany, Italy, Spain, and UK in the Dialysis Outcomes and Practice Patterns Study were administered a survey instrument in late 2017. Patients were asked about their satisfaction with their PBs, as measured through three questions (difficulty, inconvenience, dissatisfaction) on a 5-point Likert scale, with each dichotomized into average-worst versus good responses. These were used as predictors in linear regression models of continuous serum phosphorus levels and in Cox proportional hazards models of mortality, with adjustments for demographics, comorbidities, and laboratory values. Results Patients having greater difficulty, inconvenience, and dissatisfaction with their PB had higher serum phosphorus levels in adjusted models: +0.21 mg/dL (95% CI ± 0.23), +0.30(±0.21) mg/dL, and 0.36(±0.22) mg/dL, respectively; and higher odds of having serum phosphorus levels ≥6.0 mg/dL. Measures of dissatisfaction were also associated with elevated risk of mortality, with adjusted hazard ratios of 2.2 (95% CI 1.3-3.6), 1.6 (1.0-2.6), and 1.7 (1.1-2.7), respectively; this association was not strongly affected by adjustment for baseline serum phosphorous level. Conclusions Self-reported difficulty, inconvenience, and dissatisfaction in taking one’s prescribed PBs were associated with elevated serum phosphorus levels and serum phosphorus levels above clinically meaningful thresholds. While the mechanism for the association with mortality is unclear, patient-reported satisfaction should be considered when attempting to manage patient serum phosphorus levels.