The association between hyperphosphatemia and increased mortality and hospitalization in patients with end-stage renal disease (ESRD) on hemodialysis (HD) is well known, yet non-adherence to phosphate-binding treatment and dietary restrictions remains a significant problem. Three recent papers have examined the range of factors influencing adherence, while a fourth discusses the use of financial incentives and coaching to improve adherence.
Factors influencing non-adherence
Ghimire et al conducted a systematic review to highlight the key patient-, disease- and medication-related factors associated with non-adherence to all medication in HD patients. 44 articles published between 1970 and November 2014 were identified.
Overall rates of non-adherence ranged from 12.5% to 98.6%, while non-adherence to phosphate binders (PB) ranged from 13.9% to 98.6%, with an average of 52.5%. This large variation was, in part, due to the heterogeneous measures of non-adherence; with lower rates observed in papers recording pre-dialysis serum phosphate (13.9% to 45.1%) compared to self-reported measures (40.0% to 60.0%).
Factors influencing non-adherence included:
- Patient-related factors: younger age, non-Caucasian ethnicity, illness interfering family life, smoking, and living alone.
- Disease-related factors: longevity of hemodialysis (≥5 years), recurrent hospitalization, depressive symptoms and concomitant illness (e.g. diabetes and hypertension).
- Medication-related factors: daily tablet count, pill burden, number of PBs, and the complexity of the total regimen.
Other factors include: depressive symptoms, negative belief about medication and distress related to the disease, while support from healthcare providers had a significant, positive effect on adherence rates.
Ghimire and colleagues highlight the need for consensus in the assessment of adherence in order to develop and test interventions for improvement. They also stress the inclusion of psychosocial and behavioral factors in future studies.
Intentional or unintentional non-adherence?
One subject not investigated in depth by Ghimire et al, was the difference between intentional and unintentional medication adherence. In a survey of HD patients taking phosphate binders conducted by Joson et al, 65% reported at least 1 incidence of unintentional non-adherence (mainly forgetting medication) while 48% admitted intentional non-adherence due to side-effects or considering themselves asymptomatic.
Levels of intentional non-adherence in patients with uncontrolled phosphorus levels were almost twice that of the controlled group. High levels of unintentional non-adherence were associated with a greater risk of being uncontrolled.
In this study, 52% of patients showed some level of phosphorus-related knowledge – either high phosphate foods or risks associated with hyperphosphatemia – but knowledge did not equate to improved phosphorus control.
Due to the small sample size of this study the results were not significant. However, the authors highlight the need for tackling non-adherence due to forgetfulness in relation to a medication not on a fixed dosing schedule.
In a study measuring autonomous regulation, Umeukeje et al showed a positive correlation between self-motivation scores and self-reported PB adherence and a significant association between adherence and phosphate control. The authors conclude that this simple assessment could help determine the level of support a patient requires to ensure adherence.
Reese et al hypothesized that financial rewards and coaching might be effective methods of encouraging patients to reduce their phosphate levels. 36 participants, ≥18 years with SPL >5.5mg/dL, were randomized to receive coaching on diet and adherence, financial incentives or normal care.
No significant differences were found due to sample size, but there was a trend towards decline in incentivized patients: after the 70-day study, serum phosphate levels were 5.8 mg/dL in the incentives arm, 5.7 mg/dL in the coaching arm, and 6.2 mg/dL in the usual care arm.
In conclusion, larger trials are required to better understand whether incentives/and or coaching are effective methods for increasing HD patient motivation, leading to reduced serum phosphate.
- Joson CG, Henry SL, Kim S, et al. Patient-Reported Factors Associated With Poor Phosphorus Control in a Maintenance Hemodialysis Population. J Ren Nutr. 2015:1-8. doi:10.1053/j.jrn.2015.09.004.
- Ghimire S, Castelino RL, Lioufas NM, Peterson GM, Zaidi STR. Nonadherence to Medication Therapy in Haemodialysis Patients: A Systematic Review. PLoS One. 2015;10:e0144119. doi:10.1371/journal.pone.0144119.
- Umeukeje EM, Merighi JR, Browne T, et al. Self-Motivation Is Associated With Phosphorus Control in End-Stage Renal Disease. J Ren Nutr. 2015;25(5):433-439. doi:10.1053/j.jrn.2015.03.001.
- Reese PP, Mgbako O, Mussell A, et al. A Pilot Randomized Trial of Financial Incentives or Coaching to Lower Serum Phosphorus in Dialysis Patients. J Ren Nutr. 2015;25(6):510-517. doi:10.1053/j.jrn.2015.06.001.