Patients who report incomplete adherence to phosphate binder therapy are more likely to have poor phosphorus control, according to a small study. Poor knowledge of hyperphosphatemia and medication refill rates appear less consequential to patient health.

As part of an initiative to improve phosphorus control, dietitians at Kaiser Permanente Los Angeles Medical Center in California administered questionnaires on phosphorus management to 79 ethnically diverse patients (average age 64.2) receiving hemodialysis in October 2012. A modified Morisky Medication Adherence Scale captured adherence to phosphate binders. At the time, 77.2% of patients had controlled average phosphorus levels at or below 5.5 mg/dL, whereas 22.8% had uncontrolled levels above 5.5 mg/dL. Average phosphorus in the hyperphosphatemia group was 6.69 mg/dL. Overall, 48% of patients had diabetes, and 72% had a body mass index of 30 kg/m2 or above.

Compliance to phosphate binder therapy was suboptimal, with 61% accidentally forgetting to take their medication or otherwise skipping doses unintentionally. Nearly half (48%) also reported intentionally skipping their phosphate binder, typically when they experienced side effects, felt no symptoms, or were inconvenienced. Patients with poor medication adherence were 29% less likely to have controlled phosphorus. Of note, those who intentionally skipped doses appeared no more or less likely to be in phosphorus control.

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Knowledge of hyperphosphatemia was low: nearly half of patients failed to name 2 high-phosphorus foods or identify a risk of having the condition. Lack of knowledge did not appear to influence phosphorus control, nor did medication refill rates.

The findings may help inform strategies to improve phosphorus control. “In particular, the findings presented here suggest that strategies to reduce the chances of forgetting to dose medication and, to a lesser extent, to improve phosphorus-specific knowledge, could be particularly useful at improving phosphorus control,” Cherriday G. Joson, RN, BSN, of Kaiser, and colleagues wrote in the Journal of Renal Nutrition. They suggested trying interventions such as patient support groups centered on adherence and a “phosphorus fair” to show how binders work.

“Patient actions are, in part, influenced by our collective efforts to inform them about the harmful effects of excessive dietary phosphorus intake on health outcomes,” Juan Jesus Carrero, Pharm, PhD, and colleagues observed in an accompanying editorial. “Provision of pill boxes or calendar-based dispensers to help them track their daily medications is useful in other contexts, but the nature of phosphorus binder dosing requires a more sophisticated approach.”

One of the study authors disclosed research grants from Sanofi Aventis and Keryx Pharmaceuticals.

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1.    1. Joson CG, Henry SL, Kim S, et al. Patient-Reported Factors Associated With Poor Phosphorus Control in a Maintenance Hemodialysis Population. J Ren Nutr. 2016 May. doi:10.1053/j.jrn.2015.09.004.