Patient education for phosphorus management in chronic kidney disease

Abstract

Objectives: This review explores the challenges and solutions in educating patients with chronic kidney disease (CKD) to lower serum phosphorus while avoiding protein insufficiency and hypercalcemia.

Methods: A literature search including terms "hyperphosphatemia," "patient education," "food fatigue," "hypercalcemia," and "phosphorus-protein ratio" was undertaken using PubMed.

Results: Hyperphosphatemia is a strong predictor of mortality in advanced CKD and is remediated via diet, phosphorus binders, and dialysis. Dietary counseling should encourage the consumption of foods with the least amount of inorganic or absorbable phosphorus, low phosphorus-to-protein ratios, and adequate protein content, and discourage excessive calcium intake in high-risk patients. Emerging educational initiatives include food labeling using a "traffic light" scheme, motivational interviewing techniques, and the Phosphate Education Program - whereby patients no longer have to memorize the phosphorus content of each individual food component, but only a "phosphorus unit" value for a limited number of food groups. Phosphorus binders are associated with a clear survival advantage in CKD patients, overcome the limitations associated with dietary phosphorus restriction, and permit a more flexible approach to achieving normalization of phosphorus levels.

Conclusion: Patient education on phosphorus and calcium management can improve concordance and adherence and empower patients to collaborate actively for optimal control of mineral metabolism.

Keywords: concordance; educational programs; food fatigue; hyperphosphatemia; phosphorus binders; renal diet.

Figure 1

A high phosphorus/protein ratio increases mortality risk in CKD patients even after adjustment for binders, serum phosphorus, and diet. Noori N, Kalantar-Zadeh K, Kovesdy CP, Bross R, Benner D, Kopple JD. Association of dietary phosphorus intake and phosphorus to protein ratio with mortality in hemodialysis patients. Clin J Am Soc Nephrol. 2010;5(4):683–692. © American Society of Nephrology 2010. Abbreviation: CKD, chronic kidney disease.

Figure 2

Dietary phosphorus can be estimated using a regression equation that accounts for 83% of the variance and demonstrates the strong association between dietary phosphorus and protein intake. Repinted with permission Kalantar-Zadeh K, Gutekunst L, Mehrotra R, et al. Understanding sources of dietary phosphorus in the treatment of patients with chronic kidney disease. Clin J Am Soc Nephrol. 2010;5(3):519–530.12 © American Society of Nephrology 2010.

Figure 3

The use of phosphorus binders has a significant survival benefit in veterans (n = 1188) with moderate to advanced CKD. Reprinted with permission Kovesdy CP, Kuchmak O, Lu JL, Kalantar-Zadeh K. Outcomes associated with phosphorus binders in men with non-dialysis-dependent CKD. Am J Kidney Dis. 2010;56(5):842–851. © Elsevier 2010. Abbreviation: CKD, chronic kidney disease.

Figure 4

Calcium-free binders such as sevelamer are associated with reduced rates of mortality compared with calcium-based binders. Reprinted by permission from Macmillan publisher Ltd: Kidney Int. Copyright 2007.

Figure 5

A pilot study in maintenance hemodialysis patients demonstrated the benefit of egg whites (1 meal a day for 6 weeks) as a major protein source to provide a high protein/low phosphorus intake. Mean serum phosphorus decreased and mean serum albumin increased. Data graphed de novo from Taylor et al.