Knowledge of phosphorus compared with other nutrients in maintenance dialysis patients

J Ren Nutr. 2007 Sep;17(5):323-8. doi: 10.1053/j.jrn.2007.05.009.


Objective: This study's objective was to assess knowledge of phosphorus compared with other nutrients in patients undergoing maintenance dialysis (MD).

Design: We compared knowledge of phosphorus vs. other nutrients important to the MD diet (potassium, sodium, and protein) in patients undergoing hemodialysis (HD) and peritoneal dialysis (PD). We further measured gender, age, education level, and functional health literacy to assess correlations in patient nutrient knowledge. Nutrient knowledge was measured using a 25-item Chronic Kidney Disease Knowledge Assessment Tool for Nutrition (CKDKAT-N), and functional health literacy was measured using the short form of the Test of Functional Health Literacy in Adults (S-TOFHLA).

Setting and patients: Patients received maintenance outpatient PD or HD at Wisconsin Dialysis, Inc. (Madison, WI).

Main outcome measure: The main outcome measure was knowledge of phosphorus vs. knowledge of potassium, sodium, and protein.

Results: Forty-seven MD patients participated in the study (29 undergoing HD, 18 undergoing PD, 30 males, 17 females, average age of 58.6 (SD, 13.8) years, and average grade level of 1.4 (SD, 2.6) years of post-secondary education). Thirty-five participants had adequate health literacy, 4 had marginal health literacy, and 8 had inadequate health literacy. The CKDKAT-N scores ranged from 6-21 for 25 items, with a mean score of 13 (SD, 2.91). Knowledge of phosphorus compared with knowledge of other nutrients was poor (0.38 vs. 0.72, P = .003). In a comparison of HD vs. PD patient knowledge, both phosphorus (0.37 vs. 0.42, P = .231) and other nutrients (0.69 vs. 0.80, P = .115) were the same.

Conclusion: Despite regular dietary instruction, patients undergoing MD have a poor knowledge of dietary phosphorus content, compared with knowledge of other nutrients important in chronic kidney disease. Interestingly, there was no difference in nutrition knowledge when comparing PD and HD patients, despite differences in education level and health literacy between groups.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Educational Measurement
  • Educational Status
  • Female
  • Health Knowledge, Attitudes, Practice*
  • Humans
  • Kidney Failure, Chronic / therapy*
  • Male
  • Middle Aged
  • Patient Education as Topic*
  • Phosphorus / metabolism
  • Phosphorus / physiology*
  • Potassium / metabolism
  • Potassium / physiology
  • Proteins / metabolism
  • Proteins / physiology
  • Renal Dialysis* / adverse effects
  • Sodium / metabolism
  • Sodium / physiology


  • Proteins
  • Phosphorus
  • Sodium
  • Potassium