The dietary counseling given to maintenance dialysis patients may be inadequate.


Despite regular dietary instruction, patients undergoing dialysis have a poor knowledge of dietary phosphorus compared with other nutrients important in CKD, according to researchers at the University of Wisconsin Medical School in Madison.

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Judson B. Pollock, MD, and Jonathan B. Jaffery, MD, studied 29 hemodialysis (HD) patients and 18 peritoneal dialysis (PD) patients. The study population consisted of 30 men and 17 women and had an average age of 58.6 years. All patients received once-monthly dietary instruction customized by a dietitian based on each patient’s laboratory data and fluid-volume status.


The researchers measured nutrient knowledge using a 25-item Chronic Kidney Disease Know-ledge Assessment Tool for Nutrition (CKDKAT-N). This questionnaire has 25 multiple choice questions reflecting knowledge of four nutrients relevant to maintenance dialysis patients: phosphorus, protein, sodium, and potassium. Fifteen questions concern phosphorus. Drs. Pollock and Jaffery also measured functional health literature using the short form of the Test of Functional Health Literacy in Adults (S-TOFHLA). S-TOFHLA is a 36-item test that involves short reading passages with multiple-choice answers. It is administered in seven minutes. Results are scored on a scale of 0-36, with 0-16 iden-tifying inadequate health literacy, 17-22 marginal health literacy, and 23-36 adequate health literacy.


The mean CKDKAT-N scores for the HD and PD groups were 12.5 and 14, respectively, a nonsignificant difference, the authors reported in the Journal of Renal Nutrition (2007; published online ahead of print).


Among HD patients, the S-TOFHLA ranking showed that 18 had adequate health literacy, whereas four had marginal and seven had inadequate literacy. Among PD patients, 17 had adequate health literacy and one had inadequate literacy. HD and PD patients had an average of 0.8 and 2.4 years of post-secondary education, respectively, a significant difference between the groups.


The study population overall correctly answered only about 38% of phosphorus-related questions, whereas they correctly answered about 71% of questions related to protein, sodium, and potassium. Despite differences in education level and health literacy between the HD and PD groups, the group had similar nutrition knowledge.