title: Meal phosphate variability does not support fixed dose phosphate binder schedules for patients treated with peritoneal dialysis: a prospective cohort study.
abstract: BACKGROUND
  Removal of phosphate by peritoneal dialysis is insufficient to maintain normal serum phosphate levels such that most patients must take phosphate binders with their meals. However, phosphate 'counting' is complicated and many patients are simply prescribed a specific dose of phosphate binders with each meal. Therefore, our primary objective was to assess the variability in meal phosphate content to determine the appropriateness of this approach.
  
  
  METHODS
  In this prospective cohort study, adult patients with ESRD treated with peritoneal dialysis and prescribed phosphate binder therapy were eligible to participate. Participants were excluded from the study if they were unable to give consent, had hypercalcemia, were visually or hearing impaired or were expected to receive a renal transplant during the time of the study. After providing informed consent, patients kept a 3-day diet diary that included all foods and beverages consumed in addition to portion sizes. At the same time, patients documented the amount of phosphate binders taken with each meal. The phosphate content of the each meal was estimated using ESHA Food Processor SQL Software by a registered dietitian. Meal phosphate and binder variability were estimated by the Intra Class Correlation Coefficient (ICC) where 0 indicates maximal variability and 1 indicates no variability.
  
  
  RESULTS
  Seventy-eight patients consented to participate in the study; 18 did not complete the study protocol. The patients were 60 (± 17) years, predominately male (38/60) and Caucasian (51/60). Diabetic nephropathy was the most common cause of end stage kidney disease. The daily phosphate intake including snacks ranged from 959 ± 249 to 1144 ± 362 mg. The phosphate ICC by meal: breakfast 0.63, lunch 0.16; supper 0.27. The phosphate binder ICC by meal: breakfast 0.68, lunch 0.73, supper 0.67.
  
  
  CONCLUSIONS
  The standard prescription of a set number of phosphate binders with each meal is not supported by the data; patients do not appear to be adjusting their binders to match the meal phosphate content. An easy to use phosphate counting program that assists the patient in determining the appropriate amount of phosphate binder to take may enhance phosphate control.
authors.affiliation: Division of Endocrinology, Department of Medicine, Ottawa Hospital, Ottawa, ON, Canada. sleung@toh.on.ca.
authors.forename: Simon
authors.initials: S
authors.lastname: Leung
authors.affiliation: Division of Nephrology, Department of Medicine, Ottawa Hospital, University of Ottawa, Ottawa, ON, Canada. bmccormick@toh.on.ca.|Kidney Research Centre, Ottawa Hospital Research Institute, Ottawa, ON, Canada. bmccormick@toh.on.ca.
authors.forename: Brendan
authors.initials: B
authors.lastname: McCormick
authors.affiliation: Kidney Research Centre, Ottawa Hospital Research Institute, Ottawa, ON, Canada. jewagner@toh.on.ca.
authors.forename: Jessica
authors.initials: J
authors.lastname: Wagner
authors.affiliation: Division of Nephrology, Department of Medicine, Ottawa Hospital, University of Ottawa, Ottawa, ON, Canada. mbiyani@toh.on.ca.
authors.forename: Mohan
authors.initials: M
authors.lastname: Biyani
authors.affiliation: Division of Nephrology, Department of Medicine, Ottawa Hospital, University of Ottawa, Ottawa, ON, Canada. sdlavoie@toh.on.ca.
authors.forename: Susan
authors.initials: S
authors.lastname: Lavoie
authors.affiliation: Department of Medicine, University of Ottawa, Ottawa, ON, Canada.
authors.forename: Rameez
authors.initials: R
authors.lastname: Imtiaz
authors.affiliation: Division of Nephrology, Department of Medicine, Ottawa Hospital, University of Ottawa, Ottawa, ON, Canada. dzimmerman@toh.on.ca.|Kidney Research Centre, Ottawa Hospital Research Institute, Ottawa, ON, Canada. dzimmerman@toh.on.ca.|Riverside Campus of the Ottawa Hospital, 1967 Riverside Dr, Ottawa, ON, K0A 2Z0, Canada. dzimmerman@toh.on.ca.
authors.forename: Deborah
authors.initials: D
authors.lastname: Zimmerman
mesh_terms: D000284:Administration, Oral; D002119:Calcium Carbonate / Q000008:administration & dosage; D002614:Chelating Agents / Q000008:administration & dosage*; D015331:Cohort Studies; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D005260:Female; D006801:Humans; D054559:Hyperphosphatemia / Q000175:diagnosis / Q000188:drug therapy* / Q000209:etiology; D007676:Kidney Failure, Chronic / Q000150:complications / Q000175:diagnosis / Q000188:drug therapy*; D008297:Male; D008875:Middle Aged; D010530:Peritoneal Dialysis / Q000379:methods*; D010710:Phosphates / Q000008:administration & dosage* / Q000009:adverse effects; D011446:Prospective Studies; D016896:Treatment Outcome
chemical_list: D002614:Chelating Agents; D010710:Phosphates; D002119:Calcium Carbonate