NDT Advance Access originally published online on May 25, 2006
Nephrology Dialysis Transplantation 2006 21(9):2676-2677; doi:10.1093/ndt/gfl229
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Hyperphosphataemia and related mortality
Email: m.noordzij{at}amc.uva.nlSir,
With great interest we read the editorial review of Jean et al. [1] on the relationship between hyperphosphataemia and mortality in end-stage renal disease patients. The authors summarize results from the large USRDS and DOPPS studies in which associations of hyperphosphataemia and increased mortality risks were found in haemodialysis (HD) patients.
Jean et al. [1] evaluate the capacity of phosphate removal per session and per week by several dialysis techniques, including standard haemodialysis (SHD), haemodiafiltration (HDF), nocturnal daily haemodialysis (NDHD), short daily haemodialysis (SDHD) and long haemodialysis (LHD). However, the authors did not mention peritoneal dialysis (PD) treatment in their comparison, which is in our opinion, an important dialysis modality as well.
Considering phosphate balance, there are some marked differences between HD and PD treatments. Due to obligatory protein losses via the peritoneal fluid, continuous ambulatory peritoneal dialysis (CAPD) patients are often prescribed a high-protein diet containing 1.2 to 1.3 g/kg/day which provides a phosphate intake of up to 1200 mg/day [2]. Effective phosphate removal with dialysis and gastrointestinal elimination of phosphate by oral phosphate binding agents is therefore necessary to achieve a neutral phosphate balance.
With PD treatment, on average, 315 mg/day (2200 mg/week) of phosphate is removed from the body, which is less than that with different types of HD treatment [2]. The removal of phosphate in PD patients depends on the dialysate volume and besides the glucose concentration, a higher dwell volume also increases phosphate removal [3]. However, when the residual renal function diminishes, a neutral phosphate balance can only be obtained by using extremely high dialysate volumes, which is hardly feasible in clinical practice.
Although it has been shown that a somewhat better control of serum phosphate is possible in patients on CAPD compared with those on HD [2,3], phosphate control is a major problem in PD patients as well. As part of the Netherlands Cooperative Study on the Adequacy of Dialysis (NECOSAD), a large prospective multicentre study, we included a total of 1629 incident dialysis patients of whom 36% was treated with PD [4]. The majority of the 586 PD patients were treated with CAPD (87%) and had a significantly lower mean plasma phosphate concentration than HD patients 3 months after the start of dialysis (1.73 vs 1.87 mmol/l, P < 0.0001). A large proportion of both the HD and PD patients (53 and 41%, respectively) had plasma phosphate concentrations exceeding the target range advised in the K/DOQI guidelines for bone metabolism and disease [4,5]. More importantly, the all-cause mortality risk was significantly increased by 40% in HD and 60% in PD patients with plasma phosphate concentrations above the K/DOQI target [4].
We conclude that phosphate retention is, as in the HD patients, a major problem in PD patients as well and that the control of serum phosphate is a highly relevant issue in both the patient groups.
1 Department of Clinical Epidemiology and Biostatistics Academic Medical Centre University of Amsterdam Amsterdam2 Hans Mak Institute Naarden3 Department of Clinical Epidemiology Leiden University Medical Centre Leiden4 Department of Internal Medicine St. Antonius Hospital Nieuwegein and5 Department of Nephrology Academic Medical Centre University of Amsterdam Amsterdam The Netherlands
Acknowledgments
This study was funded by unrestricted grants from the Dutch Kidney Foundation, Genzyme and Amgen.
Conflict of interest statement. None declared
References
- Jean G, Chazot C, Charra B. Hyperphosphataemia and related mortality. Nephrol Dial Transplant 2006; 21: 273–280
[Free Full Text] - Hutchison AJ, Gokal R. Adequacy of calcium and phosphate balance in peritoneal dialysis. Perit Dial Int 1994; 14 [Suppl 3]: S117–S122
- Messa P, Gropuzzo M, Cleva M et al. Behaviour of phosphate removal with different dialysis schedules. Nephrol Dial Transplant 1998; 13 [Suppl 6]: 43–48
- Noordzij M, Korevaar JC, Boeschoten EW, Dekker FW, Bos WJ, Krediet RT. The K/DOQI guideline for bone metabolism and disease in CKD: association with mortality in dialysis patients. Am J Kidney Dis 2005; 46: 925–932[CrossRef][Web of Science][Medline]
- National Kidney Foundation. K/DOQI Clinical Practice Guidelines for Bone Metabolism and Disease in Chronic Kidney Disease. Am J Kidney Dis 2004; 42: S1–S202
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