NDT Advance Access originally published online on May 21, 2008
Nephrology Dialysis Transplantation 2008 23(8):2706-2707; doi:10.1093/ndt/gfn285
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Reply
E-mail: NC.vdWeerd{at}vumc.nlSir,
We thank Lornoy and De Meester for their relevant comments on our recent article [1] and their correct erratum concerning the applied membranes in reference 16 (Table 1).
Indeed, the location of the inflow of substitution fluid in haemodiafiltration (HDF) is of considerable relevance in terms of determining the efficacy of small and middle molecular weight clearance. Therefore, it is regrettable that in many of the referenced papers in the Comment (references 9, 32, 33, 41 and 43), the method of HDF is not explicitly mentioned. This lack of information is particularly present in the large observational studies on mortality. So, besides the general shortcoming of observational studies, i.e. the risk of selection bias, also the different methods of HDF could have resulted in an even greater heterogeneity in design of the studies.
Currently, more and more data on mortality rates during HDF are being presented. Apart from De Meester et al., who reported a 26% survival benefit for HDF (De Meester et al. ASN Renal Week 2007, abstract SA-PO494), a Portuguese group presented their data during the 2007 ASN meeting as well (Natario et al. ASN Renal Week 2007, abstract SU-PO559). They observed in a single-center cohort of 88 haemodialysis (HD) and HDF patients during almost 2 years of follow-up and after adjusting for baseline characteristics and comorbid conditions, a 79% decrease in mortality risk.
Recently, a 22% reduction in all-cause mortality in patients on HDF was found in a prospective observational study performed in 757 prevalent patients in Italy [2]. No difference in all-cause mortality was seen in patients on HDF using bags and online HDF. However, cardiovascular mortality was lower in patients on online HDF as compared to HDF using bags and to conventional HD. Regrettably, again the technique of HDF (pre- or postdilution) was not described in the method section.
All together, these observations underscore the need for properly designed and conducted randomized clinical trials on the effect of HDF on all-cause and CV mortality. We hope that the Dutch CONvective TRAnsport STudy (CONTRAST), in which online postdilution HDF is applied and compared to standard HD, will be such a study [3]. With the results of CONTRAST, and other comparable studies [4,5], we hope that the promising results of the large, observational studies on HDF can be confirmed. Only then can HDF be considered no longer a ‘promise for the future’, but instead an accepted treatment in terms of evidence-based medicine.
Conflict of interest statement. None declared.
1 Department of Nephrology, University Medical Center Utrecht 2 Department of Nephrology, Vrije Universiteit Medical Center Amsterdam 3 Department of Nephrology, Medical Center Rijnmond Zuid, Rotterdam 4 Julius Center of Health Sciences and Primary Care, University Medical Center Utrecht, The Netherlands
References
- Van Der Weerd NC, Penne EL, Van Den Dorpel MA, et al. Haemodiafiltration: promise for the future? Nephrol Dial Transplant (2008) 23:438–443.
[Free Full Text] - Panichi V, Rizza GM, Paoletti S, et al. Chronic inflammation and mortality in haemodialysis: effect of different renal replacement therapies. Results from the RISCAVID study. Nephrol Dial Transplant (2008).
- Penne EL, Blankestijn PJ, Bots ML, et al. Effect of increased convective clearance by on-line hemodiafiltration on all cause and cardiovascular mortality in chronic hemodialysis patients—the Dutch CONvective TRAnsport STudy (CONTRAST): rationale and design of a randomised controlled trial [ISRCTN38365125]. Curr Control Trials Cardiovasc Med (2005) 6:8.[CrossRef][Medline]
- Bolasco P, Altieri P, Andrulli S, et al. Convection versus diffusion in dialysis: an Italian prospective multicentre study. Nephrol Dial Transplant (2003) 18(Suppl_7):vii50–vii54.
- Canaud B, Morena M, Leray-Moragues H, et al. Overview of clinical studies in hemodiafiltration: what do we need now? Hemodial Int (2006) 10(Suppl 1):S5–S12.
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