Hemodiafiltration does not increase the risk for mortality in esrd

Hemodiafiltration does not increase the risk for mortality in esrd

CORRESPONDENCE ALL LETTERS TO THE EDITOR MUST BE SUBMITTED ONLINE VIA EDITORIAL MANAGER (http://ajkd.edmgr.com). Letters should be in response to an A...

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CORRESPONDENCE ALL LETTERS TO THE EDITOR MUST BE SUBMITTED ONLINE VIA EDITORIAL MANAGER (http://ajkd.edmgr.com). Letters should be in response to an AJKD article, and that article should have appeared no more than 6 months previously. The title must be different from that of the original article. Letters must not exceed 250 words (excluding references, maximum number 10) and contain no more than 1 figure or table. Letters are subject to editing and abridgment without notice and there is no guarantee that your letter will be published. Submitting the letter constitutes your permission for its publication in any current or subsequent issue or edition of AJKD, in any form or media, now known or hereafter developed.

SHORTER UNASSISTED PATENCY OF VASCULAR ACCESS AFTER ANGIOPLASTY IN WOMEN To the Editor: In their recent article, Maya et al1 compared features of vascular access stenosis in arteriovenous grafts and fistulas. They found shorter unassisted patency of vascular access after angioplasty in women than men and suggested that it may come from more aggressive myointimal hyperplasia after angioplasty in women. However, we would like to clarify this finding with different view points. As we know, the diameter of vessels in women usually is narrower than that in men, and mean access flow should be lower in women than men. Given the same access flow as the threshold for access stenosis, malfunction of vascular access will appear earlier in women than men during the development of access restenosis after angioplasty. In addition, the high incidence of atherosclerosis in women after menopause is associated with an increase in low-density lipoprotein levels and impaired antioxidant activity of high-density lipoprotein.2 Although we did not know the mean age of the women in this study, most of them may be in the postmenopausal period by interpreting their data. These possible mechanisms could contribute to the shorter unassisted patency of vascular access after angioplasty in women. Li-Ping Hsu, MD Wu-Chang Yang, MD Tzen-Wen Chen, MD, PhD Chih-Ching Lin, MD Department of Internal Medicine Division of Nephrology Veterans General Hospital Taipei Yang-Ming University School of Medicine Taipei, Taiwan

2. Zago V, Sanguinetti S, Brites F, et al: Impaired high density lipoprotein antioxidant activity in healthy postmenopausal women. Atherosclerosis 177:203-210, 2004 Originally published online as doi:10.1053/j.ajkd.2005.04.008 on June 8, 2005. © 2005 by the National Kidney Foundation, Inc. doi:10.1053/j.ajkd.2005.04.008

In Reply: Hsu et al offer 2 potential hypotheses for our observation of shorter unassisted patency of vascular access after angioplasty in women than men. First, they propose that because of the smaller vessel diameters in women, baseline access blood flows are lower in women than men. As a result, the threshold access blood flow required to trigger an intervention for access stenosis would be achieved at an earlier time. However, we previously reported that with the use of preoperative vascular mapping, artery and vein diameters used for fistula construction at our center were very similar between women and men.1 Moreover, we did not use access flow to screen for access stenosis in our study; rather, we used clinical monitoring.2 Their second hypothesis proposed that accelerated atherosclerosis in postmenopausal women contributes to shortened access patency. However, in our analysis, we did not find that age was a significant predictor of access patency after angioplasty (Table 5 in2), which argues against this potential explanation. Clearly, the shorter access patency in women is a clinically significant problem, but the reasons for this phenomenon remain unexplained. Careful prospective studies will be required to elucidate the potential mechanisms. Michael Allon, MD Ivan D. Maya, MD University of Alabama at Birmingham Birmingham, Alabama

REFERENCES 1. Miller CD, Robbin ML, Allon M: Gender differences in outcomes of arteriovenous fistulas in hemodialysis patients. Kidney Int 63:346-352, 2003 2. Maya ID, Oser R, Saddekni S, Barker J, Allon M: Vascular access stenosis: Comparison of arteriovenous grafts and fistulas. Am J Kidney Dis 44:859-865, 2004 Originally published online as doi:10.1053/j.ajkd.2005.04.009 on June 8, 2005. © 2005 by the National Kidney Foundation, Inc. doi:10.1053/j.ajkd.2005.04.009

REFERENCES

HEMODIAFILTRATION DOES NOT INCREASE THE RISK FOR MORTALITY IN ESRD

1. Maya ID, Oser R, Saddekni S, Barker J, Allon M: Vascular access stenosis: Comparison of arteriovenous grafts and fistulas. Am J Kidney Dis 44:859-865, 2004

To the Editor: Rabindranath et al1 claimed that hemodiafiltration (HDF) was associated with a significantly greater mortality risk

American Journal of Kidney Diseases, Vol 46, No 1 (July), 2005: pp 167-169

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than hemodialysis (HD). Their conclusion is not substantiated by any published trial, and the poorer outcome in the HDF group is unexplained. None of the 4 studies comparing HDF with HD (their Fig 2) was adequately powered. All were designed to test efficacy or surrogate outcomes. Follow-up was too short and mortality rates were very low, suggesting that the study patients might not share the typical risk profile of patients with end-stage renal disease. No study showed a significant trend toward poorer survival on HDF therapy. Patients participating in study B of the multicenter trial (Italian Cooperative Dialysis Study Group) were randomized to treatment with cuprophane, low-flux polysulfone, high-flux polysulfone, and high-flux HDF to analyze effects of membranes and dialysis technologies separately.2 Mortality was not significantly different among the 4 treatment groups, particularly between high-flux HD and highflux HDF. Only by adding the 3 HD groups differing in membranes did Rabindranath et al1 find significant differences between HD and HDF. This procedure is not in accordance with a prospective randomized study. Surprisingly, the study by Ward et al3 was not included in the meta-analysis. In general, it is believed that HDF is safe,4 even in the long run.5 Given the positive impacts on patient survival of higher treatment doses, high-flux membranes, preservation of residual renal function, and reduced systemic inflammation, HDF may reduce morbidity and mortality. Large randomized trials, such as the Dutch Convective Transport Study,6 are needed. Helmut Schiffl KfH Nierenzentrum München-Laim and University of Munich Munich, Germany

REFERENCES 1. Rabindranath KS, Strippoli GFM, Roderick P, Wallace SA, MacLeod AM, Daly C: Comparison of hemodialysis, hemofiltration, and acetate-free biofiltration for ESRD: Systematic review. Am J Kidney Dis 45:437-447, 2005 2. Locatelli F, Mastrangelo F, Redaelli B, et al: Effects of different membranes and dialysis technologies on patient treatment tolerance and nutritional parameters. The Italian Cooperative Dialysis Study Group. Kidney Int 50:12931302, 1996 3. Ward RA, Schmidt B, Hullin J, Hillebrand GF, Samtleben W: A comparison of on-line hemodiafiltration and highflux hemodialysis: A prospective clinical study. J Am Soc Nephrol 11:2344-2350, 2000 4. Nakai S, Iseki K, Tabei K, et al: Outcomes of hemodiafiltration based on Japanese dialysis patient registry. Am J Kidney Dis 38:S212-S216, 2001 (suppl 1) 5. Schiffl H, Lang SM: Long-term crossover comparison of ultrapure high-flux haemodialysis and online haemodiafiltration: A prospective 4 year clinical study. Blood Purif 22:384, 2004 (abstr) 6. Penne EL, Blankestijn PJ, Bots ML, et al: Resolving controversies regarding hemodiafiltration versus hemodialysis: The Dutch Convective Transport Study. Semin Dial 18:47-51, 2005

Originally published online as doi:10.1053/j.ajkd.2005.03.022 on June 7, 2005. © 2005 by the National Kidney Foundation, Inc. doi:10.1053/j.ajkd.2005.03.022

In Reply: Our systematic review evaluated the comparative performance of different renal replacement modalities, regardless of membrane flux or type.1 Based on data provided by the 2 published randomized controlled trials (RCTs)2,3 reporting mortality data, hemodiafiltration (HDF) is associated with significantly greater mortality than hemodialysis (HD). Mortality was not reported and no events were detected in the remaining published RCTs, which therefore could not contribute to the meta-analysis. The concept that meta-analysis is not possible when pooling results of underpowered trials is incorrect. Meta-analysis increases the power of individual trials that were not powered to detect certain end points. Provided that rigid criteria for design and conduct of a systematic review are followed, meta-analysis may disclose relevant findings in an early phase. In our meta-analysis of the effect of HDF compared with HD on all-cause mortality, 3 HD arms of the Italian Cooperative Dialysis Study2 were combined and compared with the HDF arm. This approach is in line with the proposed research question of our study, which is the comparative performance of different renal replacement therapy methods, and conforms to standard meta-analysis procedures.4 Ward et al5 could not contribute to the meta-analysis of all-cause mortality because the number of deaths in the treatment and control groups were not reported separately. Additionally, the investigators of the trial were contacted for clarification about these data, but no data were provided. The number of quality RCTs in nephrology, dialysis, and transplantation is small.6 We agree that large RCTs, such as the Dutch Convective Transport Study,7 are needed. Kannaiyan S. Rabindranath, MBBS Alison M. MacLeod, MD Department of Medicine and Therapeutics University of Aberdeen Aberdeen, United Kingdom Giovanni F.M. Strippoli, MD Cochrane Renal Group The Children’s Hospital at Westmead Westmead, Australia Conal Daly, MD Western Infirmary Glasgow, United Kingdom

REFERENCES 1. Rabindranath KS, Strippoli GFM, Roderick P, Wallace SA, MacLeod AM, Daly C: Comparison of hemodialysis, hemofiltration, and acetate-free biofiltration for ESRD: Systematic review. Am J Kidney Dis 45:437-447, 2005 2. Locatelli F, Mastrangelo F, Redaelli B, et al: Effects of different membranes and dialysis technologies on patient