NDT Advance Access originally published online on March 10, 2008
Nephrology Dialysis Transplantation 2008 23(5):1779-1780; doi:10.1093/ndt/gfn034
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Reply
Correspondence and offprint requests to: E-mail: acovic{at}xnet.roSir,
We thank Dr Stanley Shaldon for his interest in our article [1]. He is of course quite correct to point out that we did not discuss ‘salt’ or ‘volume’ at all. He implies we were ignorant of these factors, and of the prolonged survival of haemodialysis-treated patients in a non-standard way (long, slow dialysis with dietary salt restriction—La recette de Tassin). This is not the case, as we ourselves have reported the survival of a similarly treated cohort of patients [2]. The reason for the omission of these factors is a simple one. There are no randomized controlled trials (RCTs) of these interventions in patients on dialysis with appropriate hard end-points, and it was RCTs of this nature that our article focussed on (something made clear in the article and its companion). Dr Stanley Shaldon should not conflate single-centre retrospective reports with generalizable interventions tested by RCTs. Underpinning the rationale for the NIH trial of quotidian dialysis is the realization that one explanation for the remarkable survival in some dialysis centres offering long, slow dialysis is patient selection bias. Assertion from eminences grises that such therapies are ‘better’ cannot replace the need for high-quality evidence from clinical trials, at least not in 2008.
While the data from Cook et al. [3] are very interesting, we doubt their relevance to patients on dialysis programmes. There are many very good reasons to theorize that better control of salt, water, volume, etc. will be of survival benefit to dialysis patients, but no one, not even someone with as long and distinguished a pedigree in this arena as Dr Stanley Shaldon, has yet got around to proving this.
As for his last comment—well we would defy anyone (else) reading our article, which basically asserts that newer dialysis techniques and expensive drugs and interventions offer no survival advantage, to infer that we had a bias of the sort he implies. We can be generous in thinking that he has perseverated his interest in salt, as the word salary derives from the Latin salarium (to pay soldiers salt, at least according to Pliny the Elder).
Conflict of interest statement. As declared in the original paper.
1 Nephrology Clinic, Parhon University Hospital, Iasi, Romania 2 Renal Unit, Guy's Hospital, London, UK
References
- Covic A, Gusbeth-Tatomir P, Goldsmith D. Negative outcome studies in end-stage renal disease: how dark are the storm clouds? Nephrol Dial Transplant (2008) 23:56–61.
[Free Full Text] - Covic A, Goldsmith DJ, Venning MC, et al. Long-hours home haemodialysis—the best renal replacement therapy method? QJM (1999) 92:251–260.
[Abstract/Free Full Text] - Cook NR, Cutler JA, Obarzanek E, et al. Long term effects of dietary sodium reduction on cardiovascular disease outcomes: observational follow-up of the trials of hypertension prevention (TOHP). BMJ (2007) 334:885.
[Abstract/Free Full Text]
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