Peritoneal dialysis solutions and patient survival: does wishing make it so?

In this issue of Nephrology, Dialysis and Transplantation, Lee and colleagues (1) compare outcomes of Korean peritoneal dialysis (PD) patients who received standard dialysis fluid vs newer, 'biocompatible'dialysis solutions. This very interesting report found no significant difference in outcome of PD technique survival or its complications, such as peritonitis. However, those who received the new solution had a reduced risk of death. The authors suggest that the newer dialysis solutions may lead to sustained reduction in circulating levels of advanced glycosylation endproducts (AGEs), with a concomi- tant reduction in microvascular and macrovascular disease. Furthermore, the authors point to downstream effects of AGE binding with its receptors (RAGE), and suggest that reduced AGE production with new solutions could be followed by a parallel decline in the AGE-RAGE production of mediators of inflammation and fibrosis. The authors reported similar findings last year (2). In the previous report, they noted the weakness inherent in an uncontrolled, observational study, and quite correctly concluded that an 'appropriately designed, randomized, controlled clinical trial' was needed (2). However, instead of proceeding with such a study, they report herein the results of the same observational study, with two modifications: firstly, the period of observation has been extended another 18 months. Secondly, the sub-cohort of patients who started PD on standard solution and were subsequently changed to the new, 'biocompatible' solution during the period of observation are now removed from the analysis, whereas they were included in the 'intention to treat' analysis in the first publication (2). This is important, because the 'excluded' 305 patients who switched solutions had remarkable survival of 96, 89 and 87% at 1, 2 and 3 years. Had they not been excluded, these 305 patients would have counted as part of the standard solution group, and would have improved the overall survival of the remaining 514 patients in that group.