Evolution of protein-bound uraemic solutes during predilution haemofiltration

Background: Protein-bound uraemic toxins provoke multiple biological changes involved in uraemia. Few if any dialytic strategies remove these compounds. Methods: In this post hoc analysis of remnant samples from a randomised controlled trial, we evaluate whether predilution haemofiltration (HF) decreases the pretreatment concentration of protein- bound uraemic solutes. Patients treated with low-flux haemodialysis (HD) were enrolled into a group continuing this strategy (group A, n=8) over 6 months, whereas group B (n=12) was switched to predilution online HF. Blood was sampled at baseline and after 6 months to determine total and free concentration and percentage binding of indoxyl sulfate (IS), indole-3-acetic acid (IAA), hippuric acid (HA), p-cresol (PC) and 3-carboxy- 4-methyl-5-propyl-2-furanpropionic acid (CMPF). Results: Comparing concentrations at start versus 6 months of treatment by paired analysis, HD had no impact. In contrast, at the end of the HF period, we found a decrease in total and free PC, free IAA and total CMPF. In addition, the percentage protein binding of IAA increased significantly. However, unpaired analysis revealed no statistical difference between HD and HF, both at baseline and after 6 months of treatment for all compounds. Conclusions: Paired analysis showed a beneficial impact of predilution online HF for several proteinbound uraemic solutes. Unpaired analysis, however, showed no statistical difference.