Abstract: Objective  To compare the clearance of small, medium, and larger medium-sized molecular toxins in patients undergoing pre-dilution/post-dilution hemodiafiltration (Pre-/Post-HDF) versus medium cut-off hemodialysis (MCO-HD). Methods 22 hemodialysis patients were treated with Pre-HDF, Post-HDF and MCO-HD respectively. The urea reduction rate (URR), as well as the serum reduction rates (RR) of β2-microglobulin (β2-MG) and α1-microglobulin (α1-MG), were compared among the three modalities. Additionally, the total clearance of β2-MG, α1-MG, and albumin (ALB) in the collected dialysate was evaluated. Results The URR in the MCO-HD group was significantly higher than that in the Pre-HDF group (q=13.151, P＜0.001) and Post-HDF group (q=19.063, P＜0.001). The reduction rate of β2-MG was higher in the Post-HDF group than that in the MCO-HD group (q=4.753, P=0.005) and the Pre-HDF group (q=11.022, P＜0.001). Conversely, the reduction rate of α1-MG was significantly higher in the MCO-HD group than that in the Pre-HDF group (q=11.647, P＜0.001) and the Post-HDF group (q=7.642, P＜0.001). Regarding total removal in dialysate, the Pre HDF group showed significantly lower β2-MG clearance than the Post-HDF group (q=5.691, P=0.002) and the MCO-HD group (q =7.058, P＜0.001), whereas no significant difference was observed between the Post-HDF group and MCO-HD group (q=3.252, P=0.083). For α1-MG, total removal was significantly higher in the MCO-HD group than that in the Pre-HDF group (q=22.218, P＜0.001) and Post-HDF group (q=12.286, P＜0.001). Similarly, ALB loss in dialysate was significantly greater in the MCO HD group than in the Pre HDF (q=10.831, P＜0.001) and Post-HDF groups (q = 5.345, P=0.004).  Conclusion  Compared with Pre/Post HDF, MCO HD demonstrates superior clearance of larger medium sized molecules but is associated with more pronounced albumin loss.

Key words: Pre-hemodiafiltration, Post-hemodiafiltration, Medium cut-off hemodialysis