Abstract: Objective To compare the removal efficiencies of protein-bound uremic toxins including indoxyl sulphate (IS), p-cresyl sulphate (PCS) and hippuric acid (HA) by hemodialysis (HD), hemodiafiltration (HDF) and hemoperfusion associated with hemodialysis (HP + HD). Methods Forty- eight MHD patients were enrolled in this study. They were randomly assigned into HD group, HDF group or HP+HD group. IS, PCS and HA in serum samples before and after the treatment were determined using high-performance liquid chromatography electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS), to compare the removal
of protein-bound uremic toxins by the three dialysis modalities. Results ①Serum IS decreased from 30.96±12.55 μg/ml to 21.03±10.42 μg/ml (reduction rate [RR]=33.10±12.87%, P＜0.05) in HD group, from 32.24±17.11 μg/ml to 17.11±8.94 μg/ml (RR=43.96±14.96%, P＜0.01) in HDF group, and from 33.52±19.30 μg/ml to 14.33±9.81 μg/ml (RR=57.96±11.95%, P＜0.01) in HP+HD group. Therefore, HDF and HP+HD are more effective than HD (P＜0.05 and ＜0.01, respectively), and HP+HD is more effective than HDF (P＜ 0.05) in IS clearance. ②Serum PCS decreased from 24.87±13.64 μg/ml to 16.80±8.48 μg/ml (RR = 30.24 ± 9.27%, P＜0.05) in HD group, from 30.60±19.18 μg/ml to 15.59±12.39 μg/ml (RR=43.20±11.87%, P＜0.05) in HDF group, and from 38.92±17.24 μg/ml to 17.71±10.22 μg/ml (RR=54.22±14.37%, P＜0.01) in HP+HD group. Therefore, HDF and HP+HD are more effective than HD (P＜0.01), and HP+HD is more effective than HDF (P＜0.05) in PCS clearance. ③Serum HA decreased from 18.65±14.24 μg/ml to 7.38±5.27 μg/ml (RR=59.36±7.46%, P＜0.01) in HD group, from 27.62±16.07 μg/ml to 7.75±4.56 μg/ml (RR=69.70±11.93%, P＜0.01) in HDF group, and from 20.48±11.02 μg/ml to 6.33±4.78 μg/ml (RR= 71.20 ± 10.28%, P＜0.01) in HP+HD group. Consequently, HDF and HP+HD are more effective than HD (P＜0.01), but HP+HD and HDF are similar in HA clearance (P>0.05). Conclusion HD, HDF and HP+HD can partially remove proteinbound uremic toxins. HP+HD is better than HDF and HD in removal of these uremic toxins.

Key words: Protein-bound uremic toxins, Hemodialysis, Hemodiafiltration, Hemoperfusion