MO647: Novel Medium Cut-Off Membranes in Larger Medium Molecules Removal, How Far Can We Go?
Authors: Albrizio Paolo , Costa Silvano , Foschi Annalisa , Angelo Antonio Milani Ivo , Rindi Stefano , Zucchi Manuela , Milanesi Fabio 
Published: May 2022

Abstract

BACKGROUND AND AIMS
Dialysis with medium cut-off membranes (MCO) are growing fast during the last years thanks to the availability of an always-increasing number of membranes capable of reaching elevated clearance levels of medium molecules without significant loss of albumin. These achievements made MCO membranes an appropriate alternative to mixed diffusive-convective techniques which are frequently limited by clinical (low-performance vascular accesses) or social reasons (costs, availability). However, the term ‘medium molecules’ includes a wide spectrum of molecules with major differences in molecular weight (MW–from 0.5 to 60 KDa). Considering the human serum albumin's (HSA) MW of 64.5 KDa as the insuperable cut-off for avoiding unwanted protein loss, whereas there are many studies about clearance of medium molecules with dimensions below 25–30 KDa, fewer data are available about those with MW from 40 to ˃ 60 KDa. In this study, we evaluated the clearance proprieties of a new MCO membrane (Asahi Kasei's ViE-21X®), compared with both haemodiafiltration and hemodialysis (HD) with a well-known medium cut-off membrane (Baxter's Theranova 400®-Th400), of three medium molecules with increasing MW: free kappa chains (K-FLC 22.5 KDa), free lambda chains (L-FLC 45 KDa) and alpha-1 antitrypsin (A1AT 52–54 KDa) and measured albumin loss amount.

METHOD
We evaluated 12 patients chronically dialyzed three times a week in our Centre with mixed or post-dilutional haemodiafiltration (HDF) with various membranes. We collected blood samples before and after a common HDF session after a short interdialytic period for K-FLC, L-FLC, A1AT and HSA. Then, we collected the same data for two more sessions after a short interdialytic period conducted only with diffusive techniques, one using Th 400 and another with ViE-21X. For all molecules, we evaluated reduction ratio ± standard deviation (RR ± SD) while statistical significance (P &lt; .05) was examined with Student's t-test. All data were adjusted by dialysis length, membranes surface area, blood flow rate and ultrafiltration rate avoiding any significant difference.

RESULTS
ViE-21X demonstrated an increased RR of K- and L-FLC compared with HDF and Th 400 even without reaching a statistical significance (38.82 ± 14.53% for K-FLC versus 32.36 ± 22.62% and 30.58 ± 24.10% respectively for HDF and Th400; P = .10 versus HDF, P = 0.13 versus Th 400. 35.63 ± 14.30% for L-FLC versus 30.48 ± 22.51% and 29.36 ± 24.91% respectively of HDF and Th 400; P = .19 versus HDF, P = 0.18 versus Th 400). Both ViE-21X and Th 400 showed higher RR for the largest molecule, A1AT, compared with HDF, reaching statistical significance (24.66 ± 19.98% for ViE-12X and 24.67%±20.15% for Th 400 versus 18.46% ± 21.73% for HDF, P &lt; .05 for both). None of the techniques showed a significant loss of albumin, even if Th 400 showed a slightly greater loss compared to HDF and ViE-21X (2.59%±5.40% for HDF, 6.31%±23.61% for Th 400, 2.58%±24.24% for ViE-21X P = NS) (Figure).

CONCLUSION
Our data confirmed that studied MCO membranes can be an effective alternative to HDF in the clearance of medium molecules without any remarkable loss of albumin. Indeed, compared with HDF, they showed non-inferiority clearance levels for K- and L-LFC and a statistically significant benefit in the clearance of the studied largest one, A1AT, which has a close MW to HSA. Furthermore, according to our data, novel MCO membrane ViE-21X seems to show further benefits compared to other membranes. More studies with larger populations need to be conducted to confirm these data.