More Selective Removal of Myeloperoxidase‐Anti‐Neutrophil Cytoplasmic Antibody From the Circulation of Patients With Vasculitides Using a Novel Double‐Filtration Plasmapheresis Therapy

Our aim was to investigate the removal of myeloperoxidase‐anti‐neutrophil cytoplasmic antibody (MPO‐ANCA) from the circulation of patients with vasculitides by double‐filtration plasmapheresis (DFPP) using various primary separator and secondary separator combinations. Nineteen patients diagnosed with vasculitides positive for serum MPO‐ANCA were enrolled and received 56 sessions of DFPP. One patient received three sessions of DFPP using MPS07 (the primary filter)/EC50W (the secondary filter), nine patients received 27 sessions of DFPP using MPS07/EC20W, and the other nine patients received 26 sessions of DFPP using EC50W/EC20W. The sieving coefficients (SC) of albumin, immunoglobulin (Ig)A, IgG and IgM were measured, as well as the reduction ratio in plasma protein concentrations and MPO‐ANCA titer after a single session of DFPP. The MPS07 filter was well permeable for all the above‐mentioned plasma proteins; the EC50W and EC20W filters were permeable for albumin and IgG, less for IgA and IgM. During DFPP using MPS07/EC50W, the reduction ratio of IgG was much lower than IgM and IgA (30.5 ± 9.0% vs. 89.7 ± 5.4% and 61.7 ± 14.8%). During DFPP using MPS07/EC20W, the decline in IgM, IgA, and IgG was 94.2 ± 3.1%, 96.2 ± 2.3%, and 64.7 ± 21.0%, respectively. During DFPP using EC50W/EC20W, the decline in IgM, IgA, and IgG was 2.8 ± 12.9%, 90.9 ± 4.4%, and 43.5 ± 13.8%, respectively. The percentage reduction in MPO‐ANCA titer after a single session of DFPP using EC50W/EC20W was 34.6 ± 14.3%. DFPP using EC50W/EC20W filters may be more selective for the removal of pathogens such as IgG, with subsequently effective reduction of serum ANCA titer.