Optimal volume of processed plasma and total number of selective plasmapheresis sessions in the treatment of patients with severe generalized myasthenia gravis

The selection of the technical parameters of plasmapheresis in the treatmen t of patients with MG varies widely due to the lack of sufficient data from controlled studies to standardize the plasmapheresis procedure. Eight myas thenia gravis (MG) patients (Osserman IIb, and III) received either immunoa dsorption plasmapheresis (IA) with a TM-TR 350 (Asahi Medical Co., Tokyo, J apan) or double filtration plasmapheresis (DF) with a Cascadeflo AC-1770, w ith four in each group. A Plasmaflo AP 05 W (Asahi Medical Co., Tokyo, Japa n) was used as the plasma separator in both groups. Each course of treatmen t consisted of five sessions of aphereses on alternate days. Plasma was sam pled before and after passing through the column. Samples of plasma were an alyzed for acetylcholine receptor antibody (AchRAb) at the start of plasmap heresis and sequentially after every 0.5 L of plasma treated. The IA method cleared significantly more AchRAb during the initial treatment of 1.5 L of plasma than the DF method, especially in the initial I L (P < 0.01). The c olumn saturated after treatment of 1.5 to 2 L of plasma. It is known that o ver-saturation of column may release the already adsorbed/filtrated antibod ies. Longitudinal analysis on the serological changes during the five sessi ons revealed that the clearance obtained using the IA method was significan tly higher and more sustained after the first session of treatment compared to the DF method (P < 0.05). The titers of AchRAb were also noted to rise after the fourth session. These results suggest that 2 L of processed volum e is optimal in terms of the functional capacity of a plasmapheresis column in either IA or DF methods, and that a total of four sessions of treatment in one course may provide optimal elimination of AchRAb. I. Clin. Apheresi s 14: 177-180, 1999. (C) 1999 Wiley-Liss, Inc.