Removal Kinetics of Antibodies Against Glutamic Acid Decarboxylase by Various Plasmapheresis Modalities in the Treatment of Neurological Disorders

Plasmapheresis is one of the acute treatment modalities for neurological disorders associated with antibodies against glutamic acid decarboxylase (anti-GAD). However, there is little information about the removal kinetics of anti-GAD by various plasmapheresis modalities. Here, we investigated the removal rate of anti-GAD and fibrinogen (Fib) by immunoadsorption (IA), plasma exchange using a conventional plasma separator (OP-PE), and plasma exchange using a high cut-off selective membrane plasma separator (EC-PE) in two cases of anti-GAD-associated neurological diseases. In case 1, IA and OP-PE were used, and the percent reductions were as follows: anti-GAD: 38.2% and 69.1% and Fib: 67.7% and 68.2%, respectively. In case 2, OP-PE and EC-PE were used, and the percent reductions were as follows: anti-GAD: 65.8% and 48.5% and Fib: 68.5% and 19.8%, respectively. OP-PE could remove anti-GAD more efficiently than IA. Further, EC-PE could maintain coagulation factors such as Fib better than IA and OP-PE. It is important to select the appropriate plasmapheresis modality on the basis of the removal kinetics.