Plasma Exchange in Vasculitis
Rob Higgins, University Hospitals Coventry and Warwickshire NHS Trust

Plasma exchange (PEx) has been used as part of the treatment regimen in vasculitis for some years and its benefit has been confirmed recently by the European Vasculitis Group trial MEPEX. This compared three pulses of methylprednisolone with 7 plasma exchange treatments in acute vasculitis, all patients receiving cyclophosphamide and prednisolone. Preliminary results show that of 137 randomised patients, at 3 months, 69% of PEx patients were alive and off dialysis, compared to 49% of ivMeP patients. By 12 months, in survivors, 20% PEx patients were dialysis dependent, compared with 44% of ivMeP patients.

Why is plasma exchange effective and how might its administration be improved in the future? The removal of antibodies is considered pivotal to the success of PEx in some clinical circumstances, for example anti-GBM disease and renal transplantation across ABO or HLA antibody incompatibility. However, plasma exchange removes many potentially active factors in the plasma in addition to antibodies, and some of these could be of clinical significance in vasculitis. Consideration of this is important if technologies that allow treatment of larger volumes of plasma each day are to be evaluated. For example, protein A immunoadsorption removes little apart from antibodies, and cascade filtration removes all high molecular weight plasma components with antibodies, such as complement.

In summary, now that the beneficial role of plasma exchange in treatment of vasculitis has been confirmed by the MEPEX trial, further work to exploit the more advanced plasampheresis technologies is warranted.