Current plasmapheresis practice in the United States.

The principal differences of the USA plasmapheresis collection system from most other countries are: it is conducted by the pharmaceutical industry rather than government, it uses remunerated donors, and it draws a larger volume of plasma than is permitted elsewhere. The implications of these features are reviewed in terms of the effects on donors and the effects on the plasma supply. Protein metabolism is reviewed, and the effects of plasmapheresis on overall nitrogen balance are presented.