Apheresis

A catch-all term for the process whereby a person's blood is circulated through a machine (an apheresis unit) and separated into its component parts, with certain components being collected and the rest being returned into circulation. Depending on the many uses of apheresis--therapeutic, blood donation, etc.--the component(s) removed from the person's circulation and returned vary. For example, a platelet donor will have a portion of his/her total platelets removed from circulation so they can be later used for platelet transfusion for someone else. In a therapeutic scenario, a person with a dangerously high white blood cell count may have a portion of only his white blood cells removed and the remainder returned.