By: Ma. Lourdes Pasion, MD, FPSP Blood Bank Consultant
The automated blood collection system, Apheresis, is one of the many facilities of the Department of Pathology and Laboratory Medicine. Through this facility the donor has the option to donate just a component part of his blood unlike the traditional giving away of the whole blood effected by manual donation. A portable automated cell-separator machine called Haemonetics MCS+ installed in the Blood Bank could be programmed to collect units of blood components such as red blood cells, platelets, plasma or even peripheral blood stem cells. Hence, with the wonders of modern technology, the donors now have a choice.
Apheresis (which literally means “to remove”) involves the separation of blood into component parts, retention of the needed component and return of the remaining components to the donor. During donation, blood is drawn from the donor’s arm and flows into a sterile, single-use tubing set into a cell-separator machine. The donation process lasts from 1 to 1 ½ hours.
There are many advantages of Apheresis over manual donation:
- Apheresis gives a higher yield and fewer donors to be bled. For example, thru Apheresis, 2 units of red blood cells or 6 – 8 units of platelets could be obtained from a single donor in one session. On the other hand, to yield the same quantities, 6 – 8 donors are required in manual operation.
- More donations are possible within a period of time.
- Donors may choose to donate whole blood every three months versus every three days for plateletpheresis.
- Apheresis limits donor exposure thereby lessening the chances of transfusion transmitted disease.
- Criteria for blood donation are the same as regular manual donors.
Apheresis is not only used for blood collection, but also has therapeutic applications. In Therapeutic Apheresis (TA) whole blood is removed from a patient and separated into components (using centrifugation), one or more of which is retained. The remaining components are then recombined and returned to the patient. Hence, blood cells, plasma and plasma constituents may be removed from the circulation and replaced by normal plasma (called Therapeutic Plasma Exchange – TPE), crystalloid or colloids.
The theoretical basis for Therapeutic Apheresis is to reduce the patient’s load of a pathologic substance to levels that will allow clinical improvement. In the recently published “Clinical Applications of Therapeutic Apheresis” (Journal of Clinical Apheresis, Vol. 22 Issue 3, June 2007), diseases in which Therapeutic Apheresis is considered Category I, that is, “standard and acceptable, as primary therapy or as first line adjunct therapy ”are autoimmune diseases e.g. cryoglobulinemia, hematologic diseases like hyperleukocytosis, sickle cell disease, neurological disorders like Guillan-Barre, chronic inflammatory demyelinating polyneuropathy and myasthenia gravis.
The use of TPE for renal transplantation, antibody mediated rejection & HLA desensitization falls under Category II that includes “diseases for which TA is generally accepted but considered to be supportive or adjunctive to other, more definitive treatments, rather than a first-line therapy”. In the case of renal transplantation, Therapeutic Apheresis has a role in removing substances that are responsible for antibody-mediated rejection such as HLA antibodies (prior to transplant) and donor specific antibody (DSA) which are generated after transplantation.