Blood Purification:This method is intended to remove most pathogens, including bacteria and fungi, from donated blood through a technique called "pathogen inactivation." This process leverages the fact that the three components of blood used in transfusions—red blood cells for oxygen transport, platelets for clotting, and plasma for various functions—do not contain DNA or RNA, unlike viruses, bacteria, and fungi. By targeting and inactivating DNA or RNA, the pathogens can be selectively eradicated without damaging the blood itself.One approach to pathogen inactivation involves a chemical that, when exposed to ultraviolet light, binds to genetic material, preventing the DNA double helix strands from separating. This stops pathogens from replicating. RNA, the genetic material in certain viruses, is similarly affected. However, there is ongoing debate about the method's effectiveness against large quantities of viruses. The process is not effective against prions, which cause diseases like mad cow disease and variant Creutzfeldt-Jakob disease, because prions are proteins without DNA or RNA. Additionally, this technique cannot be used on white blood cell packs because they contain DNA, which would be inactivated by the process.For platelets, a synthetic chemical called psoralen is used. Platelets are placed in the first of three connected clear plastic bags where they interact with psoralen. They are then transferred to the second bag and exposed to ultraviolet light for about three minutes in a specialized machine. In the third bag, an absorbent material extracts the psoralen. Different chemicals are required for red blood cells since light cannot penetrate them to activate psoralen.Implementing pathogen inactivation could increase the cost of a unit of blood by approximately $50 to $100. Currently, red blood cells cost between $100 and $200 per unit, and platelets range from $200 to $600. Despite the added expense, this technique enhances transfusion safety. Platelets are stored at room temperature, making them more susceptible to bacterial contamination, which is estimated to cause 8 to 12 deaths and numerous illnesses annually in the US. Red blood cells are stored in refrigerated conditions, reducing bacterial risks, but other infectious agents, such as hepatitis B and C viruses and parasites like those causing Chagas disease, remain concerns. These nonbacterial pathogens can be inactivated using this technique.(This entry is partially based on "Technique may improve the safety of donated blood" by Andrew Pollack in The New York Times on April 2, 2002, and information from companies specializing in pathogen inactivation technology.)
