BLOOD COMPONENT SUMMARY
Use of several new blood products has increased in the past year.
PRE-STORAGE LEUKOCYTE-REDUCED COMPONENTS:
(Red blood cells and single donor platelets) have largely replaced components which are leukocyte reduced by filtration at the bedside. In September of 1998, the FDA Blood Products Advisory Committee recommended leukocyte reduction of all components. Previously, leuko-reduced components were used primarily for transplant patients and for those with a history of febrile transfusion reactions. Several hospitals in our area have now switched to leuko-reduced products for all patients. Pre-storage leukocyte reduction offers several advantages over leukocyte reduction by filtration at the bedside. Efficiency of leukocyte removal is increased, and the degree of reduction can be quantified. Bedside filtration is cumbersome for nursing staff, whereas pre-storage leuko-reduced components are no more difficult to transfuse than standard units. Pre-storage leuko-reduction also prevents white blood cells from forming cytokines during storage, and releasing them into the plasma. Several cytokines are implicated in febrile transfusion reactions (IL-1, IL-6, IL-8, and tumor necrosis factor). Pre-storage reduction also prevents white blood cell fragmentation during storage.
Advantages of leuko-reduced products over conventional units include: markedly reduced febrile transfusion reactions, markedly reduced CMV transmission/reacti-vation, and reduced HLA alloimmunization. Transfusion of leukocyte-reduced components decreases, but does not eliminate, graft vs. host disease. The drawback to leuko-reduction of components is increased expense (approximately $30.00 per red blood cell unit). This may be offset by decreased nursing and technologist time spent in evaluating suspected febrile transfusion reactions.
DONOR-RETESTED PLASMA:
Donor-retested plasma is fresh frozen plasma (FFP), prepared from a unit of whole blood collected from a single donor. The donor's serum is tested for infectious disease markers (HCV, HIV, HTLV-1, syphilis, and hepatitis-B) at the time of collection. The FFP is then stored for at least 112 days, at which time the donor is recalled and retested prior to release of the FFP. Testing the donor twice, approximately four months apart, greatly reduces the risk of collecting a unit from a sero-negative donor who is actually in the early stages of infection ("the window period"). Donor-retested plasma therefore carries a decreased risk of viral infection, as compared with conventional FFP. It does not decrease the risk of transmitting unknown viruses for which there is no current test. Donor retesting is possible due to the long storage life of fresh frozen plasma. Unfortunately, other components, such as red blood cells and platelets, have too short a storage life to permit donor retesting. Thus, although the risk of infectious disease transmission from fresh frozen plasma is reduced by donor-retested plasma, this reduction is small in patients who are simultaneously being transfused with red blood cells and/or platelets. The cost of donor-retested plasma is $66.00 per unit, as compared with $18.00 per unit for standard FFP. The major disadvantages of Donor-retested plasma are that the plasma units are older, hence the bags are more brittle. The quarantine period also decreases FFP inventory. Donor-retested plasma would be most beneficial in patients with TTP, undergoing plasma exchange with FFP, and in patients with deficiencies of Factors V or XI, for which no specific concentrate is available.
POOLED PLASMA, SOLVENT/DETERGENT TREATED:
Solvent Detergent Plasma (SDP) is prepared by collecting plasma from whole blood of apheresis donors. Approximately 2500 units of ABO specific plasma are pooled to make lots containing abut 500 liters of plasma. The pool is then chemically treated to inactivate enveloped viruses such as HIV-1 & 2, HTLV-1 & 2, hepatitis B, hepatitis C, CMV and herpes simplex virus-1. The American Red Cross holds the patent on this product, which can only be obtained from American Red Cross blood banks. The Red Cross has launched an aggressive marketing campaign for solvent/detergent plasma, which is targeted at the lay public ("Ask your physician for it by name!").
Solvent/detergent treatment does not inactivate nonenveloped viruses such as hepatitis A, human parvovirus B19 and Transfusion Transmitted Virus (TTV). Donors are not screened for hepatitis A or parvovirus because of the high prevalence of these viruses in the general population. In April, 1999, seven lots of SDP were recalled in the United States because several recipients became seropositive for Parvovirus B19 and developed viremia. Because of the risk of hepatitis A transmission, patients should probably receive hepatitis A vaccine prior to being treated with SDP. Because of the Parvovirus B19 risk, SDP should probably not be transfused to pregnant women, immunocompromised individuals and patients with hemolytic anemia.
The major advantages of SDP are viral inactivation, greater consistency of coagulation factor levels from unit to unit, standardized volume of 200 mL, and lack of large vWF multimers. The major disadvantages are the potential risks associated with pooling plasma from large numbers of donors and the high cost. Possible contamination of the donor pool with an unknown non-lipid enveloped virus or prion might pose a serious risk to a large number of recipients. The cost per unit is $124.60.
SDP is much more expensive and provides a relatively small benefit due to the efficacy of current viral screening and the recent institution of Nucleic Acid Testing (NAT) of donors for HIV and HCV. NAT will decrease the window period for HCV from 70 - 80 days to 10 - 30 days and the HIV window from 16 to 10 days. SDP will decrease the risk of viral transmission only for patients being transfused with plasma alone, because RBCs and platelets are not chemically treated. The best clinical indications for SDP appear to be treatment of coagulation factor deficiencies V and XI, where no factor concentrate is available, and plasma exchange for TTP.
Homocysteine Testing Offered
Children’s Mercy Hospital is now offering Homocysteine testing. The testing requires 1 ml of blood drawn in an EDTA (purple top) tube. The specimen should be kept on ice and spun within 30 minutes. The plasma can then be sent to CMH on ice. Turnaround time is 2 – 3 days.