The University of Rochester Medical Center Transfusion Service/Blood Bank, located 5 miles from its primary blood supplier, performs 65,000 transfusions each year in support of a 750 bed hospital. Our blood bank also supports an emergency department that serves more than 96,000 patient visits each year and has the only Level 1 trauma center within a radius of 70 miles. In addition, our institution supports services that perform liver, kidney, stem cell and heart transplants as well as a Cancer Center that currently treats about 10,000 patients each year. Universal leukoreduction of red cell and platelet transfusions was instituted in 2000 and thus did not influence the results reported. Beginning in 1990, all platelet transfusions for patients with hematologic diseases or diseases that might be treated with stem cell transplant were administered as ABO identical. The policy for virtually all other platelet transfusions until spring, 2005 was to give platelet pools that were nearest to outdate, regardless of ABO type.
When ABO identical cellular components are unavailable, it is policy to reduce non-identical plasma by saline washing prior to transfusion if time permits. Washing leads to minimal loss of red cells but about a 20% loss of platelets. A phased in approach was utilized for implementation. Initially in 1990 it became policy to transfuse only ABO identical platelets to patients with hematologic malignancies. However, in April 2005, we established a policy in which ABO identical platelets are routinely given to all patients. Because of inventory capabilities, providing only ABO identical cryoprecipitate was not a difficult change in policy. ABO identical FFP and liquid plasma were always standard practice, although AB plasma was given when emergencies occurred and the patient’s ABO type was not known. ABO identical red cells, platelets, cryoprecipitate and plasma are now routinely utilized for all transfusions except unidentified trauma patients or when ABO identical components are unavailable and the clinical need for transfusion is urgent.
Monitor of Blood Supply
Our staff routinely monitors recent blood utilization and planned transfusions. Based upon the monitor, standing blood orders are adjusted to accommodate anticipated needs. Adjustments are made both with regard to quantity and blood type. In addition, in the time frame data were collected, our institution almost exclusively used whole blood derived pooled platelets. The routine platelet dose consisted of five units of platelets. During times of platelet shortage, however, our institution would compensate by providing a number of ABO identical single donor platelets and reduced doses of whole blood platelets (e.g., pools of three or four platelets) until adequate ABO identical supplies could be attained from blood suppliers.
Our suppliers must have flexibility with standing orders and inventory replenishment to accommodate adjustments of quantity and blood type of components. It is also indispensable to have a blood supplier in close proximity for placing urgent orders. Our primary blood supplier is located just 5 miles from our hospital allowing rapid replenishment of inventory, a major advantage in providing ABO identical components.
Saline washing with one of four 2991 COBE (subsequently Gambro, now Caridian) cell washers, or another method of plasma reduction to remove incompatible plasma and soluble antigen from platelet products, is essential in our setting to avoiding transfusion of incompatible antibody ± soluble antigen. This practice allows the use of plasma depleted ABO compatible platelets when ABO identical products are unavailable.
We found it essential to have excellent communications with bedside practitioners. In the event of emergent situations, including traumas, when patient survival may be jeopardized by a delay necessitated by external sourcing or washing components, a physician or technologist may approve the use of unwashed O type red cells, unwashed ABO compatible platelets and AB type plasma or cryoprecipitate. When the patient’s blood type is unknown, group O red cells and AB plasma are transfused, and group A platelets are typically administered.
Storage for Increased Quantities of Products
It is crucial to have adequate storage for an increased inventory. We needed to increase our in-house inventory of cryoprecipitate in order to ensure availability of each ABO blood type. With an increase in frozen products, we needed to make arrangements to accommodate these products in monitored freezers that maintain the appropriate temperature. Typically we maintain a two day inventory of group A and O platelets and order B and AB platelets as needed.
Compliance with an ABO Identical Only Policy
Our most challenging cohort to treat was used as an indicator of compliance with our new policy. Transfusion data were collected for one year post implementation on surgical patients requiring at least one platelet transfusion. Patient transfusion records were reviewed from the time the patient had surgery until they were discharged from the hospital. The number of patients receiving at least one transfusion of a non-ABO identical platelet component was tabulated. The proportion of surgical patients receiving any ABO non-identical transfusions was calculated by dividing this population by the total number of surgical patients receiving platelets.
Measure of Wastage
To determine consequences of our policy on blood component outdating, a review of wastage was performed for eighteen months before and after implementation of this policy. This was an arbitrary choice of period. Total numbers of each component ordered from our blood suppliers were tabulated for each eighteen month period. Then, the numbers of components wasted in these time periods were obtained from a blood utilization report that is generated quarterly. Percent wastage per total number of components ordered was calculated for each blood component type for the eighteen months prior to and subsequent to implementation of the ABO identical blood component policy.
Rate of Transfusion Reactions and Red Cell Alloimmunization
We hypothesized that immunologic consequences due to ABO mismatched transfusions might include transfusion reactions and alloimmunization. There is evidence that inflammation, which speculatively might be caused by ABO immune complexes, can facilitate alloimmunization in animal models.15,16
Thus we compared febrile and allergic transfusion reactions for periods of four years preceding and following implementation. The primary rationale for this time period was to have a large enough number of reactions and alloimmunizations to analyze. The number of allergic and febrile transfusion reactions was obtained from the blood utilization quarterly report for the time periods of four years before and after implementation of the ABO identical blood component policy. The total numbers of components transfused were also collected during each of these time periods. The rate of transfusion reactions per total components transfused was calculated.
In 2010, based upon work suggesting that immune complexes and inflammation may alter the likelihood of alloimmunization,15,16
we examined the rate of newly detected red cell alloantibodies in our institution for the four years previous to and after instituting the new policy regarding ABO identical platelets/cryoprecipitate. The primary rationale for choosing these time periods was having a sufficiently large number of events to study. The rate of alloimmunization was calculated per antibody screen (indirect antiglobulin test) performed on patients during a given year. There were no changes in methods of antibody screening or identification during this nine year period, either methodologically or in terms of screening cell number or selection. Upon inspection of the raw data, it appeared that trend analysis was the most appropriate method of displaying the data.
As a surrogate for HLA antibody alloimmunization and platelet transfusion refractoriness, which may be increased by transfusion of ABO non-identical platelets,8
we calculated, as a percentage, the total annual use of HLA matched platelets per total platelet doses transfused during the periods 2001–2004 and 2006–2009. We did not expect to see a substantial difference as our refractoriness rate was already very low prior to the ABO identical policy. This low incidence of refractoriness is likely due to our protocol that from 1990 onward mandated transfusion of only leukoreduced, ABO identical platelets for all patients at high risk of platelet transfusion refractoriness.4,7–9
All data collection was retrospective. Chi-square testing without Yates correction was performed to determine statistical significance of categorical variables, such as the proportion of events per transfused component. For continuous variables, at test was employed for data variables with non-significantly different standard deviations, and the Mann Whitney non-parametric test was employed for analysis of changes in derived numerical data (e.g., percentages of platelets given as HLA matched). Upon inspection of the red cell alloimmunization raw data, it appeared that trend analysis was the most appropriate method of displaying the data. Linear regression was employed to determine trends, either a level trend (slope not significantly different from zero) or increasing or decreasing trend (slope significantly different from zero) A two- sided p value of <0.05 was considered significant for all determinations. Instat 3.1a (GraphPad, La Jolla, CA) was employed for all analyses.