Vol. 22 • Issue 10 • Page 40
Today, blood component therapy is a finely tuned selection process. Thanks to apheresis technology and fractionation of whole blood, a blood center can provide platelets, plasma, concentrated red blood cells and cryoprecipitates to address a wide range of disparate conditions. Concomitant with these advances, new hematologic parameters, which are direct cellular measures of hematopoiesis, are readily available. They can assist physicians in identifying the mechanism of anemia or thrombocytopenia so that the best course of therapy can be initiated.
A Look Back
Physician James Blundell performed the first successful human-to-human blood transfusion in 1818. It wasn’t until 82 years later that Karl Landsteiner, an Austrian physician, defined the ABO system. In 1907, pathologist Ludvig Hektoen was the first to suggest that a pre-transfusion cross match (now known as cross-matching) could help reduce transfusion incompatibility.1 That same year, Dr. Reuben Ottenberg performed the first blood transfusion using blood typing and cross matching.2 By 1940, physicians Landsteiner, Alex Wiener, Philip Levine and R.E. Stetson developed the Rhesus (Rh) blood classification system and the United States set up the first national blood collection program.1,2
We take for granted the discoveries that propelled transfusion medicine in the 20th century. Imagine blood banking without anticoagulants, preservative solutions, refrigeration, plastic blood bags, centrifuges, infectious disease screening, and sterility testing of platelets, leukocyte reduction and apheresis instruments for component isolation. Hematology analyzers play a key role in the quality control of the component manufacturing process, providing data that ensures the potency of certain key components prior to use.
Getting the Job Done
According to the National Blood Collection and Utilization Survey, 15,721,000 units of whole blood and red cells were collected in 2011 and the total number of all components transfused in 2011 was 20,933,000 (Executive Summary from the 2011 National Blood Collection and Utilization Survey, page 6). The AABB estimates that 41,000 units of blood are needed every day.3 Contributing 580 units on a daily basis is the Community Blood Center (CBC), Kansas City, opened in 1958. That year they collected 13,000 units of blood. Since then, they have collected 2,000,000 more units treating 800,000 patients. The CBC System has six fixed sites and 10-12 mobile units.
Community Blood Center supplies the transfusion needs for over 70 area hospitals, sending out 3,600 units of blood components each week, all from volunteer donors who are qualified using a mini-physical that includes blood pressure, pulse, and hemoglobin level. All platelets are single donor platelets collected on apheresis instruments and leukoreduction is done on all units to help prevent alloimmunization and refractoriness as recommended in the landmark TRAP study.4
In each fixed donor facility, there is a hematology analyzer used for screening the platelet counts on apheresis platelet donors. The analyzer fits perfectly into this near-donor testing setting and it is fast, easy to run and has minimal maintenance.
Managing the Product Testing Laboratory for Community Blood Centers is Jovona Powelson, MLT(ASCP). “The most important thing I do is manage our products to ensure we produce safe and potent products – that they are free of contamination and have enough red cells, platelets and clotting factors to be beneficial to the recipient.”
She added that the goal is to quickly identify those donors who may be able to donate two or even three platelet units with one apheresis session. “This platelet count value is input into the apheresis instrument to let donor center staff know how long to keep the donor on the machine to collect a single, double or triple unit. This real-time platelet count allows for better management of the apheresis process than relying on historical platelet counts and provides optimum platelet collection from the donor.”
Platelet units are sent to Powelson’s Product Testing Laboratory while red cell and plasma units go to the component laboratory for processing. In the Product Testing Laboratory is another hematology analyzer designed for blood centers with extended linearity ranges that gives them the ability to run samples in an automated or manual mode to obtain accurate cell counts on platelets up to 5 million. The analyzer also has a unique high platelet control to ensure acceptable performance at those very high platelet levels. Packed red cells also are unique in that their hematocrits can be very high. An analyzer with a ðhematocrit ðlinearity up to 75% is beneficial. Platelet counts from platelet rich plasma units are entered into a calculation that uses volume and specific gravity to provide an overall yield value. For example, if the yield is >9.6 x 1011 then it is probable that two, if not three platelet units can be filled from the single donor.
The analyzers in the blood donor centers and in the QC laboratory setting use the same technology for counting platelets and red cells. Jovona believes that it is this standardization of analyzer methodologies in donor centers and the QC lab that allows for optimized donor collections. Comparison studies are done four times/year with good correlation.
It takes up to 42 hours from blood donor draw until the availability of a unit for transfusion. Once a unit is fully tested, it is released to the Distribution Center, which gathers and fulfills the requests from the hospitals.
The FDA provides guidelines that include testing for 14 infectious diseases that Community Blood Center performs off-site. Testing is also done for the detection of HLA and Parvovirus. Community Blood Center recommends that platelets be maintained at 20 – 24 degrees Celsius and that they be placed on an agitator. Handling is geared toward forestalling any release reaction, agglutination or clumping.
Once the units arrive at the hospital, responsibility for appropriate component therapy is assumed by the hospital blood bank. Appropriate management and utilization of this precious resource is a top quality initiative in all blood banks today. A blood management program promotes the safe and clinically effective utilization practices using evidence-based transfusion guidelines. This is when new values from hematology analyzers that report the status of immature red cell and platelet populations can be valuable tools. Understanding the mechanism of anemia and thrombocytopenia can help guide the physician to the appropriate clinical care pathway.
For example, hospital laboratories may conduct additional testing to determine the hemoglobin content of the reticulocyte population (RET-He). This test can provide the physicians with information regarding iron availability for hemoglobinization. It is extremely important for the physician to understand why the patient has a low hemoglobin: Are they bleeding? Do they have a hemoglobinization problem? Are they Fe deficient? Is it a B12 deficiency? The hematology laboratory can help physicians understand the mechanism of the anemia so that the physician and blood bank work together to take the appropriate care path to help treat that patient.
Similar hematology parameters are available to help understand thrombocytopenia. The Immature Platelet Fraction (IPF), along with other clinical information can inform the physician about the bone marrow’s response to thrombocytopenia, giving insight into its cause.
New and more extensive use of hematologic parameters in transfusion medicine can now help physicians diagnose and treat patients with anemia or thrombocytopenia, allowing for targeted therapy. Hematology instrumentation also plays a role in QC and in measuring the potency of various components used in a targeted approach to transfusion medicine. We are likely to see compatibility testing addressing a higher level of matching using genomic studies, bioinformatics and RFID technology.
Barbara J. Connell is senior product manðager, Sysmex America Inc.
1. 50 Years in Hematology, American Society of Hematology
4. Leukocyte reduction and ultraviolet B irradiation of platelets to prevent alloimmunization and refractoriness to platelet transfusions. The Trial to Reduce Alloimmunization to Platelets Study Group. N Engl J Med. 1997;337:1861-1869