Glossary
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AABB
Major blood banking organization formerly known as the "American Association of Blood Banks." Founded in 1947 in the United States, AABB is now an international association of people and facilities involved in collection, processing, and transfusion of blood and progenitor cells. AABB facilitates inspections of blood banks and donor centers, publishes standards to help member facilities comply with federal guidelines, and interacts heavily with the Food and Drug Administration on behalf of the blood banking community. Their official name is now just the acronym, "AABB."
AABB Standards
Commonly used name for a publication from AABB formally known as "Standards for Blood Banks and Transfusion Services." The requirements listed in this little book are those under which all AABB-accredited facilities must operate. "Standards" (to use an even shorter name) is currently in its 26th edition (as of November 1, 2009). AABB member facilities are inspected every two years by trained volunteers based on the practices outlined in Standards. In general, the standards found here are in agreement with those from the FDA Code of Federal Regulations (CFR), but there are more industry-specific guidelines outlined in Standards than in the CFR.
Acute Lung Injury
A syndrome of lung-specific damage (without contribution from cardiac causes), thought to be caused by inflammatory processes. Acute Lung Injury (ALI) is defined (according to a 1994 consensus conference) as the acute onset of hypoxemia WITH chest x-ray evidence of pulmonary edema and WITHOUT evidence of left atrial hypertension (wedge pressure less than 18, if available). ALI is important to us in transfusion medicine as part of a specific transfusion complication known as "Transfusion-related Acute Lung Injury (TRALI)." TRALI was defined in 1995 by a consensus group convened by the National Heart, Lung, and Blood Institute (NHLBI) as "acute lung injury occurring during or within six hours of transfusion, with a clear temporal relationship to the transfusion" (Critical Care Med. 2005 Apr;33(4):721-6). In addition to transfusion, however, other things are known to be associated with ALI, including sepsis, aspiration of gastric contents, DIC, and near-drowning.
Acute Normovolemic Hemodilution (ANH)
A method of autologous blood collection involving the immediately preoperative collection of multiple units of whole blood with immediate replacement of the patient's blood volume (also known as "Isovolemic Hemodilution"). To explain the term, "acute" applies because the process is done quickly, usually immediately before the surgery begins; "normovolemic" is used due to the prompt replenishment of blood volume (most commonly with normal saline); and finally, "hemodilution" makes sense because of the first two! NOTE: In case you aren't following, the patient's blood is diluted by the acute removal of blood followed by the rapid volume replacement mentioned above. The basic principle is that during surgery, the patient bleeds more dilute blood, then, near the end of the procedure, the withdrawn blood is re-infused (in reverse order; i.e., the last units out are the first units to go back in) and the patient's blood volume is decreased through diuresis, as necessary. The units withdrawn must be labeled with the patient's name, expiration time of the product (8 hours from time of collection if stored in the operating room, 24 hours if stored in the blood bank), and the statement, "For Autologous Use Only."
ANH, in the proper hands, is elegant, cool, and makes lots of sense. Mathematically, it certainly is logical that someone would lose fewer red cells during surgery using this method. Functionally, the decrease in blood viscosity resulting from hemodilution has the potential to help the patient's heart work more efficiently during surgery. So, why the heck isn''t ANH used all that much? Two big reasons, I believe: First, performing ANH requires a knowledgeable operator (most commonly, an anesthesiologist) that understands how to collect donor blood, use the collection bags (with scales as applicable), and label the product. That combination doesn't happen very often. Second, not enough clinicians even know about ANH, and fewer still consider it as an alternative to preoperative autologous blood collection.
Adsorption
In general, the collection of materials on the surface of another material in a non-binding, non-permanent manner. In blood banking, refers to the adherence of an antibody or antigen onto the surface of a red blood cell. Adsorption is applicable in regards to both antigens and antibodies.
Antigens: Certain blood group antigens are not bound tightly to the surface of a red blood cell, but rather passively "stick" to the surface of the cell. This is most prominent in the Lewis Blood System. The non-permanent binding of these antigens means that the antigenic profile of red cells may change when the cells are introduced to another person and free-floating antigens "adsorb" to their surface.
Antibodies: Adsorption is a procedure used by blood bankers to bind antibodies to red blood cells in order to remove them from the plasma and better analyze the remaining antibodies. Here's an example: Imagine that a blood banker is trying to identify the antibodies present in a patient. The patient seems to have more than one antibody, and they are difficult to define when looking at the reactions of both antibodies together. The blood banker suspects than anti-C and anti-S are present. In order to confirm that, she could mix the patient's plasma with red blood cells from a C antigen-positive, S antigen-negative person. The suspected anti-C would be expected to bind (adsorb) to the surface of those red cells, while the suspected anti-S would remain in the plasma. Following the adsorption, the tech would centrifuge the mixture and analyze the plasma, revealing (if all worked as expected) a straightforward anti-S. Incidentally, the red cell portion of the mixture could then be undergo an elution in order to identify the anti-C bound to the surface of the red blood cells. Technically "adsorption" is a bit of a misnomer in this setting, since the binding of the antibody to the red cells is not really a "passive" non-specific process, but the term is used, nonetheless.
Allogeneic
Literally, "being genetically different although belonging to or obtained from the same species." In blood banking, allogeneic transfusion (or transplantation) is when a donor and a recipient are not the same person (in contrast to autologous transfusions). The word also applies to blood donors who are donating as volunteers, giving blood for someone else's use. Note that this term means the same as the archaic word "homologous" that is used on rare occasions.
Alloimmunization
In general, referring to production of an antibody against antigens that come from a different person of the same species. This definition is identical to what you will find for another word in the glossary: "Isoimmunization."
So, for example, a blood banker might describe hemolytic disease of the newborn as resulting from maternal "alloimmunization" to paternal antigens, while a neonatologist might decribe the same interaction as "isoimmunization." No biggie, just different terms for the same process.
Antibody Screen
A test used to detect "unexpected (i.e., non-ABO) antibodies". This test is performed on blood donors and blood recipients, to predict whether or not a major crossmatch between recipient serum/plasma and donor red blood cells will be compatible. In this test, serum or plasma is added to red blood cells from between two and four group O individuals, and examined for incompatibility (using whichever detection method is preferred by the laboratory). IMPORTANT NOTE: Group O red cells are used to take ABO antibodies out of the equation. For example, if a particular serum sample has anti-B and anti-K, we want to use red cells for detection that will react with the anti-K but not with the anti-B. Group O, K-positive red cells would fit the bill. If the antibody screen is positive, in most cases the next step would be to perform antibody identification. If the screen is negative, there is an extremely high likelihood that no significant non-ABO antibodies are present.
Apheresis
Also known as "pheresis" in blood banking circles. Apheresis is a term that literally means "to take away." That description is fairly accurate for our setting, as apheresis procedures involve the selective removal of a targeted portion of blood, with return of the non-targeted portions to the individual.
Apheresis is most commonly used in blood donor settings, where automated equipment removes whole blood from a donor, uses (most commonly) differential centrifugation to select a specific portion of the blood for harvest (e.g., platelets), and returns the vast majority of the remainder of the blood to the donor. The vast majority of platelets transfused in the United States today are collected in this manner, and a growing proportion of red blood cells and plasma are collected using this technology. Apheresis, however, can also be used in therapeutic settings, to decrease the amount of markedly elevated white blood cells (for example, in leukemics in blast crisis), remove abnormal plasma (in hyperviscosity syndromes or thrombotic thrombocytopenic purpura), remove increased numbers of platelets (essential thrombocytosis), and decrease hematocrit or iron load (polycythemia or hemochromatosis). The above examples are just a few of the more common uses of this technology.
Apheresis Platelets Leukocytes Reduced
The proper name for a unit of platelets collected using apheresis technology that has had the vast majority of white blood cells removed. This is the most commonly transfused platelet product in the US, by far. By definition, this product must meet the usual quality requirements for apheresis platelets (at least 90% having platelet counts of > 3.0 x 10^11 and end-storage pH of > 6.2), and also meet a specific quality testing requirement for residual white cells: < 5.0 x 10^6 in 95% of units tested. See the glossary entry on leukoreduction for more information on why we remove white cells from blood products.
Apheresis Red Blood Cells Leukocytes Reduced
The proper name for a product that is similar to Leukocyte reduced Red Blood Cells, but prepared using apheresis technology. In addition to the requirement for containing less than 5.0 x 10^6 residual white blood cells, there are several other requirements for apheresis LRBCs. These include: Must be made by a method known to ensure the mean hemoglobin level is > 51.0 g (or 153 ml of red cells), with 95% or more of the units sampled containing > 42.5.0 g of hemoglobin (or 128 ml of red cells).
Autoadsorption
See "Adsorption"; Autoadsorption is similar to the description of adsorption in the "Antibody" section, except it involves the deliberately induced adherence of antibodies targeted against self antigens ("autoantibodies") in order to remove those antibodies from plasma in a test environment. The remaining plasma (presumably, with the autoantibodies removed) may then be tested to see if other antibodies are present. This procedure is commonly used in the workup of a warm autoantibody to ensure the lack of other, clinically significant alloantibodies that may have been masked by the presence of the autoantibody.
Autologous
Literally, "derived or transferred from the same individual's body." In blood banking, autologous transfusions (or transplantations) are ones in which the donor and the recipient are the same person. There are multiple ways for autologous transfusions to occur, from pre-operative autologous blood donation (a person comes to a donor center and gives a unit or more of his/her own blood for use during surgery) to intra-operative blood collection (blood removed from the surgery site is given back to the patient) to post-operative blood collection (blood draining from surgery sites is given back to the patient). Note the contrast of this term to the archaic term "homologous."