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Continuing Education Activity Pretransfusion testing includes all activities from when the blood product is ordered by the physician to the final step when the blood product can be dispensed from the laboratory to the patient's bedside.The reduction and elimination of numerous clinical hazards have been demonstrated over many years.The system should recognize and correlate anti body detection results, compare previous records, concordant ABO on the recipient from at least two determinations, donor component and unit number, and ABO/Rh retype results, as well as have logic to alert the user to discrepancies between donor unit labeling and confirmatory test interpretation, and ABO incompatibilities between the recipient and the donor unit.[10] Interfering Factors Several factors influence the results of pretransfusion testing giving rise to false positive or negative results.[11] These include: Some of the causes leading to false results are mentioned below; False Positive Result Rouleaux formation Passively transferred antibodies due to transfusion of platelets or administration of IVIG Antibodies to the preservatives present in the reagents used False Negative Result Technical error The antibodies showing dosage effect may not react if the donor cells have a heterozygous expression of a particular antigen Loss of potency of the reagents used Failure to add reagents Equipment failure Massive transfusion replaces a portion of the patient's blood volume with donor blood.The information on the requisition form must be compared with that on the wristband; blood samples should not be collected if there is a discrepancy.[6] The request form: This, either in paper or electronic form, for a transfusion must contain the following information: The patient's full name, including first and last (family and given) and gender A unique identifier like date of birth (DOB) or a hospital or health card number The recipient's address The required blood component/product with appropriate dose/volume The indication for transfusion History of previous transfusion or transfusion reactions Date and time of the order Identity of the qualified medical person ordering the blood products Date and time of the intended transfusion If any special requirements, like CMVnegative unit, leukoreduced, irradiated, washed, or reduced volume Blood Sample: Pretransfusion testing requires a clotted sample from the recipient for serum and an EDTA sample for red cells and plasma.It involves the following steps: Positive patient identification Collection of the blood samples of the patient for compatibility testing ABO and Rh blood grouping of the patient and the donor unit Red blood cell Antibody screening on serum/plasma sample of the patient Selection of appropriate blood component Performance of compatibility testing Labeling of the unit with details of the product and the patient identification information Generation of compatibility report that is to be given along with the blood product It is performed to ensure that the patient is positively identified with any special requirements, that transfusion records and history are reviewed and considered, that antibody detection and identification are performed, and that appropriate units are selected.[1] Red blood cells have antigenic proteins and carbohydrates on the cell surface.In patients who have recently transfused red cells in the circulation that are interfering with phenotyping or the antigens for which commercial antisera are not available, as, in Dombrock, molecular genotyping may be utilized for ascertaining the phenotype.[9] Compatibility Testing Immediate spin method: The recipient serum/plasma is mixed with saline-suspended donor cells (major crossmatch) and vice-versa (minor crossmatch) at room temperature.However, compatibility testing should be continued and completed, and if incompatibility is detected, the recipient's physician should be notified immediately.[14] Clinical Significance In
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emergencies and before crossmatch compatible blood components are available, group O red cells and group AB plasma (some facilities use group A plasma) can be transfused appropriately.These AHG reagents are usually IgM antibodies directed against the Fc portion of those IgG molecules.[7] Testing Procedures ABO and Rh Typing The patient's ABO grouping is performed by ascertaining concordance with both cell typing (forward grouping) and serum testing (reverse typing).Compatibility testing is to be performed with maternal serum or plasma as well.[12] Evidence supports the use of fresher red cells (less than seven days after collection) when the transfusion volume in neonates is greater than 25 ml/kg.[13] Emergency release: Uncrossmatched ABO identical group or group O red cells or group O whole blood (without hemolysins) may be issued if the recipient's group is unknown.However, from the attending physician's decision to transfuse to the bedside administration of blood products, the medical staff involved, including the phlebotomist who collects the sample, the laboratory staff who performs the tests, and the staff who collects and transports the blood products to the transfusion site, which may be a ward or operating room, as well as the nurses who administer and monitor the transfusion, are an indispensable link in the transfusion chain.Transfusion medicine staff work with physicians to implement patient blood management and the rational use of blood products.The basic elements of laboratory safety include the following: Regular training of the lab personnel Use of appropriate personal protective equipment Following safe work practices Reporting of accidents and injuries The protocol should be in place to manage blood spill Hepatitis B prophylaxis to all the technical staff Enhancing Healthcare Team Outcomes Ensuring that the correct blood is delivered to the right patient requires a team effort and the involvement of clinicians, nurses, and laboratory personnel.In a "type and screen" procedure, the patient's red cells are typed for ABO and Rh (also known as D), and the patient's plasma is tested for clinically significant red cell antibodies. A "type and crossmatch" involves selecting, matching, and reserving appropriate red cell components for the transfusion recipient.Immediate spin can be the only crossmatch method when the recipient does not have current or previously detected clinically significant antibodies.[6] Antiglobulin crossmatch: In the liquid phase, i.e., tube method, 2 to 5% saline-suspended red cells of the donor unit are mixed with recipient serum and incubated at 37 C for about 45 minutes and washed to remove unbound antibodies.Weak D testing is not required in the RhD-negative samples unless the recipient is a neonate born to RhD negative mother.[6] Antibody Screening These are serological tests designed to detect clinically significant antibodies to blood group antigens using an Indirect antiglobulin test (IAT).Crossmatching by indirect antiglobulin testing method: A negative test (crossmatch compatible) indicates that the serum or plasma contains no detectable antibodies that are reactive with the red cells being transfused.Red cell antibodies of clinical significance are produced in response to pregnancy or transfusion; they can cause hemolysis or shortened survival of transfused red cells carrying the corresponding antigen (i.e., acute or delayed hemolytic transfusion reaction).Pretransfusion testing schemes Specimen Requirements and Procedure Routine testing of blood components before transfusion includes receipt of an appropriately labeled patient sample by the transfusion service, testing for ABO and Rh D, the presence of unexpected antibodies, and crossmatching red cell components with the patient sample.Accurate labeling of specimens is more critical in transfusion medicine, where specimen misidentification may result in the administration of
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incompatible blood components, leading to fatal acute hemolytic transfusion reactions.[8] Table 2: Compatibility chart for choosing the blood products Diagnostic Tests The various tests included under pretransfusion testing are mostly serological, with some assistance from molecular methods in rare instances.Fresh red cell units (less than seven days old) should be selected for large-volume transfusions (> 25 ml/kg) in neonates.[13] Selection of other blood products: All plasma-containing components should be compatible with the recipient's red cells.The AHG (antihuman globulin) phase detects the red cell antibodies, usually IgG in nature, that do not produce direct agglutination by bridging red cells to complete the microscopically detectable lattice.Additional testing strategies may be required, namely the use of enhancement media (albumin, polyethylene glycol, low ionic strength solution, or chemical/enzyme treatment of the panel cells to aid identification.Electronic crossmatch can be used as the sole method only after ensuring that the recipient has no clinically significant antibodies present historically or currently.Although there is still a heavy reliance on procedural methods for the essentially manual steps that make up the phases of the transfusion chain, recognizing this continuing vulnerability has led to increased attention to the transfusion process itself.Such red cell alloantibodies then lyse transfused red cells that possess the corresponding antigen.[2] Transfusion and pregnancy are the primary means of sensitization to red cell antigens.A patient sample after transfusion may not accurately reflect blood type or alloantibodies, depending on the ABO type of the RBCs and plasma selected for emergency resuscitation.Results, Reporting, and Critical Findings Interpretation: If the result is positive (antibody detected), antibody identification is required to determine the specificity and clinical significance of the detected antibody.All reagents used in pretransfusion testing, such as AHG reagent, must meet all quality criteria established by regulatory agencies or certification and accreditation bodies.If a patient has a clinically significant antibody, the transfusion service selects and reserves the appropriate red cell components that do not carry the corresponding antigen.The principle involved is the detection of antigen and antibody reactions by observation of agglutination or hemolysis in vitro.Date and time of specimen collection 4.Table 1.
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