Pretransfusion Compatibility Testing PDF

Chapter 13 **Pretransfusion Compatibility Testing** **Identification, Collection and Preparation of Samples** The most common cause of error is misidentification of the recipient (47%). To prevent the collection of wrong sample, compare the requisition form with the wristband identification of th...

Chapter 13 **Pretransfusion Compatibility Testing** **Identification, Collection and Preparation of Samples** The most common cause of error is misidentification of the recipient (47%). To prevent the collection of wrong sample, compare the requisition form with the wristband identification of the patient. Any discrepancies must be completely resolved prior to sample collection. The use of barcode printing rather than handwritten forms may also be useful. Hemolysis of the sample must be avoided. Hemolyzed sample can mask the hemolysis caused by antigen-antibody complexing with complement. Serum or plasma may be used for pretransfusion testing. Tubes must be labeled before leaving recipient\'s bedside and printed labels should be compared with the request form and the recipient\'s wristband. Blood sample should not be taken from intravenous (IV) tubing lines, but if the sample must be taken from an IV line, the line should be disconnected for 5 to 10 minutes and the first 10 ml of blood drawn should be discarded. Sample must be checked by the technician and should match the request form. Unlabeled sample requires that a new sample must be obtained. Samples for donor testing must be collected at the same time as the full donor unit. Donors samples should be fully labeled. RBCs from donor for pretransfusion compatibility testing can be prepared from the segment tubing from which the donor blood was collected. Both donor and recipient samples must be stored for a minimum of 7 days following transfusion for re-evaluation of expected transfusion reaction. **Compatibility Testing Protocols** The donor samples must be tested for ABO and Rh group (including a test for weak D) and antibody screen. Tests intended to prevent disease transmission must also be performed. All results must be clearly indicated on all product labels appearing on the unit. A record must be maintained for all results obtained in testing the patient samples. ABO, Rh and unexpected antibody screen test results should be included in the record. The patient\'s sample can be used for cross match for 7 days except if the patient has been transfused 14 days ago, in this case a fresh sample not more than 24 hours should be used. The sample can be used for 72 hours after transfusion. **Selection of Appropriate Donor Units** The table below illustrates the specific ABO Rh group that must be selected as well the alternative blood group for each component. Table +-----------+-----------+-----------+-----------+-----------+-----------+ | Component | Recipient | Alternati | | | | | | ABO Rh | ve | | | | | | | Blood | | | | | | | Group | | | | +===========+===========+===========+===========+===========+===========+ | | | 1^st^ | 2^nd^ | 3^rd^ | 4^th^ | | | | Choice | choice | choice | choice | +-----------+-----------+-----------+-----------+-----------+-----------+ | Blood | AB | AB | A | B | O | | | | | | | | | Select | | | | | | | Packed | | | | | | | RBCs when | | | | | | | a | | | | | | | recipient | | | | | | | must be | | | | | | | given a | | | | | | | different | | | | | | | blood | | | | | | | group | | | | | | +-----------+-----------+-----------+-----------+-----------+-----------+ | | A | A | O | | | +-----------+-----------+-----------+-----------+-----------+-----------+ | | B | B | O | | | +-----------+-----------+-----------+-----------+-----------+-----------+ | | O | O | | | | +-----------+-----------+-----------+-----------+-----------+-----------+ | | Rh + | Rh + | Rh -- if | | | | | | | nearly | | | | | | | expired | | | +-----------+-----------+-----------+-----------+-----------+-----------+ | | Rh - | Rh - | Rh + if | | | | | | | the | | | | | | | recipient | | | | | | | is a male | | | | | | | or post | | | | | | | menopause | | | +-----------+-----------+-----------+-----------+-----------+-----------+ | FFP | AB | AB | | | | | | | | | | | | Rh is not | | | | | | | important | | | | | | +-----------+-----------+-----------+-----------+-----------+-----------+ | | A | A | AB | | | +-----------+-----------+-----------+-----------+-----------+-----------+ | | B | B | AB | | | +-----------+-----------+-----------+-----------+-----------+-----------+ | | O | O | A, B, AB | | | +-----------+-----------+-----------+-----------+-----------+-----------+ | Platelet | AB | AB | A | B | O | | | | | | | | | Single | | | | | | | unit | | | | | | | specific | | | | | | | Rh group | | | | | | +-----------+-----------+-----------+-----------+-----------+-----------+ | | A | A | AB | B | O | +-----------+-----------+-----------+-----------+-----------+-----------+ | | B | B | AB | A | O | +-----------+-----------+-----------+-----------+-----------+-----------+ | | O | O | A | B | AB | +-----------+-----------+-----------+-----------+-----------+-----------+ When selecting blood for transfusion the units should be close to the expiry date except in some cases. Units should be examined visually for any abnormal or unusual appearance. **Crossmatch Testing** A crossmatch is only a part of the pretransfusion compatibility test that includes testing patient\'s serum against donor\'s blood \"RBCs\" in all phases of indirect test. The main function of the serologic crossmatch is to serve as a final check of ABO compatibility between donor and recipient and it may also detect the presence of antibody in the patient\'s serum that will react with the antigens on the donors RBCs not detected in the antibody screen. The current AABB standards state that tests to detect ABO incompatibility are sufficient if the antibody screen is negative for clinically significant antibody and no historical record exists for the detection of clinically significant antibody. The serologic crossmatch test includes an immediate spin crossmatch and an antiglobulin crossmatch. The result is interpreted as positive if there is agglutination or hemolysis and if there is none, the result is considered negative. All work should be signed by the technologist performing the test. A positive result in the crossmatch test requires explanation and the recipient should not receive a transfusion until the cause of the incompatibility has been determined. The following table illustrates the cause of the positive result and the measures to be done to resolve the case. +-----------------------+-----------------------+-----------------------+ | Investigation of | | | | Incompatible Major | | | | Crossmatches | | | +=======================+=======================+=======================+ | Result | Possible | Comments and Resolve | | | Interpretations | | +-----------------------+-----------------------+-----------------------+ | Crossmatch: + | 1. Incorrect ABO | Repeat ABO grouping: | | | grouping of | verify identity of | | Auto-control: - | patient or donor | sample. | | | | | | Antibody screen: - | | | +-----------------------+-----------------------+-----------------------+ | | 2. Patient\'s serum | Check patient\'s | | | may contain an | sample for subgroups; | | | ABO antibody | check patient\'s | | | | transfusion and | | | | transplantation | | | | histories; passive | | | | Anti-A, -B, -A,B | +-----------------------+-----------------------+-----------------------+ | | 3. Alloantibody in | Perform antibody | | | patient\'s serum | identification tests | | | reacting with | on patient\'s serum | | | antigen donor\'s | and repeat crossmatch | | | red cells but not | using units negative | | | present on | for the corresponding | | | screening cells | antigen. If studies | | | | are noninformative | | | | and patient is | | | | incompatible with | | | | only 1 unit, locate | | | | other compatible | | | | units. Antibody to | | | | low incidence | | | | antigen. | +-----------------------+-----------------------+-----------------------+ | | 4. Donor unit may | Perform DAT on donor | | | have a positive | unit; if positive, do | | | DAT | not use the unit. | +-----------------------+-----------------------+-----------------------+ | Crossmatch: + | 1. Alloantibody in | Perform antibody | | | patient\'s serum | identification | | Auto-control: - | reacting with | studies on patient\'s | | | antigens on | serum and repeat | | Antibody screen: + | donor\'s cells | crossmatch using | | | and screening | units negative for | | | cells | the corresponding | | | | antigen. | | | | | | | | If unable to identify | | | | antibody specificity, | | | | consult a reference | | | | laboratory. | +-----------------------+-----------------------+-----------------------+ | Crossmatch: + | 1. Both an | Perform | | | autoantibody and | autoadsorption of | | Auto-control: + | alloantibody may | patient serum to | | | be present in the | remove autoantibody | | Antibody screen: + | patient\'s serum | (if not recently | | | | transfused), perform | | | | antibody | | | | identification tests, | | | | repeat compatibility | | | | tests using | | | | autoadsorbed serum | +-----------------------+-----------------------+-----------------------+ | | 2. Abnormalities in | If rouleaux are seen, | | | patient\'s serum | use saline | | | owing to | replacement | | | imbalance of A/G | technique. | | | ratio | | | | | Obtain new specimen. | | | | | | | | Use caprylate-free | | | a. Plasma expanders | reagents. | | | | | | | b. Caprylate | Repeat tests using | | | antibodies | fresh saline, new | | | \"Anti-reagent in | bottles of reagent, | | | AHG\" | clean test tubes. | | | | | | | c. Contaminants | | +-----------------------+-----------------------+-----------------------+ **Computer Crossmatch** The computer crossmatch compares recent ABO serologic results and interpretations on file for both the donor and the recipient being matched and determines compatibility based on this comparison. The patient must be antibody screen negative for recent sample, and there is no history for unexpected antibody, a patient should have at least two record of ABO/Rh type in the file. **Compatibility testing in special circumstances** When the blood must be issued in an emergency the patient\'s ABO and Rh group should be determined so that group-compatible blood can be given. When there is no time to obtain and to test a sample, group O Rh negative packed cells can be used. If the patient is Rh negative and large amounts of blood is needed, conversion to Rh positive is applicable if the patient is a man or is a woman beyond child bearing age. Pretransfusion testing should be completed, and any incompatible result should be reported to the physician and the blood bank medical director. When the recipient had received large amounts of alternative blood group, the additional blood group specific units may agglutinate at immediate spin due to passive expected antibody, in this case additional units should be of the alternative blood group. Current standards does not require a crossmatch test as part of the compatibility testing for the transfusion of plasma products. In intrauterine transfusion, crossmatch testing is performed using the mother\'s serum sample. O Rh negative packed RBCs should be selected for the transfusion. Blood for exchange or transfusion of a neonate (120 days old) should be compatible with any maternal antibodies either regular antibody (Anti-A and Anti-B) or irregular antibody that could cross the placenta (IgG). The blood should be as fresh as possible and not older than 7 days. Massive transfusion has occurred when the patient had received blood volume equal to patient\'s total blood volume during 24 hours. Prolonged clotting time is due to coagulation abnormalities with disease or medication. Complete coagulation of the sample with prolonged clotting time can often be accelerated by addition of thrombin, one drop of thrombin 50U/ml to 1 ml of plasma. Protamine sulfate for heparin effects specimen. Autologous transfusion refers to donor donating for himself for future procedure. Autologous donation is useful for rare blood groups. Tests for unexpected antibody and tests for transmitted diseases are not required in this case. **Important Points** I. **Collection and Preparation of Sample** - Most fatal transfusion reactions are caused by clerical errors. - Samples and forms must contain patient's full name and unique identity number. - Writing must be legible and indelible. - Date of collection must be written on sample. - Sample must be collected within 3 days of scheduled transfusion. - A blood bank specimen must have two unique patient identifiers, the date of collection, and initials or signature of the person who collected the sample. II. **Compatibility Testing** - Confirm blood type of donor. - Check patient records (history) for results of previous tests. Perform ABO grouping, Rh typing, and antibody screening on patient. - Select donor unit based on ABO group and Rh type of patient; further consider presence of antibodies in patient by antigen-typing donor unit for the corresponding antigen. - Perform immediate spin or antiglobulin crossmatch based on current or historical serologic results. - Electronic crossmatch can replace immediate spin crossmatch when two blood types are on file for the patient and antibody screen is negative. - Positive results in the crossmatch may be caused by incorrect ABO grouping of patient or donor, alloantibody or autoantibody in patient reacting with the corresponding antigen on the donor RBCs, donor having a positive DAT, abnormalities in patient serum such as increased protein concentration (rouleaux) or contaminants in test system. III. **Compatibility Testing in Special Circumstances** - Emergencies - May have to select uncross matched, group O, Rh-negative packed RBCs. - May want to give uncross matched, group O, Rh-positive packed RBCs if male patient or female patient beyond childbearing years. - May be able to provide type-specific, uncross matched RBCs. - Plasma products units - No compatibility testing required. - Transfusion to fetus - Compatibility testing performed using mother's sample. - Donor unit must lack antigen against maternal antibody. - Group O Rh-negative donor selected when fetal type is unknown or when type is known but is not compatible with mother's type. - Transfusion to infant - Maternal sample can be used for compatibility testing. - Initial sample from infant typed for ABO (front type) and Rh. - Donor unit selected should be compatible with both mother and baby.