Blood Bank Ch.8 (Compatibility Testing)
Pretransfusion Testing Special specimen collection procedure
(30 day specimen) Pertains only to people undergoing a surgery within 30 days 1. Patient signs a document saying they have not had a transfusion/been pregnant in last 3 months 2. Specimen is drawn and a type and screen performed 3. Patient enters hospital for surgery and again signs a document saying they have not been transfused/pregnant within last 3 months 4. Data from the T&S can be used for crossmatch as long as the patient had a negative Ab screen. 5. If needed patient is issued blood with a computer crossmatch
products that need to be crossmatched only if unit contains more than 2mL RBCs
Apheresis platelets Granulocyte concentrates
Autologous Blood
Autologous blood is donated by the patient for himself, usually for or during an elective surgery. Special methods must exist to ensure these units are located and transfused to intended recipient. They must be transfused before any directed or allogeneic units are transfused to recipient.
Tagging, Inspecting, Issuing, and Transfusing Blood Products
Once compatible unit is determined suitable for transfusion, the unit is tagged for that specific patient. The tag has: - the patient's first and last name - hospital number - name of product - donor number - expiration date - ABO / D type of unit - interpretation of crossmatch (if done) - identity of person doing the test or selecting unit.
Pretransfusion Testing (Specimen Collection)
EDTA tube if policy dictates - Samples for pretransfusion testing can be used for 3 days (date of collection is day 0) - 'Should be' free of hemolysis due to confusion with testing results - Should not be diluted with IV fluid; collect below the IV site - No serum separators - Must be retained in Blood Bank 7‐10 days stored at 1‐6oC (FDA requires 7 days post‐transfusion)
Transfusing Blood Products
Patient identification is vital for safe transfusion and ultimately resides with the nursing or medical personnel who hang the unit. - Wristband with patient's full name and hospital number must be on patient and must exactly match the information on unit tag - Commercial transfusion identifiers are available • Unused units may be returned to Blood Bank within 30 minutes of issue without question • Unused units may be returned at any time if stored in a monitored refrigerator (1‐10C)
Crossmatch incompatible:
When agglutination or hemolysis is present in testing. Donor unit is unacceptable for transfusion to that patient
Crossmatch compatible:
When no agglutination or hemolysis is present in any phase of testing. Donor unit is acceptable for transfusion
Compatibility testing definition
all steps in the identification & testing of a potential transfusion recipient & donor blood before transfusion in an attempt to provide a blood product that survives in vivo & provides its intended therapeutic effect in the recipient
Fresh Frozen Plasma (FFP)
blood component prepared from whole blood, contains only the plasma portion, and is frozen soon after separation to preserve coagulation factors. Must be ABO compatible with recipient's ABO Rh is not a factor (Rh antigens only on Red cells)
what tests are included in compatibility testing:
blood typing of recipient antibody screen of recipient cross match
what can be used for the crossmatch in compatibility testing in infants younger than 4 months of age:
maternal serum can be used for the cross match
Products that do not need to be crossmatched
plasma platelet concentrates cryoprecipitate
Age of sample (transfusion)
samples should be collected no more than 3 days before the scheduled transfusion
If patient dies, how does testing proceed
testing may be suspended, but enough testing should be done to show cause of death was unrelated to uncrossmatched blood.
Passive transfusion
when an antibody is transferred to the recipient from the plasma portion of a blood product during transfusion
Steps in Compatibility Testing
1. Accurate patient identification 2. Proper sample collection, labeling, handling 3. Review of recipient's past blood bank records 4. ABO and D typing, Antibody Screen, and infectious disease testing on donor units 5. ABO and D typing, Antibody Screen on recipient 6. Crossmatch recipient's serum with donor cells 7. If recipient is determined to have a clinically significant antibody, donor units are typed and found negative for corresponding antigen, and crossmatched with recipient 8. Tagging, inspection, issue of blood products 9. Re‐identification of recipient before transfusion 10. Careful observation of recipient's vital signs following transfusion and monitoring Hgb/Hct levels for benefit of transfusion
Massive Transfusion
A massive transfusion is defined as a total blood volume exchange through transfusion during a 24 hour period • i.e. blood products transfused in a 24 hour period exceed the original blood volume of the recipient (males‐10 to 12 units whole blood). • At that point the recipient's blood no longer represents his own, but that of donor blood. • Serologic testing may be temporarily suspended until it is deemed the recipient's own blood supply has returned. That time table varies with continued transfusions. • Once the blood group of recipient is determined, type specific blood should be released to conserve inventory of Group O. • If ABO identical blood begins to run out, ABO compatible units may be released. • If recipient had clinically significant antibodies all units issued should be antigen negative, but an IS crossmatch may be used instead of AHG crossmatch.
what constitutes a massive transfusion
A total blood volume exchange through transfusion during 24 hour period, or blood products transfused in a 24 hour period exceed the original blood volume of the recipient Recipient's blood no longer represents their own, but donor blood
Regulatory Organizations
AABB: American Association of Blood Banks publishes AABB Standards for Blood Banks FDA: Food and Drug Administration publishes Code of Federal Regulations CAP: College of American Pathologists JCAHO: formerly Joint Commission on Accreditation of Health Organizations, now Joint Commission
Cross match order
ABO Type Antibody Screen Crossmatch
what antibodies are detected in the immediate spin crossmatch:
ABO antibodies
one group B D pos unit of RBCs is recieved in the transfusion service. What repeat testing is required on this donor unit:
ABO typing only
Testing Limitations
Adverse reactions following transfusion may still occur in spite of acceptable crossmatching. For example: - Viral transmission, allergic or febrile reaction - Negative Antibody Screen does not guarantee absence of antibody and compatible unit in the patient Compatible crossmatch does not guarantee optimum red cell survival or expected increase in Hgb due to... Continued bleeding Liver or spleen sequestration of red cells Delayed transfusion reaction due to undetectable Ab
Pretransfusion Testing (requisition/identifiers)
Because blood and blood components are considered drug therapy a physician order (requisition) is required to perform testing or provide blood components (basically this is the same as a prescription) - Must have 2 patient identifiers: first and last name and hospital number most commonly used - Patient age or date of birth - Test is ordered as 'crossmatch' or 'type and hold' - Designation of time needed: "Routine" or "STAT" = ASAP - Contact information of requesting physician and staff to call when order is ready • Patient identity: - Wristbands with first and last name, hospital number, date of birth, etc. - Phlebotomist must ask patient his name and compare name on requisition, and preprinted specimen labels for identical information - Wristband must be attached to patient, not wall or bed • Sample collected and labeled before leaving patient bedside. - No pre‐labeled tubes should be used - Documentation of phlebotomist identity is required
detection of serological incompatibility between donor RBCs & recipient serum is performed in the:
Cross match
Crossmatch Testing
Crossmatch: mixing of cells from donor with serum/plasma from the recipient. • Hemolysis or agglutination at any phase indicates recipient antibodies reacting with donor antigens 1) Crossmatch: mix donor cells with recipient plasma 2) Immediate spin/read (may either stop here or go on) 3) Add 2 drops of potentiator 4) 37C incubate, IS and read 5) Wash 3X 6) Add AHG, IS and read
Cryoprecipitate
Cryoprecipitate: blood component recovered from a controlled thaw of FFP; The cold insoluble precipitate is rich in coagulation factor VIII, von Willebrand's factor, factor XIII, and fibrinogen. Also used to make "fibrin glue" to help seal surgical wounds and control bleeding Must remain at R.T. after thawing Expires 4 hours after pooling
Massive Transfusion Protocol (MTP)
Goal is to replicate transfusion of whole blood. • No standard method at this time • See UK and Lexington VA's MTP as an example
Which product is crossmatched with the recipient before transfusion if the unit contains greater than 2mL of RBCs:
Granulocyte concentrates
Granulocyte concentrates
Granulocyte concentrates: blood component collected by cytopheresis; Contains a minimum of 1 x 10^10 granulocytes. Contains leukocytes, platelets and 20‐50 ml of red cells Must be crossmatched and ABO/Rh compatible Maintained at room temperature and must be given within 24 hrs. following collection
what ABO & D types are selected for RBC units issued to a patient in emergency release:
Group O, D neg
Non‐Red Cell Blood Products includes
FFP Platelets Cryoprecipitate Granulocyte concentrate
(T or F) a crossmatch demonstrating a 2+ agglutination is interpreted as compatible
False
(T or F) a crossmatch detects most errors in the identification of antigens on patient RBCs
False
(T or F) an immediate spin crossmatch of a D-positive recipient with a D-negative donor unit is usually incompatible
False
(T or F) the only component that requires crossmatching is a unit of RBCs
False
1 unit of packed RBCs increase:
Hct by 3% or Hgb by 1g/dL
what incompatibilities are detected in the antiglobulin phase of a cross match:
IgG alloantibodies in recipient serum
3 Types of Crossmatches
Immediate‐spin crossmatches (IS‐XM) - Recipient plasma plus donor RBC, spin, read Computer crossmatches - Logic in computer program ensures patient ABO type is compatible with RBC unit Antiglobulin XM - IS crossmatch carried out all the way through the AHG step
Infants Younger than 4 months of age
Infants younger than 4 months have not produced their own antibodies. Any that are present are of maternal origin. At 4‐6 months, infants will begin to make their own antibodies if challenged through transfusion. Initial compatibility testing includes ABO and D typing. Reverse grouping not needed Initial antibody screen is performed on either infant's or mother's specimen. - If clinically significant antibodies are found, unit needs to be antigen negative or crossmatch compatible at AHG. - Crossmatching would continue until maternal antibody is no longer detectable. - If antibody screen is negative, no further crossmatches or antibody screen tests are needed during current admission as long as red cells used are ABO compatible with infant and specific for D typing of infant
Select uncrossmatched RBC units for issuing both male and females
Males receive O pos Females O neg Once patient is ABO/D typed they receive type specific
Pheresis platelets
Pheresis platelets (>95% of all platelet transfusions): platelets obtained from whole blood from ONE person; a single bag contains a minimum of 3 x 10^11 platelets. Platelets from one donor minimizes chance of alloimmunization (platelet and HLA antibodies) Does NOT have to be ABO or Rh compatible Rh is not a factor Must remain at rotating at room temperature and expires in 5 days of collection
compare pheresis & pooled platelets
Pheresis platelets are from one donor Pooled are from several- hence "pooled"
The Requisition
Physician's order for blood transfusion must be on file prior to issuing blood. • Person transporting blood to patient for transfusion must present a request form to blood bank staff indicating product desired and the patient for whom it is intended • This form is checked carefully and independently by both persons against the unit tag, and the unit tag information is checked against the unit label
Platelet concentrate
Platelet concentrate (<5% of all platelet transfusions): platelets obtained from whole blood; a single bag contains a minimum of 5.5 x 10^10 platelets. Usually transfused as pool of 5‐6 platelet concentrates ABO does NOT have to be compatible Rh is not a factor Must remain at rotating R.T. and expires in 5 days of collection and 4 hours after pooling
Purpose of Crossmatch
Prevent life‐threatening or uncomfortable transfusion reactions • Maximize in vivo survival of transfused RBCs • Serves as a double check of ABO errors caused by patient misidentification or donor unit mislabeling • In the presence of a clinically significant antibody or history of one, crossmatch provides second means of antibody detection and checks results of Antibody Screen. Last step to catch an incompatibility
Pretransfusion Testing Previous record review
Previous record review - AABB Standards require comparison of results of current blood type with that performed over past 12 months. - AABB also requires previous records consulted for typing problems, antibodies identified, transfusion reactions, and special transfusion requirements - All past clinically significant antibodies are to be honored regardless of results of antibody screen and/or identification in current specimen
Emergency Release of Uncrossmatched Blood
Procedures exist to issue uncrossmatched blood in an emergency. - AABB requires requesting physician must sign a request for uncrossmatched blood - A specimen and requisitions must be sent to Blood Bank for testing to begin immediately after units are released. - Segments from units are pulled prior to release to use for crossmatching after initial units have been released. - Units issued are tagged with a conspicuous tag indicating the units are UNCROSSMATCHED (AABB requirement). ABO/D typing is performed ASAP and type specific units are issued if time permits. - If patient's type is unknown, then Group O units are issued: Rh pos for males and Rh neg for females - As soon as patient's type is known, type specific units can be released. - Antibody Screen on specimen is begun immediately - Crossmatches on issued units are performed immediately - Additional units are crossmatched as needed. • If a positive result is noticed at any step of process, the patient's physician must be notified immediately. • Further transfusion should be delayed if possible, but physician must make that decision. • Antibody identification or any other unexpected problem should be resolved as quickly as possible. • The Blood Bank medical director may be notified if life threatening problem exists for the patient. Blood Bank personnel must "stay ahead" by crossmatching additional units, thawing plasma or cryoprecipitate, pooling platelets as needed. • If patient dies, further testing may be suspended depending on policy. • However enough testing should be completed to show cause of death was unrelated to transfusion of uncrossmatched blood.
An antiglobulin crossmatch is performed with a donor RBC unit. The antiglobulin crossmatch result is a 2+ agglutination reaction. What is the most likely explanation for this result:
Recipient possesses an IgG alloantibody
A recipient's antibody screen is negative, however the recipient is incompatible with the selected donor unit. what is a possible explanation:
Recipient possesses an antibody to a low frequency antigen
Selection of Compatible Blood Products
Recipients should receive ABO identical red cells whenever possible. - If transfusion of 2 mL or more of RBCs, the donor's red cells must be ABO compatible with recipient's serum • ABO antibodies in transfused plasma products should be ABO compatible with recipient's red cells • D‐positive blood components should be selected for D positive recipients. • D negative recipients should receive D negative red cells, especially women of child‐bearing age. • If recipient has a clinically significant antibody, he should receive antigen negative red cells
Crossmatch Today
The need to be cost effective led to decisions to detect only clinically significant antibodies, those that cause delayed or immediate destruction of red cells. • ABO incompatibility detection is still most significant • When Antibody Screen for clinically significant antibodies is negative, computer crossmatch is now being practiced in some hospitals
Inspecting and Issuing Blood Products
The unit is visually checked for hemolysis, clots, discoloration, or other abnormal appearance. • These checks are documented with name of person issuing the blood and the transporting person. • The date/time of issue and the unit's destination are documented. • After transfusion is complete, a copy of the tag is attached to patient's chart
Compatibility Testing vs. Crossmatch
These two terms are used synonymously. Compatibility testing includes crossmatch, but also includes: - Accurate recipient (patient) identification - Sample collection and handling - Required pre‐transfusion testing Process begins with the transfusion request and ends with the transfusion of blood product to the patient. Pre‐transfusion testing ensures the greatest compatibility between the donor unit and recipient.
Computer Crossmatch Requirements
Two identical ABO typing interpretations must have been made on recipient at present or in the past - ABO typing is always done on the current sample - The second ABO typing interpretation may be a retype of current sample, a separate current sample, or a typing in historical record - ABO typing performed by 2 technologists or 2 samples at different times by same technologist - ABO typing by an instrument counts as one typing. Each Blood Bank determines its own policy Computer system must include: • Donor unit information: product name, ABO/Rh type, unique number, and the interpretation of the ABO confirmation test • Recipient ABO/D typing • Logic to alert user to ABO incompatibility between donor unit and recipient and between donor unit label and the ABO confirmation test • Method to verify the correct entry of all data. Advantages: - Reduced plasma sample volume needed for testing - More efficient - Faster to get blood to the patient - Staffing flexibility - Better blood inventory management
Immediate Spin Crossmatch
Usage: When there is no evidence of antibodies in current sample or past history - Recipient serum + 4% saline suspension of donor RBCs mixed in tube, centrifuged immediately. - Absence of agglutination or hemolysis is negative test and unit may be considered acceptable - Detects ABO incompatibility and meets AABB/FDA Standards Incompatibility may be due to: 1. ABO incompatibility; 2. Patient serum exhibiting rouleaux 3. Patient may have cold autoantibodies or cold alloantibodies not detected in antibody screen
Computer Crossmatch
Usage: only when recipient does not have clinically significant antibodies in current or past samples • Programmed in to the Laboratory Information System • Computer checks for ABO incompatibility in selecting appropriate units for transfusion instead of serologic crossmatch. • Computer should have a flag indicating patient is eligible or ineligible for the electronic crossmatch
AHG Crossmatch
Usage: when patient has current or past clinically significant antibody - Antigen negative donor units are selected by typing units with commercial high‐titered antisera - AHG crossmatch includes IS, 37oC, and AHG phases - Enhancement media used same as Antibody Screen - Auto adsorbed serum may be used for crossmatching to eliminate masking alloantibody by autoantibody Positive reactions with AHG crossmatch may be due to: Unit may be ABO incompatible Unit may have positive DAT Unit may not have been antigen typed or designated incorrectly Patient may have antibody to low incidence antigen that was not on screening cells, but present on donor cells
Regulatory Standards
• AABB and FDA apply standards to blood banks and transfusion services in U.S. • CAP and JCAHO also inspect blood banks, etc. • AABB Standards requires - Crossmatch must be performed using recipient's serum or plasma and a segment directly from donor unit - Exception is emergency when blood may be released prior to crossmatch
AABB Standards
• AABB defines crossmatch as a technique that "shall use methods that demonstrate ABO incompatibility and clinically significant antibodies to red cell antigens and shall include a AHG test". • Exception: If no clinically significant antibodies are found in current sample nor in history, an immediate spin (IS) crossmatch is acceptable to detect ABO incompatibility.
Transfusion to Infants Younger Than 4 Months of Age
• Donor centers usually provide attached satellite bags to transfusion services that transfuse infants. • These attached satellite bags allow a full donor unit to be divided into 4 smaller units called "pedipacks". • The pedipacks can be further subdivided into smaller aliquots allowing entry through injection sites by syringe for much smaller aliquots for transfusion (5‐10ml). • This method transfuses the same infant(s) repeatedly if multiple transfusions are needed. This limits exposure to undetected diseases or immunologic stimuli from donor blood.
Pretransfusion Testing for Non‐Red Cell Products
• Frozen plasma, platelets and cryoprecipitate contain almost no red cells and do not need to be crossmatched. • Granulocyte concentrates do contain some red cells (>2 mL) and must be crossmatched.
Type and Hold Protocols
• Some surgery procedures use little or no blood. • The physician will request a 'TH' indicating only to perform ABO/D typing and Antibody Screen. • Unless clinically significant antibodies are detected, Type and Hold order for surgery patients will require no units crossmatched, but merely set aside in case of unexpected need. • If clinically significant antibodies are detected then antigen negative units are crossmatched and held for possible transfusion to the patient.
Maximum Surgical Blood Order Schedule (MSBOS)
• To expedite surgery requests for blood, some facilities have developed with the approval and cooperation of their surgeons, a list of surgery procedures and the number of units required for each one. • This is done by obtaining the average number of units used for the various procedures. • The Blood Bank personnel can manage blood inventory by looking at surgery schedule for next day and knowing how many units should be available.
