PRE-TRANSFUSION COMPATIBILITY TESTING

Transcription

1 PRE-TRANSFUSION COMPATIBILITY TESTING I. Purpose: To select red blood cell components that will: A. Have acceptable survival when transfused. B. Not harm the recipient. II. Requirements: According to AABB Standards for Blood Banks and Transfusion Services, the following procedures must be part of pre-transfusion compatibility testing for any components containing red blood cells (RBCs): A. Positive Identification of Recipient and Recipient s Blood Sample The MOST important step! The majority of transfusion related deaths are due to errors in patient identification 1. Request (considered a prescription) must include: a. Two independent, unique patient identifiers. May include any of the following, according to institutional policy: 1) Recipient s first and last name. 2) Medical record number or registration number. 3) Date of birth 4) Social Security Number 5) A commercially prepared Blood Bank armband with a unique alphanumeric identifier. b. Component and number of units requested, along with any special processing requirements (e.g. irradiation, CMV negative). c. Name of responsible physician. 2. Specimen requirements: a. Labeling 1) Compare request form information to recipient s identification band. 2) Specimen must be labeled at the patient s bedside with the 2 unique patient identifiers, date of collection, and identification of phlebotomist. Additional information may be required be institutional policy. CLS 422 Clinical Immunohematology I Student Lab Page 1 of 7

2 3) All information on the request and specimen label must be accurate and legible. If there is doubt as to the recipient s identity, a new specimen should be collected. b. Acceptable Specimens: 1) Plasma often from an EDTA specimen a) Advantages - no fibrin clots, better volume yield b) Disadvantages - small fibrin strands, complement is inactivated 2) Serum must not be from a gel separator tube a) Advantages - does not interfere with complement-dependant antibodies b) Disadvantages - must wait for clotting process to complete before testing; clinically insignificant complement-dependant antibodies may complicate testing c. Age of specimen 1) Samples from patients who have been pregnant or transfused within preceding 3 months must be collected within 3 days of transfusion. 2) Once the initial testing is complete, additional units may be crossmatched using the original specimen for the next 3 days. (Collection day is day 0) d. Storage of specimen - recipient s blood sample and sample of donor s RBCs must be kept at 1-6 o C for at least 7 days after transfusion. B. ABO and Rh Typing of Recipient s Blood 1. Any discrepant results should be resolved before blood is transfused. In emergency situations, if the discrepancy cannot be resolved in a timely manner, transfuse O Rh Negative packed red blood cells and AB plasma products. 2. Weak D testing is not required on the recipient s specimen, according to AABB Standards. C. Antibody Screen on Recipient s Plasma or Serum: 1. Detect as many clinically significant antibodies as possible. a. Method must include incubation at 37 o C followed by an antiglobulin test, using a reagent that contains anti-igg. CLS 422 Clinical Immunohematology I Student Lab Page 2 of 7

3 b. Each negative AHG test must be followed by a control system (tube method). Other test methodologies are controlled as directed by the manufacturer, and as approved by the FDA. 2. Detect as few clinically insignificant antibodies as possible. a. The I.S. phase may be omitted to eliminate those antibodies reacting predominantly at temperatures below 37 o C. b. Monospecific anti-igg AHG reagent may be used rather than polyspecific antiglobulin containing anti-c 3 d, since reagents that contain anti-complement activity enhance detection of antibodies that are clinically insignificant. 3. If the recipient has a history of clinically significant antibodies, testing need only show that no additional antibodies have been formed (selected cell panel). 4. Complete the procedure in a timely manner. - Time of incubation is dependent on enhancement used. D. Check of Recipient s History 1. Record of ABO/Rh 2. History of clinically significant antibodies 3. Difficulties working with recipient s specimen (e.g. rouleaux, cold agglutinins, etc.) 4. Special transfusion requirements (e.g. irradiation, CMV Negative, etc.) 5. Previous adverse reactions to transfusion 6. Additional information that may be useful includes: a. Transfusion history, including date of last transfusion. b. Diagnosis c. Current medications or treatment d. Age of recipient 7. If records are computerized, there must be a mechanism for performing the records check during computer downtimes. CLS 422 Clinical Immunohematology I Student Lab Page 3 of 7

4 E. Test on Donor s Blood (performed by collecting facility) 1. ABO and Rh (including weak D) 2. Screen for unexpected antibodies, if donor has a history of transfusion or pregnancy. 3. Infectious diseases: a. Hepatitis B surface antigen (HbsAg) [earliest indicator of hepatitis infection] b. anti-hbc c. anti-hcv d. anti-hiv 1 / 2 e. anti-htlv I / II [cancer causing viruses] f. serologic test for syphilis (STS) g. West Nile virus (seasonal) h. NAT testing used for HCV RNA and HIV-1 RNA (detects as few as 10 copies of viral RNA) 4. Transfusion service confirms the ABO on each unit and the Rh of Rh Negative units before transfusing. F. Selection of Red Blood Cell Units 1. ABO/Rh type appropriate for recipient a. ABO specific blood should be given whenever possible. Circumstance may dictate use of group compatible but not group identical (group specific). 1) Neonates may receive Group O units to avoid maternal anti-a, -B,-A,B. 2) Patients with a positive DAT due to anti-a, -B, or -A,B may be given group O. 3) Unavailability of certain groups (e.g. AB, may be given another group) 4) In order to meet special requirements (antigen negative, CMV Negative) another group may be given. CLS 422 Clinical Immunohematology I Student Lab Page 4 of 7

5 b. Rh 5) In cases of urgent need, O Rh Negative units are given until ABO/Rh of recipient can be determined. The physician takes full legal responsibility, documented by the signing of an Emergency Release Form. 1) Rh Negative units may be given to an Rh Positive individual. 2) Rh Negative individuals should receive Rh Negative RBC units. 3) In the rare instances (availability) that Rh Positive units must be given to an Rh Negative recipient, it may be necessary to obtain approval from the Medical Director. There should be a policy to evaluate the need for Rh Immune Globulin (RhIG) in the recipient to prevent stimulation of anti-d. 2. Antigen negative If the recipient has a clinically significant antibody, the donor units selected must be negative for the corresponding antigen. G. Performance of crossmatch 1. Serologic crossmatch - 2 drops of the recipient s plasma (or serum) and 1 drop of a 2-5% suspension of donor red blood cells. Donor sample comes from a segment that is attached to the unit. a. If the screen for unexpected or clinically significant antibodies is negative and there is no history of clinically significant antibodies, an immediate spin crossmatch [ISXM] is all that is necessary in order to confirm ABO compatibility. b. If the screen for unexpected or clinically significant antibodies is positive or if the recipient has a history of clinically significant antibodies, I.S., 37 o C and AHG phases are performed using units that are negative for the target antigen(s) [AGXM]. 1) The I.S. phase detects ABO incompatibility. 2) The 37 o C and AHG phases are performed to verify donor compatibility with the recipient s antibody. 2. Computer (electronic) crossmatch - If the antibody screen is negative and there is no history of clinically significant antibodies, a computer crossmatch may take the place of the I.S. crossmatch, provided the following: CLS 422 Clinical Immunohematology I Student Lab Page 5 of 7

6 a. The computer system and computer crossmatch procedure have been validated on-site to insure only ABO compatible components can be selected for transfusion. b. Incorrect and nonsensical data must be recognized and rejected by the system. c. There have been 2 determinations of the recipient s ABO and Rh (one determination must be made from the current pretransfusion specimen). d. The computer logic will detect and alert the user to discrepancies between the ABO/Rh on the unit label and the ABO/Rh entered when the unit was retyped. e. Computer logic will detect and alert the user to ABO/Rh incompatibility between the unit and the recipient. f. Advantages of the computer crossmatch include: 1) Smaller amount of sample needed 2) Reduced use of supplies and reagents 3) Fewer false positive reactions to investigate 4) Reduced handling of samples by laboratory personnel 5) Reduced inventory of RBC units is often possible 3. Recording Results a. The Code of Federal Regulations (CFR) mandates that results of compatibility testing be recorded immediately after observation, in a permanent fashion that follows a logical system allowing for easy retrieval. b. Both observations (reactions) and interpretations should be recorded. c. There should be a record identifying the person performing the testing. d. Incompatible tests should be identified, and follow up work to resolve the incompatibility documented. H. Labeling and identifying components with recipient s information 1. Unit tag/label must include: a. Patient s 2 unique identifiers, as they appear on the armband, request and specimen. b. Interpretation of compatibility test CLS 422 Clinical Immunohematology I Student Lab Page 6 of 7

7 c. Identification number of donor unit 2. Tag/label may also include: a. ABO/Rh of recipient and donor b. Expiration date of unit and of crossmatch c. Identification of person performing compatibility test III. Functions of Pretransfusion Compatibility Testing A. Pre-transfusion testing will: 1. Verify ABO compatibility 2. Ensures that the recipient is issued designated blood components 3. Detects most clinically significant antibodies B. Pre-transfusion testing will not: 1. Guarantee that the recipient will not be stimulated to form a new antibody (alloimmunization) 2. Detect all clerical errors 3. Detect Rh testing errors 4. Detect antibodies to antigens not present on the screen cells, or antibodies to white blood cell or platelet antigens CLS 422 Clinical Immunohematology I Student Lab Page 7 of 7