L03. Ch 11 - Pretransfusion Testing PDF

PRETRANSFUSION Chapter 11 TESTING PREAMBLE  PowerPoints are a general over view and are provided to help students take notes over the video lecture ONLY.  PowerPoints DO NOT cover the details needed for the Unit exam ...

PRETRANSFUSION Chapter 11 TESTING PREAMBLE  PowerPoints are a general over view and are provided to help students take notes over the video lecture ONLY.  PowerPoints DO NOT cover the details needed for the Unit exam  Each student is responsible for READING the TEXTBOOK for details to answer the UNIT OBJECTIVES  Unit Objectives are your study guide (not this PowerPoint)  Test questions cover the details of UNIT OBJECTIVES found only in your Textbook! 1  COMPREHENSIVE PROCESS USED TO SELECT BLOOD FOR A PATIENT Identification of the patient and donor and collection of appropriate samples for testing. Testing of the donor sample. Testing of the patient sample and review of past blood bank records. Selection of appropriate donor units Crossmatching Re-identification of the patient before infusion of blood. PROBLEMS No testing procedure can prevent sensitization of the recipient to foreign red blood cell antigens No testing can avoid a delayed transfusion reaction caused by antibody present in subdetectable amounts No testing can guarantee normal survival of transfused cells 2  TRANSFUSION Benefits of transfusion should always be weighed against the potential risks Results more favorable if pretransfusion testing is carefully performed COLLECTION AND PREPARATION OF SAMPLES AABB Standards require following information on request forms First and last name Hospital number Helpful information Sex, age Diagnosis History Physician 3  POSITIVE PATIENT IDENTIFICATION Labeling 80% of transfusion deaths are due to clerical errors Clerical errors are the greatest threat to safe transfusion therapy. Exact procedures for proper identification of the patient, patient sample, and donor unit must be established and used by all staff responsible for each aspect of transfusion therapy in order to prevent the occurrence of errors. IDENTIFICATION Patient’s wristband I.D. must always be compared with the requisition form Any discrepancies must be completely resolved before sample is taken If the patient does not have a wristband or if identity is unknown, some form of positive identification must be attached to the patient before collection. 4  IDENTIFICATION Commercially manufactured identification systems using preprinted tags and numbers Physical barrier – plastic combination lock matching the combination from the patient’s wristband. COLLECTING PATIENT SAMPLES No hemolysis – will mask activation of complement by antigen/antibody complexes Serum – preferred – tests for complement Plasma – cannot test for complement – small fibrin clots difficult to distinguish from agglutination 10 ml of blood for testing if no serological problems 5  COLLECTING PATIENT SAMPLES Tubes must be labeled at bedside Compare with the patient's wristband and requisition Labels attached to tubes in tamperproof manner Writing MUST be legible COLLECTING PATIENT SAMPLES Label with Patient’s full name Hospital ID number Date of sample collection Phlebotomist must initial Additional pertinent information by SOP of facility 6  COLLECTING PATIENT SAMPLES No samples taken from IV tubing lines Samples should not be drawn from above an infusion unless disconnected for 5 to 10 minutes – first 10 ml taken should be discarded Blood bank tech must confirm the information before testing performed All discrepancies must be resolved COLLECTING PATIENT SAMPLES Tested as soon as possible Serum separated from red blood cells as soon as possible after clotting If testing cannot be performed immediately, if not stoppered and kept at 1 to 6 0 C Perform within 72 hours after collection WHY? 7  ADDITIONAL INFORMATION  Cells can be washed before use to remove plasma or serum – interfere with testing  2 to 5% suspension of red cells  Follow manufacturers directions DONOR SAMPLES  Samples for donor testing must be collected at the same time as the full donor unit.  Donor information and medical histor y card  Unique number code on donor unit  Donor cells obtained from segments 8  DONOR SAMPLES Donor segment is saved in a properly labeled test tube Donor and recipient samples must be stored for a minimum of 7 days following transfusion Carefully labeled and kept 1 to 6 0 C Adequate volume for retesting in case of a transfusion reaction. COMPATIBILITY TESTING PROTOCOLS Testing donor samples at collecting facility AABB standards ABO and Rh grouping including a test for weak D and Du Tests to prevent disease transmission Screening test for unexpected antibodies 9  TESTING DONOR SAMPLES Transfusing facility Confirm ABO and Rh cell grouping Weak D or D u not required Testing performed using in-date, licensed reagents according to manufactures’ directions Follow protocol of facility COMPATIBILITY TESTING PROTOCOLS Testing of Patient’s Sample Record of all results must be maintained Records must be retrievable Same ID number assigned each time a patient is admitted for treatment Verification of previous results Any discrepancies must be resolved 10  TESTING PATIENT’S SAMPLE Records include ABO and Rh grouping Notations concerning unusual serologic reactions Identity of unexpected antibodies Most important, in case subdetectable antibodies in current sample ABO and Rh and antibody screening of the patient’s serum can be performed in advance or at the same time of as the crossmatch TESTING PATIENT’S SAMPLE Medical history Medications Recent blood transfusions Previous pregnancies 11  ABO GROUPING ABO group is most critical pretransfusion serologic test Performed on slides or in tubes Tubes offer greater sensitivity Must resolve ABO discrepancies If miss ABO grouping cannot be determined anywhere else in tests RH GROUPING Rh testing with anti-D Rh control run with Rh tests to avoid Rh-negative patients as Rh positive If control is positive – Rh test is invalid DAT then performed on patient’s RBCs To determine if autoantibodies or alloantibodies is responsible for positive control 12  RH GROUPING Positive DAT found – Rh can be performed using special reagents If Rh group of recipient cannot be determined and transfusion is essential, Rh negative blood should be given Test for weak D is not necessary, given Rh negative blood Some patients who type as Rh positive may produce anti-D following transfusion ANTIBODY SCREENING Unexpected antibodies Object to detect many clinically significant antibodies as possible Clinically significant Reactive at 37 0 C and/or Coombs Known to have caused transfusion reaction ABO, Rh, Kell, Duffy, Kidd, SsU, Sometimes Le a, MN, P 1 , Lutheran (Lu a, Lu b) 13  ANTIBODY SCREENING ABO most critical Most other antibodies do not cause HTR Detection of unexpected antibodies important Selection of donor RBC that are likely to survive in patient’s circulation Weakly reactive antibodies that are capable of reacting with their antigens at 37 0C decrease survival ANTIBODY SCREENING Testing is performed using selected group O red cells that are known to carry optimal representation of important blood group antigens Testing can be performed well in advance of anticipated transfusion, allowing ample time for identification of any unexpected antibody Incubation of screening tests at or below room temperature is not advocated Antibodies that react at lower temps in vitro do not complex with antigens in vivo 14  ANTIBODY SCREENING Screening cells are single or pooled donor Group O cells. However, single screening cells offer more sensitivity. Screening cells come in 2 or 3 vials each. Each vial (donor) has been phenotyped for each antigen. 18 antigens are required on at least one of the vials: D, C, E, c, e, M, N, S, s, P 1 , Le a , Le b , K, k, Jk a , Jk b , Fy a and Fy b ANTIBODY SCREENING Antigen lacking from one cell is present on the other One sample in each set should carry the products of homozygous genes for Jk a and c If antigen is heterozygous may not react Anti-IgG Coombs reagent is used Sensitivity enhanced by increasing serum and albumin or PEG 15  ANTIBODY SCREENING Screening cells can be treated with proteolytic enzymes (papain or ficin) to enhance detection of some antibodies Rh and Kidd Other antibodies are lost when treated with enzymes Anti-Ml, N, S. Fya and Fy b More sensitive testing required by Those with known antibodies Unexplained transfusion reactions GET YOUR PHONES READY!  https://play.kahoot.it/v2/?quizId=dcaa50c7-d36d-4242-af90- f727a1a51b72 16  BREAK TIME SELECTION OF APPROPRIATE DONOR UNITS Patient’s own ABO and Rh group If unavailable, use blood that does not contain all of the antigens carried on the patient’s own RBC’s A or B packed cells can be given to an AB person Group O packed cells can be used for all patients 17  SELECTION OF APPROPRIATE DONOR UNITS Rh negative can be given to Rh positive Rh positive should not be given to Rh negative women of childbearing age If emergency, Rh positive is acceptable to Rh negative if no anti-D present 80% of Rh neg who receive 200 ml Rh pos cells form anti-D Must be signed off by Medical Director CHOICE OF ALTERNATIVE BLOOD GROUPS (SEE CHART) Patient’s Blood Group Alternative Blood Group O None A O B O AB A, B, O 18  CROSSMATCHING OR COMPATIBILITY TESTING Crossmatching Donor cells with patient’s serum Compatibility Testing Review of patient’s past blood bank history and records ABO and Rh grouping of donor and recipient Antibody screening Crossmatch CROSSMATCHING 99% of significant antibodies found in screening Two main functions of crossmatch Final check of ABO compatibility between donor and patient Detect presence of antibody in patient’s serum that will react with donor cells not on screening cells. 19  CROSSMATCHING I. Type and Screen Patients undergoing surgical procedures in which blood is unlikely to be used II. Minor crossmatch Similar to reverse ABO grouping (donor serum with patient cells) Eliminated (no longer performed) Low incident antibody in donor probably not cause a transfusion reaction MAJOR CROSSMATCH TESTS III. Immediate Spin Crossmatch Mix patient’s serum and donor cells and centrifuge immediately Absence of hemolysis or agglutination indicates compatibility IV. Type & screen with an immediate spin crossmatch referred to as abbreviated crossmatch 99.9% effective in preventing occurrence of incompatible transfusion 20  ANTIGLOBULIN CROSSMATCH Immediate spin Albumin or PEG added 37 0 C incubation Coomb’s reagent added Auto control usually done, although AABB Standards does not require it INTERPRETATION OF RESULTS Tubes must be labeled so that contents can be identified at any stage Supernatant should be examined for hemolysis – positive Use wiggle and tilt method to read button Violent shaking or tapping of tubes may give false negative response Jagged button edge is indicative of positive result 21  INTERPRETATION OF RESULTS Smooth button edge and swirling free cells indicate a negative reaction. Negative results are read microscopically Negative crossmatch and negative antibody screen does mean that no RBC antibodies are present. 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.  Three steps are required for this process: 1. The patient's ABO group and Rh type has been done twice and entered in the computer (one group can consist of a record but one must be done on a current in-date specimen).  The computer must alert the technologis t if there is a discrepancy between the two groups. 2. The donor ABO (and Rh types, if negative) have been confirmed and entered in the computer. The donor' unit identification number, component name, and ABO/Rh type must also be entered in the computer (manually or by scanning the bar code label on the unit).  The computer system will alert the technologist to ABO & Rh discrepancies between information on the donor label and results of donor confirmatory testing. 22  COMPUTER CROSSMATCH 3. The computer system will alert the technologist to ensure correct data entry and interpretation, e.g., prevent group O test results from being misinterpreted as group A.  The computer system will alert the technologist to ABO and Rh discrepancies patient and donor groups.  The program should be programed to prevent assigning ABO incompatible blood (e.g., group A red cells to a group O recipient) and to give an alert when assigning Rh-positive red cells to Rh- negative recipients. COMPUTER CROSSMATCH  An electronic crossmatch is nothing more than using a computer to assign a unit of blood to a patient.  The sole purpose of the electronic crossmatch is to confirm ABO compatibility between patient and donor.  It cannot prevent hemolytic transfusion reactions caused by patient antibodies that are missed by the antibody screen; it cannot prevent hemolytic reactions due to patient misidentification errors.  Note: Most transfusion services do not yet use the electronic crossmatch because their information systems do not meet the AABB criteria. 23  RESOLVING INCOMPATIBILITIES Positive results requires explanation Antibody screening test reviewed Auto control test reviewed CAUSES OF POSITIVE RESULTS Incorrect ABO grouping of patient or donor Alloantibody in patient’s serum If red cells of all donors are not compatible, screening cells positive – antibody against antigen of high incidence or multiple antibodies Screening negative and only one donor positive – low incident antibody Screening negative, anti-A 1 24  CAUSES OF POSITIVE RESULTS Autoantibody in patient’s serum reacting with corresponding antigen on donor red cells Auto control will be positive Perform Panel Prior coating of donor red cells with protein DAT CAUSES OF POSITIVE RESULTS Abnormalities in patient’s serum A/G ratio imbalance – multiple myeloma Plasma expanders present Antibody against additives in albumin may cause false-positive Contaminants in test system Dirty glassware Bacteria contaminant Chemical contaminants in saline Fibrin clots Review Table 11-4 for causes of positive Pretransfusion Tests. 25  EMERGENCY BLOOD RELEASE Get a pretransfusion sample from patient if possible Give O negative units Change to O positive if patient is not a woman of child bearing age. Get emergency requisition signed by physician Perform type and antibody screen on patient’s pretransfusion sample Group specific should be given as soon as possible TRANSFUSION OF PLASMA PRODUCTS Pretransfusion testing is not required Plasma units should be compatible with the recipients ABO RBC type If large amounts given Donor plasma and patient cell testing may be performed 26  NEONATAL TRANSFUSIONS Blood for an exchange or regular transfusion of a neonate (younger than 4 months of age) should be compatible with any maternal antibodies that have entered the infant’s circulation and are reactive at 37°C or AHG. ABO and Rh testing required. Antibody detection testing required. Blood should be as fresh as possible, not older than 7 days. INTRAUTERINE TRANSFUSIONS Blood for intrauterine transfusion must be compatible with maternal antibodies capable of crossing the placenta. Fetal ABO and Rh known/not known situations for group specific/group O Rh negative products Check for maternal antibodies/donor antigens. No fetomaternal ABO or Rh incompatibility Crossmatch testing is performed using the mother’s serum sample. 27  MASSIVE TRANSFUSIONS Total blood volume within 24 hours Compatibility testing can be eliminated at the discretion of the transfusion service physician following policy If known to have antibody, all units tested to be sure the offending antigen is not present If no time, decision can be made to give antigen and treat immune problem later SPECIMENS WITH PROLONGED CLOTTING TIME Problems with clotting Medication Coagulation abnormalities Fibrin clots may form Interfere with agglutination readings May add thrombin to speed up clotting Small amount of protamine sulfate can be added to counteract effects of heparin 28  AUTOLOGOUS TRANSFUSION Removal and storage of blood or components from a donor for donors use ABO and Rh groups of units are tested Tests for unexpected antibodies and tests for disease transmission are not required Units are labeled “For Autologous Use Only” LIMITATIONS OF COMPATIBILIT Y TESTING No current testing procedure can guarantee “problem free” testing Some RBCs may not survive normally in recipient Some units may hemolyze In vivo compatibility can be determined by labeling donor cells with radioactive chromium 29  EFFECTIVE BLOOD UTILIZATION Aware of the need to use blood efficiently Maximum surgical blood order schedule (MSBOS) helps to promote efficiency Establish realistic blood ordering Agreed on by staff surgeons Type and screen REIDENTIFICATION OF PATIENT Final link is to reestablish of identity of intended recipient and selected donor product Actual product and accompanying record of testing must be verified as relating to the same donor unit Two records Statement of compatibility retained as part of patient’s record Label or tag attached to the unit stating the identity of the recipient and donor unit 30  REIDENTIFICATION OF PATIENT Before blood is removed from blood bank to patient Person releasing blood and person picking up unit must verify all information Before transfusion, two professionals must verify identity of patient If unit is returned to blood bank Within specified time frame Not entered Not warmed above 10 0C or below 1 0C FUTURE OF COMPATIBILIT Y Progressing rapidly Red Cell Substitutes Automation with pretransfusion testing – continuous flow or batch analyzers Microplates Solid phase Dry plate Point of care testing Dipstick tests dot immunobinding Specific and sensitive NASA – use in space 31  POSTAMBLE  READ the TEXTBOOK for the details to answer the UNIT OBJECTIVES.  USE THE UNIT OBJECTIVES AS A STUDY GUIDE  All test questions come from detailed material found in the TEXTBOOK (Not this PowerPoint) and relate back to the Unit Objectives 32