Guide Questions: 1.
What is detected by the immediate spin phase?
Designed to detect compatibility of IgM type type of antibodies in patient's serum against antigen on donor red cells in saline phase, i.e. ABO compatibility testing. IgM antibodies react best at cold temperatures. An immediate spin, saline major crossmatch used to determine ABO compatibility in patients with no demonstrable clinically significant antibodies and a negative history of antibody formation. Under some conditions, this determination of ABO compatibility can also be accomplished by an electronic crossmatch. This is performed if: a. There is no clinically significant unexpected antibodies detected in the antibody screen using reagent red blood cells that are not pooled. b. There is no record of previous detection of clinically significant antibodies.
2.
What is detected by the warm saline phase?
Where the immunologic reaction between red cells suspended in saline medium and the antibody occurs at room temperature. IgG antibodies react best at warm temperatures, and a nd no visible agglutination commonly seen.
3.
What is detected by the high protein phase
Where the red cells are suspended in the antibody (serum) with 22% albumin (protein) and incubated for 30 min at 37C. The high protein environment enhances agglutination of univalent antibodies such as Rh group. The modern use of LISS has helped to reduce the incubation time for 30 to 15 min. use of LISS eliminates the use of albumin. The high protein phase can demonstrate antibodies in the Rh system. Presence of agglutination or hemolysis indicates incompatibility. incompatibility. The high protein phase does not only strengthen or enhance the reactions but also reveals antibodies not demonstrable by the saline-antiglobulin test. Causes agglutination by adjusting zeta potential between RBCs. Detects IgG type of antibody.
4. What is detected by the AHG phase? In addition to saline phase compatibility testing (IgM antibodies detection), AHG testing is designed to detect compatibility of IgG type of antibodies in patient's serum against antigen on donor's red cells. AHG phase involves the addition of antiglobulin sera to the incubated test tubes. With this addition, antihuman antibodies present in the sera become attached to the antibody globulin in the RBCs, causing agglutination. The antiglobulin phase detects most incomplete antibodies in the blood group systems, including Rh, Kell, Kidd and Duffy BGS. AHG acts as a bridge cross-linking red cells sensitized with IgG antibody or complement. AHG has specificity for the FC portion of the heavy chain of the human IgG molecule or complement components. Modern Blood Banking and Transfusion Practices By Denise M Harmening Page67-69
Post Lab Conference Questions: 1. How is an incompatible cross match resolved or further investigated? a. ABO grouping should be immediately repeated, especially if strong compatibility is observed in a reading taken after immediate spin. b. If the antibody screening test is positive, antibody identification panel studies would allow antibody specificity; which then permits selection of units lacking the antigens for compatibility testing c. Monitor the patient for signs of delayed hemolysis d. A DAT should be performed on the Donor’s RBC e. Problems with rouleaux can be often resolved using the saline replacement technique. f. Compatibility testing could then be performed using the autoabsorbed serum. (autoadsorption of the patient’s serum to remove autoantibody activity) 2. What are the different precautions and sources of error in the serologic cross match? Precautions: Handle the sample gently to prevent hemolysis, which can mask hemolysis, which can mask hemolysis of the donor’s RBCs. Label the sample with the patient’s name, the hospital or blood bank number, the date, and the phlebotomist initials.
Indicate on the laboratory request the amount and type of blood component needed. If more than 72 hours have elapsed since an earlier transfusion. Previously crossmatched donor blood must be crossmatched with a new recipient serum sample to detect newly acquired incompatibilities before transfusion. If the patients scheduled for surgery and has received blood during the past 3 months, be aware that his blood needs to be crossmatched again if his surgery is rescheduled to detect recently acquired incompatibities.
Sources of error: 1. Incorrect ABO grouping of the patient or donor. 2. All alloantibody in the patient’s serum reacting with the corresponding antigen on donor RBCs. 3. An auto antibody in the patient’s serum reacting with the corresponding antigen on donor RBCs. 4. Prior coating of the donor RBCs with protein, resulting in a positive anti human globulin test. 5. Abnormalities in the patient’s serum. 6. Contaminants in the test system 3. What are the different types of cross matching? There are two types of cross matching (i) major cross matching and (ii) minor cross matching. Major cross matching, the cells of the donor are directly matched against the plasma of recipient. It is important to ensure that antibodies present in the recipient’s plasma do not harm the donor’s red cells. Minor cross matching, the donor’s plasma is checked against the red cells of the recipient. It is called minor cross matching against because it is not so important, as the small volume of the donor’s plasma is diluted in a large volume of the recipient’s plasma. Therefore, the titre of antibodies present in the donor’s plasma falls to such a low level after transfusion that they are quite unlikely to damage the red cells of the recipient. Reference: Nursing: Deciphering diagnostic tests: edited by Lippincott Williams & Wilkins page 177; Modern Blood Banking and Transfusion Practices By Denise M Harmening Page 249 Textbook Of Practical Physiology - 2Nd Edn. By G.K. & Pal, Pal, Pravatipg 98
Angeles University Foundation College of Allied Medical Professions
Written Report in Blood Banking (Lab) Crossmatching
Submitted By: Bautista, Jericho Escoto, Jannie Hazel Pineda, Katreena Marie Serrano, Sheena
Submitted to: Mrs. Engracia Arceo Mr. Michael Tanglao
