Introduction to immunohaematology

1. 4 Introduction to immunohaematology BY Dr: Dalia Kamal

2. Cross matching • What are Blood Typing and Cross matching? • Blood typing is a test used to find out what specific blood type you have. Blood types are categorized using a blood typing system called the ABO system. The four main categories in the ABO system are: • Type A • Type B • Type AB • Type O • Your blood type depends on the presence of certain antigens on your red blood cells(RBCs). Antigens are proteins that cause your immune system to produce antibodies. 

3. If you need a blood transfusion or transplant, another technique called crossmatching is performed prior to the transfusion or transplant. There are several other antigens beside the major ones listed above. Crossmatching will help to detect the minor ones. Blood typing and crossmatching together are used to prevent harmful interactions between your blood and donor blood.

4. Cross matching • is a way to test your blood against a donor's blood to make sure they are fully compatible. • Crossmatching takes 45 minutes to an hour. • It's essentially a trial transfusion done in test tubes to see exactly how your blood will react with potential donor blood.

5. Steps: • 1- Collect 2ml of EDTA-anticoagulated blood from donor and recipient. • 2- Centrifuge blood samples for 1 minute in bench top centrifuge at approximately 1,000 rpm and remove plasma to prelabelled test tubes. • 3- Make a 2% red cell suspension of each specimen in physiological saline (0.85% NaCl) solution. This can be done by placing 0.02ml of concentrated red cells in 0.98ml of saline solution contained in test tube; mixing, centrifuging, and washing three times; and resuspending washed red cells in a equal volume of saline solution.

6. Major cross match Recipient plasma Donor RBCs Minor cross match Donor plasma Recipient RBCs Recipient control Recipient plasma

7. A Major cross match Donor RBC 1 drop Recipient plasma 2 drops

8. A Minor cross match Doner plasma 2 drops Recipient RBC 1 drop

9. A Recipient control Recipient RBC 1 drop Recipient plasma 2 drops

10. 4- Place two drops of the donor’s cell suspension in a test tube and mix. 5- In a second tube similarly place equal volumes of donor’s plasma and recipient’s cell suspension (minor cross match). 6-Equal volumes of doner’s cell suspension with recipient plasma (major cross match). 6- To check for autoagglutination, set up controls in the manner by mixing donor’s red cells with its own plasma. 7- Shake rack of tubes and incubate for 30 minutes at room temperature, then centrifuge for 1 minute at 1,000 rpm. 8- If no agglutination is observed, transfer a small amount to a glass slide and examine under the low power of the microscope.

11. Immediate Spin Technique (IST) 2 drops 22oC Patient serum Immediate centrifuge ABO incompatibility 1 drop, 5% Donor RBC • Detects only IgM antibody, reactive at 22oC. • Clinically significant IgG antibody reactive at 37oC not detected

12. Conventional AHG-crossmatch Detects clinically significant (IgG) antibody 2 drops AHG Mix properly 2 drops No agglutination = compatible 3 washes Patient serum 1 drop, 5% Centrifuge Incubation 37oC, 1 hr Agglutination = incompatible Donor RBC