cross match and transfusions

Question 1

What antigens and antibodies are present in the 4 blood groups

Answer 1

Group A = A antigen and b antibodies

Group B = B antigen and A antibodies

Group AB = AB antigens and no antibodies

Group O = no antigens and AB antibodies

Question 2

What is the RhD blood group

Answer 2

• Majority of people are rhesus positive
• People who are rhesus negative have potential to make anti-D antibodies if exposed to the RhD antigen in positive blood like in pregnancy or transfusion
• Anti-D antibodies can cause haemolytic disease of newborn and contractions

Question 3

What is forward grouping

Answer 3

• Tests the patients antigen
• Tests the presence of A or B antigens on patients RBCs
• 3-5% of patients red cell suspension
• Monoclonal antisera (Anti-A and anti-B) cells are added
• Haemagglutination if antigen present

Question 4

What is reverse grouping

Answer 4

• Tests the patients antibodies
• Test patient plasma for Anti-A and Anti-B antibodies
• Patient plasma added to suspensions of group A1 red cells and group B red cells
• Expression of antigen varies - if strong A1
• A1 antigen suspension used to test reverse grouping to improve validity

Question 5

What is involved in an antibody screening test

Answer 5

• Used to screen plasma for other red cell antibodies other than Anti-A and Anti-B
• Plasma incubated in panel of screening reagent red cells expressing significant antigens
• Alloantibodies are present if haemagluttination occurs

Question 6

What is involved in an antibody identification test

Answer 6

• Performed if the screening test is positive
• Red cell antibody identified and donor blood must be cross matched to make sure it doesn’t have that antigen
• Specific RBC panels are used to identify alloantibodies
• People can develop alloanibodies to other blood group antigens if exposed to them eg. Transfusion of pregnancy

-Patient plasma added to red cell suspension and looked at for haemagglutination

Question 7

What steps are involved in the final crossmatch

Answer 7

• Final check ABO compatibility between donor and recipient
• Electronic crossmatch- faster, less waste, reduced lab work, can’t be used for patients with significant allo antibodies

-Serological crossmatch- Plasma of patient added to donor red blood cells