MLPAO Transfusion Medicine Fundamentals 1 — Questions and Answers
Question 1: What are the major ABO blood group antigens and their corresponding antibodies?
- Group A has A antigen and anti-A; Group B has B antigen and anti-B
- Group A has A antigen and anti-B; Group B has B antigen and anti-A; Group O has no antigens and both anti-A and anti-B; Group AB has both antigens and no antibodies (Correct answer)
- All groups have both antigens and antibodies
- Group O has O antigen and anti-O
Correct answer: Group A has A antigen and anti-B; Group B has B antigen and anti-A; Group O has no antigens and both anti-A and anti-B; Group AB has both antigens and no antibodies
In the ABO system, individuals produce antibodies against the ABO antigens they lack (Landsteiner's rule). Group A has A antigen with anti-B, Group B has B antigen with anti-A, Group O has no A or B antigens with both anti-A and anti-B, and Group AB has both antigens with no ABO antibodies.
Question 2: What is the Rh(D) antigen and why is it clinically significant?
- A minor antigen with no clinical relevance
- The most immunogenic red cell antigen after A and B, causing hemolytic disease of the fetus/newborn and transfusion reactions (Correct answer)
- An antigen found only on white blood cells
- An antigen that causes autoimmune disease
Correct answer: The most immunogenic red cell antigen after A and B, causing hemolytic disease of the fetus/newborn and transfusion reactions
The Rh(D) antigen is the most immunogenic non-ABO red cell antigen. D-negative individuals exposed to D-positive red cells (through transfusion or pregnancy) can develop anti-D, which causes hemolytic transfusion reactions and hemolytic disease of the fetus and newborn (HDFN). Rh immunoglobulin (RhIg) prevents alloimmunization.
Question 3: What are the components of pre-transfusion testing (type and screen)?
- ABO/Rh typing only
- ABO/Rh typing and antibody screen (indirect antiglobulin test) (Correct answer)
- Crossmatch only
- Complete blood count and coagulation panel
Correct answer: ABO/Rh typing and antibody screen (indirect antiglobulin test)
Pre-transfusion testing includes: 1) ABO grouping (forward and reverse), 2) Rh(D) typing, and 3) antibody screening (indirect antiglobulin test/IAT) to detect unexpected red cell antibodies. If the antibody screen is positive, antibody identification is performed before crossmatch-compatible blood can be issued.
Question 4: What is the difference between forward (cell) typing and reverse (serum) typing in ABO grouping?
- They test for the same thing using different reagents
- Forward typing detects antigens on patient red cells using known anti-A and anti-B; reverse typing detects antibodies in patient serum using known A and B cells (Correct answer)
- Forward typing is performed first; reverse typing is a confirmation only
- Forward typing uses patient serum; reverse typing uses patient cells
Correct answer: Forward typing detects antigens on patient red cells using known anti-A and anti-B; reverse typing detects antibodies in patient serum using known A and B cells
Forward typing identifies ABO antigens on patient red blood cells by testing with known anti-A and anti-B reagents. Reverse typing detects ABO antibodies in patient serum/plasma by testing against known A1 and B reagent red cells. Both must agree for a valid ABO type. Discrepancies require investigation before issuing blood.
Question 5: What is the indirect antiglobulin test (IAT) and what does it detect?
- It detects antibodies bound to red cells in vivo
- It detects antibodies in patient serum/plasma that react with red cell antigens in vitro, using antihuman globulin (AHG) reagent (Correct answer)
- It detects complement on patient cells
- It measures red cell antigen strength
Correct answer: It detects antibodies in patient serum/plasma that react with red cell antigens in vitro, using antihuman globulin (AHG) reagent
The IAT (indirect Coombs test) detects antibodies in patient serum that have attached to test red cells during incubation. After washing to remove unbound antibodies, antihuman globulin (AHG) reagent is added, which bridges IgG-coated red cells causing visible agglutination. It is used for antibody screening, identification, and crossmatching.
Question 6: Which blood group system is most commonly associated with hemolytic disease of the fetus and newborn (HDFN)?
- ABO system
- Rh system (specifically anti-D) (Correct answer)
- Kell system
- Duffy system
Correct answer: Rh system (specifically anti-D)
While ABO HDFN is most common, Rh (anti-D) HDFN is the most clinically severe form. An Rh-negative mother carrying an Rh-positive fetus can develop anti-D, which crosses the placenta and destroys fetal red cells. RhIg (WinRho/Rhogam) prophylaxis at 28 weeks and after delivery has dramatically reduced anti-D HDFN.
MLPAO Transfusion Medicine Fundamentals 1
What are the major ABO blood group antigens and their corresponding antibodies?