MLPAO Transfusion Medicine Advanced Practice Flashcards

What is the antibody screening cell (screening cells) composition and why are they group O?

Answer: Group O cells lack A and B antigens, preventing ABO antibodies from masking other clinically significant antibodies

Antibody screening cells are always group O to avoid reactions with naturally occurring anti-A and anti-B (which are expected and clinically managed through ABO-compatible crossmatch). Using group O cells ensures that only unexpected, potentially clinically significant antibodies are detected. Screening cells express a wide range of clinically significant antigens.

What is phenotype matching and when is it clinically important?

Answer: Extended antigen matching beyond ABO/Rh(D) to prevent alloimmunization in patients requiring chronic transfusions

Phenotype matching involves selecting donor red cells that match the patient's extended red cell antigen profile (typically Rh (C, c, E, e) and Kell, sometimes Duffy, Kidd, and MNS). It is particularly important for patients with sickle cell disease, thalassemia, and other conditions requiring chronic transfusion to reduce alloimmunization risk.

What is the febrile non-hemolytic transfusion reaction (FNHTR) and how is it managed?

Answer: A temperature rise ≥1°C during or within 4 hours of transfusion without hemolysis, caused by cytokines or recipient antibodies against donor white cells

FNHTR is characterized by fever (≥1°C rise), chills, and rigors during or within 4 hours of transfusion, without evidence of hemolysis. It is caused by cytokines accumulated during storage or by recipient anti-HLA antibodies reacting with residual donor leukocytes. Pre-storage leukoreduction has significantly reduced FNHTR incidence. Management includes stopping the transfusion, ruling out hemolytic reaction, and administering antipyretics.

What is the warm autoimmune hemolytic anemia (WAIHA) and how does it complicate transfusion?

Answer: IgG autoantibodies that react with patient's own red cells at 37°C, causing hemolysis and making crossmatch incompatible with all donor units

WAIHA is caused by IgG autoantibodies (usually anti-e or anti-Rh specificity) that react at 37°C with the patient's own red cells. The autoantibody reacts with all panel cells and all donor units appear incompatible. Special techniques (autoabsorption, alloadsorption) are needed to exclude underlying alloantibodies. 'Least incompatible' blood may need to be issued in life-threatening situations.

What is the Lewis blood group system and why are Lewis antibodies usually clinically insignificant?

Answer: Lewis antibodies are typically IgM, cold-reactive, and do not cause HDFN because Lewis antigens are not well-developed on fetal red cells and are adsorbed from plasma

Lewis antibodies (anti-Lea, anti-Leb) are typically IgM, react at room temperature or below, and are usually clinically insignificant. Lewis antigens are not intrinsic to the red cell membrane but are adsorbed from plasma, so they are not well-developed on fetal red cells (no HDFN risk). Lewis antibodies may be neutralized by Lewis substance in transfused plasma.

What is the antibody titration and when is it performed in prenatal testing?

Answer: Serial dilution of maternal serum to determine the strength of a clinically significant antibody; performed to monitor risk of HDFN

Antibody titration involves testing serial two-fold dilutions of maternal serum against antigen-positive red cells to determine the highest dilution that still shows reactivity. For anti-D, a titer of 16 or higher (or a rise of two or more dilutions) typically triggers referral for fetal monitoring. Titers are performed at defined intervals during pregnancy.