MLPAO Transfusion Medicine Case-Based Practice 2 — Questions and Answers
Question 1: An emergency trauma patient arrives with massive hemorrhage. Blood type is unknown. What should the blood bank issue?
- Wait for type and screen results before issuing blood
- Issue group O Rh-negative (or O Rh-positive for males) uncrossmatched red blood cells and group AB plasma (Correct answer)
- Issue random blood products
- Issue group A red blood cells
Correct answer: Issue group O Rh-negative (or O Rh-positive for males) uncrossmatched red blood cells and group AB plasma
In emergency massive hemorrhage, group O red blood cells are issued without waiting for typing. O Rh-negative is preferred for females of childbearing potential to prevent Rh sensitization. O Rh-positive can be used for males and post-menopausal females to conserve the limited O-negative supply. Group AB plasma is issued as the universal plasma donor type.
Question 2: A patient requires chronic transfusion for sickle cell disease. What special blood bank considerations apply?
- Standard ABO/Rh matching only
- Extended phenotype matching (Rh C, c, E, e, and K at minimum) to reduce alloimmunization risk, plus HbS-negative donor units (Correct answer)
- No special considerations
- Only autologous transfusion
Correct answer: Extended phenotype matching (Rh C, c, E, e, and K at minimum) to reduce alloimmunization risk, plus HbS-negative donor units
Sickle cell disease patients have a high alloimmunization rate (25-50%) due to antigen differences between donor (predominantly Caucasian) and recipient (predominantly African descent) populations. Canadian guidelines recommend extended matching for Rh (C, c, E, e) and Kell at minimum. Donor units should be sickle-negative (HbS-negative). Phenotypically similar donors should be actively recruited.
Question 3: A patient's antibody screen is positive with all three screening cells at the antiglobulin phase. What does this suggest?
- Anti-D
- Possible warm autoantibody, antibody to a high-frequency antigen, or multiple alloantibodies (Correct answer)
- Anti-K
- Negative antibody screen
Correct answer: Possible warm autoantibody, antibody to a high-frequency antigen, or multiple alloantibodies
Panreactivity (reactivity with all screening cells) suggests: 1) A warm autoantibody (reacting with a ubiquitous self-antigen), 2) An antibody to a high-frequency antigen (>99% of population), or 3) Multiple alloantibodies together reacting with all cells. An autocontrol (patient serum + patient cells) helps differentiate: if positive, autoantibody is likely; if negative, alloantibody to a high-frequency antigen is more likely.
Question 4: A patient has anti-Jk(a) identified 3 years ago but the current antibody screen is negative. Can the electronic crossmatch be used?
- Yes, since the current screen is negative
- No — once a clinically significant antibody is identified, an antiglobulin crossmatch with antigen-negative units is always required, regardless of current screen results (Correct answer)
- Yes, but only if two typings are on file
- The patient needs fresh plasma exchange first
Correct answer: No — once a clinically significant antibody is identified, an antiglobulin crossmatch with antigen-negative units is always required, regardless of current screen results
A history of a clinically significant antibody (especially Kidd antibodies, which are known for evanescence) permanently disqualifies a patient from electronic crossmatch. Jk(a)-negative units must be selected and an antiglobulin crossmatch performed. This antibody history must be maintained in the blood bank records and communicated across institutions.
Question 5: A cord blood sample has a positive DAT with anti-IgG. The mother is group O Rh-positive and the baby is group A Rh-positive. What is the most likely cause?
- Rh HDFN
- ABO hemolytic disease of the newborn due to maternal anti-A (IgG) crossing the placenta (Correct answer)
- Autoimmune hemolytic anemia in the newborn
- Laboratory error
Correct answer: ABO hemolytic disease of the newborn due to maternal anti-A (IgG) crossing the placenta
The most likely cause is ABO HDFN. Group O mothers produce IgG anti-A and anti-B (in addition to IgM), which can cross the placenta and coat the fetal A or B red cells. ABO HDFN is usually mild but can occasionally cause significant jaundice requiring phototherapy. An eluate from the baby's cells would confirm anti-A.
Question 6: A patient develops urticaria (hives) during a platelet transfusion. There is no fever, hypotension, or respiratory distress. What is the management?
- Stop the transfusion permanently
- Stop the transfusion, administer antihistamine, and if symptoms resolve, resume the same transfusion at a slower rate (Correct answer)
- Give epinephrine immediately
- Initiate transfusion reaction investigation for hemolysis
Correct answer: Stop the transfusion, administer antihistamine, and if symptoms resolve, resume the same transfusion at a slower rate
Mild allergic reactions (urticaria only, no systemic symptoms) are managed by temporarily stopping the transfusion, administering an antihistamine (diphenhydramine), and resuming the same unit at a slower rate once symptoms resolve (usually within 30 minutes). If symptoms progress to anaphylaxis (hypotension, bronchospasm), the transfusion must be permanently stopped.
MLPAO Transfusion Medicine Case-Based Practice 2
An emergency trauma patient arrives with massive hemorrhage.
Blood type is unknown.
What should the blood bank issue?