CSMLS Transfusion Science Principles Questions and Answers — Questions and Answers
Question 1: An ABO discrepancy is observed in a 75-year-old patient. The forward grouping shows Anti-A: 4+, Anti-B: 0. The reverse grouping shows A1 cells: 0, B cells: 1+. An autocontrol is negative. What is the most probable cause of this discrepancy?
- A subgroup of A
- Presence of a cold autoantibody
- Rouleaux formation due to high protein levels
- Age-related decrease in anti-B antibody production (Correct answer)
Correct answer: Age-related decrease in anti-B antibody production
The forward type is clearly Group A. The reverse grouping confirms the absence of anti-A but shows a weak (1+) reaction with B cells. In elderly patients, it is common for isoagglutinin (antibody) titres, such as anti-B, to decrease, leading to weak or missing reactions in the reverse group. The negative autocontrol makes a cold autoantibody less likely.
Question 2: A bone marrow transplant recipient requires a red blood cell transfusion. To prevent Transfusion-Associated Graft-Versus-Host Disease (TA-GVHD), which of the following component modifications is most critical?
- Washed
- Irradiated (Correct answer)
- CMV Seronegative
- Leukoreduced
Correct answer: Irradiated
Irradiation is the only method that inactivates donor T-lymphocytes, which are responsible for causing TA-GVHD in severely immunocompromised recipients, such as bone marrow transplant patients. While leukoreduction removes most white cells and CMV-seronegative units prevent cytomegalovirus transmission, they do not reliably prevent TA-GVHD.
Question 3: Fifteen minutes into a red blood cell transfusion, a patient develops fever, chills, hypotension, and reports red-coloured urine. The post-transfusion direct antiglobulin test (DAT) is positive. What is the most likely type of transfusion reaction?
- Febrile Non-Hemolytic Reaction
- Anaphylactic Reaction
- Acute Hemolytic Transfusion Reaction (AHTR) (Correct answer)
- Bacterial Contamination
Correct answer: Acute Hemolytic Transfusion Reaction (AHTR)
The combination of fever, chills, hypotension, hemoglobinuria (red urine), and a positive DAT strongly indicates an Acute Hemolytic Transfusion Reaction. This is a medical emergency caused by the rapid destruction of donor red blood cells by recipient antibodies, most often due to ABO incompatibility.
Question 4: An RhD-negative mother has just delivered an RhD-positive infant. The mother's antibody screen is negative. According to Canadian guidelines, what is the primary purpose of administering Rh Immune Globulin (RhIG) to the mother within 72 hours?
- To treat any potential hemolytic disease in the current newborn
- To suppress the mother's existing anti-D antibodies
- To prevent the mother from forming anti-D that could affect future RhD-positive pregnancies (Correct answer)
- To clear passive anti-D from a previous antenatal injection
Correct answer: To prevent the mother from forming anti-D that could affect future RhD-positive pregnancies
Postpartum RhIG provides passive anti-D to the mother. This passive antibody binds to and clears any RhD-positive fetal red cells that may have entered her circulation during delivery, preventing her immune system from recognizing the D antigen and becoming actively immunized. This protects future RhD-positive fetuses from Hemolytic Disease of the Fetus and Newborn.
Question 5: A patient has a history of a clinically significant antibody, anti-K, but their current antibody screen is negative. Which of the following is the most appropriate crossmatch procedure to ensure safety?
- Electronic crossmatch is acceptable because the current antibody screen is negative.
- A full antiglobulin (IAT) crossmatch using K-antigen negative donor units. (Correct answer)
- An immediate spin crossmatch to confirm ABO compatibility is sufficient.
- No crossmatch is needed if O Negative units are provided.
Correct answer: A full antiglobulin (IAT) crossmatch using K-antigen negative donor units.
A history of a clinically significant antibody is critical information. Even if the antibody is currently undetectable, the patient could have an anamnestic response upon re-exposure. Therefore, antigen-negative units must be selected, and a full antiglobulin (IAT) crossmatch must be performed to ensure serological compatibility and detect any low-titer antibodies.
Question 6: According to Canadian Standards Association (CSA) Z902 standards, what is the correct storage temperature range for Platelet concentrates?
- 1 to 6°C
- -18°C or colder
- 37 ± 1°C
- 20 to 24°C (Correct answer)
Correct answer: 20 to 24°C
CSA Z902 standards require that platelet components be stored at a controlled room temperature of 20 to 24°C with continuous gentle agitation to maintain their viability and function. Storing them at refrigerated temperatures (1 to 6°C) causes irreversible activation and loss of function.
CSMLS Transfusion Science Principles Questions and Answers
An ABO discrepancy is observed in a 75-year-old patient.
The forward grouping shows Anti-A: 4+, Anti-B: 0.
The reverse grouping shows A1 cells: 0, B cells: 1+.
An autocontrol is negative.
What is the most probable cause of this discrepancy?