Medical Laboratory Technician Blood Bank and Transfusion Questions and Answers — Questions and Answers
Question 1: A patient's antibody screen is positive. The antibody identification panel shows reactivity with all panel cells, and the auto-control is also positive. All reactions are occurring at the AHG phase. Which of the following is the MOST likely cause of these results?
- A cold autoantibody
- Multiple alloantibodies
- A warm autoantibody (Correct answer)
- An antibody to a high-prevalence antigen
Correct answer: A warm autoantibody
A warm autoantibody will react with the patient's own red cells (positive auto-control) and all reagent red cells used in the panel because they all possess the common antigens the autoantibody is directed against. The reactions are typically observed at the AHG (37°C) phase. A cold autoantibody typically reacts at room temperature or colder. Multiple alloantibodies would likely show a varying pattern of reactivity, and the auto-control would be negative. An antibody to a high-prevalence antigen would cause reactivity with all panel cells, but the auto-control would be negative.
Question 2: A unit of Red Blood Cells is issued from the blood bank at 08:00 for a routine transfusion. At 08:20, the nurse calls to report that the patient's IV has failed and the transfusion has not been started. The unit has been stored in a transport cooler with appropriate coolant packs. What is the correct course of action?
- Discard the unit immediately because it has been out of the blood bank for over 15 minutes.
- Return the unit to the blood bank immediately for proper storage. (Correct answer)
- Tell the nurse to keep the unit at the bedside until a new IV is established, as long as it is within 4 hours.
- Begin the transfusion as soon as a new IV is started, regardless of the time.
Correct answer: Return the unit to the blood bank immediately for proper storage.
According to AABB Standards, a blood component that has been issued but not transfused can be returned to the blood bank for reissue only if it has not been warmed above 10°C or cooled below 1°C during storage and transport. Since the unit was not spiked and was maintained at the correct temperature in a validated cooler, it can be immediately returned to the blood bank's monitored refrigerator. The 30-minute rule applies to units kept at room temperature without a validated cooling system.
Question 3: Which of the following blood components must be stored at 20-24°C with continuous, gentle agitation?
- Fresh Frozen Plasma (FFP)
- Red Blood Cells (RBCs)
- Cryoprecipitate
- Platelets (Correct answer)
Correct answer: Platelets
Platelets must be stored at room temperature (20-24°C) with continuous gentle agitation to maintain their viability and prevent aggregation. Red Blood Cells are stored at 1-6°C. Fresh Frozen Plasma and Cryoprecipitate are stored in a frozen state, typically at or below -18°C.
Question 4: During a pretransfusion compatibility test, a medical laboratory technician finds that the patient's ABO/Rh type is A positive, and the antibody screen is negative. The crossmatch is performed with an A positive donor unit. The immediate spin crossmatch is incompatible (4+). What is the MOST likely cause of this discrepancy?
- The patient has an antibody to a low-prevalence antigen present on the donor's red cells.
- The donor unit is incorrectly labeled and is actually group B.
- The patient has a cold-reacting alloantibody not detected by the screen.
- The patient has an A2 subtype with the presence of anti-A1. (Correct answer)
Correct answer: The patient has an A2 subtype with the presence of anti-A1.
An A2 individual can produce anti-A1, which would react with A1 cells from the donor unit, causing an incompatibility at immediate spin. The antibody screen is typically performed with O cells, which would not detect anti-A1. An incorrect donor unit label (e.g., group B) would also cause incompatibility, but the A2 with anti-A1 scenario is a classic cause for this specific set of results. An antibody to a low-prevalence antigen is possible but less common, and a cold antibody should have been detected on the screen if the appropriate cells were used.
Question 5: A transfusion reaction workup is initiated on a patient who developed fever, chills, and flank pain 15 minutes into a red blood cell transfusion. The initial laboratory investigation includes a clerical check, a visual check for hemolysis in the post-transfusion specimen, and a Direct Antiglobulin Test (DAT). Which of these findings would most strongly suggest an acute hemolytic transfusion reaction?
- A clerical error discovered on the patient's wristband.
- A negative DAT on the post-transfusion specimen.
- Pink or red plasma in the centrifuged post-transfusion specimen. (Correct answer)
- The patient's temperature increased by 1°C.
Correct answer: Pink or red plasma in the centrifuged post-transfusion specimen.
Pink or red plasma (hemoglobinemia) in a post-transfusion specimen is a key indicator of intravascular hemolysis, which is the hallmark of a severe acute hemolytic transfusion reaction. A clerical error is a common cause but not a direct finding of hemolysis. A DAT can be positive, but the visual presence of free hemoglobin in the plasma is a more immediate and dramatic indicator of red cell destruction in this clinical context. An increase in temperature is a symptom but is also common in febrile, non-hemolytic reactions.
Question 6: What is the primary purpose of irradiating cellular blood components?
- To prevent bacterial contamination of the unit.
- To prevent transfusion-associated graft-versus-host disease (TA-GVHD). (Correct answer)
- To extend the shelf-life of Red Blood Cells.
- To inactivate viruses such as CMV and HIV.
Correct answer: To prevent transfusion-associated graft-versus-host disease (TA-GVHD).
Irradiation of cellular blood products (Red Blood Cells and Platelets) exposes the component to a measured dose of gamma radiation or x-rays to damage the DNA of donor T-lymphocytes. This renders them incapable of dividing and mounting an immune response against the recipient, thus preventing transfusion-associated graft-versus-host disease (TA-GVHD), a rare but often fatal complication.
Medical Laboratory Technician Blood Bank and Transfusion Questions and Answers
A patient's antibody screen is positive.
The antibody identification panel shows reactivity with all panel cells, and the auto-control is also positive.
All reactions are occurring at the AHG phase.
Which of the following is the MOST likely cause of these results?