Medical Laboratory Technician Exam Medical Laboratory Technician Blood Banking and Transfusion 1 — Questions and Answers
Question 1: A patient receiving a red blood cell transfusion develops fever, chills, and hypotension 30 minutes into the infusion. The post-transfusion plasma appears pink. Which action should the technologist perform FIRST after the transfusion is stopped?
- Perform a direct antiglobulin test (DAT) on the pre-transfusion sample
- Return the blood bag and all attached tubing to the blood bank with a new post-transfusion blood sample (Correct answer)
- Issue O-negative blood for an emergency transfusion
- Repeat the ABO typing on the original donor unit
Correct answer: Return the blood bag and all attached tubing to the blood bank with a new post-transfusion blood sample
When an acute hemolytic transfusion reaction is suspected, the blood bag with all attached tubing and a new post-transfusion sample must be returned to the blood bank immediately. This allows comparison of pre- and post-transfusion specimens, visual inspection for hemolysis, and repeat compatibility testing—the foundational steps of a transfusion reaction workup.
Question 2: An antibody identification panel shows reactivity in a pattern consistent with anti-E. Before reporting, the technologist should confirm the patient's phenotype for the E antigen. If the patient is E-positive, what is the most appropriate interpretation?
- The anti-E is a clinically insignificant cold-reactive antibody
- The result is likely due to a rouleaux artifact; saline replacement should be performed
- The antibody is probably an alloantibody directed against a high-frequency antigen
- The antibody may be an autoantibody or a mimicking alloantibody; additional testing is required (Correct answer)
Correct answer: The antibody may be an autoantibody or a mimicking alloantibody; additional testing is required
An antibody with an apparent anti-E pattern in an E-positive patient cannot be a true alloanti-E (patients do not make alloantibodies to antigens they express). The pattern may represent an autoantibody with E-like specificity or a mimicking alloantibody. Adsorption studies and additional panel work are required to clarify specificity before antigen-negative blood is selected.
Question 3: A group A, Rh-positive patient has an unexpected positive antibody screen. The technologist performs an antibody identification panel and finds reactivity only with cells expressing the Lea antigen. The reaction strength is 1+ at immediate spin and is not enhanced at 37°C or AHG phase. What is the most appropriate course of action?
- Provide Lea-negative, crossmatch-compatible blood for all future transfusions
- Report anti-Lea as a clinically significant antibody requiring antigen-negative blood
- Document anti-Lea as a clinically insignificant cold-reactive antibody and provide ABO/Rh-compatible blood (Correct answer)
- Perform a warm autoadsorption before proceeding with antigen-negative selection
Correct answer: Document anti-Lea as a clinically insignificant cold-reactive antibody and provide ABO/Rh-compatible blood
Anti-Lea is typically IgM, reacts best at room temperature, does not react at 37°C or AHG phase, and is considered clinically insignificant because it does not cause hemolytic transfusion reactions at physiologic temperature. Standard practice is to document the antibody and provide ABO/Rh-compatible blood without the requirement for Lea-negative units.
Question 4: During pretransfusion testing, a technologist detects a mixed-field agglutination pattern when testing a patient's cells with anti-A serum. The patient's medical history notes a recent bone marrow transplant from a group O donor. What is the most likely explanation?
- The patient has a weak A subgroup such as A3
- The mixed-field pattern indicates a positive DAT
- Engraftment of donor O cells is producing a mixed population of A and O red cells (Correct answer)
- The reagent anti-A has deteriorated and should be replaced
Correct answer: Engraftment of donor O cells is producing a mixed population of A and O red cells
Post-bone marrow transplant patients often show mixed-field agglutination due to chimerism—a coexisting population of recipient (group A) and donor (group O) red cells in circulation during engraftment. This is expected and should be correlated with the transplant history rather than attributed to a subgroup or reagent failure.
Question 5: A massive transfusion protocol is activated for a trauma patient. After receiving 12 units of packed red blood cells, the patient develops prolonged bleeding from IV sites. Which laboratory finding best supports transfusion-associated dilutional coagulopathy?
- Platelet count of 180,000/µL and PT within normal limits
- Prolonged PT and aPTT with a fibrinogen level of 80 mg/dL (Correct answer)
- Elevated fibrinogen and shortened thrombin time
- Hemoglobin of 7 g/dL with normal coagulation studies
Correct answer: Prolonged PT and aPTT with a fibrinogen level of 80 mg/dL
Massive transfusion with packed red blood cells (which contain no coagulation factors or platelets) dilutes the patient's clotting factors and fibrinogen. A prolonged PT and aPTT combined with a critically low fibrinogen (<100 mg/dL) are hallmarks of dilutional coagulopathy and indicate the need for fresh frozen plasma, cryoprecipitate, and platelets.
Question 6: A technologist is performing a weak D (Du) test on a sample typed as Rh-negative by the immediate spin method. The indirect antiglobulin test yields a 2+ reaction with anti-D. How should this result be interpreted, and what are the implications for this patient as a blood recipient?
- The patient should be classified as Rh-positive and may receive Rh-positive blood without risk of anti-D formation
- The patient is weak D and should be classified as Rh-negative for transfusion purposes to prevent alloimmunization (Correct answer)
- The result indicates a false positive due to inadequate washing; the test should be repeated
- Weak D patients are always Rh-negative donors but can receive Rh-positive blood safely
Correct answer: The patient is weak D and should be classified as Rh-negative for transfusion purposes to prevent alloimmunization
Current AABB standards recommend that patients who type as weak D be treated as Rh-negative for transfusion purposes. Although most weak D types (especially types 1–3) are unlikely to form anti-D, caution is warranted because some weak D variants (partial D) lack certain D epitopes and can produce alloanti-D when exposed to conventional Rh-positive blood.
Medical Laboratory Technician Exam Medical Laboratory Technician Blood Banking and Transfusion 1
A patient receiving a red blood cell transfusion develops fever, chills, and hypotension 30 minutes into the infusion.
The post-transfusion plasma appears pink.
Which action should the technologist perform FIRST after the transfusion is stopped?