Medical Laboratory Technician Blood Banking and Transfusion Questions and Answers — Questions and Answers
Question 1: A patient with a known IgA deficiency requires a transfusion of packed red blood cells. To prevent a potential anaphylactic transfusion reaction, which modification should be performed on the blood product?
- Irradiation
- Leukoreduction
- Washing (Correct answer)
- Volume reduction
Correct answer: Washing
Washing red blood cells with sterile saline removes the majority of the plasma, which contains proteins like IgA. In an IgA-deficient patient who has developed anti-IgA antibodies, transfusing plasma-containing products can trigger a severe anaphylactic reaction. Irradiation prevents transfusion-associated graft-versus-host disease, and leukoreduction minimizes febrile reactions and CMV transmission, but neither process removes plasma proteins.
Question 2: A blood sample from a 28-year-old, Rh-negative female who is 28 weeks pregnant shows a positive antibody screen. An antibody panel is performed, and the technologist identifies anti-D. What is the most likely reason for this finding?
- The patient has formed an autoantibody.
- The patient is experiencing a delayed hemolytic transfusion reaction.
- The patient received a routine antenatal dose of Rh Immune Globulin (RhIG). (Correct answer)
- The patient has a previously unidentified subgroup of Rh.
Correct answer: The patient received a routine antenatal dose of Rh Immune Globulin (RhIG).
Rh Immune Globulin (RhIG) is a concentrated solution of IgG anti-D, given to non-sensitized Rh-negative mothers at approximately 28 weeks gestation to prevent immunization to the D antigen. This passively administered anti-D will cause the antibody screen to be positive. While the other options are possible causes for a positive antibody screen, the patient's specific history (Rh-negative, 28 weeks pregnant) makes the recent administration of RhIG the most probable cause.
Question 3: During the crossmatch process, an MLT receives the following ABO typing results for a patient: Anti-A: 4+, Anti-B: 0, A1 Cells: 0, B Cells: 2+. What is the most likely cause of this ABO discrepancy?
- The patient may have a cold alloantibody.
- The patient is likely an A2 subgroup with anti-A1. (Correct answer)
- There is an issue with the patient's red cells, such as acquired B antigen.
- The patient is immunocompromised, leading to weak or missing antibodies.
Correct answer: The patient is likely an A2 subgroup with anti-A1.
The forward type indicates the patient is Group A. The reverse type shows an expected reaction with B cells but an unexpected weak (2+) reaction with A1 cells. This pattern is characteristic of a Group A2 individual who has produced an anti-A1 antibody. This is a relatively common and clinically benign discrepancy. A cold alloantibody would likely react with both A1 and B cells if the corresponding antigen was present, and missing antibodies would result in no reaction with B cells.
Question 4: An immunocompromised patient is scheduled to receive a unit of packed red blood cells from a blood relative. To prevent transfusion-associated graft-versus-host disease (TA-GVHD), which of the following is the most critical modification for this blood product?
- Leukoreduction
- Washing
- Freezing and deglycerolizing
- Gamma irradiation (Correct answer)
Correct answer: Gamma irradiation
Gamma irradiation is the only method that effectively prevents TA-GVHD by inactivating donor T-lymphocytes, rendering them incapable of proliferating and attacking the recipient's tissues. This is especially critical for immunocompromised recipients and when receiving blood from a relative, where there is a higher chance of shared HLA types. Leukoreduction reduces the number of white cells but does not eliminate the risk.
Question 5: A patient experiences a fever and chills 30 minutes after the start of a red blood cell transfusion. The transfusion is stopped immediately. A post-transfusion reaction workup reveals a negative DAT and no visual evidence of hemolysis in the post-transfusion specimen. This clinical picture is most consistent with which type of transfusion reaction?
- Acute hemolytic transfusion reaction (AHTR)
- Febrile non-hemolytic transfusion reaction (FNHTR) (Correct answer)
- Allergic transfusion reaction
- Transfusion-associated circulatory overload (TACO)
Correct answer: Febrile non-hemolytic transfusion reaction (FNHTR)
A febrile non-hemolytic transfusion reaction (FNHTR) is characterized by a fever and chills during or shortly after a transfusion, without evidence of red cell destruction (hemolysis). The negative DAT and lack of hemolysis rule out an AHTR. An allergic reaction typically involves hives and itching, and TACO involves respiratory distress and signs of fluid overload.
Question 6: An antibody panel has been performed on a patient with a positive antibody screen. To confirm the identity of a suspected antibody, such as anti-Jka, and to ensure other clinically significant antibodies are not being missed, the technologist must follow the 'rule of three.' What does this rule require?
- The patient's serum must be reactive with at least three different crossmatch-compatible units.
- The antibody must be identified by three different technologists before reporting.
- The patient's serum must be non-reactive with at least three antigen-positive cells and reactive with three antigen-negative cells.
- The patient's serum must be reactive with at least three antigen-positive cells and non-reactive with at least three antigen-negative cells. (Correct answer)
Correct answer: The patient's serum must be reactive with at least three antigen-positive cells and non-reactive with at least three antigen-negative cells.
The 'rule of three' in antibody identification provides statistical confidence (p-value ≤ 0.05) that the identified antibody is correct and the reactivity is not due to chance. It requires demonstrating that the patient's serum reacts with at least three panel cells that are positive for the corresponding antigen and does not react with at least three panel cells that are negative for that antigen.
Medical Laboratory Technician Blood Banking and Transfusion Questions and Answers
A patient with a known IgA deficiency requires a transfusion of packed red blood cells.
To prevent a potential anaphylactic transfusion reaction, which modification should be performed on the blood product?