MLPAO Transfusion Medicine Fundamentals 2 — Questions and Answers
Question 1: What is the purpose of the crossmatch in transfusion medicine?
- To determine the patient's blood type
- To detect serological incompatibility between the donor red cells and patient serum before transfusion (Correct answer)
- To screen for irregular antibodies
- To determine if the donor blood is sterile
Correct answer: To detect serological incompatibility between the donor red cells and patient serum before transfusion
The crossmatch is the final compatibility check that tests patient serum/plasma against donor red blood cells. An immediate-spin crossmatch detects ABO incompatibility. An antiglobulin crossmatch (full crossmatch) is required when the patient has clinically significant antibodies. Electronic (computer) crossmatch is used when the antibody screen is negative.
Question 2: What is the universal red blood cell donor type and why?
- Type AB positive
- Type O negative, because O red cells lack A and B antigens and D antigen (Correct answer)
- Type A positive
- Type B negative
Correct answer: Type O negative, because O red cells lack A and B antigens and D antigen
Type O negative is the universal red blood cell donor because the red cells lack A, B, and D antigens, minimizing the risk of ABO and Rh-related transfusion reactions. O negative blood is used in emergency situations when there is no time for typing. However, it is a limited resource (about 7% of the Canadian population).
Question 3: What is the universal plasma donor type?
- Type O
- Type AB (Correct answer)
- Type A
- Type B
Correct answer: Type AB
Type AB plasma is the universal plasma donor because it contains no anti-A or anti-B antibodies, making it safe for recipients of any ABO type. This is the opposite of red cell donation, where O is universal. AB plasma is used in emergency situations and for patients with unknown blood types requiring plasma transfusion.
Question 4: What are the signs and symptoms of an acute hemolytic transfusion reaction?
- Only mild itching
- Fever, chills, flank/back pain, hemoglobinuria, hypotension, DIC, and renal failure (Correct answer)
- Delayed fever occurring 5-10 days after transfusion
- Mild urticaria only
Correct answer: Fever, chills, flank/back pain, hemoglobinuria, hypotension, DIC, and renal failure
Acute hemolytic transfusion reactions (usually ABO-incompatible) present with fever, chills, back/flank pain, chest tightness, hemoglobinuria (dark urine), hypotension, and can progress to DIC, shock, and renal failure. Immediate action includes stopping the transfusion, maintaining IV access, and notifying the blood bank for investigation.
Question 5: What is the required sample labeling for pre-transfusion testing in Canada?
- Patient name only
- Patient name and room number
- Two independent patient identifiers on both the sample tube and the requisition, verified at the bedside at the time of collection (Correct answer)
- Any label is acceptable
Correct answer: Two independent patient identifiers on both the sample tube and the requisition, verified at the bedside at the time of collection
Canadian Standards Association (CSA) standards require positive patient identification at the bedside with two independent identifiers (typically name and unique identifier such as health card number or hospital ID). The sample must be labeled at the bedside, not pre-labeled. Unlabeled or mislabeled samples must be rejected — this is the single most important step in preventing fatal ABO-incompatible transfusions.
Question 6: What is Rh immune globulin (RhIg) and when is it administered?
- An antibiotic given to Rh-positive mothers
- Anti-D immunoglobulin given to Rh-negative mothers to prevent alloimmunization against D antigen (Correct answer)
- A vaccine against Rh disease
- An immunosuppressant for all pregnant women
Correct answer: Anti-D immunoglobulin given to Rh-negative mothers to prevent alloimmunization against D antigen
RhIg (WinRho, Rhogam) contains anti-D antibodies that destroy any fetal D-positive red cells in the mother's circulation before her immune system can respond. In Canada, it is given to Rh-negative mothers at 28 weeks gestation and within 72 hours after delivery of an Rh-positive baby, as well as after any potentially sensitizing event.
MLPAO Transfusion Medicine Fundamentals 2
What is the purpose of the crossmatch in transfusion medicine?