MLPAO Transfusion Medicine Case-Based Practice 1 — Questions and Answers
Question 1: A patient types as group A on forward typing but group O on reverse typing. What should the technologist investigate?
- Report as group A
- Investigate the ABO discrepancy — possible weak A subgroup, missing anti-B, cold antibodies, or technical error (Correct answer)
- Report as group O
- Repeat forward typing only
Correct answer: Investigate the ABO discrepancy — possible weak A subgroup, missing anti-B, cold antibodies, or technical error
An ABO discrepancy (forward and reverse do not agree) must be investigated before a blood type is assigned. This pattern (A forward, O reverse) could indicate a weak A subgroup (A2, Ax) where the patient has anti-A1 as well as expected anti-B. Additional testing includes anti-A1 lectin, A1 and A2 cells, room temperature incubation, and patient history review.
Question 2: A nurse calls reporting that a patient is having rigors and fever 15 minutes into a red cell transfusion. What are the immediate steps?
- Slow the transfusion rate
- STOP the transfusion immediately, keep the IV line open with saline, check patient and unit identification, notify the physician and blood bank, and send required post-reaction specimens (Correct answer)
- Continue transfusion and give acetaminophen
- Administer epinephrine immediately
Correct answer: STOP the transfusion immediately, keep the IV line open with saline, check patient and unit identification, notify the physician and blood bank, and send required post-reaction specimens
The immediate response to any suspected transfusion reaction is: 1) STOP the transfusion, 2) Keep IV open with normal saline, 3) Verify patient and unit identification at the bedside, 4) Notify the physician and blood bank, 5) Send post-reaction blood and urine specimens. The blood bank will perform transfusion reaction investigation including DAT, visual inspection for hemolysis, and repeat ABO/Rh.
Question 3: An antibody screen is positive at the antiglobulin (AHG) phase. The antibody identification panel shows reactivity with all Jk(a)-positive cells and no reactivity with Jk(a)-negative cells. What is the antibody?
- Anti-K
- Anti-Jk(a) (Correct answer)
- Anti-D
- Anti-Fy(a)
Correct answer: Anti-Jk(a)
The reactivity pattern — positive with all Jk(a)-positive cells and negative with all Jk(a)-negative cells — identifies anti-Jk(a). Kidd antibodies are clinically significant, cause complement-mediated hemolysis, and are notorious for evanescence (dropping to undetectable levels). Jk(a)-negative, crossmatch-compatible units must be provided.
Question 4: A D-negative pregnant woman at 28 weeks gestation has a negative antibody screen. What action should be taken?
- No action needed
- Administer antenatal Rh immune globulin (RhIg) at 28 weeks as prophylaxis (Correct answer)
- Perform a Kleihauer-Betke test immediately
- Induce labour early
Correct answer: Administer antenatal Rh immune globulin (RhIg) at 28 weeks as prophylaxis
Standard of care in Canada is to administer antenatal RhIg (300 µg IM) at 28 weeks gestation to D-negative women with negative antibody screens. This prevents sensitization from small fetomaternal hemorrhages that may occur during the third trimester. Additional RhIg is given postpartum within 72 hours if the baby is D-positive.
Question 5: A patient with known anti-E requires 2 units of red blood cells for surgery. How should compatible blood be provided?
- Any ABO/Rh-compatible blood is acceptable
- Select E-negative, ABO/Rh-compatible units and perform an antiglobulin crossmatch (Correct answer)
- Use O-negative blood without crossmatch
- Only autologous blood can be used
Correct answer: Select E-negative, ABO/Rh-compatible units and perform an antiglobulin crossmatch
For a patient with anti-E, E-antigen-negative donor units must be selected. ABO and Rh(D) compatibility is also required. Since the patient has a clinically significant antibody, an antiglobulin crossmatch (not electronic crossmatch) must be performed to confirm serological compatibility. The antibody history must be maintained permanently in the patient's transfusion record.
Question 6: A post-transfusion DAT is positive with anti-IgG but negative with anti-C3d. The eluate contains anti-c. What type of reaction is this?
- Febrile non-hemolytic transfusion reaction
- Delayed hemolytic transfusion reaction due to an anamnestic anti-c response (Correct answer)
- Autoimmune hemolytic anemia
- Bacterial contamination
Correct answer: Delayed hemolytic transfusion reaction due to an anamnestic anti-c response
A positive post-transfusion DAT with anti-IgG and an eluate showing anti-c indicates a delayed hemolytic transfusion reaction. The patient was previously sensitized to the c antigen, and anti-c was undetectable at the time of the pre-transfusion antibody screen. Re-exposure to c-positive donor cells triggered an anamnestic response, producing anti-c that now coats the transfused cells.
MLPAO Transfusion Medicine Case-Based Practice 1
A patient types as group A on forward typing but group O on reverse typing.
What should the technologist investigate?