Component modifications

8 DOH Abu Dhabi (HAAD) lab licensing practice questions on Component modifications, part of Blood Banking. The first 8 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

1. Question 1 · Easy

   A patient who must receive irradiated cellular components needs further transfusions. Which component can be issued without irradiation?

   1. ADeglycerolized red cells
   2. BApheresis platelets
   3. CGranulocyte concentrate
   4. DFresh frozen plasma

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   Answer: D · Fresh frozen plasma

   Freezing plasma without a cryoprotectant kills the few leukocytes it contains, so thawed plasma and cryoprecipitate carry no viable lymphocytes and do not need irradiation. Red cells, platelets and granulocytes all contain viable T cells. Red cells frozen in glycerol are a trap: the glycerol protects lymphocytes as well as red cells, so deglycerolized units still need irradiation. The irradiation requirement should be flagged on the patient's record so that every cellular component is checked at issue.

   • A: Glycerol protects lymphocytes during freezing, so deglycerolized red cells still need irradiation.
   • B: Platelets contain viable lymphocytes and must be irradiated for at-risk patients.
   • C: Granulocyte concentrates are rich in viable lymphocytes and are always irradiated.

2. Question 2 · Medium

   Prestorage leukoreduction prevents febrile reactions better than filtration at the bedside because:

   1. APrestorage filters also remove plasma proteins
   2. BBedside filters do not remove the lymphocytes in the unit
   3. CWhite cells are removed before they release cytokines
   4. DCytokines are destroyed by cold storage

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   Answer: C · White cells are removed before they release cytokines

   During storage, white cells in a unit, especially in platelets kept at room temperature, release cytokines such as IL-1, IL-6, IL-8 and TNF-alpha. These cytokines cause fever when transfused, and a bedside filter cannot remove them once they have formed. Filtering soon after collection removes the white cells before they make cytokines, and the process can be quality controlled at the blood center. Bedside filters have also been linked to hypotensive reactions in patients taking ACE inhibitors.

   • A: Leukoreduction filters do not remove plasma proteins to any useful degree.
   • B: Bedside filters remove lymphocytes well; the problem is the cytokines already in the unit.
   • D: Cytokines are not destroyed by cold; they accumulate during storage.

3. Question 3 · Hard

   A newborn needs an exchange transfusion. The only irradiated red cell unit available is 18 days old and was irradiated 10 days ago. What is the main concern, and the best action?

   1. AViable lymphocytes; irradiate the unit a second time
   2. BLow 2,3-DPG; warm the unit before the exchange
   3. CHigh potassium; use a fresh unit irradiated just before use
   4. DHigh potassium; filter the unit at the bedside

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   Answer: C · High potassium; use a fresh unit irradiated just before use

   Irradiation damages the red cell membrane and speeds the leak of potassium into the supernatant, on top of the leak from storage. In a large-volume transfusion to a newborn, this potassium can cause a fatal arrhythmia. Guidelines therefore advise fresh red cells (UK BSH guidance: under 5 days old) irradiated shortly before use (within 24 hours), or washing or volume reduction if that is not possible. The effect of irradiation on lymphocytes does not wear off, so irradiating again has no purpose.

   • A: Irradiation effects do not wear off; a second dose only adds membrane damage.
   • B: 2,3-DPG falls with storage, but potassium is the danger in a neonatal exchange, and warming does not correct it.
   • D: Leukoreduction filters do not remove potassium from the supernatant.

4. Question 4 · Easy

   Which method reliably brings a whole blood-derived red cell unit to the leukoreduced standard?

   1. AGamma or X-ray irradiation of the unit
   2. BA leukocyte-reduction filter
   3. CBuffy coat removal alone
   4. DWashing in normal saline

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   Answer: B · A leukocyte-reduction filter

   Leukocyte-reduction filters remove more than 99.9% (about 3 to 4 logs) of white cells by adhesion and sieving, bringing a unit below 5 x 10^6 leukocytes (AABB) or 1 x 10^6 (Council of Europe). Filtration is best done soon after collection (prestorage). Buffy coat removal and washing lower the white cell count but not enough to meet these standards. Irradiation leaves the white cells in the unit and only stops lymphocytes from dividing.

   • A: Irradiation inactivates lymphocytes but does not remove any white cells.
   • C: Removing the buffy coat takes out most white cells, but not enough on its own to meet the standard.
   • D: Washing removes plasma and some white cells, but not enough to meet the standard.

5. Question 5 · Medium

   A patient with leukemia has had repeated urticaria and wheezing with platelet transfusions despite antihistamine premedication. Which modification is most appropriate?

   1. AHLA-matched platelets
   2. BLeukoreduced platelets
   3. CIrradiated platelets
   4. DWashed or plasma-reduced platelets

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   Answer: D · Washed or plasma-reduced platelets

   Allergic reactions are caused by the recipient's antibodies, usually IgE, reacting with proteins in the donor plasma. Removing most of the plasma, by washing or by replacing it with platelet additive solution, removes most of the allergen and prevents repeat reactions. Washing is done in an open system, shortens the expiry to a few hours and loses some platelets, so it is kept for recurrent or severe reactions. Irradiation, HLA matching and leukoreduction do not change the plasma content.

   • A: HLA matching treats immune refractoriness, not allergy to plasma proteins.
   • B: Leukoreduction prevents febrile reactions and HLA immunization, not allergic ones.
   • C: Irradiation prevents TA-GVHD but leaves the plasma proteins in place.

6. Question 6 · Hard

   Which donor and recipient HLA types put an immunocompetent recipient at the highest risk of TA-GVHD if the unit is not irradiated?

   1. ADonor A1, A3, B7, B8; recipient A1, A2, B8, B44
   2. BDonor A1, A2, B8, B44; recipient A1, B8 (homozygous)
   3. CDonor A3, A11, B7, B35; recipient A1, A2, B8, B44
   4. DDonor A1, B8 (homozygous); recipient A1, A2, B8, B44

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7. Question 7 · Easy

   By AABB standards, the minimum irradiation dose delivered to the central midplane of a blood component canister is:

   1. A100 Gy (10,000 cGy)
   2. B25 Gy (2,500 cGy)
   3. C5 Gy (500 cGy)
   4. D2.5 Gy (250 cGy)

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8. Question 8 · Medium

   Which risks does leukoreduction of blood components reduce?

   1. AAcute hemolytic reactions caused by ABO-incompatible units
   2. BBacterial contamination of platelet units
   3. CFebrile reactions, HLA immunization and CMV transmission
   4. DTransfusion-associated graft-versus-host disease

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