MCQ: Pathology

4 clinical MCQs in Pathology. A 45-year-old male develops sudden fever, flank pain, and red-brown urine shortly after a. Free notes for medical students...

Questions, Answers & Explanations

1. Q1. A 45-year-old male develops sudden fever, flank pain, and red-brown urine shortly after a blood transfusion begins. What is the most crucial initial management step?

   • Immediately stop the transfusion and maintain intravenous access with normal saline.
   • Administer a broad-spectrum antibiotic and closely monitor for signs of septic shock.
   • Obtain blood cultures from the patient and the blood bag, then notify the blood bank.
   • Administer intravenous paracetamol and antihistamines, then slow down the transfusion rate.

   Answer: Immediately stop the transfusion and maintain intravenous access with normal saline.

   Explanation: The symptoms described are classic for an acute haemolytic transfusion reaction, which is the most serious immediate reaction. The most critical first step is to immediately stop the transfusion to prevent further haemolysis and potential life-threatening complications. Maintaining IV access with normal saline is also important for supportive care. Other steps like sending samples and administering specific treatments follow this initial action. ---

2. Q2. A patient experiences an unexpected drop in haemoglobin and mild jaundice approximately 7 days after receiving a blood transfusion. A direct antiglobulin test (DAT) is positive. Which blood group system is most notoriously associated with this type of reaction?

   • The ABO blood group system due to common pre-formed IgM antibodies.
   • The Rh blood group system, often involving anti-D following Rh-positive exposure.
   • The Duffy blood group system, known for its association with malaria resistance.
   • The Kidd blood group system, notorious for causing anamnestic antibody responses.

   Answer: The Kidd blood group system, notorious for causing anamnestic antibody responses.

   Explanation: The timing (3-10 days post-transfusion), fall in Hb, mild jaundice, and positive DAT are consistent with a delayed haemolytic transfusion reaction (DHTR). DHTRs occur when low-level alloantibodies, often not detected on initial antibody screens, are boosted by the transfused RBCs, leading to an anamnestic immune response. The Kidd blood group system is particularly notorious for causing these types of reactions, as Kidd antibodies can rapidly disappear from circulation, making them difficult to detect prior to transfusion. ---

3. Q3. Which of the following blood products has the shortest shelf life and the highest risk of bacterial contamination, primarily due to its specific storage temperature?

   • Platelet concentrates, stored at 20-24°C with constant agitation for 5 days.
   • Packed red blood cells, stored at 1-6°C for up to 35-42 days.
   • Fresh frozen plasma, stored at -18°C for up to 12 months.
   • Cryoprecipitate, stored frozen at -18°C for an extended period of 12 months.

   Answer: Platelet concentrates, stored at 20-24°C with constant agitation for 5 days.

   Explanation: Platelet concentrates are stored at room temperature (20-24°C) with agitation for only 5 days. This warmer storage temperature, necessary to maintain platelet function, unfortunately also provides an ideal environment for bacterial growth, making them the blood product with the highest risk of bacterial contamination and shortest shelf life. ---

4. Q4. A severely immunocompromised patient requires a blood transfusion. To prevent a rare but highly fatal transfusion reaction, which specific modification should be requested for the blood product?

   • Leukoreduction to remove white blood cells and prevent febrile non-haemolytic reactions.
   • Irradiation with gamma radiation to inactivate donor T-lymphocytes.
   • Washing with saline to remove plasma proteins and prevent allergic reactions.
   • CMV-negative blood from seronegative donors to prevent cytomegalovirus transmission.

   Answer: Irradiation with gamma radiation to inactivate donor T-lymphocytes.

   Explanation: Transfusion-associated Graft-versus-Host Disease (TA-GvHD) is a rare but highly fatal complication, especially in immunocompromised patients. It occurs when viable donor T-lymphocytes engraft in the recipient and attack host tissues. Irradiation of blood products with gamma radiation inactivates these donor T-lymphocytes, effectively preventing TA-GvHD. ---