Module 5: Transfusion Medicine: Practice Questions
1. (Concept T1b) A 38-year-old woman with a history of immune thrombocytopenic purpura (ITP) has been treated with corticosteroid therapy for the past year. She has had a cough for the past month, and a chest radiograph shows a right lower lung nodule. Fine needle aspiration biopsy of this nodule is proposed. A platelet count in this woman below which of the following levels should indicate the need for platelet transfusion prior to this procedure?
A. 50,000/microliter
B. 100,000/microliter
C. 150,000/microliter
D. 200,000/microliter
Answer: A.
In general, no spontaneous bleeding due to thrombocytopenia will occur with platelet counts above 100,000/microliter, assuming platelet function is normal. It is unlikely that spontaneous bleeding will occur until the platelet count drops below 10,000/microliter. Between 10,000 and 50,000/microliter, most patients will not have spontaneous bleeding from thrombocytopenia. However, procedures with hemostatic challenge carry an increased risk for bleeding complications, and it is best to have sufficient platelets to cover such events. For most surgical procedures, a platelet count of 50,000/microliter is adequate. In neurosurgical cases where tolerance for any bleeding is minimal, then platelet transfusion to a count more than 100,000/microliter may be necessary.
2. (Concept T4) A 37-year-old woman with acute myelogenous leukemia receives chemotherapy. She develops pancytopenia and requires multiple blood product transfusion with packed red blood cells and platelets. She then develops the sudden onset of fever with tachycardia a day following the last transfused unit. Which of the following transfusion-associated infections has she most likely acquired?
A. Hepatitis B
B. Hepatitis C
C. HIV-1
D. Plasmodium falciparum
E. Staphylococcus aureus
Answer: E: Staphylococcus aureus.
Despite the concerns raised over transfusion-associated viral infections such as hepatitis and HIV, bacterial infection remains the greatest risk with transfused blood products. Considerable progress has been made in testing for viral agents, so the risks have declined to very low levels. The donor interview effectively screens for malaria (Plasmodium infections). Some bacteria are psychrophilic (Yersinia enterocolitica) and have a propensity to grow even at cold temperatures used for storage of red blood cell and plasma products. However, platelets are labile and must be kept at room temperature, which favors growth of any bacterial contaminants. The findings in this case are consistent with acute bacterial infection.
3. (Concept T6) A 58-year-old man comes to the emergency department with worsening fatigue and maroon-colored stools for the past day. On examination his blood pressure is 80/40 mm Hg. His oxygen saturation is 50%. His Hct is 17%. His electronic medical record documents his blood type from testing last year as type A positive. Which of the following orders for packed red blood cells is most appropriate for this man?
A. Type and screen for type A positive cells
B. Type and cross for type A positive cells
C. Emergent release of type A positive cells
D. Type and screen for type O negative cells
E. Type and cross for type O negative cells
F. Emergent release of type O negative cells
Answer: C: Emergent release of type A positive cells.
Blood will ordinarily not be released for transfusion until compatibility testing is completed. However, under emergency conditions, blood products may be released without a crossmatch if the patient is in danger of dying if transfusion is delayed. In such cases, if the patient blood type is not known, then group O Rh negative (O neg) blood can be released without compatibility testing. In cases in which the patientŐs blood type is reliably known, then type-specific blood or RBCs of the same ABO and Rh group may be released. The ordering physician must sign a release form for emergent use of blood products without compatibility testing. A full crossmatch takes 45 minutes to complete, and this cannot be shortened. In fact, arguing about testing is counterproductive because it takes time away from performing important work. If the patient is hemorrhaging, sign the emergency release form.
4. (Concept T8) A 22-year-old gravida 2 para 1 woman is at 17 weeks gestation. She notes minimal fetal movement. Fetal ultrasound examination shows fetal hydrops. The maternal blood type is A negative. Which of the following test results on maternal blood is most likely to be present?
A. Decreased haptoglobin
B. Decreased unconjugated estriol
C. Increased alpha-fetoprotein
D. Increased bilirubin
E. Positive indirect Coombs test
F. Positive serologic test for HIV
Answer: E: Positive indirect Coombs test.
Given that the maternal blood type is Rh negative, and with history of prior pregnancy, and with hydrops in the current pregnancy, there is a strong possibility that erythroblastosis fetalis is present. The most common cause for this is prior maternal immunization, either from pregnancy or blood product transfusion, that elicited antibodies to the 'D' antigen. In this case, a prior Rh positive infant may have led to alloimmunization of the mother, who is now producing antibodies that cross the placenta to attach to fetal red cells, leading to their destruction. This situation might have been prevented with testing that determined an Rh incompatibility was present in the first pregnancy, and giving the mother Rh immune globulin (also called anti-D immune globulin, Rho(D) immune globulin, or RhoGAM) at the time of birth to lessen the chance for alloimmunization. It is possible that other red cell antigens could elicit similar alloimmunization, but these are less likely to do so than the 'D' antigen. The indirect Coombs test is positive in the mother, because she has the circulating anti-D, while the direct Coombs test would be positive in the fetus or neonate following birth, because the anti-D has attached to the corresponding antigen on the fetal red blood cells.
5. (T9) A 45-year-old man with selective IgA deficiency has a severe anemia. He requires transfusion therapy. Which of the following is recommended to decrease the risk for transfusion reaction in this man?
A. Autologous blood
B. Gamma irradiation
C. Leukoreduction filtration
D. RhoGAM
E. Washed red blood cells
Answer: E: Washed red blood cells.
Washing the RBCs reduces plasma proteins, including immunoglobulins, including anti-IgA. This reduces the risk for allergic transfusion reactions, and anaphylactic transfusion reactions in persons with selective IgA deficiency.
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