Coag 2.2 Platelet and Vascular Disorders Flashcards
- Thrombotic thrombocytopenic purpura (TTP) is characterized by:
A. Prolonged PT
B. Increased PLT aggregation
C. Thrombocytosis
D. Prolonged APTT
B. Increased PLT aggregation
TTP is a quantitative PLT disorder associated with increased intravascular PLT activation and aggregation resulting in thrombocytopenia. PT and APTT results are normal in TTP.
- Thrombocytopenia may be associated with:
A. Splenectomy
B. Hypersplenism
C. Acute blood loss
D. Increased proliferation of pluripotent stem cells
B. Hypersplenism
Hypersplenism is associated with thrombocytopenia. In this condition, up to 90% of PLTs can be sequestered in the spleen, causing decreases in circulatory PLTs. Splenectomy, acute blood loss, and increased proliferation of pluripotent stem cells are associated with thrombocytosis.
- Aspirin prevents PLT aggregation by inhibiting the action of which enzyme?
A. Phospholipase
B. Cyclo-oxygenase
C. Thromboxane A2 (TXA2) synthetase
D. Prostacyclin synthetase
B. Cyclo-oxygenase
Aspirin prevents PLT aggregation by inhibiting the activity of the enzyme cyclo-oxygenase. This inhibition prevents the formation of TXA2, which serves as a potent PLT aggregator.
- Normal PLT adhesion depends on:
A. Fibrinogen
B. Glycoprotein Ib
C. Glycoprotein IIb–IIIa complex
D. Calcium
B. Glycoprotein Ib
Glycoprotein Ib is a PLT receptor for VWF. Glycoprotein Ib and VWF are both necessary for a normal PLT adhesion. Other proteins that play a role in PLT adhesion are glycoproteins V and IX.
- Which of the following test results is normal in a patient with classic von Willebrand disease?
A. PLT aggregation
B. APTT
C. PLT count
D. Factor VIII:C and von Willebrand factor (VWF) levels
C. PLT count
Von Willebrand disease is an inherited, qualitative PLT disorder that results in increased bleeding, prolonged APTT, and decreased factor VIII:C and VWF levels. The PLT count and morphology are generally normal in von Willebrand disease, but PLT aggregation in the PLT function assay is abnormal.
- Bernard–Soulier syndrome is associated with:
A. Decreased factor IX
B. Decreased factor VIII
C. Thrombocytopenia and giant PLTs
D. Abnormal PLT function test results
C. Thrombocytopenia and giant PLTs
Bernard–Soulier syndrome is associated with thrombocytopenia and giant PLTs. It is a qualitative PLT disorder caused by the deficiency of glycoprotein Ib. In Bernard–Soulier syndrome, PLT aggregation in the PLT function assay is abnormal. Factor VIII and IX assays are not indicated for this diagnosis.
- When performing PLT aggregation studies, which set of PLT aggregation results would most likely be associated with Bernard–Soulier syndrome?
A. Normal PLT aggregation to collagen, adenosine diphosphate (ADP), and ristocetin
B. Normal PLT aggregation to collagen, ADP, and epinephrine (EPI); decreased aggregation to ristocetin
C. Normal PLT aggregation to EPI and ristocetin; decreased aggregation to collagen and ADP
D. Normal PLT aggregation to EPI, ristocetin, and collagen; decreased aggregation to ADP
B. Normal PLT aggregation to collagen, ADP, and epinephrine (EPI); decreased aggregation to ristocetin
Bernard–Soulier syndrome is a disorder of PLT adhesion caused by deficiency of glycoprotein Ib. PLT aggregation is normal in response to collagen, ADP, and EPI but abnormal in response to ristocetin.
- Which set of PLT responses would be most likely associated with Glanzmann thrombasthenia?
A. Normal PLT aggregation to ADP and ristocetin; decreased aggregation to collagen
B. Normal PLT aggregation to collagen; decreased aggregation to ADP and ristocetin
C. Normal PLT aggregation to ristocetin; decreased aggregation to collagen, ADP, and EPI
D. Normal PLT aggregation to ADP; decreased aggregation to collagen and ristocetin
C. Normal PLT aggregation to ristocetin; decreased aggregation to collagen, ADP, and EPI
Glanzmann thrombasthenia is a disorder of PLT aggregation. PLT aggregation is normal in response to ristocetin, but abnormal in response to collagen, ADP, and EPI.
- Which of the following is a characteristic of acute immune thrombocytopenic purpura?
A. Spontaneous remission within a few weeks
B. Predominantly seen in adults
C. Nonimmune PLT destruction
D. Insidious onset
A. Spontaneous remission within a few weeks
Acute immune thrombocytopenic purpura is an immune-mediated disorder found predominantly in children. It is commonly associated with infection (primarily viral). It is characterized by abrupt onset, and spontaneous remission usually occurs within several weeks.
- TTP differs from DIC in that:
A. APTT is normal in TTP but prolonged in DIC
B. Schistocytes are not present in TTP but are present in DIC
C. PLT count is decreased in TTP but normal in DIC
D. PT is prolonged in TTP but decreased in DIC
A. APTT is normal in TTP but prolonged in DIC
TTP is a PLT disorder in which PLT aggregation increases, resulting in thrombocytopenia. Schistocytes are present in TTP as a result of microangiopathic hemolytic anemia (MAHA); however, the PT and APTT are both normal. In DIC, the PT and APTT are both prolonged, the PLT count is decreased, and schistocytes are seen in the peripheral blood smear.
- Several hours after birth, a baby boy develops petechiae and purpura and hemorrhagic diathesis. The PLT count is 18 × 109/L. What is the most likely explanation for the low PLT count?
A. Drug-induced thrombocytopenia
B. Secondary thrombocytopenia
C. Neonatal alloimmune thrombocytopenia
D. Neonatal DIC
C. Neonatal alloimmune thrombocytopenia
Neonatal alloimmune thrombocytopenia is similar to the hemolytic disease of the fetus and newborn. It results from immunization of the mother by fetal PLT antigens. The offending antibodies are commonly anti-PLT antigen A1 (PlA1), also referred to as human platelet antigen (HPA) 1a. These alloantibodies are directed against glycoproteins IIb/IIIa, Ib/IX, Ia/IIb, and CD 109. Maternal antibodies cross the placenta, resulting in thrombocytopenia in the fetus.
- Which of the following is associated with post-transfusion purpura (PTP)?
A. Nonimmune thrombocytopenia/alloantibodies
B. Immune-mediated thrombocytopenia/alloantibodies
C. Immune-mediated thrombocytopenia/autoantibodies
D. Nonimmune-mediated thrombocytopenia/autoantibodies
B. Immune-mediated thrombocytopenia/alloantibodies
PTP is a rare form of alloimmune thrombocytopenia characterized by severe thrombocytopenia occurring after transfusion of blood or blood products. PTP is caused by antibody-related PLT destruction in previously immunized patients. In the majority of cases, the alloantibody produced is against PlA1 (HPA-1a).
- Hemolytic uremic syndrome (HUS) is associated with:
A. Fever, thrombocytosis, anemia, and renal failure
B. Fever, granulocytosis, and thrombocytosis
C. Escherichia coli 0157:H7
D. Leukocytosis and thrombocytosis
C. Escherichia coli 0157:H7
HUS is caused by E. coli 0157:H7. It is associated with ingestion of E. coli–contaminated foods and is commonly seen in children. The clinical manifestations in HUS are fever, diarrhea, thrombocytopenia, MAHA, and renal failure.
- Storage pool deficiencies are defects of:
A. PLT adhesion
B. PLT aggregation
C. PLT granules
D. PLT production
C. PLT granules
Storage pool deficiencies are defects of PLT granules. Most commonly, a decrease in PLT-dense granules is present with decreased release of ADP, ATP, calcium, and serotonin from PLT-dense granules.
- Lumi-aggregation measures:
A. PLT aggregation only
B. PLT aggregation and adenosine triphosphate (ATP) release
C. PLT adhesion
D. PLT glycoprotein Ib
B. PLT aggregation and adenosine triphosphate (ATP) release
Lumi-aggregation measures PLT aggregation and ATP release. It is performed on whole blood diluted with saline. PLT aggregation is measured by impedance, whereas ATP release is measured by addition of luciferin to a blood sample. There is no ATP release in storage pool deficiencies.
