HEMOSTASIS

Question 1

Which of the following lists the steps of the hemostatic response in the correct order?
a. Fibrinolysis → injury → secondary hemostasis → primary hemostasis
b. Injury → primary hemostasis → secondary hemostasis → fibrinolysis
c. Injury → secondary hemostasis → primary hemostasis → fibrinolysis
d. Injury → fibrinolysis → primary hemostasis → secondary hemostasis

Answer 1

b. Injury → primary hemostasis → secondary hemostasis → fibrinolysis

When damage occurs to the endothelium, primary hemostasis occurs first, resulting in the formation of the primary platelet plug. Secondary hemostasis occurs next, which results in the formation of a stable fibrin clot. The last action is fibrinolysis, which results in the breakdown of the clot.

Question 2

Which of the following properties renders the vessel wall prothrombotic?
a. Negatively charged surface
b. Production of prostacyclin and nitric oxide
c. Release of tissue factor
d. Inactivation of thrombin

Answer 2

c. Release of tissue factor

Under normal circumstances, vessels are non-thrombotic. Factors that contribute to this include a negatively charged surface; the inhibition of platelet activation through prostacyclin, nitric oxide, and ADPase; and the inactivation of thrombin through heparin sulfate and thrombomodulin. Once damaged, tissue factor is one of the substances released that favors the formation of clots. Other prothrombotic substances include the secretion of platelet-activating factor and von Willebrand factor.

Question 3

Which of the following is not true regarding platelets?
a. Platelets are not affected by aspirin
b. Platelets have a life span of 7 to 10 days
c. Platelets undergo shape change and develop pseudopods when activated
d. Von Willebrand factor serves as a bridge between platelets and collagen

Answer 3

a. Platelets are not affected by aspirin

Aspirin inhibits cyclooxygenase, which blocks thromboxane A2 (TXA2) synthesis, thereby making platelets nonfunctional for the life span of the platelets.

Question 4

Which of the following factors binds to platelets via the glycoprotein IIb/IIIa receptor?
a. Von Willebrand factor
b. Factor II
c. Fibrinogen
d. Thrombin

Answer 4

c. Fibrinogen

Both fibrinogen and von Willebrand factor (vWF) bind to platelets. Fibrinogen binds to platelets via the GbIIb/IIIa receptor. vWF binds through the GpIb/IX receptor.

Question 5

Which of the following is not an agonist of platelet aggregation?
a. Saline
b. ADP
c. Collagen
d. Epinephrine

Answer 5

a. Saline

Platelet agonists include collagen, adenosine diphosphate (ADP), thrombin, epinephrine, thromboxane A2 (TXA2), and arachidonic acid.

Question 6

Which enzyme is blocked by the presence of aspirin?
a. Phospholipase A2
b. Cyclooxygenase
c. Protein kinase
d. ATPase

Answer 6

b. Cyclooxygenase

Aspirin inhibits cyclooxygenase, which blocks thromboxane A2 (TXA2) synthesis, thereby making platelets nonfunctional for their life span.

Question 7

Secondary hemostasis occurs when a sufficient stimulus is present to cause the release of internal ADP, synthesis and release of thromboxane A2, and increased calcium release.
a. True
b. False

Answer 7

a. True

For secondary aggregation to occur, sufficient stimulus must be present. The stimulus occurs after internal adenosine diphosphate and calcium are released, along with the synthesis and release of thromboxane A2 (TXA2). Primary aggregation is reversible.

Question 8

Which of the following factors is called prothrombin?
a. Fibrinogen
b. Factor II
c. Factor X
d. Factor XIII

Answer 8

b. Factor II

Factor II is also called prothrombin.

Question 9

Which of the following factors usually results in no clinical bleeding when deficient?
a. Factor XII
b. Factor IX
c. Factor VIII
d. Factor VIi

Answer 9

a. Factor XII

A deficiency of factor XII, as well as prekallikrein and high-molecular-weight kininogen, does not usually manifest with clinical bleeding. Deficiencies of factors IX, VIII, and VII all generally present with clinical bleeding depending on the degree of deficiency.

Question 10

The step necessary for the functionary factors II, VII, IX, and X is called the ______________ step.
a. Oxidation
b. Hydrolysis
c. Cleavage
d. γ-Carboxylation

Answer 10

d. γ-Carboxylation

Vitamin K is required for the γ-carboxylation step of the formation of factors II, VII, IX, and X and proteins C and S. In this step, an additional carboxyl group is added to the g-carbon of the glutamic acid residues on the factors. Without this step, the factor is formed, but is not functional because binding to a negatively charged phospholipid surface cannot occur.

Question 11

Monitoring of the intrinsic pathway is accomplished by performing which of the following analytical tests?
a. PT
b. PTT
c. Thrombin time
d. Fibrinogen assay

Answer 11

b. PTT

The intrinsic pathway of hemostasis can be monitored through the partial thromboplastin time (PTT) assay. The prothrombin time (PT) assay can be used to monitor the extrinsic pathway. The thrombin time test assesses the formation of fibrin. The fibrinogen assay is used to measure fibrinogen levels.

Question 12

Monitoring of the extrinsic pathway is accomplished by performing which of the following analytical tests?
a. PT
b. PTT
c. Thrombin time
d. Fibrinogen assay

Answer 12

a. PT

The prothrombin time (PT) assay can be used to monitor the extrinsic pathway. The intrinsic pathway of hemostasis can be monitored through the partial thromboplastin time (PTT) assay. The thrombin time test assesses the formation of fibrin. The fibrinogen assay is used to measure fibrinogen levels.

Question 13

Which of the following cleaves the fibrinopeptides from fibrinogen?
a. Factor VIII
b. Thrombin
c. Tissue factor
d. Factor XIII

Answer 13

b. Thrombin

One of thrombin’s many actions is to cleave fibrinopeptides A and B from fibrinogen. This step results in the formation of a fibrin monomer, which can then continue to aggregate with other fibrin monomers. Factor VIII participates in the common pathway. Tissue factor is released by the endothelium during the initial stages leading to primary aggregation. Factor XIII is involved in the covalent cross-linking of D domains of fibrin to form a stable fibrin clot.

Question 14

Activation of factor VII after the release of tissue factor initiates which of the following pathways?
a. Intrinsic pathway
b. Extrinsic pathway
c. Common pathway
d. Fibrinolytic pathway

Answer 14

b. Extrinsic pathway

Factor VII is involved in the extrinsic pathway of coagulation, along with tissue factor.

Question 15

Which of the following is not true?
a. Factor VIII is a cofactor for factor IXa
b. Factor V is a cofactor for factor Xa
c. Protein K is a cofactor for protein C
d. High-molecular-weight kininogen is a cofactor for factor XIIa

Answer 15

c. Protein K is a cofactor for protein C

Protein S is a cofactor for protein C.

Question 16

If a deficiency of this factor is present, the cross-linking of fibrin will not occur.
a. Factor II
b. Factor V
c. Factor XI
d. Factor XIII

Answer 16

d. Factor XIII

Factor XIII covalently cross-links the D domains of fibrin to form a urea-insoluble clot. Factors II, V, and XI are involved in other parts of the hemostasis pathway.

Question 17

Factor VIII is protected from degradation when circulating in the plasma by its carrier protein __________.
a. Factor IX
b. Thrombin
c. Von Willebrand factor
d. Glycoprotein IIb/IIIa

Answer 17

c. Von Willebrand factor

Von Willebrand factor circulates as the vWF/VIII complex. If circulating alone, factor VIII will be quickly degraded.

Question 18

Which of the following factors is associated with hemophilia B?
a. Factor VIII
b. Factor IX
c. Factor XI
d. Fibrinogen

Answer 18

b. Factor IX

A deficiency of factor IX is called hemophilia B. Hemophilia A is associated with a deficiency of factor VIII. Hemophilia C is associated with a deficiency of factor XI.

Question 19

The activation of plasmin results in which of the following?
a. The formation of a fibrin clot
b. The formation of the bridge between platelets and the vessel wall
c. The start of the process to break down a fibrin clot
d. The point at which the intrinsic and extrinsic pathways feed into the common pathway

Answer 19

c. The start of the process to break down a fibrin clot

Fibrinolysis is the process of breaking down a fibrin clot. The activation of plasmin by plasminogen activators begins this process.

Question 20

Which of the following proteins is degraded by plasmin?
a. Fibrin
b. Fibrinogen
c. A and B
d. None of the above

Answer 20

c. A and B

Plasmin is a serine protease with broad specificity against proteins that are susceptible to trypsin degradation. In terms of the hemostatic pathway, plasmin has an effect against fibrin, fibrinogen, and factors V and VIII.

Question 21

Streptokinase differs from urokinase plasminogen activator (uPA) in that:
a. Streptokinase activates plasminogen to plasmin conversion, whereas uPA inhibits the conversion
b. uPA is effective only when given as a medication
c. Streptokinase is an exogenous activator, whereas uPA is a physiologic activator
d. No difference exists between streptokinase and uPA

Answer 21

c. Streptokinase is an exogenous activator, whereas uPA is a physiologic activator

There are physiologic and exogenous plasminogen activators. The exogenous plasminogen activators include streptokinase and staphylokinase. The physiologic plasminogen activators include tissue-type plasminogen activator and urokinase-type plasminogen activator.

Question 22

Which of the following are fibrin degradation products?
a. Fragment X
b. Fragment Y
c. Fragment D
d. All of the above

Answer 22

d. All of the above

When plasmin cleaves fibrin, the breakdown products that are formed include fragment X, fragment Y, fragment D, and fragment E. Fragment X has a limited binding ability for thrombin. Fragments Y, D, and E all inhibit fibrin polymerization and inhibit platelet aggregation.

Question 23

Which of the following describes the role of PAI-1 in hemostasis?
a. Plasminogen activator inhibitor–1 limits the activation of plasminogen
b. Plasminogen activator inhibitor–1 stimulates the activation of plasminogen
c. Plasminogen activator inhibitor–1 is involved in limiting clot formation in vessels
d. Plasminogen activator inhibitor–1 blocks platelet binding to the fibrin clot

Answer 23

a. Plasminogen activator inhibitor–1 limits the activation of plasminogen

Plasminogen activator inhibitor-1 has a significant role in limiting the activation of plasminogen.

Question 24

Which of the following fibrinolytic inhibitors is useful when a2-antiplasmin activity has been exhausted?
a. PAI-1
b. Thrombin-activatable fibrinolysis inhibitor
c. a2-Macroglobulin
d. Plasminogen

Answer 24

c. a2-Macroglobulin

a2-Macroglobulin has wide specificity against many proteases. It generally is not used until a2-antiplasmin is consumed.

Question 25

Positive feedback control of the hemostatic response is accomplished by: a. Fibrin binding to thrombin to limit further activation b. Fibrin degradation products interfere with fibrin formation and polymerization c. Thrombin activates platelets and promotes the release of platelet factor V d. Thrombin initiates activation of the protein C pathway

Answer 25

c. Thrombin activates platelets and promotes the release of platelet factor V There are both positive and negative feedback mechanisms in the control of hemostasis. Positive feedback mechanisms include the thrombin activation of platelets, release of platelet factor Va, exposure of the negatively charged surface, and activation of factors Va and VIIIa. Negative feedback mechanisms include thrombin’s involvement in the protein C pathway, tissue factor pathway inhibitor (TFPI) inactivation of factor Xa, fibrin binding to thrombin, and the interference of fibrin degradation products (FDPs) in fibrin formation and polymerization.

Question 26

Which of the following descriptions best describes the actions of protein S? a. Protein S inactivates factors Va and VIIIa b. Protein S is involved in the activation of thrombin c. Protein S serves as a cofactor for protein C d. None of above are functions of protein S

Answer 26

c. Protein S serves as a cofactor for protein C In the protein C pathway, protein S serves as a cofactor C. Protein S circulates bound to C4BP. In the presence of protein S and calcium, activated protein C inactivates factors Va and VIIIa.

Question 27

A child presents to the pediatrician after having recovered from a viral infection, because the child now has petechiae. The pediatrician orders laboratory testing, and the results reveal that the platelets are decreased. An increase in lymphocytes and eosinophils is also found. What is the probable diagnosis? a. Acute ITP b. Chronic ITP c. NAIT d. Medication reaction

Answer 27

a. Acute ITP Acute idiopathic thrombocytopenic purpura (ITP) is typically observed in children (ages 2-4) and follows viral infections. Affected patients may be asymptomatic or have severe mucosal bleeding. Patients will have a decrease in platelets and increase in lymphocytes and eosinophils. Patients with chronic ITP are usually adults.

Question 28

Which of the following tests would help to differentiate between Bernard-Soulier syndrome and Glanzmann’s thrombasthenia? a. Bleeding time b. Platelet count c. PT d. Response to ADP, collagen, and epinephrine in an aggregation assay

Answer 28

d. Response to ADP, collagen, and epinephrine in an aggregation assay Bernard-Soulier syndrome and Glanzmann’s thombasthenia are both qualitative platelet disorders. The bleeding time will be prolonged in both conditions. The platelet count may be affected in either disorder. Platelets are not assessed using prothrombin time (PT). The conditions can be differentiated using platelet aggregation tests. In patients affected with Bernard-Soulier, responses to adenosine diphosphate (ADP), collagen, and epinephrine will be normal, whereas the response to ristocetin is abnormal. The Glanzmann’s abnormal responses are observed with ADP, collagen, and epinephrine, but normal with ristocetin.

Question 29

Glanzmann’s thrombasthenia is best described as a: a. Platelet deficiency b. Deficiency of glycoprotein Ib/IX c. Deficiency of glycoprotein IIb/IIIa d. Deficiency of dense granules

Answer 29

c. Deficiency of glycoprotein IIb/IIIa The pathophysiology of Glanzmann’s thrombasthenia is the deficiency of GpIIb/IIIa.

Question 30

The lack of a secondary wave of platelet aggregation in response to ADP is associated with which of the following disorders? a. Bernard-Soulier syndrome b. Gray platelet syndrome c. Glanzmann’s thrombasthenia d. ∆-Storage pool disease

Answer 30

d. ∆-Storage pool disease In ∆-storage pool deficiency, platelets have a decrease in or absence of dense granules. This results in the lack of a secondary wave of aggregation when the agonist adenosine diphosphate (ADP) is used. Aggregation with collagen and epinephrine is also deficient. A normal response to ristocetin is observed.

Question 31

A young boy is taken to his pediatrician because his parents noticed that he seems to bleed easily and has swollen knees. The following test results were obtained: PT = normal Fibrinogen = Normal Platelet count = Normal aPTT = Prolonged aPTT with normal pooled plasma = Corrected the aPTT Which of the following statements best describes the next steps? a. The pediatrician should order factor assays for factors VIII and IX b. The pediatrician should order factor assays for factors X and V c. The pediatrician should order platelet aggregation testing d. The pediatrician should request a molecular test for the factor V Leiden defect

Answer 31

a. The pediatrician should order factor assays for factors VIII and IX The abnormal partial thromboplastin time (PTT) and normal prothrombin time (PT) suggest a deficiency of a factor in the intrinsic pathway. Given the sex, age, and type of bleeding, evaluations of factors VII and IX should be performed to check for hemophilia A or B. A normal PT rules out the possibility of a common pathway deficiency, which rules out a deficiency of X or V. The symptoms and laboratory results are not suggestive of a platelet abnormality. Factor V Leiden is a condition associated with thrombosis.

Question 32

Which of the following results would be expected in a patient with dysfibrinogenemia? a. Normal PT, normal aPTT, prolonged thrombin time b. Abnormal PT, normal aPTT, prolonged thrombin time c. Abnormal PT, abnormal aPTT, normal thrombin time d. Normal PT, normal aPTT, normal thrombin time

Answer 32

a. Normal PT, normal aPTT, prolonged thrombin time In dysfibrinogenemia, the structure of fibrinogen is abnormal. Fibrin still forms, resulting in normal PT and PTT evaluations. As a result of the structural abnormality, the thrombin time that assesses fibrinogen to fibrin formation is affected.

Question 33

In factor deficiencies, normal PT and aPTT results may be recorded until a factor level is ________. a. Less than 30% b. Less than 50% c. Less than 75% d. Less than 100%

Answer 33

a. Less than 30% Because of compensation of other factors in the hemostatic pathway and the sensitivity of the reagents, factor levels must be reduced to 30% or less before prolongation is observed.

Question 34

The following results were obtained from a patient who recently underwent major surgery. PT = Prolonged Fibrinogen = Decreased D-Dimer = Positive APTT = Prolonged Platelet count = Decreased Which of the following conditions is likely? a. Fibrinogenolysis b. Fibrinogen deficiency c. Disseminated intravascular coagulation d. Vitamin K deficiency

Answer 34

c. Disseminated intravascular coagulation Disseminated intravascular coagulation is a disorder of consumption. Coagulation proteins, including fibrinogen, and platelets are all consumed in thrombi, resulting in a prolongation of the prothrombin time (PT) and partial thromboplastin time (PTT) and decreased fibrinogen and platelet count. The D-dimer is significant and can help rule out other conditions, because it indicates that thrombi are being formed. The D-dimer would be negative in fibrinogenolysis, fibrinogen deficiencies, and vitamin K deficiency. In vitamin K deficiencies, the fibrinogen assay, platelet count, and D-dimer assay would be normal.

Question 35

Which of the following conditions is not usually associated with thrombosis? a. Protein C deficiency b. Antithrombin deficiency c. Factor V Leiden mutation d. Factor V deficiency

Answer 35

d. Factor V deficiency Factor V deficiency results in a bleeding condition because it is part of the common pathway. Both the prothrombin time (PT) and partial thromboplastin time (PTT) would be abnormal. Protein C deficiency, antithrombin deficiency, and the factor V Leiden mutation are all associated with thrombosis

Question 36

Which of the following accelerates the activity of antithrombin? a. Coumadin b. Aspirin c. Heparin d. tPA

Answer 36

c. Heparin Heparin is an anticoagulant that functions by significantly accelerating the activity of antithrombin.

Question 37

Which of the following tests is helpful in differentiating fibrinogenolysis from DIC? a. PT b. aPTT c. Fibrinogen d. D-Dimer

Answer 37

d. D-Dimer Fibrinogenolysis is a condition in which plasmin is generated without the generation of thrombin or thrombi. As clots are not formed, D-dimers are not produced. In disseminated intravascular coagulation, thrombi are formed, and after fibrinolysis, D-dimers are measurable in the blood.

Question 38

A patient who has been receiving a broad spectrum antibiotic is found to have a prolonged PT. After running a couple of factor assays, you conclude that both the factor X and factor VII levels are decreased. The PT corrected when mixed with normal pooled plasma. What is a possible cause? a. Inherited factor deficiency b. Circulating anticoagulant c. Vitamin K deficiency d. Effect resulting from antibiotic presence in plasma

Answer 38

a. Inherited factor deficiency An abnormal prothrombin time (PT) will be observed in deficiencies or in the presence of an inhibitor. When patient plasma is mixed with normal pooled plasma, the deficient factor is added back, resulting in a correction of the PT. If an inhibitor was present, the PT mix with normal pooled plasma would not result in a correction.

Question 39

Which of the following descriptions best describes the principle of platelet aggregation? a. The decrease in optical density is observed after the addition of an agonist in platelet-poor plasma b. The increase in optical density is observed after the addition of an agonist in platelet-rich plasma c. The decrease in optical density is observed after the addition of an agonist in platelet-rich plasma d. The increase in optical density is observed after the addition of an agonist in platelet-poor plasma

Answer 39

c. The decrease in optical density is observed after the addition of an agonist in platelet-rich plasma The principle of the platelet aggregation assays is that the formation of platelet aggregates will decrease the optical density of platelet-rich plasma when an agonist is added. If added to platelet-poor plasma, aggregation would not occur, because of the lack of platelets.

Question 40

When performing platelet aggregation assays, which of the following is an important preanalytical factor? a. The patient should have fasted overnight b. The patient must refrain from aspirin containing products for 7 days before testing c. After collection, the specimen can be frozen before transport to the laboratory d. All of the above are important

Answer 40

b. The patient must refrain from aspirin containing products for 7 days before testing The goal of the platelet aggregation assay is to assess platelet function. If platelets are not functional, as is the case when aspirin is ingested, the results will not be reflective of the patient’s platelets. Fasting is not required. Freezing the plasma will cause the platelets to aggregate before evaluation.

Question 41

Which of the following conditions will cause an increase in fibrinogen levels? a. DIC b. Afibrinogenemia c. Acute phase reactions d. Liver disease

Answer 41

b. Afibrinogenemia Fibrinogen is an acute phase protein that will cause levels to increase in conditions in which an acute phase reaction is observed. In disseminated intravascular coagulation, fibrinogen is a protein that is consumed. Fibrinogen levels are absent in afibrinogenemia. In liver disease, fibrinogen production is decreased.

Question 42

Which of the following describes the principle of the thrombin time test? a. After the addition of thromboplastin, the time needed for plasma to form a clot is measured b. Patient plasma is mixed with thrombin deficient plasma, and the time to clot is measured c. An excess of thrombin is added to patient plasma, and the time to clot is measured d. Clot solubility is assessed using 5 M urea

Answer 42

c. An excess of thrombin is added to patient plasma, and the time to clot is measured The thrombin time test is performed by adding an excess of thrombin to the patient specimen to assess fibrinogen-to fibrin formation. Thromboplastin is used in the prothrombin time (PT) assay. The 5 M urea solubility test is used to assess factor XIII levels.

Question 43

When performing a factor assay for factor VIII, the MLS accidentally added factor IX - deficient plasma to the patient specimens. Which of the following best describes the expected results? a. The test will not be affected because the correct factor-deficient plasma was added b. The test will not be affected because factor-deficient plasma is not needed in a factor assay c. The test results will not be an assessment of factor VIII levels because factor VIII is present in the factor IX deficient plasma d. The test results will be an assessment of factor IX levels and can be calculated using the factor VIII standard curve

Answer 43

c. The test results will not be an assessment of factor VIII levels because factor VIII is present in the factor IX deficient plasma Factor IX–deficient plasma contains all coagulation factors with the exception of factor IX. If added to asses a patient’s factor VIII level, the factor VIII present in the deficient plasma will result in an analytical error.

Question 44

What are the reagents needed to perform the aPTT test? a. Calcium chloride b. Partial thromboplastin c. A and B d. None of the above

Answer 44

c. A and B Calcium chloride and partial thromboplastin are the needed reagents for the partial thromboplastin time (PTT) assay.

Question 45

Which of the following tests is reported in conjunction with the INR? a. PT b. APTT c. Thrombin time d. Fibrinogen assay

Answer 45

a. PT The international normalized ratio (INR) is reported out in conjunction with the prothrombin time (PT) result. It helps to standardize the PT results for variations in instrumentation, reagents, and personnel.

Question 46

The following test results were obtained on a patient who is being seen for easy bruising. Bleeding time = Increased aPTT = Prolonged (mix with normal pooled plasma corrected aPTT) ADP, collagen, epinephrine platelet aggregation = Normal PT = Normal Platelet count = Normal Ristocetin platelet aggregation = Absent Which of the following conditions is expected? a. Hemophilia A b. Hemophilia B c. Von Willebrand’s disease d. Factor XII deficiency

Answer 46

c. Von Willebrand’s disease von Willebrand’s disease is a qualitative platelet disorder. In this condition, the platelet aggregation response to ristocetin is abnormal. The bleeding time is increased as a result of the qualitative defect in the platelets. Although von Willebrand factor (vWF) is not assessed in the partial thromboplastin time (PTT) assay, vWF also carries around factor VIII in the circulation to protect it from degradation. Therefore a decrease in vWF sometimes results in a prolongation of the PTT assay because of the lower factor VIII levels, which are corrected by the addition of normal pooled plasma.

Question 47

During a lengthy overseas trip, a 60-year old man went to a laboratory in Italy to have PT measured to assess his dosage of Coumadin. Typically, in the United States, his results are in the range of 17 to 18 seconds, with an average INR of 1.75. In the laboratory in Italy, his PT was 20.2 seconds and his INR was 1.74. Which of the following descriptions best describes the situation? a. The patient is taking excessive anticoagulation medication, causing his PT to be prolonged b. An error is expected in the results from the laboratory in Italy c. The result is not concerning because the INR results are essentially the same d. He should immediately return to the United States for further assessment

Answer 47

c. The result is not concerning because the INR results are essentially the same International normalized ration (INR) results of 1.75 and 1.74 are essentially the same. The INR is used to standardize the prothrombin time (PT) assays among laboratories and is compared to assess degree of anticoagulation when the testing is performed at different laboratories.

Question 48

During presurgical testing, the aPTT for a patient was longer than 120 seconds. The patient’s history for bleeding is negative. The result was corrected after mixing with normal pooled plasma. The surgery is delayed because the surgeon is concerned about bleeding. Which of the following descriptions best describes this situation? a. The patient is at risk for a bleeding incident if the surgery proceeds b. The patient likely has a circulating inhibitor c. The patient likely has a deficiency of a contact factor that is not associated with bleeding d. The sample was likely contaminated with heparin

Answer 48

c. The patient likely has a deficiency of a contact factor that is not associated with bleeding It is likely that this patient has a deficiency of one of the contact factors (factor XII, prekallikrein, or high-molecular-weight kininogen). Although the deficiency of these factors results in a very prolonged partial thromboplastin time (PTT), bleeding complications are not observed.

Question 49

A 30-year-old woman with a history of miscarriages is being seen by an obstetrician/gynecologist. Which of the following tests would be included in a panel to assess her condition? a. DRVVT b. PT and PTT c. PT and PTT using normal pooled plasma mix d. All of the above

Answer 49

d. All of the above In a patient with a history of miscarriages, one concern is the presence of lupus anticoagulants. To assess this condition, a panel would include the following tests to rule in or rule out the presence of such an anticoagulant: dilute Russell viper venom time (DRVTT, to indicate an anticoagulant against phospholipids), prothrombin time (PT) and partial thromboplastin time (PTT), and PT and PTT with normal pooled plasma (to rule out a factor deficiency and demonstrate the presence of an inhibitor).

Question 50

A patient presents to the emergency department with symptoms consistent with a DVT. Which of the following tests is helpful as a screening test for the factor V Leiden mutation? a. Protein S assay b. Antithrombin assay c. Prothrombin 20210 molecular test d. APCR test

Answer 50

d. APCR test The activated protein C resistance (APCR) test is a screening test that will be abnormal in the presence of a factor V Leiden defect. It is a clot-based test based on the inability of activated factor V to be inactivated that is quick to perform and cheaper than the molecular-based factor V Leiden test. The other tests listed (protein S, antithrombin, and prothrombin 20210) are all associated with deep vein thromboses if abnormal, but will be normal in the presence of the factor V Leiden defect.