2.1 Coagulation and Fibrinolytic Systems/Reagents and Methods Flashcards
What of the following initiates in vito coagulation by activation of factor VII?
A. Protein C
B. Tissue factor (TF)
C. Plasmin activator
D. Thrombomodulin (TM)
B. Tissue factor (TF)
Which of the following clotting factors plays a role in clotting formation in vitro, but not in vito?
A. Factor VIIa
B. Factor IIa
C. Factor XIIa
D. Factor Xa
C. Factor XIIa
The anticoagulant of choice for most routine coagulation studies is:
A. Sodium oxalate
B. Sodium citrate
C. Heparin
C. Ethylenediaminetetraacetic acid (EDTA)
B. Sodium citrate
Which anticoagulant: blood ratio is correct for coagulation procedures?
A. 1:4
B. 1:5
C. 1:9
D. 1:10
C. 1:9
Which results would be expected for PT and APTT in a patient with polycythemia?
A. Both prolonged
B. Both shortened
C. Normal PT, prolonged APTT
D. Both normal
A. Both prolonged
The volume of blood in a polycythemic patient contains so little plasma that excess anticoagulant remains and is available to bind to reagent calcium, thereby resulting in prolongation of PT and APTT. For more accurate results, the plasma: anticoagulant ratio can be modified by decreasing the amount of anticoagulant in the collection tube by using the following formula: (0.00185)(V)(100-H) = C, where V = blood volume in milliliters (mL); H= patient’s hematocrit (Hct); and C = volume (mL) of anticoagulant. A new sample should be drawn to rerun the PT and APTT tests.
Which reagents are used in the PT test?
A. Thromboplastin and sodium chloride
B. Thromboplastin and potassium chloride
C. Thromboplastin and calcium
D. Actin and calcium and chloride
C. Thromboplastin and calcium
Which test would be abnormal in a patient with factor X deficiency?
A. PT only
B. APTT only
C. PT and APTT
D. Thrombin time (TT)
C. PT and APTT
Which clotting factors is not measured by the PT and APTT tests?
A. Factor VIII
B. Factor IX
C. Factor V
D. Factor XIII
D. Factor XIII
A modification of which procedure can be used to measure fibrinogen?
A. PT
B. APTT
C. TT
D. Fibrin degradation products
C. TT
Which of the following characterizes vitamin K?
A. It is required for biological activity of fibrinolysis
B. It’s activity is enhanced by heparin therapy
C. It is required for carboxylation of glutamate residues of some coagulation factors
D. It is made by endothelial cells
C. It is required for carboxylation of glutamate residues of some coagulation factors
Vitamin K is necessary for activation of vitamin K-dependent clotting factors (II, VII, IX, and X). This activation is accomplished by carboxylation of glutamic acid residues of the inactive clotting factors. The activity of vitamin K is not enhanced by heparin therapy. Vitamin K is present in a variety of foods and is also the only vitamin made by the organisms living in the intestine.
Which fragments of fibrin clot degradation are measured by the D-dimer test?
A. Fragments X and Y
B. Fibrinopeptide A and B
C. Fragments D and E
D. The D-D domains
D. The D-D domains
D-dimer is a specific product resulting from digestion of cross-linked fibrin only. It consists of two D domains called D-D fragment and is a marker for thrombosis and fibrinolysis. In the D-dimer test, monoclonal antibody is directed against D-dimer antigen by using a variety of automated instruments. The D-dimer test is used to diagnose acute and chronic disseminated intravascular coagulation (DIC) and to rule out thromboembolic disorders. Fragments X, Y, D, and E are produced by the action of plasmin on fibrinogen and fibrin. Polypeptide A and B are produced by the proteolytic action of thrombin on fibrinogen to form a fibrin clot.
Which of the following clotting factors are measured by the APTT test?
A. Factors II, VII, IX, X
B. Factors VII, X, II, I
C. Factors XII, XI, IX, VIII, X, V, II, I
D. Factors XII, VII, X, V, II, I
C. Factors XII, XI, IX, VIII, X, V, II, I
Which coagulation test(s) would be abnormal in a patient with vitamin K deficiency?
A. PT only
B. PT and APTT
C. Fibrinogen level
D. TT
B. PT and APTT
Patients with vitamin K deficiency exhibit decreased production of functional prothrombin proteins (factors II, VII, IX, and X). Decreased levels of these factors prolong both PT and APTT.
Which of the following is correct regarding the international normalized ratio (INR)?
A. It uses the international sensitivity ratio (ISR)
B. It standardizes PT results
C. It standardizes APTT results
D. It is used to monitor heparin therapy
B. It standardizes PT results
INR is used to standardize PT results to adjust for the differences in thromboplastin reagents made by different manufacturers and used by various institutions. The INR calculations uses the international sensitivity index (ISI) value and is used to monitor an oral anticoagulant, such as warfarin. INR is not used to standardize APTT testing.
Which of the following is referred to as an endogenous activator of plasminogen?
A. Streptokinase
B. Transamidase
C. Tissue plasminogen activator (tPA)
D. tPA inhibitor
C. Tissue plasminogen activator (tPA)
tPA is an endogenous (produced in the body) activator of plasminogen. It is released from the endothelial cells by the action of protein C. It converts plasminogen to plasmin. Streptokinase is an exogenous (not made in the body) activator of plasminogen.
Which protein is the primary inhibitor of the fibrinolytic system?
A. Protein C
B. Protein S
C. alpha2-Antiplasmin
D. alpha2-Macroglobulin
C. alpha2-Antiplasmin
alpha2-Antiplasmin is the main inhibitor of plasmin. It inhibits plasmin by forming a 1:1 stoichiometric complex with any free plasmin in plasma and, thus prevents binding of plasmin to fibrin and fibrinogen.
Which of the following statements is correct regarding the D-dimer test?
A. Levels are decreased in DIC
B. Test detects polypeptides A and B
C. Test detects fragments D and E
D. Test has a negative predictive value
D. Test has a negative predictive value
The D-dimer assay evaluates fibrin degradation. It is a nonspecific screening test that shows increased values in many conditions in which fibrinolysis is increased, such as DIC and fibrinolytic therapy. The D-dimer test is widely used to rule out thrombosis and thrombotic activities. The negative predictive value of a test is the probability that a person with a negative result is free of the disease that the test is meant to detect. Therefore, a negative D-dimer test result rules out thrombosis, and further laboratory investigations are not required.
A protein that plays a role in both coagulation and PLT aggregation is:
A. Factor I
B. Factor VIII
C. Factor IX
D. Factor XI
A. Factor I
Factor I (fibrinogen), along with the glycoprotein IIb-IIIa complex, is necessary for PLT aggregation. Factor I is also substrate in the common pathway of coagulation. Thrombin acts on fibrinogen to form fibrin clots.
A standard 4.5-mL blue-top tube filled with 3.0 mL of blood was submitted to the laboratory for PT and APTT tests. The sample is from a patient undergoing surgery the following morning for a tonsillectomy. Which of the following is the necessary course of action by the medical laboratory scientist?
A. Run both tests in duplicate and report the average result
B. Reject the sample and request a new sample
C. Report the PT results
D. Report the APTT result
B. Reject the sample and request a new sample
A 4.5 mL. blue-top tube contains 4.5 mL blood + 0.5 mL sodium citrate. The tube should be 90% full. A tube with 3.0 mL blood should be rejected because the quantity is not sufficient (QNS). QNS samples alter the necessary blood: anticoagulant ratio (9.1). The excess anticoagulant in a QNS sample binds to the reagent calcium, resulting in prolongation of PT and APTT.
Which statement is correct regarding sample storage for the PT test?
A. Stable for 24 hours if the sample is capped
B. Stable for 24 hours if the sample is refrigerated at 4C
C. Stable for 4 hours if the sample is stored at 4C
D. Should be run within 8 hours
A. Stable for 24 hours if the sample is capped
According to Clinical Laboratory Standards Institute (CLSI) guidelines, plasma samples for PT testing, if capped, are stable for 24 hours at room temperature. Refrigerating the sample causes cold activation of factor VII and, therefore, shortened PT results. APTT samples are stable for 4 hours if stored at 4C.
In primary fibrinolysis, the fibrinolytic activity results in response to:
A. Increased fibrin formation
B. Spontaneous activation of fibrinolysis
C. Increased fibrin monomers
D. DIC
B. Spontaneous activation of fibrinolysis
Primary fibrinolysis is a rare pathological condition in which spontaneous systemic fibrinolysis occurs. Plasmin is formed in the absence of coagulation activation and clot formation. Primary fibrinolysis is associated with increased production of plasminogen and plasmin, decreased plasmin removal from the circulation, and spontaneous bleeding.
Plasminogen deficiency is associated with:
A. Bleeding
B. Thrombosis
C. Increased fibrinolysis
D. Increased coagulation
B. Thrombosis
Plasminogen deficiency is associated with thrombosis. Plasminogen is an important component of the fibrinolytic system. Plasminogen is activitated to plasmin, which is necessary for the degradation of fibrin clots to prevent thrombosis. When plasminogen is deficient, plasmin is not formed, causing a defect in the clot lysing processes.
Which of the following clotting factors are activated by thrombin that is generated by tissue pathways (TF-VIIa)?
A. Factors XII, XI
B. Factors XII, I
C. Factors I, II
D. Factors V, VIII
D. Factors V, VIII
Which substrate is used in a chromogenic factor assay?
A. p-nitroaniline (pNa)
B. Chloroprenol red
C. Prussian blue
D. Ferricyanide
A. p-nitroaniline (pNa)
The chromogenic, or amidolytic, assays use a color-producing substance, known as chromophore. The chromophore used for the coagulation laboratory is pNa. pNA is bound to synthetic oligopeptide substrate. The protease cleaves the chromogenic substrate at the site binding the oligopeptide to the pNa, which results in release of pNa. Free pNa has a yellow color; the color intensity of the solution is proportional to protease activity and is measured by a photodetector at 405 nm.
Which of the following antibodies is used in the D-dimer assay?
A. Polyclonal antibody directed against X and Y fragments
B. Polyclonal antibody directed against D-dimer
C. Monoclonal antibody against D and E fragments
D. Monoclonal antibody against D-dimer
D. Monoclonal antibody against D-dimer
