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Which of the following initiates in vivo 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 vivo?
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
D. Ethylenediaminetetraacetic acid (EDTA)
B. Sodium citrate
Sodium citrate (3.2% or 3.8%) is the anticoagulant of choice for routine coagulation testing because it binds calcium reversibly, allowing tests like PT and aPTT to function properly once calcium is reintroduced during analysis.
Other anticoagulants like EDTA, heparin, and oxalate interfere with clotting factors or enzyme reactions, making them unsuitable for coagulation assays.
Which anticoagulant:blood ratio is correct for coagulation procedures?
A. 1:4
B. 1:5
C. 1:9
D. 1:10
C. 1:9
This ratio ensures proper calcium binding without excess dilution, maintaining accurate results for tests like PT and aPTT.
Incorrect ratios can cause falsely prolonged or shortened clotting times, especially if the tube is under- or overfilled.
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
Which reagents are used in the PT test?
A. Thromboplastin and sodium citrate
B. Thromboplastin and potassium chloride
C. Thromboplastin and calcium
D. Actin and calcium 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 factor 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 process
C. TT
Which of the following characterizes Vitamin K?
A. It is required for biological activity of fibrinolysis
B. Its 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
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
Which of the following clotting factors are measured by the APTT test?
A. Factors II, VII, IX, X
B. Factors VII, X, V, 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
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
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)
Which protein is the primary inhibitor of the fibrinolytic system?
A. Protein C
B. Protein S
C. Alpha 2-Antiplasmin
D. Alpha 2-Macroglobulin
C. Alpha 2-Antiplasmin
α₂-Antiplasmin binds free plasmin, forming an inactive complex that prevents excessive fibrin or fibrinogen breakdown and maintains clot stability.
It’s the key plasma regulator of fibrinolysis, working with PAI-1 to restrict fibrin degradation to the clot site and prevent systemic bleeding.
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 test detects cross-linked fibrin degradation products, and a negative result effectively rules out active thrombosis or DIC, giving it a high negative predictive value.
Negative predictive value (NPV) means that if the test is negative, it is highly likely the patient truly doesn’t have the disease or condition being tested for.
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
Fibrinogen serves as the precursor of fibrin in coagulation and also acts as a bridging molecule between platelets, binding to GPIIb/IIIa receptors to promote platelet aggregation and stable clot formation.
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 result
D. Report the APTT result
B. Reject the sample and request a new sample
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
CLSI and many modern lab protocols: PT is stable up to 24 hours at room temperature (capped tube) if unopened and properly mixed — which matches Answer A.
If the sample is opened or stored cold (4°C), factor activity (especially VII) can degrade or activate, leading to inaccurate results — so refrigeration isn’t recommended.
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
In primary fibrinolysis, plasminogen is inappropriately activated to plasmin without prior fibrin formation, leading to degradation of fibrinogen and clotting factors and resulting in bleeding without thrombosis.
Plasminogen deficiency is associated with:
A. Bleeding
B. Thrombosis
C. Increased fibrinolysis
D. Increased coagulation
B. Thrombosis
Which of the following clotting factors are activated by thrombin that is generated by tissue pathway (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. Chlorophenol red
C. Prussian blue
D. Ferricyanide
A. p-nitroaniline (pNa)
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