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01 Hematology > Coagulation > Flashcards

Coagulation Flashcards

1
Q

What molecule acts to link platelets to exposed collagen?

A

von Willebrand factor

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2
Q

What are the major two compounds released by platelets upon activation?

A

ADP and Thromboxane A2

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3
Q

What sample tube are coagulation samples collected in? What do these vials contain? What is the proper ratio of sample: this compound?

A

Blue topped- contain citrate; 9:1

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4
Q

On what kind of sample are coagulation tests performed?

A

Plasma

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5
Q

What is the difference between plasma and serum?

A

Serum contains very little coagulation factor and complement because there is no anticoagulant added

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6
Q

How is the intrinsic coagulation pathway tested?

A

Activated partial thrombolastin time (aPTT)

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7
Q

What is the initial step of the intrinsic coagulation cascade?

A

Trauma to vessels exposes blood to collagen and factor XII is activated

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8
Q

What is the function of FVa and what other factor is required for this action?

A

Converts prothrombin to thrombin with the aid of FVa

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9
Q

What is the action of thrombin (IIa) in the coagulation cascade?

A

Cleavage of fibrinogen to fibrin

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10
Q

How is the extrinisic pathway clinically tested?

A

Prothrombin time (PT)

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11
Q

What is the initiating step of the intrinsic pathway of coagulation?

A

Trauma to vascular wall or extravascular tissue exposes Tissue Factor (III) which forms a complex with FVII, activating FVII

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12
Q

What is the action of the TF-FVIIa complex?

A

Activation of X to Xa

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13
Q

What is the normal PT range?

A

12-15 sec

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14
Q

What clinical coagulation tests will be abnormal in a patient with an extrinsic pathway deficiency?

A

Prolonged PT time only

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15
Q

What clinical coagulation tests will be abnormal in a patient with an intrinsic pathway deficiency?

A

Prolonged aPTT

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16
Q

What clinical coagulation tests will be abnormal in a patient with an common pathway deficiency?

A

Prolonged PT and aPTT

17
Q

A Vit. K deficiency would decrease the synthesis of which coagulation cascade factors?

A

II, VII, IX, and X

18
Q

Approximately what percent of a normal level of a coagulation factor is generally sufficient to yield a normal PT or aPTT?

A

20-40%

19
Q

What is a mixing study?

A

The mixing of a normal plasma sample with a deficient sample to access PT

20
Q

In what case would adding a factor through a mixing study not correct a prolonged clotting time?

A

If the prolonged result is due to an inhibitor

21
Q

If a mixing test is immediately abnormal what does it indicate? If the mixing study immediately results in a normal time, but later points show abnormality, what does it indicate?

A

Immediately abnormal= heparin or lupus inhibitor; Later abnormal= antibody inhibitor to clotting factor

22
Q

What is the normal range for PTT?

A

25-36 seconds

23
Q

What is Lupus anticoagulant?

A

LAC interferes with phospholipid-dependent coagultion tests like PT and PTT

24
Q

What two assays are performed for lupus anti-coagulant?

A

Dilute Russell’s viper venom test (DRVVT) and Hexagonal phase phospholipid neutralization test

25
Q

What coagulation factor does DRVVT work on?

A

RVV activates factor X

26
Q

What is thrombin time a measure of?

A

Measures the conversion of fibrinogen to fibrin after addition of excess thrombin to undiluted plasma

27
Q

What is the #1 reason for prolonged thrombin time?

A

Heparin

28
Q

What is the relationship between fibrinogen concentration and thrombin time?

A

Inversely proportional

29
Q

What coagulation factor cross-links fibrin?

A

FXIII

30
Q

How does platelet agregometry work? What does it measure?

A

Based off of light impedance; Measures platelet aggregation

31
Q

What are the three most common platelet function defects?

A

Bernard-Soulier Syndrome, Glanzmann thrombasthenia, and von Willebrand’s disease

32
Q

What was bleeding time used to test for? What is used today instead?

A

To test for vWF deficiency; PFA- 100 Platelet function analyzer

01 Hematology (16 decks)

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