Laboratory Studies of Hemostasis - Wong

Question 1

What is INR used for

Answer 1

concentration of warfarin - anticoagulant therapy

Question 2

What would an anti-Xa test be used for?

Answer 2

heparin concentration

Question 3

sodium citrate tube

Answer 3

blue top tube

- anticoagulant

Question 4

What are causes of prolonged bleeding time

Answer 4

thrombocytopenia
VWD
platelet dysfunction
vascular dysfunction

Question 5

Prothrombin time

Answer 5

• platelet poor plasma obtained from blood sample
• citrate
• tissue factor, phospholipid, calcium as reagents
• time to clot detection
• sensitive to factor VII

Question 6

How does warfarin affect PT?

Answer 6

elevated PT

- affects factor VII

Question 7

What does heparin do?

Answer 7

binds AT III which binds anti-coag factors in intrinsic and extrinsic

Question 8

How does heparin affect PT?

Answer 8

elevated PT

Question 9

What are the common pathway factors?

Answer 9

I (fibrinogen), II, V, X

1x2x5=10

Question 10

What happens if you don’t have enough fibrinogen

Answer 10

prolonged PT

- fibrin isn’t adequately getting properly formed

Question 11

What do inhibitors lead to?

Answer 11

elevated PT

Question 12

How do you calculate INR

Answer 12

PT/PT(normal) raised to the ISI (international sensitivity index)

Question 13

What is added to the tube when checking for aPTT

Answer 13

• add an activator - silica, kaolin
• phospholipid
• calcium
• tissue factor is not used

Question 14

What can elevated FVIII cause to the aPTT

Answer 14

shortened

Question 15

What does a FVIII inhibitor do to PTT

Answer 15

elevated aPTT

Question 16

How is thrombin time measured?

Answer 16

thrombin and calcium are added to the plasma

• measure clot formation
• conversion of fibrinogen to fibrin

Question 17

What can cause an elevated thrombin time

Answer 17

heparin

Question 18

How would dysfibrinogenemia/hypofibrinogemia affect thrombin time

Answer 18

elevated thrombin time

Question 19

How can you confirm that a prolonged TT is due to heparin?

Answer 19

test using reptilase will be normal

Question 20

What will the TT and the reptilase be in dysfibrinogemia?

Answer 20

TT and reptilase are prolonged and immunologic assay for fibrinogen will be normal

Question 21

What are autoantibodies specific to?

Answer 21

lupus-like type or secondary to an underlying autoimmune disorder

Question 22

What are alloantibodies

Answer 22

anti-factor VIII in a patient with hemophilia A following factor VIII concentrate infusion

Question 23

what is the autoantibody specificity of lupus-like coagulant?

Answer 23

plasma beta2-glycoprotein I which binds to coagulation factors

Question 24

What is PF4?

Answer 24

neutralizes heparin in heparin level determination

- when samples aren’t properly spun down

Question 25

How quickly should assays be run?

Answer 25

less than 2 hours because factor V and VIII are labile

Question 26

what is the steps of the mixing study

Answer 26

first exclude heparin - immediate and incubate mixture of patient and normal plasma - see if it corrects

Question 27

What would lupus anticoagulant cause in the mixing study

Answer 27

won't correct | - nonspecific inhibitor

Question 28

Patient with PT of 22 sec, PTT of 67 - normal fibrinogen - no recent history of coumadin or heparin - mixing study: PT: 13 sec, PTT: 32 sec

Answer 28

factory deficiency because correction of PT and PTT

Question 29

How do you test for lupus-like anticoagulant

Answer 29

factory specific inhibitor

Question 30

Which 3 factors are not associated with bleeding?

Answer 30

factor XII, prekallikrein, kininogen are not associated with bleeding

Question 31

What does the factor V leiden mutation cause?

Answer 31

resistance to protein C | - increase inability to clot

Question 32

protein S/C deficiency

Answer 32

less ability to activate factor V = more clotting

Question 33

ATIII

Answer 33

major inhibitory protein for clotting cascade

Question 34

lupus anticoagulant

Answer 34

LA = immunoglobulin which interfere with steps of clotting resulting in prolonged coagulation

Question 35

What causes the antiphospholipid antibody syndrome?

Answer 35

increase in cardiolipin and beta2-glycoprotein I antibodies

Question 36

What does APS criteria require

Answer 36

1 clinical and 1 laboratory finding